Exploring Offshore Sediment Evidence of the 1755 CE Tsunami (Faro, Portugal): Implications for the Study of Outer Shelf Tsunami Deposits

Round 1

Reviewer 1 Report

[Structure of the paper]

Some parts of this paper would be better to be reorganized;

L135-141 might be suitable to introduction.

L147-150 and some of the subsection “Supporting data” could be moved to a new section “Previous study”. To show originality of this paper, authors should clearly separate what they did from what previous study had done before.

The first paragraph of Section 4.1 (1755 CE deposit) basically relies on chronology. Before making correlation of the event deposit with historical event (Lisbon tsunami in this case), origin of the event deposit should be carefully discussed. In this point of view, L525-547 and most parts of Section 4.2 should be placed before Section 4.1, and then correlation with the Lisbon event should be mentioned as a possible cause.

 

[Cs peaks] It would be good to show detection limit of Cs in the graphs. It will help readers to recognize peaks of Cs. By the way, it is hard for me to recognize two peaks of Cs (1963 and 1986). In core M106, I was not sure why the second horizon from the top is not estimated as 1986.

 

[Multi proxy data]

L339-340 “The tsunami layer contains mean grain size peaks in both cores.” I was not sure which horizons the authors mean. There seems to have no peaks in mean grain size. Please rephrase or clarify it, for example, by arrows indicating peaks.

L344 “Peaks of carbonate content in the tsunami layer are coherent in both cores.” This is also difficult to follow. Please explain the details.

 

[Sand composition]

L440 “A general difference in sand composition between core M107 and M106 is coherent.” This sounds unclear. Authors could rephrase it, or explain more detailedly.

 

 

Author Response

Response to Reviewer 1 Comments
We would like to thank the reviewer for his work of carefully reading the manuscript and making suggestions to improve this work. Here, we present the response to the different points made by the reviewer.


Point 1: [Structure of the paper]
Some parts of this paper would be better to be reorganized;
L135-141 might be suitable to introduction.
L147-150 and some of the subsection “Supporting data” could be moved to a new section
“Previous study”. To show originality of this paper, authors should clearly separate what they did from what previous study had done before.
The first paragraph of Section 4.1 (1755 CE deposit) basically relies on chronology. Before making correlation of the event deposit with historical event (Lisbon tsunami in this case), origin of the event deposit should be carefully discussed. In this point of view, L525-547 and most parts of Section 4.2 should be placed before Section 4.1, and then correlation with the Lisbon event should be mentioned as a possible cause.

Response to Point 1: [Structure of the paper]
L135-141: This part is now replaced according to the reviewer’s suggestion right before the study area section 1.1..
L147-150: We agree and made a new section in the introduction called “1.2. Previous Study” according to the reviewer’s suggestion. However, the methodology remains the same since this data is used in the specific core sections and is part of the present work.
Section 4: Within the section 4.1. the suggested change was accepted, and the discussion of possible other high-energy events is now placed before the discussion of the age correlation with the 1755 CE tsunami. With the new section 1.2., however, we think it is better to keep the original structure since the origin of the event deposit is now clearer.


Point 2: [Cs peaks]
It would be good to show detection limit of Cs in the graphs. It will help readers to recognize peaks of Cs. By the way, it is hard for me to recognize two peaks of Cs (1963 and 1986). In core M106, I was not sure why the second horizon from the top is not estimated as 1986.

Response to Point 2: [Cs peaks]
The detection limits are now shown in the figure. Also, as pointed out by the reviewer, the Cs peaks are hard to recognized and we decided to not indicate single peaks but correlate the fall out events to the increased Cs values in general.


Point 3: [Multi proxy data]
L339-340 “The tsunami layer contains mean grain size peaks in both cores.” I was not sure which horizons the authors mean. There seems to have no peaks in mean grain size. Please rephrase or clarify it, for example, by arrows indicating peaks.
L344 “Peaks of carbonate content in the tsunami layer are coherent in both cores.” This is also difficult to follow. Please explain the details.

Response to Point 3: [Multi proxy data]
L339-340 The core depths of the grain size peaks are now written in the text to clarify: “The tsunami layer contains mean grain size peaks in both cores. However, it is subtle in core M106 (at core depth 71 cm and 69 cm) and more pronounced in core M107 (at core depth 23 cm and 20 cm), where it is directly linked with the increase of gravel content. In the post-tsunami layer, mean grain size is decreasing with minor variations.”
L344 We changed the phrasing to clarify the sentence of the carbonate peaks to “Peaks of carbonate content in the tsunami layer are visible in both cores”


Point 4: [Sand Composition]:
L440 “A general difference in sand composition between core M107 and M106 is coherent.” This sounds unclear. Authors could rephrase it, or explain more detailedly.

Response to Point 4: [Sand composition]
L440 This sentence was changed and rephrased for better clarity: “A general difference in SC between core M107 and M106 is apparent: (1) In the shallower shelf core M107 higher percentages of terrigenous components (ca. 50 %) are present compared to the deeper shelf core M106 (ca. 30 %). (2) In core M106, percentages of benthic foraminifera are higher, and percentages of mollusks are lower compared to core M107”

Author Response File: Author Response.pdf

Reviewer 2 Report

Major comment

In geological studies of tsunami, around the world, reliable identification methods for tsunami deposits have not yet been established. This is because it is difficult to extract information for identification of only-tsunami events as there is little information specific to tsunami deposits. Therefore, the accumulation of correct geological fundamental information for recognizing tsunami deposits is one of the most important points in paleo-tsunami research.

As shown in this study, sediment cores have a range of ages that can cover the 1755 Lisbon earthquake and tsunami event. Therefore, it is possible that the deposits or effects of the tsunami are preserved in these sediment core samples. However, even if the effects of the tsunami as a proxy may be preserved, whether the effects of the tsunami can be identified is another issue.

Generally, the effects of tsunamis and the identification of tsunami deposits are evaluated in terrestrial areas and deposits. This is because it is relatively easy to identify proxies originating from the sea. On the other hand, it is difficult to identify proxies originating from the sea in marine areas because it is very difficult to find marine-derived substances in ocean sediments and area. This seems to be a commonly recognized issue among tsunami deposit researchers worldwide. Therefore, it would be of great benefit to researchers if new recognition methods are developed.

This article does not include much important basic information such as the lithology of the drilling cores. Therefore, it is impossible to determine whether the effect of a tsunami is indeed preserved in these cores and whether this method is effective as a new way to recognize tsunami deposits. A study should include at least one figure that clearly shows a high resolution photograph, CT image, or geological column of core samples that gives a clear overview of the deposited geologic layers. Only small photos with little detail are currently provided and only one figure of the computed tomography scan showing the entire core is presented. The CT photographs (Figure 4) are unclear. Is there no characteristic sedimentary structure in the two cores? For these reasons, it is recommended the paper’s authors create geological columns.

When looking at the upward trend of the two cores’ magnetic susceptibility, why are they so different (Figure 5)? Are the “depth of tsunami deposits” in core 106 and core 107 same? Both lithological characteristics and results are clearly visible in core 106. There is also a risk that core 107 will lead to a different interpretation. Based on these points, it is necessary to create a figure showing the lithology or proxy contrast with the samples of previous studies and to be compared with the studies (e.g. Quintela et al. 2016). It is also important to reinforce the core stratigraphic information. It should be pointed out that the method used in this study may be applicable to other regions in the future, but the contrast is slightly unclear. From the current composition of the core samples, although the Lisbon tsunami should be discussed within the paper, the main theme is the certification of tsunami deposits. If the site is close to other research sites, it is better to change to a structure that handles the Lisbon tsunami deposits from the beginning.

The possibility of identifying and comparing tsunami deposits on the seabed is the most important point in this research, but I would like you to narrow down your focus by looking at the research field as broadly as possible.

 

Minor comments

Result section:For Tabble1 does not have much meaning, it is recommended to show it again as geological columns.

Table 2: Classification of sand components.　>sand size components?

Figure 2: I would like you to increase the resolution of the photos in Figure 2.

Figure 6: I do not understand the meaning of the colors in (b)1, 2, 3, so please add the color chart or color legend and I want you to enlarge the size of the 3 and adjust the scale.

L361-L422: Why does the CaCO3 decrease toward the top of the core 107? It shows the opposite trend to the core 106.

Figure 7: The components appear to be clearly separated by source.

Discussion section: Please make it clear whether the purpose of the discussion is the identification or the characteristics of 1755 tsunami deposits already identified.

 

Reference:

Franziska Whelan and Dieter Kelletat (2005) Boulder Deposits on the Southern Spanish Atlantic Coast: Possible Evidence for the 1755 AD Lisbon Tsunami? Science of Tsunami Hazards, 23, 25-38.

Rodriguez-Vidal, Joaquin, Caceres, L., Abad, M et al. (2011) The recorded evidence of AD 1755 Atlantic tsunami on the Gibraltar coast. Journal of Iberian Geology, 37, 177-93.

 

Comments for author File: Comments.pdf

Author Response

Response to Reviewer 2 comments

 

We would like to thank the reviewer for his work of carefully reading the manuscript and making suggestions to improve this work. Here, we present the response to the different points made by the reviewer within the general review text and with specific comments.

Point 1:

This article does not include much important basic information such as the lithology of the drilling cores. Therefore, it is impossible to determine whether the effect of a tsunami is indeed preserved in these cores and whether this method is effective as a new way to recognize tsunami deposits. A study should include at least one figure that clearly shows a high-resolution photograph, CT image, or geological column of core samples that gives a clear overview of the deposited geologic layers. Only small photos with little detail are currently provided and only one figure of the computed tomography scan showing the entire core is presented. The CT photographs (Figure 4) are unclear. Is there no characteristic sedimentary structure in the two cores? For these reasons, it is recommended the paper’s authors create geological columns.

Response to Point 1:

We included a new section (1.2.) which describes and depicts the lithology of the cores. The Figures resolution are also increased including core photographs, CT-scan (only available for core M106). As shown in the geological columns in the new Figure 2, sedimentary structures are rare. However, we could identify possible laminations at the base of the probable tsunami layer in core M106 (Figure 7). This Figure was also re-made as suggested by the reviewer. It has now a better quality, an added color scale and core depth correlation between pictures are enhanced.

 

Point 2: When looking at the upward trend of the two cores’ magnetic susceptibility, why are they so different (Figure 5)? Are the “depth of tsunami deposits” in core 106 and core 107 same? Both lithological characteristics and results are clearly visible in core 106. There is also a risk that core 107 will lead to a different interpretation. Based on these points, it is necessary to create a figure showing the lithology or proxy contrast with the samples of previous studies and to be compared with the studies (e.g.Quintela et al. 2016). It is also important to reinforce the core stratigraphic information.

Response to Point 2:

The upward trends of the magnetic susceptibility (MS) in the two cores have similar patterns. However, the sedimentation rate of core M106 is much higher compared to core M107. This results in slightly different MS trends and also in different depths of the probable 1755 CE tsunami layer in the two cores. Another difference of these cores is their location, which results in very different lithologies (Figure 2, 5, 8d). Throughout the text, this work is compared with relevant other studies of possible 1755 CE tsunami layers in the offshore environment (i.e. Quintela et al (2016), Abrantes et al. (2005), (2008)). As indicated in the discussion section 4.2., the bounds of the tsunami layer are difficult to establish, and we also tried to carefully correlate the possible tsunami layer depths of core M106 with the core VC2B that was studied by Quintela et al. (2016) since they are in proximity to each other (~ 400 m apart). The core stratigraphy information are now depicted in core logs in Figure 2.

