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Site-Specific Seismic Hazard Analysis: New Perspectives, Open Issues and Challenges

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A special issue of Geosciences (ISSN 2076-3263). This special issue belongs to the section "Geophysics".

Deadline for manuscript submissions: closed (31 March 2018) | Viewed by 72078

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Special Issue Editors

Dr. Valerio Poggi

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Guest Editor

Global Earthquake Model (GEM) Foundation, Pavia, Italy
Interests: applied geophysics; engineering seismology; probabilistic seismic hazard assessment; local seismic response; ambient vibration

Dr. Olga-Joan Ktenidou

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Guest Editor

National Observatory of Athens, Athens, Greece
Interests: engineering seismology; site response and amplification; ground motion attenuation and variability

Dr. Graeme Weatherill

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Guest Editor

GFZ German Research Centre for Geosciences, Helmholtz Centre Potsdam, Germany
Interests: probabilistic seismic hazard assessment; engineering seismology; ground motion attenuation; seismic source characterization; infrastructure hazard and risk analysis

Special Issue Information

Dear Colleagues,

Ground shaking induced by destructive earthquakes can be highly variable, even over small areas, as it has been shown at the local scale to be largely dependent on near-surface geology heterogeneities. Unfavorable site conditions—not uncommon in high-risk urban environments—threaten to increase ground motion amplitude and duration.

In order to properly account for the effect of local seismic response, accurate modelling of heterogeneous upper-crustal and soil behavior is necessary. However, this requires detailed knowledge of the subsurface geology, often difficult or too expensive to obtain over numerous sites. Previously, seismic hazard analyses relied on the spatial ergodicity assumption to collect sufficient data for reliable predictions. However, this resulted in high uncertainties.

Nowadays, we can reduce the high epistemic uncertainty by performing site-specific seismic hazard analysis thanks to the introduction of novel site-characterisation geophysical techniques and sophisticated instrumentation, data availability from dense seismic networks, and recent improvements in ground-motion modelling. Nevertheless, this shift introduces numerous issues and new challenges to the scientific community.

For this Special Issue in Geosciences, we encourage original contributions from a wide range of topics related to site-response analysis, ground motion modelling and seismic hazard, with a particular focus on the reduction of uncertainties. This includes, but is not limited to, the following areas:

Seismic site characterization using state-of-the-art geophysical techniques, e.g., controlled source vs. ambient vibration;
Advances in numerical/analytical modelling of low-velocity sites, including surface/subsurface topography;
Non-linear soil response;
Site attenuation;
Data mining and harmonization of soil properties;
Development of new site-specific empirical ground motion prediction models;
Definition of innovative and improvement of existing site proxies;
Site-specific seismic hazard studies (deterministic/probabilistic);

We are looking forward to receiving novel contributions to these research fields in this Special Issue.

Dr. Valerio Poggi
Dr. Olga-Joan Ktenidou
Dr. Graeme Weatherill
Guest Editors

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Keywords

Site-specific seismic hazard
Local seismic response analysis
Site characterization techniques
Empirical ground motion prediction
Numerical ground motion modelling
Seismic microzonation studies
Uncertainty reduction

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Research

15 pages, 4240 KiB

Open AccessArticle

Combined Geophysical and Geotechnical Approaches for Microzonation Studies in Hispaniola Island

by Myriam Belvaux, Kristel Meza-Fajardo, Jaime Abad, Didier Bertil, Agathe Roullé, Santiago Muñoz and Claude Prépetit

Geosciences 2018, 8(9), 336; https://doi.org/10.3390/geosciences8090336 - 5 Sep 2018

Cited by 7 | Viewed by 4411

Abstract

In this paper, we describe recent studies for the geophysical and geomechanical characterization of soils in Hispaniola (Greater Antilles), an island threatened by the eventual rupture of major seismogenic fault systems. The investigations were performed for four different cities settled on complex geological formations in Haiti (Cap-Haïtien, Port-au-Prince) and the Dominican Republic (Santo Domingo, Santiago de los Caballeros). We present the complete methodology we implemented for mapping zones of homogeneous seismic response and for microzonation studies, but each main stage of investigation is described as it was conducted in one or two cities. Therefore, first we present our site-characterization technique applied to Santo Domingo and Santiago de los Caballeros, which is based on geotechnical data, geophysical multichannel analysis of surface waves, and ambient-noise recordings. Then we present the site-response analysis through numerical analysis with nonlinear soil models that we performed for the city of Cap-Haïtien. Finally, we describe the amplification factors for site-specific response spectra that we derived for the microzonation of Port-au-Prince. We argue for the implementation of a multidisciplinary approach built upon complementary field geological, geophysical, and geotechnical data rather than solely depending on geophysical measures for the characterization of V_S30. In addition, we explore the compatibility of the soil classes recommended by the International Building Code (IBC) in the context of local seismic amplification. Full article

