Multi-Source SAR-Based Surface Deformation Analysis of Edgecumbe Volcano, Alaska, and Its Relationship with Earthquakes

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

This manuscript presents a comprehensive analysis of nearly 30 years of surface deformation at Edgecumbe Volcano by integrating multi-source SAR datasets (ERS-1/2, ALOS-1, and Sentinel-1) with time-series InSAR techniques (PS-InSAR and SBAS-InSAR). The study employs the Mogi model and MCMC inversion methods to characterize the spatiotemporal evolution of the magmatic source and innovatively establishes a dynamic relationship between volcanic deformation and seismic activity. The methodology is systematically structured, the dataset spans a significant temporal range, and the findings contribute to volcanic hazard assessment and early warning. After a thorough review of the manuscript, I have the following suggestions for improvement:

1. The deformation rate unit is inconsistently presented as "mm/year" in Lines 28–29, 369, and 384, while "mm/yr" is used elsewhere. It is recommended to standardize the unit format throughout the manuscript.
2. Line 34: The abstract states, "cumulative LOS displacement exceeding 200 mm," whereas Section 4.3 indicates that the ascending and descending tracks show approximately 200 mm and 250 mm of displacement, respectively. To ensure accuracy, revise this to "cumulative LOS displacement reaching approximately 210 mm and 250 mm in the ascending and descending tracks, respectively."
3. Lines 147–149: The manuscript states that 1,652 earthquakes within a 150 km radius were selected, but the selection criteria (e.g., magnitude range, depth constraints) are not specified. It is recommended to provide a detailed explanation of the filtering criteria for seismic events.
4. The description of PS-InSAR and SBAS-InSAR processing steps in Section 3 is relatively general. Consider elaborating on key processing algorithms, methodological frameworks, and critical parameters used in data processing.
5. Lines 456–459: The study adopts the Mogi model, assuming a point source in an elastic half-space, for magmatic source inversion. Clarify the rationale behind choosing this model and discuss its applicability and potential uncertainties in the Discussion section.
6. Lines 553–555: The manuscript mentions that winter snow cover and summer vegetation affect coherence. Consider expanding this discussion by summarizing strategies employed to mitigate seasonal decorrelation effects in the InSAR analysis.
7. Lines 589–592: The data availability statement provides links to datasets but does not specify the exact data products used (e.g., ALOS-1 PALSAR Level 1.1). It is recommended to explicitly list the dataset levels to enhance reproducibility.
8. Lines 626, 645: Some journal names in the reference list are not consistently italicized. Please revise to ensure compliance with journal formatting guidelines.

Author Response

We thank very much for the constructive and helpful comments from reviewer. We have made numerous changes based on their suggestions. Every revision to the manuscript has been marked up using the “Track Changes” function in the paper. The followings are the detailed responses to the comments and suggestions. Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

The authors have conducted a detailed analysis of Edgecumbe Volcano's deformation process using nearly three decades of SAR imagery. They highlight that since 2018, volcanic activity has facilitated the expansion of the magma source and intensified surface deformation, with magma volume changes estimated through Mogi model inversions. This is an interesting and valuable study, and I believe it deserves publication after some minor revisions.

Major Comments:

The primary deformation signals of Edgecumbe Volcano are derived from Sentinel-1 observations, while pre-2015 signals appear insignificant, resembling an abrupt shift rather than a continuous trend. This raises uncertainties regarding whether the observed long-term variations reflect true deformation signals or observational noise.

Early SAR data, including ERS and ALOS, exhibit lower acquisition quality and observation density (as seen in Figures 4 and 9), whereas Sentinel-1 data—particularly in Figure 11—demonstrate significantly improved observation quality.

The authors have made a commendable effort to incorporate ERS and ALOS data in assessing long-term deformation trends. However, it is strongly recommended to conduct an uncertainty analysis of early SAR observations.

Additionally, integrating regional GNSS data and seismic activity records would strengthen the study's conclusions, rather than relying solely on post-2015 data.

 

Minor Comments:

The color scale of topographic elevation in Figure 1 is inconsistent across the subfigures, making cross-panel comparisons difficult. It is recommended to adjust the scale for consistency. Additionally, subfigure (d) should be enlarged to improve clarity and enhance the visibility of details.

In subfigure (c), the range of seismic activity is too broad. It is suggested to narrow the range and modify the color mapping to reflect temporal variations, which would better illustrate the correlation between seismic activity and volcanic deformation.