Point 3: It should be pointed out that the method used in this study may be applicable to other regions in the future, but the contrast is slightly unclear.

 

Response to Point 3:

In the last part of section 4.2. it is pointed out that the sediment composition (SC) analysis, reinforced by multivariate analysis and site specific XRF-ratios/counts is suitable for similar studies in other regions. Also, we suggest to apply this methodology in other possible tsunami layers of the same cores (see section 1.2.). Another suggestion we made is to study sedimentary structures at high resolution (e.g. CT-scans as shown in Figure 7). This might reveal sedimentary structures related to the tsunami event action as we wrote also as a conclusion.

 

Point 4: From the current composition of the core samples, although the Lisbon tsunami should be discussed within the paper, the main theme is the certification of tsunami deposits. If the site is close to other research sites, it is better to change to a structure that handles the Lisbon tsunami from the beginning.

 

Response to Point 4:

 

As described in the introduction this site is very close to other research sites that deal with the 1755 CE tsunami. However, only one work was done in water depths > 50 m (Quintela et al. 2016). We outlined in the manuscript, that the correlation of the 1755 CE tsunami can be made. That is why we write about the 1755 CE event already in the introduction. We also think this is now clearer with the new section 1.2..

 

Point 5: The possibility of identifying and comparing tsunami deposits on the seabed is the most important point in this research, but I would like you to narrow down your focus by looking at the research field as broadly as possible.

 

Response to Point 5:

 

Our focus in this work is not tsunami deposits in general, but the study of tsunami deposits in the shelf environment > 50 m. We compared our results to other similar studies from all around the world (as broadly as possible) in the discussion and thereby narrowed down the focus to this specific depositional environment. Like this we think further works that deal with similar offshore deposits have a better idea of the impact that tsunamis can have in these environments.

 

Point 6: For Tabble1 does not have much meaning, it is recommended to show it again as geological columns.

 

Response to Point 6:

 

This table is now also visualized in the geological column in Figure 1 in “1.2. Previous Study”. We think it is clarifying the specific core levels (or samples) that we studied in detail.

 

Point 7: Table 2: Classification of sand components.>sand size components?

Response to Point 7:

This has been rephrased accordingly to: “Classification of sand sized components”.

Point 8: Figure 2: I would like you to increase the resolution of the photos in Figure 2.

 

Response to Point 8:

 

The resolution of this figure is now increased.

 

Point 9: Figure 6: I do not understand the meaning of the colors in (b)1, 2, 3, so please add the color chart or color legend and I want you to enlarge the size of the 3 and adjust the scale.

 

Reponse to Point 9:

 

A color scale for the radio density is now added to the figure. Also, picture 3 is now enlarged and the core depth scale adjusted.  

 

Point 10: L361-L422: Why does the CaCO3 decrease toward the top of the core 107? It shows the opposite trend to the core 106.

 

Reponse to Point 10:

 

This is now clearer since the CaCO₃ content is now depicted for the whole core length in Figure 2. The CaCO₃ content decreases in both cores towards the top of the core.  

 

Point 11: Figure 7: The components appear to be clearly separated by source.

 

Reponse to Point 11:

 

Yes, we agree that the source of the sediment deposits at core locations M106 and M107 differ. This is already described in the introduction and our results support this known fact. 

 

Point 12: Discussion section: Please make it clear whether the purpose of the discussion is the identification, or the characteristics of 1755 tsunami deposits already identified.

Response to Point 12:

In the new section 1.2. we describe how the specific layers of the present study were chosen. In this previous work, a layer was identified which could be a result of a high-energy event and age estimations (based on ²¹⁰Pb and ¹⁴C) suggest the 1755 CE tsunami as a possible event. We made many alterations in the manuscript and hope the purpose of the discussion (correlating the layer to the 1755 CE event and making implications to study possible tsunami deposits in similar environments) is now clarified.

Author Response File: Author Response.pdf

Reviewer 3 Report

General Review Comments:

This paper presents analyses from sections of two cores collected at different depths on the outer shelf offshore southern Portugal, focusing on an assumed deposit from the 1755 CE tsunami. Offshore tsunami deposits from depths below the storm wave base have potential advantages over onshore deposits of a more complete record of past tsunamis without the need for tsunami layers to be distinguished from storm surge deposits, but a disadvantage is that these layers are difficult to identify. In this study, a multi-proxy approach is used on sections of the cores containing a previously identified high-energy deposit, revealing subtle evidence that appears consistent with deposition in the 1755 CE tsunami.

The paper is generally well laid out and well illustrated. The authors appear to have completed a thorough and careful analysis. The ultimate conclusion is that the tsunami layers are not well defined, but various lines of evidence are compatible with deposition in the 1755 tsunami, including age ranges that overlap with 1755 and statistical analyses that separate samples from the tsunami layers from those in adjacent sediments on the basis of subtle differences. The paper includes the first use of quartz grain microtextural analysis on offshore tsunami deposits, and perhaps an important conclusion for future studies is that this is not a useful technique to distinguish offshore tsunami deposits.

In terms of weaknesses, descriptions of data trends etc are often inaccurate and should be carefully revised (e.g., see specific comments below for lines 347, 352, 358, 443, 456, 631). Significant revision is also required to improve the clarity of the text – I have noted many examples by line number below, often making suggestions on how the phrasing could be improved (assuming I correctly understand the intended meaning).

The main weakness of the paper is the initial identification of the tsunami layer in each core, which is essentially used to groundtruth various proxies. This interpretation, which is not adequately explained, is critical to the analyses, interpretations and conclusions of the paper. L79 states “in preliminary work, sedimentological data and age estimations show identifiable layers probably originating from the backwash of the 1755 CE tsunami in these cores [39].” The reference is to a conference abstract, which itself does not explain how these layers are identifiable as tsunami deposits. The same reference is cited in Fig. 3: “Vertical [horizontal?] grey bars represent possible high energy event layers (abrupt sedimentation) detected by .. [39].” It seems that the shallowest grey bar in each core is interpreted as the tsunami deposit, but it is never explained why these intervals were interpreted as high energy event deposits (e.g., the grain size is not particularly high, or is actually lower, compared to the underlying “pre-tsunami” sediment – Fig. 4). L81-84 mentions another core collected close to M106 by Quintela et al. (2016), where the 1755 tsunami deposit “has already been detected through the identification of a coarser layer coupled with a significant increase in coastal foraminifera species, controlled by compatible…age estimations”. From L506: “Another correlation of the deposit in core M106 is the similar core depths (~75 cm to 40 cm) for the possible 1755 tsunami deposits in Quintela et al. in proximity to core M106.” From this reference, it is notable that the tsunami deposit is described as a 47 cm thick silty layer with 3 obvious peaks of coarse-grained material that coincide with 3 peaks in coastal foraminifera. The tsunami deposit assumed in M106 is only 9 cm thick with slightly coarser material at the base (but mean grain size is less than the underlying material). [The foraminifera analysis described by Quintela (isolating coastal forams from ubiquitous shelf species) appears much more promising for detection of shelf tsunami deposits than the methods described in the present paper.] The authors may have excellent reason for pre-identifying the tsunami layers in the two cores, but this must be clearly explained in the paper.

A related weakness is that most analyses (except age dating, MS, and imaging) are presented only for very limited (< 30 cm) sections of each core, extending less than 10 cm above and below each assumed tsunami deposit. The limited analysis makes it impossible for the reader to comprehend long-term trends. E.g., part of the discussion (L668-676) centres on changes in sedimentation around the time of the tsunami, possibly due to changes in coastal morphology, climate, or land use. But these sedimentation changes are not clear to the reader.

Specific Review Comments by Line Number:

L17: How can “sedimentary records” be “adapted to local and regional conditions”? I suggest deleting the second part of this sentence.

L27: “no remarkable terrestrial signal is present” – I suggest changing this to “only a subtle terrestrial signal is present” to more accurate reflect the paper’s findings.

L37: “Defining a coastal hazard of tsunamis” implies a specific tsunami-related hazard (e.g., inundation, or coastal erosion), but I think you mean tsunami hazard in the more general sense. I suggest changing “a..” to “the coastal hazard of tsunamis”.

L43: “making the selection of the study area a key-criteria”. Criteria are plural for criterion, but what is the selection a criterion for? I suggest rephrasing: “making the selection of the study area of key importance”.

L46: I suggest rewording from “Only a modest part of tsunami research is analyzing the present deeper offshore sedimentary records [..] and even less possible historical…” to “Relatively few studies have focussed on analyzing deeper offshore… and even fewer have involved possible historical…”.

L52: “This process [resuspension of seafloor material by the inland propagating tsunami wave] is traced by an erosional contact at the onset of tsunami units”. I suggest you change “onset” to “base”, to be more descriptive. I think you are talking about tsunami deposits in the offshore environment here, but this is not clear in the text – please clarify.

L53-55: The middle part of this sentence doesn’t make sense: “..and widely differing geological settings (in coastal and shelf environments) such as topography/bathymetry and sediment sources..”. If I understand correctly, I suggest changing to “.., and widely differing coastal and shelf settings characterized by varying topography/bathymetry and sediment sources, ..”.

L56: “This makes a clear identification based on a single characteristic very unlikely”. Please clarify if you mean identification of a tsunami deposit, or of a particular sedimentation process.

L62: “..were utilized..” -> “have been utilized”.

L68: I suggest changing the word “investigate” to “illuminate”. The sediment component behavior cannot “help investigate”.

L72: “fresh surfaces on quartz surfaces” -> “fresh surfaces on quartz grains”.

L87: Here, “SC” is defined as “sand component”, but elsewhere in the manuscript it seems to stand for “sand component analysis”, e.g., L201: “the SC incorporates”. And in the Fig. 4 caption (L372), “SC” is defined as “sediment composition”. Please revise the manuscript for consistency.

L92: Suggested change: “for exploring its usages for tsunami deposits identification” -> “ to explore its potential for tsunami deposit identification”.

L96: Suggested change: “when the set of proxies allowing to detect tsunami signatures .. is more elaborated” -> “with a larger set of proven proxies for tsunami signatures in sedimentary records.”

L97: Suggested change “exploring the offshore tsunami sediments will aid coastal risk assessments in means of tsunami hazards” -> “exploring offshore tsunami sediments will aid assessment of tsunami hazard and risk”.

L99: “1.3 Study Site”. There are no sections 1.1 or 1.2. Renumber this one.

L100,101: Change “referred as” to “referred to as” or “hereafter”.

Figure 1: An inset larger scale map should be added, to provide regional context for international readers. This should include at least the whole country of Portugal. The two cores of the present study could also be labelled on the smaller scale map, for easier reference, especially for anyone printing in black and white.

L117: Pluralize “current”.

L123: Vale de Lobo (referred to as the study area) should be labelled on the map in Fig. 1.

L125: “are dominating” -> “dominate”.

L137: “out of 7 approved historical tsunamis” – the word “approved” should be changed to something like “verified” or “documented”.

L138: “recognized historically as the most severe tsunami that ever hit Europe”. The time period for “ever” is not very clear, despite the use of the word “historically”. I suggest a change to “recognized as the most damaging tsunami that hit Europe in historical times (i.e., in the last X years)”. (E.g., this discounts the prehistoric Storegga slide tsunami).

L140: “tsunami deposits that can be small in variation and size” – this meaning is unclear.