(This article belongs to the Special Issue Site-Specific Seismic Hazard Analysis: New Perspectives, Open Issues and Challenges)

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28 pages, 10793 KiB

Open AccessArticle

Integration of Site Effects into Probabilistic Seismic Hazard Assessment (PSHA): A Comparison between Two Fully Probabilistic Methods on the Euroseistest Site

by Claudia Aristizábal, Pierre-Yves Bard, Céline Beauval and Juan Camilo Gómez

Geosciences 2018, 8(8), 285; https://doi.org/10.3390/geosciences8080285 - 30 Jul 2018

Cited by 17 | Viewed by 5684

Abstract

The integration of site effects into Probabilistic Seismic Hazard Assessment (PSHA) is still an open issue within the seismic hazard community. Several approaches have been proposed varying from deterministic to fully probabilistic, through hybrid (probabilistic-deterministic) approaches. The present study compares the hazard curves that have been obtained for a thick, soft non-linear site with two different fully probabilistic, site-specific seismic hazard methods: (1) The analytical approximation of the full convolution method (AM) proposed by Bazzurro and Cornell 2004a,b and (2) what we call the Full Probabilistic Stochastic Method (SM). The AM computes the site-specific hazard curve on soil,

H C (S_{a}^{s} (f))

, by convolving for each oscillator frequency the bedrock hazard curve,

H C (S_{a}^{r} (f))

, with a simplified representation of the probability distribution of the amplification function,

A F (f)

, at the considered site The SM hazard curve is built from stochastic time histories on soil or rock corresponding to a representative, long enough synthetic catalog of seismic events. This comparison is performed for the example case of the Euroseistest site near Thessaloniki (Greece). For this purpose, we generate a long synthetic earthquake catalog, we calculate synthetic time histories on rock with the stochastic point source approach, and then scale them using an adhoc frequency-dependent correction factor to fit the specific rock target hazard. We then propagate the rock stochastic time histories, from depth to surface using two different one-dimensional (1D) numerical site response analyses, while using an equivalent-linear (EL) and a non-linear (NL) code to account for code-to-code variability. Lastly, we compute the probability distribution of the non-linear site amplification function,

A F (f)

, for both site response analyses, and derive the site-specific hazard curve with both AM and SM methods, to account for method-to-method variability. The code-to-code variability (EL and NL) is found to be significant, providing a much larger contribution to the uncertainty in hazard estimates, than the method-to-method variability: AM and SM results are found comparable whenever simultaneously applicable. However, the AM method is also shown to exhibit severe limitations in the case of strong non-linearity, leading to ground motion “saturation”, so that finally the SM method is to be preferred, despite its much higher computational price. Finally, we encourage the use of ground-motion simulations to integrate site effects into PSHA, since models with different levels of complexity can be included (e.g., point source, extended source, 1D, two-dimensional (2D), and three-dimensional (3D) site response analysis, kappa effect, hard rock …), and the corresponding variability of the site response can be quantified. Full article

(This article belongs to the Special Issue Site-Specific Seismic Hazard Analysis: New Perspectives, Open Issues and Challenges)

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20 pages, 2752 KiB

Open AccessArticle

A Site Amplification Model for Crustal Earthquakes

by M. Abdullah Sandıkkaya and L. Doğan Dinsever

Geosciences 2018, 8(7), 264; https://doi.org/10.3390/geosciences8070264 - 17 Jul 2018

Cited by 13 | Viewed by 4502

Abstract

A global dataset which is composed of more than 20,000 records is used to develop an empirical nonlinear soil amplification model for crustal earthquakes. The model also includes the deep soil effect. The soil nonlinearity is formulated in terms of input rock motion and soil stiffness. The input rock motion is defined by the pseudo-spectral acceleration at rock site condition (PSA_rock) which is also modified with between-event residual. Application of PSA_rock simplifies the usage of the site model by diminishing the need of using the period-dependent correlation coefficients in hazard studies. The soil stiffness is expressed by a Gompertz sigmoid function which restricts the nonlinear effects at both of the very soft soil sites and very stiff soil sites. In order to surpass the effect of low magnitude and long-distant recordings on soil nonlinearity, the nonlinear site coefficients are constrained by using a limited dataset. The coefficients of linear site scaling and deep soil effect are obtained with the full database. The period average of site-variability is found to be 0.43. The sigma decreases with decreasing the soil stiffness or increasing input rock motion. After employing residual analysis, the region-dependent correction coefficients for linear site scaling are also obtained. Full article