 

Author Response

We thank very much for the constructive and helpful comments from reviewer. We have made numerous changes based on their suggestions. Every revision to the manuscript has been marked up using the “Track Changes” function in the paper. The followings are the detailed responses to the comments and suggestions. Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

The authors effectively monitored long-term surface deformations induced by Edgecumbe Volcano's activity using multi-source InSAR data and analyzed their correlation with regional seismic events. Their data processing, Mogi source inversion, and subsequent linkage analysis between surface deformations and seismicity are all commendably executed. However, my sole suggestion is that the authors should conduct a more in-depth accuracy analysis of the InSAR data. From the presented results, although the InSAR dataset for the Edgecumbe Volcano region captures deformation signals, prominent noise and uneven deformation time series (likely due to severe decorrelation and noise contamination in this area) are evident. Under such conditions, the magnitude of InSAR-derived deformations may be significantly compromised, directly introducing biases into the final geophysical modeling results. I recommend the authors systematically address the impacts of InSAR data errors—for example, by quantifying noise levels, evaluating decorrelation effects through coherence analysis, and propagating uncertainties into the inversion framework—to strengthen the robustness of their conclusions.

Author Response

We thank very much for the constructive and helpful comments from reviewer. We have made numerous changes based on their suggestions. Every revision to the manuscript has been marked up using the “Track Changes” function in the paper. The followings are the detailed responses to the comments and suggestions. Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 4 Report

Comments and Suggestions for Authors

This manuscript explores surface deformation analysis of Edgecumbe Volcano utilizing multi-source SAR imagery and evaluates its correlation with regional seismic activity. The manuscript is well analyzed and written, featuring good use of SAR techniques and model inversions. However, some significant issues need to be addressed before publication.

Line 1: The title should clearly indicate the location, Alaska.

Lines 118-119: The inset map (Figure 1c) should include more detailed fault lines and possibly a clearer depiction of the Queen Charlotte Fault to show geological relevance.

Line 131: Clarify briefly why depths between 4 and 9 km for earthquakes are significant for volcanic monitoring.

Lines 176-178: Explicitly justify why SBAS-InSAR was preferred or complementarily used alongside PS-InSAR for this study.

Lines 184-190: You mentioned seasonal exclusion for coherence. Did you test any alternative coherence threshold methods or compare against other seasonal compensation methods?

Lines 234-235: You mentioned RMS evaluation but didn't clarify how you addressed or minimized residual errors beyond using this metric. This should be expanded.

Lines 270-275: Clarify the rationale behind choosing 0.4 amplitude dispersion threshold specifically, since volcanic terrains might require a different threshold due to complex terrain.

Lines 336-337: Snow cover causing significant decorrelation is discussed. Did you consider the impact of snow density or thickness on decorrelation? If not, briefly justify why these were not included.

Lines 379-387: The deformation analysis between 2007 and 2010 shows subsidence. However, it isn't clear if you cross-validated these observations with any ground-based GPS or geological field surveys. Including such validation (or at least discussing its absence) would strengthen your findings. 

Figures 15 & 16: While residuals are shown, the interpretation of these residuals is missing. Discuss explicitly why residuals might occur and their potential implications on the model accuracy.

Author Response

We thank very much for the constructive and helpful comments from reviewer. We have made numerous changes based on their suggestions. Every revision to the manuscript has been marked up using the “Track Changes” function in the paper. The followings are the detailed responses to the comments and suggestions. Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 5 Report

Comments and Suggestions for Authors

Comments on the paper

 

Multi-source SAR-based Surface Deformation Analysis of Edgecumbe Volcano and Its Relationship with Earthquakes

By Shuangcheng Zhang, Ziheng Ju,Yufen Niu, Lu Zhong, Qianyou Fan, Jinqi Zhao, Zhengpei Zhou, Jinzhao Si1, Xuhao Li1, Yiyao Li

 

I must warn about the fact that my review refers to the geophysical content, while I am not a specialist of the specific methods of analysis, which are a concern for strict specialists.

The authors investigate the relationship between seismic activity and uplift of the area surrounding an apparently quiescent volcano.

The results look interesting and significant. The uplift of the area is correlated with an increase of seismic activity, which they interpret as an increase of the magma volume beneath the volcano.

Certainly, there is need for extensive application of these monitoring techniques applied to several different volcanoes. Therefore, the paper is mostly welcome.

The paper reading is pleasant with a good English editing.

As a geophysicist, I would like very much if crustal stress would be monitored by acoustic emission techniques, plus soil exhalation monitored at a few crucial sites in the volcanic era. In fact, soil exhalation is a crucial geophysical parameter, which is poorly known, and largely variable from one volcano to another.

Summarizing, to my understanding, the paper is valuable, and similar papers should be encouraged.

I suggest to accept the paper as it is.

Just a “technical” suggestion. I recommend the authors to put at the end of the paper a list of acronyms. In fact, every reader who is interested in a detailed reading of specific sections of the paper will find a great help by this list, suited to focus on the topics of his concern.

Author Response

We thank very much for the constructive and helpful comments from reviewer. We have made numerous changes based on their suggestions. Every revision to the manuscript has been marked up using the “Track Changes” function in the paper. The followings are the detailed responses to the comments and suggestions. Please see the attachment.

Author Response File: Author Response.pdf

Round 2

Reviewer 4 Report

Comments and Suggestions for Authors

The authors have answered to all my comments well. I have no further queries.