L160: “Supporting data, i.e. data obtained from previous works … previously described by Drago et al. [39].” I don’t think it’s useful to include this reference here or to refer to it as previous works. It is a conference abstract – although presumably the presentation/poster did include these data, the abstract itself does not, so the current paper will become the primary source. I also suggest renaming section 2.1 to be more descriptive of the analyses included.

L178, 182 and throughout manuscript: Data are plural. Change to “data were”, “data have been”, etc.

L201: Please clarify a “1 Φ interval” of grain size for non-specialist readers.

L202: “identified under a binocular” – add “microscope”.

L203: “SCA” is not defined.

L204: “subdivided into 12 components (Table 2)” – only 11 are listed in the table.

L211: “binocular” -> “microscope”.

L229: “as” -> “including”.

L242: “This allows possible discrimination with statistical reliability because originating from greater sample sizes compared to the analysis of analyzing specific single microtextures.” To fix the grammar, I suggest “…reliability due to the greater sampling compared to the analysis of single microtextures”.

L244: “occupation” -> “area”.

Table 3: “BP = before present” – please clarify if this is “before 1950” as it is commonly defined?

L261: What is meant by “elaborated” in “elaborated marine reservoir effect value” - calculated or averaged? Please clarify the following text (L263-266) if the value is averaged, extrapolated, or interpolated from the 9 database points.

L263: “closets” -> “closest”.

L274: Suggested change “sedimentation of sediments” -> “deposition of sediments”.

L277: ‘bacon’ -> ‘rbacon’?

L279: Change section title from “Statistic” to “Statistical analysis” or similar.

L307: remove “sediment” from “sediment sedimentation rates”.

Figure 3: The final part of the figure (bottom right) is mislabelled (c) instead of (d).

L321: “excised” -> “excluded”.

L323: Typo: “sedimentaion”.

L324: “210Pb_xs” -> “210Pb_ex”

L327: “Vertical grey bars represent possible high energy event layers (abrupt sedimentation))” – there are no vertical grey bars – do you mean horizontal?

L344: “Peaks of carbonate content in the tsunami layer are coherent in both cores.” Coherent relative to what? There seem to be peaks in carbonate content throughout the analyzed sections of both cores.

L347: “MS is generally higher in core M106 compared to core M107 with values ranging from 1 to 4.5 [10-7 SI] and 4.2 to 5 [10-7 SI], respectively.” This wording implies that the 1-4.5 [*10-7] range is for core M106, but Fig. 4 shows this range for M107.

L348: “In core M106 between 70 cm to 55 cm, MS increases with a distinct peak at depth 63 cm” – the increase from 70 to 63 cm does not continue to 55 cm.

L349: “In core M107, MS varies less”. See comment on L347 – M107 has a larger range in MS than M106. It is hard to compare the degree of variation given the very different plot scales.

L352: “pre to post tsunami depths are within an interval that mostly defines a plateau of magnetic susceptibility values between 100 and 32 cm. Despite some oscillations, such interval seems to interrupt the increase of susceptibility observed below 100 cm and above 32 cm.” I don’t see this plateau, but an overall trend of values that increase more gradually than the intervals immediately above (32 to about 10) and below (100 down to ~140). This could perhaps be changed to “a relative plateau”, being specific about what it is relative to.

L358: “the pre-tsunami range is characterized by very stable magnetic susceptibility values, the tsunami one by a sharp increase, and the post-tsunami by oscillations between 15 cm and 9 cm that interrupt the general increase observed below and above.” The pre-tsunami range has gradually increasing values. The oscillations noted between 15 and 9 cm continue from 9 to 0 cm.

L361: “XRF data show great variability between samples that is relatively higher in core M106 compared to core M107”. I don’t agree that there is higher variability in M106 – looking at the scale of the XRF plots, 3 out of 4 are zoomed in 2-4 times for M106 compared to M107. The values show a significantly larger range in M107, except for the Al+Si plot, where variability is similar.

L362: “the Ti/Ca ratio is lower in core M106” – the values plotted are less negative than for M107. Please clarify.

L363: “the Al+Si elemental counts show increased values in the tsunami layer relative to the post- and pre-tsunami units”. This is not very convincing, but it is clearer when comparing average values between the 3 horizons.

L369: In the caption, magnetic susceptibility should be listed after MGS and CaCo3, not before.

L371: Please define “MoR”.

L386: “up to 810 HU” -> “down to 810 HU”.

L396: reference to Fig. 8 should follow (not precede) first reference to Fig. 7 – switch the order of these figures if necessary.

L396: “PCA, LDA and HCL were conducted on these data matrices and variables slightly differ” -> “…matrices with slightly different variables”.

L409: “Post tsunami samples show higher MS and carbonate-content compared to the upper layers” -> “..compared to the lower layers”.

L411: This is a very long paragraph – here is a good place to break it, between the LDA and PCA descriptions.

L424 (Fig. 7 caption): If I understand correctly, the numbers correspond to the sample depth (cm) – state this in the caption.

L430: “red arrows, the longer the more contribution” -> “red arrows: length proportional to contribution”.

L438 (Figure 8): Comparisons between the 2 cores would be much easier if (a) and (b) were plotted at the same scale on the x axes.

L441: To avoid confusion, I suggest adding the word shelf as a descriptor: shallower “shelf” core M107 and deeper “shelf” core M106. Also “is present” -> “are present”.

L443: “Core M107 shows a slight trend of decreasing biogenic components toward the top of the studied section” – this trend is not apparent to my eye in Fig. 8b, particularly for “other biogenic” components.

L453: “0ther biogenic components and benthic foraminifera (up to 25 %)” – these peaks appear closer to 35%.

L455: “In the possible tsunami layers, no remarkable peak …can be observed in both cores..” -> “In the possible tsunami layer, no remarkable peak … can be observed in either core ..”.

L456: “higher percentages of mollusk shells/fragments … are present in the high-energy event layer” – this is not clearly apparent for core M107 – similar peaks occur throughout the studied section.

L477: “the samples” -> “the quartz grain samples”.

L477: “The predominant microtexture is dissolution with mean values above 50 %”. Unless I am misreading Fig. 10 (top right), almost all (7 of 9) the mean values shown by triangles are less than 50%.

L491: Add “tsunami” after “the 1755 CE”.

L497: “Recorded historical tsunamis have the advantage to allow chronological correlation between potential event layer as a first basis.” Unclear meaning, likely due to poor grammar.

L505: I suggest you change “confirm a correlation” to “suggest a likely correlation”. Age overlap with the 1755 event is consistent with a correlation but does not preclude another possibility.

L506: Suggested change to improve clarity: “Another correlation of the deposit in core M106 is the similar core depths (~ 75 cm to 40 cm) for the possible 1755 tsunami deposits in Quintela et al. [22] in proximity to core M106” -> “The deposit in core M106 also likely correlates, on the basis of similar core depths (..), to possible 1755 tsunami deposits in proximity [how close?] to core M106, as described by Quintela et al. [22]”.

L511: “chapter 4.2” -> “section 4.2”.

L514: “it is suggested to have a precision of at least a few hundred years to allow the implication of tsunami frequency”. This wording implies uncertainties should be a few hundred years or higher. Suggested change to: “..precision within a few hundred years or less..”.

L515: “errors indicated by the age model are 243 yrs and 468 yrs for the tsunami units of core M106 and M107” - according to the 95% confidence intervals cited on L316-318, these values are 245 and 482 yrs.

L521-524: Please provide a little more detail on the 1761 tsunami – did it have a similar source region, and similar area of impact? Specify that the documented lower severity affected the relevant region.

L528: “db” in the equation should have “b” as subscript to match the parameter definition.

L530: “the boundary between deep-water (0.5 · wavelength (L) < d) and intermediate-water (0.5 L > d < 0.05 L)” – I believe the intermediate water expression should read “0.5L > d < 0.05L”. To clarify, you could add “i.e., d = 0.5L”.

L537: “As tsunami backwash flows, flash floods can generate hyperpycnal flows..” -> “Similar to tsunami backwash flows,..”.

L540: “Latter” -> “The latter”.

L546: “elaborated” -> “documented”.

L549-608: The material in this very long paragraph would be more clearly conveyed in shorter paragraphs. E.g., the discussion of grain sizes and energy could be separated from that of proxies for onshore source regions, and from discussions of mollusks, MS, and MT.

L555: Suggested change to improve clarity: “But also the absence of grain size variations [2,21], as well as decreases [18] are reported, especially, in greater water depths (> 50 m)” -> “The absence of both grain size variations [..] and decreased grain size [..] are also reported, especially in water depths > 50 m.”

L558: “same tsunami layer” -> “correlative interpreted tsunami layer”.

L596: “This hypothesis can further explain the minor grain size variation within the tsunami layer in core M106, as well as the lack of the pronounced fine-material input in the upper tsunami unit of core M107”. It’s not clear what you mean by “this hypothesis”, and the 2^nd part of the sentence is not explained – does it relate to the more landward location of M107?

L598: Suggested change: “The MT analysis has not resulted in a clear tsunami-related signature” -> “the MT analysis did not detect a clear tsunami-related signature”.

L600: “Figure 9” -> “Figure 10”.

L609: “Setting limits for offshore paleo-tsunamis in the sedimentary record” -> “Detecting the upper and lower bounds of offshore tsunami deposits”.

L610: “lead to affect” -> “affect”.

L615: “The authors” – which authors?

L616: “exclusive reworking” -> “extensive reworking”?

L617: “tsunami unit” -> “presumed tsunami unit”.

L620: “internal sedimentary structures (i.e. of lamination or ripples below [below 70 cm] (Fig. 6b) can be related to the action of erosion….interpreted as a reworking of the sediments by the landward propagating tsunami wave”. In Fig. 6b, these laminations extend from ~70 to 80 cm depth in the core, going below the base of the assumed tsunami layer (assumed for all the analyses in this paper).

L623: “more significant evidence” -> “more significant piece of evidence”.

L623: “low numbers of total foraminifera tests at the onset of the tsunami unit in both cores (Figure 6)” – this is clear in M106, but not in M107. Also, the reference should be to Figure 8, not 6.

L627: “due to” -> “based on”.

L631: “it is possible to verify that χLF values within tsunamigenic layers of both cores mostly agree with an interruption of the overall increasing trend (Figure 5)”. Firstly, tsunamigenic means capable of generating a tsunami. Secondly, this statement is not supported by the data shown in Fig. 5. In core M106 there is an increasing trend through the interpreted tsunami layer, in contrast to more stable values in the underlying ~25 cm. A similar feature (steeper increase) is also seen in the tsunami unit of M107, relative to the underlying sediment.

L640-644: “the combination of many small pieces of evidence … confirms a deposition by the 1755 CE tsunami of the two units under study”. I find this statement too strong, and suggest the authors soften it, e.g., to “…are consistent with deposition by ..”.

L650: “can be assumed” -> “might be concluded”.

L656: “offshore tsunami deposits are composed only to ~ 30 % of onshore material” -> “offshore tsunami deposits are only ~30% composed of onshore-derived material”.

L660: “discrepancies between the normal marine sedimentation” -> “..between periods of normal ..”.

L661: “the fact, that only the 1755 CE tsunami left geological evidence onshore of well documented historical tsunamis”. Unclear – do you mean “the fact that, among several well-documented historical tsunamis, only the 1755 CE tsunami left geological evidence onshore”?