(This article belongs to the Special Issue Site-Specific Seismic Hazard Analysis: New Perspectives, Open Issues and Challenges)

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22 pages, 3814 KiB

Open AccessArticle

Vulnerability and Site Effects in Earthquake Disasters in Armenia (Colombia). I—Site Effects

by Francisco J. Chávez-García, Hugo Monsalve Jaramillo, Marisol Gómez Cano and José J. Vila Ortega

Geosciences 2018, 8(7), 254; https://doi.org/10.3390/geosciences8070254 - 9 Jul 2018

Cited by 9 | Viewed by 4908

Abstract

The city of Armenia, Colombia has been repeatedly subjected to moderate magnitude earthquakes. Damage in that city for the 1999 (Mw6.2) event was disproportionate (maximum observed EMS-92 intensity of IX), even considering the small epicentral distance (18 km). Two main factors have been invoked: Site effects and vulnerability of the building stock. We re-analyze available data on site effects, including: Records of aftershocks of the 1999 event, ambient noise records obtained using standalone stations, array records of ambient noise, and available shear wave profiles from seismic cone measurements. We estimate local amplification from spectral ratios of earthquake records relative to a reference site, the horizontal relative to the vertical component (HVSR, Horizontal-to-Vertical Spectral Ratios) of earthquakes and ambient noise records, and ratios of response spectra relative to a reference site or to simulated ground motion. These estimates are compared to amplification functions computed for 1D soil models, inverted from microtremor array observations. Our estimates of site effects for Armenia are therefore robust and bring together results previously available only in internal reports. We show that spectral ratios relative to a reference site may fail to estimate the amplification level. Site effects in Armenia are relatively homogeneous. Although site amplification is very significant and contributed to the observed damage, it does not account for the irregular damage distribution observed in 1999. Full article

(This article belongs to the Special Issue Site-Specific Seismic Hazard Analysis: New Perspectives, Open Issues and Challenges)

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15 pages, 4308 KiB

Open AccessArticle

Site Characterization by Dynamic In Situ and Laboratory Tests for Liquefaction Potential Evaluation during Emilia Romagna Earthquake

by Antonio Cavallaro, Piera Paola Capilleri and Salvatore Grasso

Geosciences 2018, 8(7), 242; https://doi.org/10.3390/geosciences8070242 - 29 Jun 2018

Cited by 36 | Viewed by 5201

Abstract

To investigate the geotechnical soil properties of Emilia Romagna Region, a large series of in situ tests, laboratory tests and geophysical tests have been performed, particularly at the damaged city of Scortichino—Bondeno. Deep site investigations have been undertaken for the site characterization of the soil also along the Burana-Scortichino levee. Borings, Piezocone tests (CPTU) and dynamic in situ tests have been performed. Among them, Multichannel Analysis of Surface Waves test (MASW) and Seismic Dilatometer Marchetti Tests (SDMT) have been also carried out, with the aim to evaluate the soil profile of shear wave velocity (V_s). Resonant Column Tests (RCT) were also performed in laboratory on reconstituted solid cylindrical specimens. The Seismic Dilatometer Marchetti Tests were performed up to a depth of 32 m. The results show a very detailed and stable shear wave profile. The shear wave profiles obtained by SDMT have been compared with other laboratory tests. A comparison between the in situ small shear strain, laboratory shear strain and shear strain obtained by empirical correlations, was also performed. Finally, using the results of SDMT tests, soil liquefaction phenomena have been analyzed with a new procedure based on SDMT, using the soil properties obtained by field and laboratory tests. Full article

(This article belongs to the Special Issue Site-Specific Seismic Hazard Analysis: New Perspectives, Open Issues and Challenges)

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18 pages, 5180 KiB

Open AccessArticle

Site Effect Assessment of the Gros-Morne Hill Area in Port-au-Prince, Haiti, Part B: Mapping and Modelling Results

by Sophia Ulysse, Dominique Boisson, Claude Prépetit and Hans-Balder Havenith

Geosciences 2018, 8(7), 233; https://doi.org/10.3390/geosciences8070233 - 23 Jun 2018