L666: “other older events might show a very clear signature” – why the use of “might”? Have these layers been tied to historical tsunamis?

L668: “change in sedimentation dynamics in general observed by PCA results including both cores (Figure 4; Figure 7c, d)”. What is the time period for this change. The cited figures cover only a short period of time including only 6-8 cm (~100 yrs) below the tsunami layer. Grain size is not shown lower down the core to illustrate longer term changes, e.g., relating to the Little Ice Age as mentioned on L675.

L675: Spell out LIA abbreviation.

L676-677: “responded in increased input of terrigenous material into the shelf. However … infer about this change” -> “resulted in an increased input .. to the shelf. However … interpret this change”.

L692: “Hence, investigating offshore tsunami sediments is important to complete the dataset of tsunami events. Only if a complete dataset is available including tsunami deposits, recurrence intervals of tsunami hazard can be inferred”. Awkward wording. I suggest “Hence, investigating offshore tsunami sediments is important to complete the dataset of tsunami events and enable accurate estimation of recurrence intervals for tsunami hazard assessment.”

L695: “the findings .. can be used down core on other possible tsunami layers” – have other possible tsunami layers been identified in these cores? Or would your methods need to be applied to the whole length in order to detect possible tsunami deposits?

L703: “Differences between non-tsunami samples and presumed tsunami samples are ..” -> “Relative to non-tsunami samples, presumed tsunami samples have ..”.

L706: “backed up by matching age correlations” -> “with deposit age ranges that overlap the 1755 CE event”.

L707: “subtle terrestrial fingerprint…implies the usage of methodologies that can reveal sedimentary structures” – unclear meaning. Do you mean that the finding of a terrestrial fingerprint means that these methods should then be used?

L709-715: Seems this conclusion should be adapted – the authors have shown that microtextural analysis of quartz grains is not a useful way of identifying tsunami deposits in shelf settings, unlike for onshore high-energy deposits.

L716: This point is not very clearly made in the discussion and requires analysis further below and above the inferred tsunami layer.

L718: This is only a contradiction if older tsunami events are shown to have stronger signatures in shelf sediments – this was not clearly outlined.

L720: This final point is unclear and needs to be substantially rewritten.

Author Response

Response to Reviewer 3 comments

 

We would like to thank the reviewer for his very helpful work of carefully reading the manuscript and making many suggestions to improve this work. Here, we present the response to the different points made by the reviewer within the general review text and with specific comments.

Point 1: In terms of weaknesses, descriptions of data trends etc are often inaccurate and should be carefully revised (e.g., see specific comments below for lines 347, 352, 358, 443, 456, 631). Significant revision is also required to improve the clarity of the text – I have noted many examples by line number below, often making suggestions on how the phrasing could be improved (assuming I correctly understand the intended meaning).

 

Response to Point 1:

 

The description of data trend was extensively rephrased with the many helpful comments to specific lines made by the reviewer. The same was done to improve the clarity of the text including English language corrections as mostly indicated by the reviewer comments.

 

Point 2: The main weakness of the paper is the initial identification of the tsunami layer in each core, which is essentially used to groundtruth various proxies. This interpretation, which is not adequately explained, is critical to the analyses, interpretations and conclusions of the paper. L79 states “in preliminary work, sedimentological data and age estimations show identifiable layers probably originating from the backwash of the 1755 CE tsunami in these cores [39].” The reference is to a conference abstract, which itself does not explain how these layers are identifiable as tsunami deposits. The same reference is cited in Fig. 3: “Vertical [horizontal?] grey bars represent possible high energy event layers (abrupt sedimentation) detected by .. [39].” It seems that the shallowest grey bar in each core is interpreted as the tsunami deposit, but it is never explained why these intervals were interpreted as high energy event deposits (e.g., the grain size is not particularly high, or is actually lower, compared to the underlying “pre-tsunami” sediment – Fig. 4). L81-84 mentions another core collected close to M106 by Quintela et al. (2016), where the 1755 tsunami deposit “has already been detected through the identification of a coarser layer coupled with a significant increase in coastal foraminifera species, controlled by compatible…age estimations”. From L506: “Another correlation of the deposit in core M106 is the similar core depths (~75 cm to 40 cm) for the possible 1755 tsunami deposits in Quintela et al. in proximity to core M106.” From this reference, it is notable that the tsunami deposit is described as a 47 cm thick silty layer with 3 obvious peaks of

coarse-grained material that coincide with 3 peaks in coastal foraminifera. The tsunami deposit assumed in M106 is only 9 cm thick with slightly coarser material at the base (but mean grain size is less than the underlying material). [The foraminifera analysis described by Quintela (isolating coastal forams from ubiquitous shelf species) appears much more promising for detection of shelf tsunami deposits than the methods described in the present paper.] The authors may have excellent reason for pre-identifying the tsunami layers in the two cores, but this must be clearly explained in the paper.

 

Response to Point 2:

 

We agree that the initial identification of the tsunami layer in each core might be seen as a main weakness. For that reason, we included a new section which intends to clarify the selection of the specific core layers for the present study. Indeed, this layer selection is the base of the present study and has not been published yet (besides an ASTARTE report 2.43, that can now be found online on the website http://www.astarte-project.eu/index.php/deliverables.html). In this new section, we  are now presenting some data obtained in this previous work , including core descriptions, XRF-data, MS data and CaCO₃-content in order to clarify how high-energy event layers were detected, including the event layer studied in the present work  which has been pointed out as probbaly related to the 1755 CE tsunami event.

 

Point 3: A related weakness is that most analyses (except age dating, MS, and imaging) are presented only for very limited (< 30 cm) sections of each core, extending less than 10 cm above and below each assumed tsunami deposit. The limited analysis makes it impossible for the reader to comprehend long-term trends. E.g., part of the discussion (L668-676) centres on changes in sedimentation around the time of the tsunami, possibly due to changes in coastal morphology, climate, or land use. But these sedimentation changes are not clear to the reader.

 

Response to Point 3:

 

Other long-term trends are now shown in Figure 2 (section 1.2.) to make it easier to comprehend long-term trends in the studied cores. However, the focus of the present study is the specific sections that were selected for the sand composition analysis and the further statistical analysis. The changes in sedimentation might be now clearer with this new Figure 2 and the core descriptions in section 1.2.. But, as mentioned in section 4.2., the bounds of the tsunami layer remain speculative and this change of sedimentation needs further investigation. The hypothesis that the 1755 CE tsunami might have changed sedimentation dynamics is in our opinion worth to mention and to be added to the already existing hypothesis such as the LIA-hypothesis, costal morphology changes, or land use.

 

Point 4: 17: How can “sedimentary records” be “adapted to local and regional conditions”? I suggest deleting the second part of this sentence.

 

Response to Point 4:

 

Second part of the phrase has been removed as suggested by the reviewer.

Point 5: L27: “no remarkable terrestrial signal is present” – I suggest changing this to “only a subtle terrestrial signal is present” to more accurate reflect the paper’s findings.

Response to Point 5:

The sentence has been changed to improve accordance with the conclusions according to reviewer’s suggestion.

Point 6: L37: “Defining a coastal hazard of tsunamis” implies a specific tsunami-related hazard (e.g., inundation, or coastal erosion), but I think you mean tsunami hazard in the more general sense. I suggest changing “a..” to “the coastal hazard of tsunamis”.

Response to Point 6:

The sentence has been rephrased for more clarity of the text in accordance to the reviewer’s suggestion.

Point 7: L43: “making the selection of the study area a key-criteria”. Criteria are plural for criterion, but what is the selection a criterion for? I suggest rephrasing: “making the selection of the study area of key importance”.

Response to Point 7:

The grammar of the sentence has been improved for more clarity of the text in accordance to the reviewer’s suggestion.

Point 8: L46: I suggest rewording from “Only a modest part of tsunami research is analyzing the present deeper offshore sedimentary records [..] and even less possible historical…” to “Relatively few studies have focussed on analyzing deeper offshore… and even fewer have involved possible historical…”.

Response to Point 8:

The sentence has been rephrased to improve clarity of the text in accordance to the reviewer’s suggestion.

Point 9: L52: “This process [resuspension of seafloor material by the inland propagating tsunami wave] is traced by an erosional contact at the onset of tsunami units”. I suggest you change “onset” to “base”, to be more descriptive. I think you are talking about tsunami deposits in the offshore environment here, but this is not clear in the text – please clarify.

 

Response to Point 9:

 

We changed “onset” to “base” and added “offshore” for clarity in accordance to the reviewer’s suggestion.

Point 10: L53-55: The middle part of this sentence doesn’t make sense: “..and widely differing geological settings (in coastal and shelf environments) such as topography/bathymetry and sediment sources..”. If I understand correctly, I suggest changing to “.., and widely differing coastal and shelf settings characterized by varying topography/bathymetry and sediment sources, ..”.

Response to Point 10:

We corrected the meaning of the sentence (geological settings à coastal and shelf settings) according to the reviewer’s suggestion.

Point 11: L56: “This makes a clear identification based on a single characteristic very unlikely”. Please clarify if you mean identification of a tsunami deposit, or of a particular sedimentation process.

Response to Point 11:

We clarified the meaning of the sentence by adding “tsunami deposit” according to the reviewer’s suggestion.

Point 12: L62: “..were utilized..” -> “have been utilized”.

Response to Point 12:

We corrected the grammar of the sentence “..were utilized..” à “have been utilized” according to the reviewer’s suggestion.

Point 13: L68: I suggest changing the word “investigate” to “illuminate”. The sediment component behavior cannot “help investigate”.

Response to Point 13:

We replaced “investigate” by “illuminate” for better choice of words according to the reviewer’s suggestion.

Point 14: L72: “fresh surfaces on quartz surfaces” -> “fresh surfaces on quartz grains”.

Response to Point 14:

We changed words (“surfaces” à “grains”) according to the reviewer’s suggestion.

Point 15: L87: Here, “SC” is defined as “sand component”, but elsewhere in the manuscript it seems to stand for “sand component analysis”, e.g., L201: “the SC incorporates”. And in the Fig. 4 caption (L372), “SC” is defined as “sediment composition”. Please revise the manuscript for consistency.

Response to Point 15:

We corrected the use of the abbreviation SC, which stands for “sand composition”, in the manuscript. The same was done for MT which stands for “microtextures on quartz grain surfaces”.

Point 16: L92: Suggested change: “for exploring its usages for tsunami deposits identification” -> “ to explore its potential for tsunami deposit identification”.

Response to Point 16:

We rephrased “for exploring its usages” to “to explore its potential” according to the reviewer’s suggestion.

Point 17: L96: Suggested change: “when the set of proxies allowing to detect tsunami signatures .. is more elaborated” -> “with a larger set of proven proxies for tsunami signatures in sedimentary records.”

Response to Point 17:

We changed the sentence according to the reviewer’s  suggestion: “when the set of proxies allowing to detect tsunami signatures .. is more elaborated” -> “with a larger set of proven proxies for tsunami signatures in sedimentary records.”

Point 18: L97: Suggested change “exploring the offshore tsunami sediments will aid coastal risk assessments in means of tsunami hazards” -> “exploring offshore tsunami sediments will aid assessment of tsunami hazard and risk”.

Response to Point 18:

We changed the sentence according to the reviewer’s  suggestion: “exploring the offshore tsunami sediments will aid coastal risk assessments in means of tsunami hazards” -> “exploring offshore tsunami sediments will aid assessment of tsunami hazard and risk.

Point 19: L99: “1.3 Study Site”. There are no sections 1.1 or 1.2. Renumber this one.

Response to Point 19:

The study site section is renumbered from “1.3.” to “1.1.”.

Point 20: L100,101: Change “referred as” to “referred to as” or “hereafter”.

Response to Point 20:

L100,101: Corrected grammar according to the reviewer’s suggestion.

Point 21: Figure 1: An inset larger scale map should be added, to provide regional context for international readers. This should include at least the whole country of Portugal. The two cores of the present study could also be labelled on the smaller scale map, for easier reference, especially for anyone printing in black and white.

Response to Point 21:

The inset map and the labels of the cores are in the original figure (pdf version that was attached). I apologize for not checking the conversion of ‘Word’. Location of Vale de Lobo is added, and the core symbols are changed for black and white prints.

Point 22: L117: Pluralize “current”.

Response to Point 22:

We corrected the grammar according to the reviewer’s suggestion.

Point 23: L123: Vale de Lobo (referred to as the study area) should be labelled on the map in Fig. 1.

Response to Point 23:

Vale de Lobo location has been added to Figure 1.

Point 24: L125: “are dominating” -> “dominate”.

Response to Point 24:

Grammar changed according to reviewer’s suggestion.

Point 25: L137: “out of 7 approved historical tsunamis” – the word “approved” should be changed to something like “verified” or “documented”.

Response to Point 25:

Words were changed (“approved” to “verified”) according to reviewer’s suggestion.

Point 26: L138: “recognized historically as the most severe tsunami that ever hit Europe”. The time period for “ever” is not very clear, despite the use of the word “historically”. I suggest a change to “recognized as the most damaging tsunami that hit Europe in historical times (i.e., in the last X years)”. (E.g., this discounts the prehistoric Storegga slide tsunami).

Response to Point 26:

Phrasing has been changed to improve clarity of time period à now: “recognized as the most damaging tsunami that hit Europe since Roman times”.

Point 27: L140: “tsunami deposits that can be small in variation and size” – this meaning is unclear.

Response to Point 27:

We rephrased to enhance clarity according to the reviewer’s suggestion.

Point 28: L160: “Supporting data, i.e. data obtained from previous works … previously described by Drago et al. [39].” I don’t think it’s useful to include this reference here or to refer to it as previous works. It is a conference abstract – although presumably the presentation/poster did include these data, the abstract itself does not, so the current paper will become the primary source. I also suggest renaming section 2.1 to be more descriptive of the analyses included.

Response to Point 28:

We included the new section 1.2. as the primary source for this data. Please see Response to Point 2.

Point 29: L178, 182 and throughout manuscript: Data are plural. Change to “data were”, “data have been”, etc.

Response to Point 29:

Grammar was changed in these lines and in the whole manuscript (to “data were…”) according to the reviewer’s suggestion.

Point 30: L201: Please clarify a “1 Φ interval” of grain size for non-specialist readers.

Response to Point 30:

We added the reference to Krumbein 1934 to make it clear to non-specialist readers according to the reviewer’s suggestion.

Point 31: L202: “identified under a binocular” – add “microscope”

Response to Point 31:

We added “microscope” to “..binocular” according to the reviewer’s suggestion.  

Point 32: L203: “SCA” is not defined.

Response to Point 32:

Abbreviation was changed according to the reviewer’s suggestion.

Point 33: L204: “subdivided into 12 components (Table 2)” – only 11 are listed in the table.

Response to Point 33:

The reviewer is right and “12” was corrected to “11” according to the reviewer’s suggestion.

Point 34: L211: “binocular” -> “microscope”.

Response to Point 34:

We added “microscope” to “..binocular” according to the reviewer’s suggestion.

Point 35: L229: “as” -> “including”.

Response to Point 35:

Words have been changed according to the reviewer’s suggestion.

Point 36: L242: “This allows possible discrimination with statistical reliability because originating from greater sample sizes compared to the analysis of analyzing specific single microtextures.” To fix the grammar, I suggest “…reliability due to the greater sampling compared to the analysis of single microtextures”.

Response to Point 36:

We changed grammar and rephrased according to the reviewer’s suggestion.

Point 37: L244: “occupation” -> “area”.

Response to Point 37:

Words have been changed according to the reviewer’s suggestion (“occupation” to “area”).

Point 38: Table 3: “BP = before present” – please clarify if this is “before 1950” as it is commonly defined?

Response to Point 38:

Table 3: We specified, that BP means before 1950 and added to the text according to the reviewer’s suggestion.

Point 39: L261: What is meant by “elaborated” in “elaborated marine reservoir effect value” - calculated or averaged? Please clarify the following text (L263-266) if the value is averaged, extrapolated, or interpolated from the 9 database points.

Response to Point 39:

We changed “elaborated” to “calculated”. The 9 values were averaged for the deltaR: “This yield ∆R = 268 ± 122 based on the average of 9 points out of this database ([79], http://calib.org/marine/references.php).”

Point 40: L263: “closets” -> “closest”.

Response to Point 40:

We corrected the spelling.

Point 41: L274: Suggested change “sedimentation of sediments” -> “deposition of sediments”.

Response to Point 41:

We changed the words according to the reviewer’s suggestion (“sedimentation” to “deposition”).

Point 42: L277: ‘bacon’ -> ‘rbacon’?

Response to Point 42:

We corrected the spelling according to the reviewer’s suggestion (“bacon” to “rbacon”).

Point 43: L279: Change section title from “Statistic” to “Statistical analysis” or similar.

Response to Point 43:

We changed the title of section to “2.4. Statistical Analysis” according to the reviewer’s suggestion.

Point 44: L307: remove “sediment” from “sediment sedimentation rates”.

Response to Point 44:

We removed “sediment” according to the reviewer’s suggestion.

Point 45: Figure 3: The final part of the figure (bottom right) is mislabelled (c) instead of (d).

Response to Point 45:

Labels are now changed to a,b,c and d.

Point 46: L321: “excised” -> “excluded”.

Response to Point 46:

The words have been changed (“excised” to “excluded”) according to the reviewer’s suggestion.

Point 47: L323: Typo: “sedimentaion”.

Response to Point 47:

Typo corrected.

Point 48: L324: “210Pb_xs” -> “210Pb_ex”

Response to Point 48:

²¹⁰Pb_ex was corrected in the whole manuscript to ²¹⁰Pb_xs, which is the English way of abbreviating excess, ex being the Portuguese and french way.

Point 49: L327: “Vertical grey bars represent possible high energy event layers (abrupt sedimentation))” – there are no vertical grey bars – do you mean horizontal?

Response to Point 49:

We agree with the  reviewer and changed from “vertical” to “horizontal” according to the reviewer’s suggestion.

Point 50: L344: “Peaks of carbonate content in the tsunami layer are coherent in both cores.” Coherent relative to what? There seem to be peaks in carbonate content throughout the analyzed sections of both cores.

Response to Point 50:

We changed for a more correct meaning (“coherent” to “visible”).

Point 51: L347: “MS is generally higher in core M106 compared to core M107 with values ranging from 1 to 4.5 [10-7 SI] and 4.2 to 5 [10-7 SI], respectively.” This wording implies that the 1-4.5 [*10-7] range is for core M106, but Fig. 4 shows this range for M107.

Response to Point 51:

We agree and corrected the mix up of MS values in the sentence.

Point 52: L348: “In core M106 between 70 cm to 55 cm, MS increases with a distinct peak at depth 63 cm” – the increase from 70 to 63 cm does not continue to 55 cm.

Response to Point 52:

We corrected grammar for more clarity. MS values are increased in the section between 70 and 55 cm and hast a distinct peak at 63 cm. However, it is not increasing until 55.

Point 53: L349: “In core M107, MS varies less”. See comment on L347 – M107 has a larger range in MS than M106. It is hard to compare the degree of variation given the very different plot scales.

Response to Point 53:

We removed “MS varies less and” since the scales are different, and the variation is thus hard to compare as suggested by the reviewer.

Point 54: L352: “pre to post tsunami depths are within an interval that mostly defines a plateau of magnetic susceptibility values between 100 and 32 cm. Despite some oscillations, such interval seems to interrupt the increase of susceptibility observed below 100 cm and above 32 cm.” I don’t see this plateau, but an overall trend of values that increase more gradually than the intervals immediately above (32 to about 10) and below (100 down to ~140). This could perhaps be changed to “a relative plateau”, being specific about what it is relative to.

Response to Point 54:

The sentence is now re-phrased to: “Considering mass-normalized magnetic susceptibility c_LF for both cores (including all samples) (Figure 6) it is verified for core M106 that pre to post tsunami depths are within an interval that mostly defines a relative plateau of magnetic susceptibility values between 100 and 32 cm compared to adjoining lower and upper core sections.”. We agree that it is rather a relative plateau. 

Point 55: L358: “the pre-tsunami range is characterized by very stable magnetic susceptibility values, the tsunami one by a sharp increase, and the post-tsunami by oscillations between 15 cm and 9 cm that interrupt the general increase observed below and above.” The pre-tsunami range has gradually increasing values. The oscillations noted between 15 and 9 cm continue from 9 to 0 cm.

Response to Point 55:

We changed the MS trend description in the sentence to: “... the pre-tsunami range is characterized by very stable, gradually increasing magnetic susceptibility values, the tsunami one by a sharp increase, and the post-tsunami by oscillations starting at 15 cm that interrupt the general increase observed below.”

Point 56: L361: “XRF data show great variability between samples that is relatively higher in core M106 compared to core M107”. I don’t agree that there is higher variability in M106 – looking at the scale of the XRF plots, 3 out of 4 are zoomed in 2-4 times for M106 compared to M107. The values show a significantly larger range in M107, except for the Al+Si plot, where variability is similar.

Response to Point 56:

We agree to reviewer’s comment. The scales are different, and it is hard to compare the variability in this plot. Sentence is now rephrased and corrected. Also, in the new Figure 2 the scale is the same for both cores to allow a better comparison.

Point 57: L362: “the Ti/Ca ratio is lower in core M106” – the values plotted are less negative than for M107. Please clarify.

Response to Point 57:

Yes, we made a mistake. The Ti/Ca ratio is higher than in core M106 due to  the more negative values of core M106 compared to M107. We changed “lower” to “higher” in this sentence.

Point 58: L363: “the Al+Si elemental counts show increased values in the tsunami layer relative to the post-and pre-tsunami units”. This is not very convincing, but it is clearer when comparing average values between the 3 horizons.

Response to Point 58:

We agree with the reviewer’s comment that it is not clear without writing the mean values of the 3 units. We added a new sentence to include the mean values for clarity.

Point 59: L369: In the caption, magnetic susceptibility should be listed after MGS and CaCo3, not before.

Response to Point 59:

We changed the caption sentence structure according to the reviewer’s suggestion.

Point 60: L371: Please define “MoR”.

Response to Point 60:

MoR defintion is now added in section “2.1 Supporting data” at (previous) L197.

Point 61: L386: “up to 810 HU” -> “down to 810 HU”.

Response to Point 61:

We agree and  corrected “up to 810 HU” to “down to 810 HU” according to the reviewer’s suggestion.

Point 62: L396: reference to Fig. 8 should follow (not precede) first reference to Fig. 7 – switch the order of these figures if necessary.

Response to Point 62:

We agree. However, it is not necessary to cite this Figure at this point and like this we can remain the succession of these two figures.

Point 63: L396: “PCA, LDA and HCL were conducted on these data matrices and variables slightly differ” -> “…matrices with slightly different variables”.