Cited by 4 | Viewed by 3590

Abstract

This paper presents the general results in terms of maps, as well as geological and numerical models of a site effect study, that aimed at a better understanding of the ground motion amplification on the Gros-Morne hill, in the southeastern part of Port-au-Prince, Haiti, which might have influenced the 2010 event damage pattern in that area. These maps and models are based on multiple geophysical–seismological survey outputs that are presented, in detail, in Part A of this publication. Those outputs include electrical resistivity tomography sections, P-wave velocity profiles, S-wave logs, estimates of the fundamental resonance frequency for many locations, as well as earthquake recordings at three sites and associated site amplification assessment for the top of the hill. Related results are discussed in Part A with respect to outputs and interpretations that had been published earlier by other research teams for the same site. Our results only partly confirm the strong seismic amplification effects highlighted by some of the previous studies for this hill site, which had been attributed to the influence of local topographic and soil characteristics on seismic ground motion. Here, we focus on the imaging of different site effect components over the entire survey area; we present maps of shear wave velocity variations, of changing fundamental resonance frequencies, and of related estimates of soft soil/rock thickness, of peak spectral amplitudes, and of ambient ground motion polarization. Results have also been compiled within a 3D surface–subsurface model of the hill, which helps visualize the geological characteristics of the area, which are relevant for site effect analyses. From the 3D geomodel, we extracted one 2D geological section along the short-axis of the hill, crossing it near the location of Hotel Montana on top of the hill, which had been destroyed during the earthquake, and has now been rebuilt. This cross-section was used for dynamic numerical modelling of seismic ground motion, and for related site amplification calculation. The numerical results are compared with the site amplification characteristics that had been estimated from the ambient vibration measurements and the earthquake recordings. Full article

(This article belongs to the Special Issue Site-Specific Seismic Hazard Analysis: New Perspectives, Open Issues and Challenges)

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20 pages, 5352 KiB

Open AccessArticle

One-Dimensional Nonlinear Seismic Response Analysis Using Strength-Controlled Constitutive Models: The Case of the Leaning Tower of Pisa’s Subsoil

by Gabriele Fiorentino, Camillo Nuti, Nunziante Squeglia, Davide Lavorato and Stefano Stacul

Geosciences 2018, 8(7), 228; https://doi.org/10.3390/geosciences8070228 - 22 Jun 2018

Cited by 10 | Viewed by 5551

Abstract

The Leaning Tower of Pisa was built between 1173 and 1360 and began to lean at the beginning of its construction. Extensive investigations to reveal the causes of the tilting only began in the early 20th century. Although few earthquakes have been recorded, there is a renewed interest in the seismic behavior of the tower triggered by the availability of new data and technologies. This paper highlights the influence of using new strength-controlled constitutive models in case of 1D nonlinear response analysis. This is an aspect that has been poorly investigated. Most of the computer codes currently available for nonlinear seismic response analysis (SRA) of soil use constitutive models able to capture small-strain behavior, but the large-strain shear strength is left uncontrolled. This can significantly affect the assessment of a 1-D response analysis and the Leaning Tower’s subsoil can be useful for this study as it represents a well-documented and well-characterized site. After a geological and geotechnical description of the subsoil profile and a synthesis of available data, the seismic input is defined. One-dimensional SRAs were carried out by means of a computer code which considers an equivalent-linear soil modelling and two codes which assume nonlinear soil response and permit to use strength-controlled constitutive models. All the parameters were calibrated on the basis of the same soil data, therefore allowing for a direct comparison of the results. Full article

(This article belongs to the Special Issue Site-Specific Seismic Hazard Analysis: New Perspectives, Open Issues and Challenges)

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33 pages, 15218 KiB

Open AccessArticle

Hybrid GMPEs for Region-Specific PSHA in Southern Italy

by Maria D’Amico, Giovanni Lanzano, Marco Santulin, Rodolfo Puglia, Chiara Felicetta, Mara Monica Tiberti, Antonio Augusto Gomez-Capera and Emiliano Russo

Geosciences 2018, 8(6), 217; https://doi.org/10.3390/geosciences8060217 - 14 Jun 2018