Response to Point 63:

We changed “differ” to “different”.

Point 64: L409: “Post tsunami samples show higher MS and carbonate-content compared to the upper layers” -> “..compared to the lower layers”.

Response to Point 64:

We changed “upper” to “lower” according to the reviewer’s suggestion.

Point 65: L411: This is a very long paragraph – here is a good place to break it, between the LDA and PCA descriptions.

Response to Point 65:

We added a break in this paragraph to increase readability according to the reviewer’s suggestion.

Point 66: L424 (Fig. 7 caption): If I understand correctly, the numbers correspond to the sample depth (cm) – state this in the caption.

Response to Point 66:

We added in the caption of Figure 7 the correspondence of the numbers to the sample depths (cm) for more clarity according to the reviewer’s suggestion.

Point 67: L430: “red arrows, the longer the more contribution” -> “red arrows: length proportional to contribution”.

Response to Point 67:

We changed the sentence according to the reviewer’s suggestion.

Point 68: L438 (Figure 8): Comparisons between the 2 cores would be much easier if (a) and (b) were plotted at the same scale on the x axes.

Response to Point 68:

Scales have been changed in Figure 8 to have matching scales of (a) and (b).

Point 69: L441: To avoid confusion, I suggest adding the word shelf as a descriptor: shallower “shelf” core M107 and deeper “shelf” core M106. Also “is present” -> “are present”.

Response to Point 69:

We added “shelf” for more clarity and corrected grammar.

Point 70: L443: “Core M107 shows a slight trend of decreasing biogenic components toward the top aof the studied section” – this trend is not apparent to my eye in Fig. 8b, particularly for “other biogenic” components.

Response to Point 70:

This sentence has now been removed. The biogenic components are the sum of all biogenic components but it does not show a significant trend.

Point 71: L453: “Other biogenic components and benthic foraminifera (up to 25 %)” – these peaks appear closer to 35%.

Response to Point 71:

The value has been corrected to “up to 36 %” and has been verified.

Point 72: L455: “In the possible tsunami layers, no remarkable peak …can be observed in both cores..” -> “In the possible tsunami layer, no remarkable peak … can be observed in either core ..”.

Response to Point 72:

We corrected the choice of word and grammar according to reviewer’s suggestion.

Point 73: L456: “higher percentages of mollusk shells/fragments … are present in the high-energy event layer” – this is not clearly apparent for core M107 – similar peaks occur throughout the studied section.

Response to Point 73:

We agree to the reviewer’s comment and a higher percentage of mollusc fragments in core M107 is not visible in Figure 8. We have changed the sentence accordingly.

Point 74: L477: “the samples” -> “the quartz grain samples”. L477: “The predominant microtexture is dissolution with mean values above 50 %”. Unless I am misreading Fig. 10 (top right), almost all (7 of 9) the mean values shown by triangles are less than 50%.

Response to Point 74:

We added “quartz grain” in the sentence and changed the sentence to increase clarity.

Point 75: L491: Add “tsunami” after “the 1755 CE”.

Response to Point 74:

We added “tsunami” to increase the clarity of the sentence.

Point 75: L497: “Recorded historical tsunamis have the advantage to allow chronological correlation between potential event layer as a first basis.” Unclear meaning, likely due to poor grammar.

Response to Point 75:

We accepted the suggested change of the reviewer to increase clarity.

Point 76: L505: I suggest you change “confirm a correlation” to “suggest a likely correlation”. Age overlap with the 1755 event is consistent with a correlation but does not preclude another possibility

Response to Point 76:

We accepted the suggested sentence of the reviewer to increase clarity of the correlation meaning.

Point 77: L506: Suggested change to improve clarity: “Another correlation of the deposit in core M106 is the similar core depths (~ 75 cm to 40 cm) for the possible 1755 tsunami deposits in Quintela et al. [22] in proximity to core M106” -> “The deposit in core M106 also likely correlates, on the basis of similar core depths (..), to possible 1755 tsunami deposits in proximity [how close?] to core M106, as described by Quintela et al. [22]”.

Response to Point 77:

We accepted the suggested sentence of the reviewer to increase clarity of this sentence.

Point 78: L511: “chapter 4.2” -> “section 4.2”.

Response to Point 78:

We changed “chapter” to “section”.

Point 79: L514: “it is suggested to have a precision of at least a few hundred years to allow the implication of tsunami frequency”. This wording implies uncertainties should be a few hundred years or higher. Suggested change to: “..precision within a few hundred years or less..”.

Response to Point 79:

We changed grammar according to reviewer’s suggestion to improve the clarity and the actual meaning of the sentence.

Point 80: L515: “errors indicated by the age model are 243 yrs and 468 yrs for the tsunami units of core M106 and M107” - according to the 95% confidence intervals cited on L316-318, these values are 245 and 482 yrs.

Response to Point 80:

The errors of the age model according to the 95 % confidence interval are 246 yrs and 468 yrs for core M106 and M107, respectively. Values are now corrected and verified in L316-318 and in L515.

Point 81: L521-524: Please provide a little more detail on the 1761 tsunami – did it have a similar source region, and similar area of impact? Specify that the documented lower severity affected the relevant region.

Response to Point 81:

We added some more detail about the 1761 tsunami, which includes the source area and the effects on the land (the effects of this tsunami were minor compared to the severe effects of the 1755 tsunami)

Point 82: L528: “db” in the equation should have “b” as subscript to match the parameter definition.

Response to Point 82:

We changed db to b in the whole manuscript according to the reviewer’s suggestion.

Point 83: L530: “the boundary between deep-water (0.5 · wavelength (L) < d) and intermediate-water (0.5 L > d < 0.05 L)” – I believe the intermediate water expression should read “0.5L > d < 0.05L”. To clarify, you could add “i.e., d = 0.5L”.

Response to Point 83:

We cannot see a difference between the reviewer’s suggestion and the actual sentence. Also, 0.5L >d<0.05L is the correct expression for intermediate water.

Point 84: L537: “As tsunami backwash flows, flash floods can generate hyperpycnal flows..” -> “Similar to tsunami backwash flows,..”.

Response to Point 84:

We corrected “As” to “Similar to” as suggested by the reviewer.

Point 85: L540: “Latter” -> “The latter”.

Response to Point 85:

We corrected “Latter” to “The latter” as suggested by the reviewer.

Point 86: L546: “elaborated” -> “documented”.

Response to Point 86:

We corrected “elaborated” to “documented” as suggested by the reviewer.

Point 87: L549-608: The material in this very long paragraph would be more clearly conveyed in shorter paragraphs. E.g., the discussion of grain sizes and energy could be separated from that of proxies for onshore source regions, and from discussions of mollusks, MS, and MT.

Response to Point 87:

We have not changed the structure in shorter paragraphs, because the structure is pleasing us like it is.

Point 88: L555: Suggested change to improve clarity: “But also the absence of grain size variations [2,21], as well as decreases [18] are reported, especially, in greater water depths (> 50 m)” -> “The absence of both grain size variations [..] and decreased grain size [..] are also reported, especially in water depths > 50 m.”

 

Response to Point 88:

 

We corrected to suggested change by the reviewer.

Point 89: L558: “same tsunami layer” -> “correlative interpreted tsunami layer”.

Response to Point 89:

We changed “same tsunami layer” to “correlative interpreted tsunami layer” to enhance clarity as suggested by the reviewer.

Point 90: L596: “This hypothesis can further explain the minor grain size variation within the tsunami layer in core M106, as well as the lack of the pronounced fine-material input in the upper tsunami unit of core M107”. It’s not clear what you mean by “this hypothesis”, and the 2nd part of the sentence is not explained – does it relate to the more landward location of M107?

Response to Point 90:

We changed the sentence to increase the clarity: “This could further explain (1) the minor grain size variation within the tsunami layer in core M106, and (2) the lack of the pronounced fine-material input in the upper tsunami unit of core M107 (Figure 5) because of the more landward location.”

Point 91: L598: Suggested change: “The MT analysis has not resulted in a clear tsunami-related signature” -> “the MT analysis did not detect a clear tsunami-related signature”.

Response to Point 91:

We corrected to the suggested sentence of the reviewer.

Point 92: L600: “Figure 9” -> “Figure 10”.

Response to Point 92:

We changed “Figure 9” to “Figure 10” as suggested by the reviewer.

Point 93: L609: “Setting limits for offshore paleo-tsunamis in the sedimentary record” -> “Detecting the upper and lower bounds of offshore tsunami deposits”.

Response to Point 93:

We changed the sentence to the suggested sentence of the reviewer.

Point 94: L610: “lead to affect” -> “affect”.

Response to Point 94:

We corrected “lead to affect” to “affect” as suggested by the reviewer.

Point 95: L615: “The authors” – which authors?

Response to Point 95:

We clarified who was meant by “The authors” in this sentence.

Point 96: L616: “exclusive reworking” -> “extensive reworking”?

Response to Point 96:

We removed the word “exclusive”.

Point 97: L617: “tsunami unit” -> “presumed tsunami unit”.

Response to Point 97:

We added “presumed” as suggested by the reviewer.

Point 98: L620: “internal sedimentary structures (i.e. of lamination or ripples below [below 70 cm] (Fig. 6b) can be related to the action of erosion….interpreted as a reworking of the sediments by the landward propagating tsunami wave”. In Fig. 6b, these laminations extend from ~70 to 80 cm depth in the core, going below the base of the assumed tsunami layer (assumed for all the analyses in this paper).

Response to Point 98:

Yes, the CT-scans reveal possible tsunami related structures also within the pre-tsunami layer. However, the main anomaly is restricted to the base of the tsunami layer. Regarding the statistical analysis level 80 cm of core M106 seems to be the best suited level for the base. But, as outlined in the discussion, the limits of the tsunami layer remain speculative …

Point 99: L623: “more significant evidence” -> “more significant piece of evidence”.

Response to Point 99:

We added “piece of” as suggested by the reviewer.

Point 100: L623: “low numbers of total foraminifera tests at the onset of the tsunami unit in both cores (Figure 6)” – this is clear in M106, but not in M107. Also, the reference should be to Figure 8, not 6.

Response to Point 100:

We added “piece of” as suggested by the reviewer and “both core” is replaced by “core M106” and corrected also the Figure number.

Point 101: L627: “due to” -> “based on”.

Response to Point 101:

We changed “due to” to “based on” as suggested by the reviewer.

Point 102: L631: “it is possible to verify that χLF values within tsunamigenic layers of both cores mostly agree with an interruption of the overall increasing trend (Figure 5)”. Firstly, tsunamigenic means capable of generating a tsunami. Secondly, this statement is not supported by the data shown in Fig. 5. In core M106 there is an increasing trend through the interpreted tsunami layer, in contrast to more stable values in the underlying ~25 cm. A similar feature (steeper increase) is also seen in the tsunami unit of M107, relative to the underlying sediment.

Response to Point 102:

This sentence has been revised. The word “tsunamigenic” has been replaced and the description of the results were adapted according to the reviewer’s suggestion.

Point 103: L640-644: “the combination of many small pieces of evidence … confirms a deposition by the 1755 CE tsunami of the two units under study”. I find this statement too strong, and suggest the authors soften it, e.g., to “…are consistent with deposition by ..”.

Response to Point 103:

We changed “confirm” to “are consistent with” as suggested by the reviewer. Like this, the statement is less strong based on the small evidences.

Point 104: L650: “can be assumed” -> “might be concluded”.

Response to Point 104:

We changed “can be assumed” to “might be concluded” as suggested by the reviewer to soften the statement.

Point 105: L656: “offshore tsunami deposits are composed only to ~ 30 % of onshore material” -> “offshore tsunami deposits are only ~30% composed of onshore-derived material”.

Response to Point 105:

We changed the sentence structure as suggested by the reviewer.

Point 106: L660: “discrepancies between the normal marine sedimentation” -> “..between periods of normal ..”.

Response to Point 106:

We changed “between the” to “between periods of” as suggested by the reviewer.

Point 107: L661: “the fact, that only the 1755 CE tsunami left geological evidence onshore of well documented historical tsunamis”. Unclear – do you mean “the fact that, among several well-documented historical tsunamis, only the 1755 CE tsunami left geological evidence onshore”?

Response to Point 107:

We changed sentence to enhance clarity as suggested by the reviewer.

Point 108: L666: “other older events might show a very clear signature” – why the use of “might”? Have these layers been tied to historical tsunamis?

Response to Point 108:

We removed “might” because we agree that it is a very clear signature. Although, this work is not yet published in a peer-reviewed journal.

Point 109: L668: “change in sedimentation dynamics in general observed by PCA results including both cores (Figure 4; Figure 7c, d)”. What is the time period for this change. The cited figures cover only a short period of time including only 6-8 cm (~100 yrs) below the tsunami layer. Grain size is not shown lower down the core to illustrate longer term changes, e.g., relating to the Little Ice Age as mentioned on L675.

Response to Point 109:

Long term trends of the sediment characteristics are now displayed in the new figure in “1.2. Previous study”.

Point 110: L675: Spell out LIA abbreviation.

Response to Point 110:

We spelled out Little Ice Age (LIA) as suggested by the reviewer.

Point 111: L676-677: “responded in increased input of terrigenous material into the shelf. However … infer about this change” -> “resulted in an increased input .. to the shelf. However … interpret this change”.

Response to Point 111:

We changed the words in this sentence to enhance the clarity as suggested by the reviewer.

Point 112: L692: “Hence, investigating offshore tsunami sediments is important to complete the dataset of tsunami events. Only if a complete dataset is available including tsunami deposits, recurrence intervals of tsunami hazard can be inferred”. Awkward wording. I suggest “Hence, investigating offshore tsunami sediments is important to complete the dataset of tsunami events and enable accurate estimation of recurrence intervals for tsunami hazard assessment.”

Response to Point 112:

We rewrote the sentence for better English using the text suggested by the reviewer.

Point 113: L695: “the findings .. can be used down core on other possible tsunami layers” – have other possible tsunami layers been identified in these cores? Or would your methods need to be applied to the whole length in order to detect possible tsunami deposits?

Response to Point 113:

Yes, other possible high-energy layers have been identified. We added the new section 1.2. to clarify that.

Point 114: L703: “Differences between non-tsunami samples and presumed tsunami samples are ..” -> “Relative to non-tsunami samples, presumed tsunami samples have ..”.

Response to Point 114:

We changed the sentence structure as suggested by the reviewer.

Point 115: L706: “backed up by matching age correlations” -> “with deposit age ranges that overlap the 1755 CE event”.

Response to Point 115:

We changed the expression of the sentence for more clarity as suggested by the reviewer.

Point 116: L707: “subtle terrestrial fingerprint…implies the usage of methodologies that can reveal sedimentary structures” – unclear meaning. Do you mean that the finding of a terrestrial fingerprint means that these methods should then be used?

Response to Point 116:

We enhanced the clarity of the sentence by rephrasing it.

Point 117: L709-715: Seems this conclusion should be adapted – the authors have shown that microtextural analysis of quartz grains is not a useful way of identifying tsunami deposits in shelf settings, unlike for onshore high-energy deposits.

Response to Point 117:

We added the suggested part of the reviewer as a new point to the conclusions and clarified the different usefulness between onshore and offshore studies.

Point 118: L716: This point is not very clearly made in the discussion and requires analysis further below and above the inferred tsunami layer.

Response to Point 118:

After adding the new section 1.2. and the changes we applied in the text, we think it should clearer now.

Point 119: L718: This is only a contradiction if older tsunami events are shown to have stronger signatures in shelf sediments – this was not clearly outlined.

Response to Point 119:

We explained in the discussion that there are stronger signatures of an older tsunami event in the shelf sediments. Also, we changed some words in the respective sentences to enhance clarity.

Point 120: L720: This final point is unclear and needs to be substantially rewritten.

Response to Point 120:

We have rewritten this final point and think it is clearer now.

 

Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

The manuscript was greatly improved by the revisions of the authors.
Please consider the fix of following sections.

Readers can understand enough the tsunami deposit unit from Figure 2 and the manuscript, so Table 1 can be removed (or Appendix). One of the reasons is that this paper has many Figures and Tables in the first place.
The order shown in the Figure 2 (core107>core106) is only reversed here. In other figures, the displayed order is 106>107.

Please align the scale interval on the horizontal axis in Figure 8 (a) and (b).

please recheck the "Reference" and figure captions.

Author Response

Response to Reviewer 2 Comments – Round 2

 

We would like to thank the reviewer again for making suggestions to improve this work.

Point 1: Readers can understand enough the tsunami deposit unit from Figure 2 and the manuscript, so Table 1 can be removed (or Appendix). One of the reasons is that this paper has many Figures and Tables in the first place.

Response to Point 1:

We removed the table as suggested by the reviewer and instead refer to Figure 2.

Point 2: The order shown in the Figure 2 (core107>core106) is only reversed here. In other figures, the displayed order is 106>107.

Response to Point 2:

We changed the order of the cores in Figure 2 as suggested by the reviewer. Also, we changed the order of the description of the cores in the text accordingly.

Point 3: Please align the scale interval on the horizontal axis in Figure 8 (a) and (b).

Response to Point 3:

We aligned the scale interval on the horizontal and vertical axis in Figure 8 (a) and (b) as suggested by the reviewer.

Point 4: Please recheck the "Reference" and figure captions.

Response to Point 4:

We checked the references and the figure captions in the manuscript.

Author Response File: Author Response.pdf

Reviewer 3 Report

The authors have addressed almost all the concerns raised in the previous review. In particular, the additions of section 1.2 and Figure 2 serve to explain the basis for identifying the potential tsunami deposits in the cores. I do not find the data entirely convincing, but am satisfied that readers are now provided the data to assess the identification. A few minor points brought up in the first review still need to be addressed, as well as some additional (mainly wording) changes to new parts of the text.

 

Point 8: L46: I suggest rewording from “Only a modest part of tsunami research is analyzing the present deeper offshore sedimentary records [..] and even less possible historical…” to “Relatively few studies have focussed on analyzing deeper offshore… and even fewer have involved possible historical…”.

Response: The sentence has been rephrased to improve clarity of the text in accordance to the reviewer’s suggestion.

Follow up: A couple of words got lost in the change (now L53) – “offshore” -> “offshore sedimentary records”.

 

Point 60: L371: Please define “MoR”.

Response: MoR defintion is now added in section “2.1 Supporting data” at (previous) L197.

Follow up: I still could find no definition of MoR in this section or elsewhere in the paper.

 

Point 75: L497: “Recorded historical tsunamis have the advantage to allow chronological correlation between potential event layer as a first basis.” Unclear meaning, likely due to poor grammar.

Response: We accepted the suggested change of the reviewer to increase clarity.

Follow up: The sentence remains unchanged – now L606. The meaning remains unclear.

 

Point 82: L528: “db” in the equation should have “b” as subscript to match the parameter definition.

Response: We changed db to b in the whole manuscript according to the reviewer’s suggestion.

Follow up: The suggestion was not to change “db” to “b” as you have done, but to make the notation in the equation the same as in the text, with b as subscript to d: d_b. I think you should change the b in both places to d_b.

 

Point 83: L530: “the boundary between deep-water (0.5 · wavelength (L) < d) and intermediate-water (0.5 L > d < 0.05 L)” – I believe the intermediate water expression should read “0.5L > d < 0.05L”. To clarify, you could add “i.e., d = 0.5L”.

Response: We cannot see a difference between the reviewer’s suggestion and the actual sentence. Also, 0.5L >d<0.05L is the correct expression for intermediate water.

Follow up: Yes, it seems I made a mistake in my comment, but there is still a problem in the text. The intermediate water expression should read “0.5L > d > 0.05L”. Your current text defines intermediate water depth as d less than 0.05L and also less than 0.5 L, when it should lie between those values.

 

Point 86: L546: “elaborated” -> “documented”.

Response: We corrected “elaborated” to “documented” as suggested by the reviewer.

Follow up: This change has not been made in the revised manuscript (now L604).

 

Point 109: L668: “change in sedimentation dynamics in general observed by PCA results including both cores (Figure 4; Figure 7c, d)”. What is the time period for this change. The cited figures cover only a short period of time including only 6-8 cm (~100 yrs) below the tsunami layer. Grain size is not shown lower down the core to illustrate longer term changes, e.g., relating to the Little Ice Age as mentioned on L675.

Response: Long term trends of the sediment characteristics are now displayed in the new figure in “1.2. Previous study”.

Follow up: You should refer the reader to this new Figure (2) here (now L759-761)

 

Point 117: L709-715: Seems this conclusion should be adapted – the authors have shown that microtextural analysis of quartz grains is not a useful way of identifying tsunami deposits in shelf settings, unlike for onshore high-energy deposits.

Response: We added the suggested part of the reviewer as a new point to the conclusions and clarified the different usefulness between onshore and offshore studies.

Follow up: The new wording (L806-808) could be improved for clarity: e.g. “Although tsunami samples showed a minor increase in percussion marks, this increase was insignificant, and no other possible tsunami signature was detected, suggesting that microtextural analysis is not useful for identifying tsunami deposits in shelf settings, unlike for onshore high-energy deposits”.

 

Point 120: L720: This final point is unclear and needs to be substantially rewritten.

Response: We have rewritten this final point and think it is clearer now.

Follow up: A bit clearer, but still needs some work. E.g.:

“The here inferred implications” -> “The methods described here”.

“can be applied for other older tsunami events” -> “can be applied to other potential tsunami deposits”.

“dataset of occurred tsunami events” -> “dataset of past tsunamis”.

 

New points:

In places, revisions have led to typos or words running together etc, including L33, 44, 49, 68.

L5: I’m confused by the increase in number of authors from 6 to 11 – is this related to the addition of section 1.2?

L153: ASTTARTE -> ASTARTE

L160: “base is not well defined but ondulated” – do you mean undulating, as in wavy? It could still have a sharp undulating base – maybe you mean gradational, as is clear in the next point? Could edit to: “base is not well defined, and there is a gradual transition ..”.

L162: alternated -> alternating

L175: Typo: “bellow”.

L179-181: “The mean grain size … present several fluctuations along the core, namely at 181 346, 316, 263, 194, 140 and 73 cm bsf.” Looking at Fig. 2B, it’s not at all clear to me why these depths are cited as the location of fluctuations, as if there are spikes at those particular depths – it would be much better to describe in more detail how grain size fluctuates.

L183: “sand percentage .. showing a sharper and clear increase or decrease along core”. The meaning is unclear without describing specific changes or intervals.

L185: till -> to.

L198: carbonated -> carbonate.

L199: at -> in.

L202: “decrease on the carbonates content…..subtle downwards these depths” -> “decrease in carbonate content…subtle below these depths”.