Cited by 2 | Viewed by 4029

Abstract

This paper describes the main findings of the project HYPSTHER (HYbrid ground motion prediction equations for PSha purposes: the study case of souTHERn Italy; supported by the Italian Institute of Geophysics and Volcanology). The goal of the project is to develop a methodological approach to retrieve hybrid Ground Motion Prediction Equations (GMPEs) based on integration of recorded and synthetic data. This methodology was applied to the study area of southern Italy, focusing on the southern Calabria and Sicily regions. The target area was chosen due to the expected high seismic hazard levels, despite the low seismic activity in recent decades. In addition, along the coast of the study area, there are many critical infrastructures, such as chemical plants, refineries, and large ports, which strongly increase the risk of technological accidents induced by earthquakes. Through the synthetic data, the predictions of the hybrid GMPEs have been improved under near-field conditions, with respect to empirical models for moderate to large earthquakes. Attenuation at distances greater than 50 km is instead controlled by the empirical data, because attenuation is faster with distance. The aleatory variability of the hybrid models has strong impact on probabilistic seismic hazard assessment, as it is lower than the sigma of the empirical GMPEs. The use of the hybrid GMPEs specific for the study area can produce remarkable reductions in hazard levels for long-return periods, mainly due to changes in median predictions and reduction of the aleatory variability. Full article

(This article belongs to the Special Issue Site-Specific Seismic Hazard Analysis: New Perspectives, Open Issues and Challenges)

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12 pages, 2968 KiB

Open AccessArticle

A Hybrid Empirical Green’s Function Technique for Predicting Ground Motion from Induced Seismicity: Application to the Basel Enhanced Geothermal System

by Benjamin Edwards, Nadine Staudenmaier, Carlo Cauzzi and Stefan Wiemer

Geosciences 2018, 8(5), 180; https://doi.org/10.3390/geosciences8050180 - 15 May 2018

Cited by 3 | Viewed by 4257

Abstract

A method is described for the prediction of site-specific surface ground motion due to induced earthquakes occurring in predictable and well-defined source zones. The method is based on empirical Green’s functions (EGFs), determined using micro-earthquakes at sites where seismicity is being induced (e.g., hydraulic fracturing and wastewater injection during shale oil and gas extraction, CO₂ sequestration, and conventional and enhanced geothermal injection). Using the EGF approach, a ground-motion field (e.g., an intensity map) can be calculated for a potentially felt induced event originating within the seismic zone. The approach allows site- and path-specific effects to be mapped into the ground-motion field, providing a local ground-motion model that accounts for wave-propagation effects without the requirement of 3D velocity models or extensive computational resources. As a test case, the ground-motion field for the mainshock (M_L = 3.4, M = 3.2) resulting from the Basel Enhanced Geothermal System (EGS) was simulated using only seismicity recorded prior to the event. We focussed on peak ground velocity (PGV), as this is a measure of ground motion on which Swiss norms for vibration disturbances are based. The performance of the method was significantly better than a previously developed generic ground-motion prediction equation (GMPE) for induced earthquakes and showed improved performance through intrinsic inclusion of site-specific effects relative to predictions for a local GMPE. Both median motions and the site-to-site ground-motion variability were captured, leading to significantly reduced misfit relative to the generic GMPE. It was shown, however, that extrapolation beyond units of a couple of magnitude leads to significant uncertainty. The method is well suited to a real-time predictive hazard framework, for which shaking estimates are dynamically updated in light of newly recorded seismicity. Full article

(This article belongs to the Special Issue Site-Specific Seismic Hazard Analysis: New Perspectives, Open Issues and Challenges)

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14 pages, 3805 KiB

Open AccessArticle

Development of Three-Dimensional Soil-Amplification Analysis Method for Screening for Seismic Damage to Buried Water-Distribution Pipeline Networks

by Kohei Fujita, Tsuyoshi Ichimura, Motoki Kazama, Susumu Ohno and Shingo Sato

Geosciences 2018, 8(5), 170; https://doi.org/10.3390/geosciences8050170 - 9 May 2018

Viewed by 3901

Abstract

A soil-amplification analysis method is developed that uses high-resolution ground data and a three-dimensional nonlinear dynamic finite-element method to screen for possible areas of seismic damage to buried water-distribution pipeline networks. The method is applied to a cut-and-fill developed area in Japan, whose water-distribution pipeline network was severely damaged in the 2011 off the Pacific Coast of Tohoku Earthquake. The obtained soil amplification is compared with known points of pipeline damage to check the validity of the analysis. A sensitivity test is also conducted to account for uncertainties in the properties of the ground material. From the results, it is expected that the developed soil-amplification method could be used to screen for possible damage to buried pipelines in a given area, and used to support methods for estimating damage to buried pipelines based on observations and seismic indices. Full article