L205-208: These elements are not shown in Figure 2.

L213: “past tsunami episodes” -> “past tsunamis” or “past tsunami events”. An episode usually refers to a period of time, rather then a discrete event.

L219: “At core’s top” – at the top of which core, or should it be “at the top of the cores”?

L222: “several anomalous layers were identified as simultaneous coincidence of several properties’ significant changes” – awkward wording – I suggest “several anomalous layers were identified on the basis of significant coincident changes in several properties”.

L224-228: These changes are not very convincing – in particular, most of the anomalous layers do not appear to have increased Fe/Ca and Si/Ca compared to other parts of the cores. The reader also doesn’t have the basis to judge (iii) magnetic mineral phases variations and environmental magnetic parameters – what is meant by these? These data are not provided.

L226: “increased of the” -> “increases in”.

L229: indicated -> indicating.

L824: SC -> SS (for Sabine Schmidt).

L1003: Is there good reason why the authors (Terrinha et al.) of the ASTARTE report are not listed in the citation here?

Author Response

Response to Reviewer 3 Comments – Round 2

 

We would like to thank the reviewer again for putting all this work and making suggestions to improve this work essentially. (The new line numbers you suggested are not the same of the document we can download).

Point 1:

Point 8: L46: I suggest rewording from “Only a modest part of tsunami research is analyzing the present deeper offshore sedimentary records [..] and even less possible historical…” to “Relatively few studies have focussed on analyzing deeper offshore… and even fewer have involved possible historical…”.

Response: The sentence has been rephrased to improve clarity of the text in accordance to the reviewer’s suggestion.

Follow up: A couple of words got lost in the change (now L53) – “offshore” -> “offshore sedimentary records”.

Response to Point 1:

We added “sedimentary records” after “offshore” in this sentence as suggested by the reviewer.

Point 2:

Point 60: L371: Please define “MoR”.

Response: MoR defintion is now added in section “2.1 Supporting data” at (previous) L197.

Follow up: I still could find no definition of MoR in this section or elsewhere in the paper.

Response to Point 2:

We defined MoR in the methodology (section 2.1. Supporting Data) with the following sentence: “The ratio of incoherent over coherent scattering (MoR) is used as an indicator of organic matter content [64].”. (This was probably a transmission error)

Point 3:

Point 75: L497: “Recorded historical tsunamis have the advantage to allow chronological correlation between potential event layer as a first basis.” Unclear meaning, likely due to poor grammar.

Response: We accepted the suggested change of the reviewer to increase clarity.

Follow up: The sentence remains unchanged – now L606. The meaning remains unclear.

Response to Point 3:

We changed the sentence to: “Recorded historical tsunamis have the advantage to allow chronological correlation between the year of the tsunami event and the potential event layer as a first basis”.

Point 4:

Point 82: L528: “db” in the equation should have “b” as subscript to match the parameter definition.

Response: We changed db to b in the whole manuscript according to the reviewer’s suggestion.

Follow up: The suggestion was not to change “db” to “b” as you have done, but to make the notation in the equation the same as in the text, with b as subscript to d: d_b. I think you should change the b in both places to d_b.

Response to Point 4:

We changed “b” to “d_b” in the equation and in the text as suggested by the reviewer.

Point 5:

Point 83: L530: “the boundary between deep-water (0.5 · wavelength (L) < d) and intermediate-water (0.5 L > d < 0.05 L)” – I believe the intermediate water expression should read “0.5L > d < 0.05L”. To clarify, you could add “i.e., d = 0.5L”.

Response: We cannot see a difference between the reviewer’s suggestion and the actual sentence. Also, 0.5L >d<0.05L is the correct expression for intermediate water.

Follow up: Yes, it seems I made a mistake in my comment, but there is still a problem in the text. The intermediate water expression should read “0.5L > d > 0.05L”. Your current text defines intermediate water depth as d less than 0.05L and also less than 0.5 L, when it should lie between those values.

Response to Point 5:

We agree to the reviewer’s comment and changed the equation to “0.5L > d > 0.005L” accordingly.

Point 6:

Point 86: L546: “elaborated” -> “documented”.

Response: We corrected “elaborated” to “documented” as suggested by the reviewer.

Follow up: This change has not been made in the revised manuscript (now L604).

Response to Point 6:

We changed the word “elaborated” to “documented” as suggested by the reviewer in the sentence of the river discharges.

Point 7:

Point 109: L668: “change in sedimentation dynamics in general observed by PCA results including both cores (Figure 4; Figure 7c, d)”. What is the time period for this change. The cited figures cover only a short period of time including only 6-8 cm (~100 yrs) below the tsunami layer. Grain size is not shown lower down the core to illustrate longer term changes, e.g., relating to the Little Ice Age as mentioned on L675.

Response: Long term trends of the sediment characteristics are now displayed in the new figure in “1.2. Previous study”.

Follow up: You should refer the reader to this new Figure (2) here (now L759-761)

Response to Point 7:

We added “(see also Figure 2)” as suggested by the reviewer.

Point 8:

Point 117: L709-715: Seems this conclusion should be adapted – the authors have shown that microtextural analysis of quartz grains is not a useful way of identifying tsunami deposits in shelf settings, unlike for onshore high-energy deposits.

Response: We added the suggested part of the reviewer as a new point to the conclusions and clarified the different usefulness between onshore and offshore studies.

Follow up: The new wording (L806-808) could be improved for clarity: e.g. “Although tsunami samples showed a minor increase in percussion marks, this increase was insignificant, and no other possible tsunami signature was detected, suggesting that microtextural analysis is not useful for identifying tsunami deposits in shelf settings, unlike for onshore high-energy deposits”.

Response to Point 8:

We changed the whole sentence to the suggested version of the reviewer.

Point 9:

Point 120: L720: This final point is unclear and needs to be substantially rewritten.

Response: We have rewritten this final point and think it is clearer now.

Follow up: A bit clearer, but still needs some work. E.g.:

“The here inferred implications” -> “The methods described here”.

“can be applied for other older tsunami events” -> “can be applied to other potential tsunami deposits”.

“dataset of occurred tsunami events” -> “dataset of past tsunamis”.

Response to Point 9:

We applied all the suggested changes of the reviewer to this sentence.

Point 10: In places, revisions have led to typos or words running together etc, including L33, 44, 49, 68.

Response to Point 10:

Point 11: L5: I’m confused by the increase in number of authors from 6 to 11 – is this related to the addition of section 1.2?

Response to Point 11:

Yes, it is related to the section 1.2. and its origin. The work for section 1.2. has contribution of all these new authors and was never published before. We made sure that everyone also contributed to the whole manuscript. That was the reason for the longer revision.

Point 12: L153: ASTTARTE -> ASTARTE

Response to Point 12:

We corrected the typo “ASTARTTE” to “ASTARTE”.

Point 13: L160: “base is not well defined but ondulated” – do you mean undulating, as in wavy? It could still have a sharp undulating base – maybe you mean gradational, as is clear in the next point? Could edit to: “base is not well defined, and there is a gradual transition ..”.

Response to Point 13:

We rephrased the sentence to the suggested version of the reviewer.

Point 14: L162: alternated -> alternating

Response to Point 14:

We changed the word “alternated” to “alternating” as suggested by the reviewer.

Point 15: L175: Typo: “bellow”.

Response to Point 15:

We corrected the typo “bellow” to “below”.

Point 16: L179-181: “The mean grain size … present several fluctuations along the core, namely at 181 346, 316, 263, 194, 140 and 73 cm bsf.” Looking at Fig. 2B, it’s not at all clear to me why these depths are cited as the location of fluctuations, as if there are spikes at those particular depths – it would be much better to describe in more detail how grain size fluctuates.

Response to Point 16:

We rephrased this sentence and tried to make it clearer: “The mean grain size ranges from ca. 35 μm at the base to ca. 11 μm at the upper core section. This general decrease in mean grain size entails marked and successive decreases at specific core levels (at ca. 316, 263, 215, 133 and 73 cm bsf) with minor oscillations between these levels.”.

Point 17: L183: “sand percentage .. showing a sharper and clear increase or decrease along core”. The meaning is unclear without describing specific changes or intervals.

Response to Point 17:

We rephrased the sentence and made a comparison with the mean grain size since the sand percentages are mimicking the mean grain size variations.

Point 18: L185: till -> to.

Response to Point 18:

We changed the word “till” to “to” as suggested by the reviewer.

Point 19: L198: carbonated -> carbonate.

Response to Point 19:

We corrected the word “carbonated” to “carbonate” as suggested by the reviewer.

Point 20: L199: at -> in.

Response to Point 20:

We changed the word “at” to “in” as suggested by the reviewer.

Point 21: L202: “decrease on the carbonates content…..subtle downwards these depths” -> “decrease in carbonate content…subtle below these depths”.

Response to Point 21:

We rephrased the whole sentence according to the reviewer’s suggestion.

Point 22: L205-208: These elements are not shown in Figure 2.

Response to Point 22:

We added the reference to the “not shown here, see [60]” for the profiles of elements considered involved in diagenetic processes (Mn, V, Co, S).

Point 23: L213: “past tsunami episodes” -> “past tsunamis” or “past tsunami events”. An episode usually refers to a period of time, rather then a discrete event.

Response to Point 23:

We changed “past tsunami episodes” to “past tsunami events” to enhance the clarity of this sentence as suggested by the reviewer.

Point 24: L219: “At core’s top” – at the top of which core, or should it be “at the top of the cores”?

Response to Point 24:

Yes, we meant “at the top of the cores” and changed it accordingly as suggested by the reviewer.

Point 25: L222: “several anomalous layers were identified as simultaneous coincidence of several properties’ significant changes” – awkward wording – I suggest “several anomalous layers were identified on the basis of significant coincident changes in several properties”.

Response to Point 25:

We rephrased the sentence as suggested by the reviewer for more clarity.

Point 26: L224-228: These changes are not very convincing – in particular, most of the anomalous layers do not appear to have increased Fe/Ca and Si/Ca compared to other parts of the cores. The reader also doesn’t have the basis to judge (iii) magnetic mineral phases variations and environmental magnetic parameters – what is meant by these? These data are not provided.

Response to Point 26:

Concerning the Fe/Ca and Si/Ca indicators of the anomalous layers: In fact, most of the event layers are not defined such as clear increases, but are instead marked by shifts or anomalous behaviour regarding other trends (such as mean grain size variations) along the cores, as it is stated in the section 1.2.).

We added again the reference to the ASTARTE deliverable 2.43. With the new section 1.2. we made a compromise showing at least some results of the preliminary work to understand the selection of the studied layers probable related to the 1755 CE tsunami. However, we must keep this section as short as possible to not overload the content of this work.

Point 27: L226: “increased of the” -> “increases in”.

Response to Point 27:

We corrected and changed the words from “increased of the” to “increases in” as suggested by the reviewer.

Point 28: L229: indicated -> indicating.

Response to Point 28:

We corrected the word “indicated” to “indicating” in this sentence as suggested by the reviewer.

Point 29: L824: SC -> SS (for Sabine Schmidt).

Response to Point 29:

We corrected the typo “SC” to “SS”.

Point 30: L1003: Is there good reason why the authors (Terrinha et al.) of the ASTARTE report are not listed in the citation here?

Response to Point 30:

No there is no good reason for it. Authors are now listed instead of just “ASTARTE”.

 

 

Author Response File: Author Response.pdf