(This article belongs to the Special Issue Site-Specific Seismic Hazard Analysis: New Perspectives, Open Issues and Challenges)

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22 pages, 8345 KiB

Open AccessArticle

Site Effect Assessment of the Gros-Morne Hill Area in Port-au-Prince, Haiti, Part A: Geophysical-Seismological Survey Results

by Sophia Ulysse, Dominique Boisson, Claude Prépetit and Hans-Balder Havenith

Geosciences 2018, 8(4), 142; https://doi.org/10.3390/geosciences8040142 - 23 Apr 2018

Cited by 6 | Viewed by 5169

Abstract

After the M = 7.0 Haiti earthquake in 2010, many teams completed seismic risk studies in Port-au-Prince to better understand why this not extraordinarily strong event had induced one of the most severe earthquake disasters in history (at least in the Western World). Most highlighted the low construction quality as the main cause for the disaster, but some also pointed to possible soil and topographic amplification effects, especially in the lower and central parts of Port-au-Prince (e.g., close to the harbor). However, very detailed local studies of such site effects have not been completed yet. A Belgian-Haitian collaboration project was established in order to develop a detailed local seismic hazard study for Gros-Morne hill located in the district of Pétion-Ville, southeast of Port-au-Prince. In order to have a better understanding of the amplification on the Gros-Morne hill, in the southeastern part of Port-au-Prince, site effects were investigated by using near surface geophysical methods. The horizontal to vertical spectral ratio technique was applied to ambient vibrations and earthquake data, and multichannel analysis of surface waves and P-wave refraction tomography calculation were applied to seismic data. Standard spectral ratios were computed for the S-wave windows of the earthquake data recorded by a small temporary seismic network. Electrical resistivity tomography profiles were also performed in order to image the structure of the subsurface and detect the presence of water, if any. The spectral ratio results generally show low to medium (1.5–6) resonance amplitudes at one or several different resonance frequencies (for the same site), between 0.5 and 25 Hz. At most of the investigated sites, the fundamental resonance frequency varies between 7 and 10 Hz. By using the multichannel surface wave analyses of the seismic data, we were able to determine shear wave velocities ranging between 200 and 850 m/s, up to a depth of about 15–20 m. From the refraction analysis, we were able to delineate P-waves velocities of 500 to 1500–2000 m/s at the studied sites. The outputs were locally compared with the resistivity data from the electrical profiles. Thus, the overall data indicate a moderate site effect at Gros-Morne hill, with a great variability in site amplification distribution. Initial estimates of local site effects were made on the basis of those outputs and the earthquake recordings. Our results are finally discussed with respect to outputs and interpretations that had been published earlier for the same site. Those results only partly confirm the strong seismic amplification effects highlighted by previous papers for this hill site, which had been explained by the effects of the local topographic and soil characteristics. Full article

(This article belongs to the Special Issue Site-Specific Seismic Hazard Analysis: New Perspectives, Open Issues and Challenges)

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25 pages, 11266 KiB

Open AccessArticle

Basin Resonance and Seismic Hazard in Jakarta, Indonesia

by Athanasius Cipta, Phil Cummins, Masyhur Irsyam and Sri Hidayati

Geosciences 2018, 8(4), 128; https://doi.org/10.3390/geosciences8040128 - 7 Apr 2018

Cited by 29 | Viewed by 9152

Abstract

We use earthquake ground motion modelling via Ground Motion Prediction Equations (GMPEs) and numerical simulation of seismic waves to consider the effects of site amplification and basin resonance in Jakarta, the capital city of Indonesia. While spectral accelerations at short periods are sensitive [...] Read more.

V_{S 30}

, average shear-wave velocity at topmost 30 m of soil), our results suggest that, for basins as deep as Jakarta’s, available GMPEs cannot be relied on to accurately estimate the effect of basin depth on ground motions at long periods (>3 s). Amplitudes at such long periods are influenced by trapping of seismic waves in the basin, resulting in longer duration of strong ground motion, and interference between incoming and reflected waves as well as focusing at basin edges may amplify seismic waves. In order to simulate such phenomena in detail, a basin model derived from a previous study is used as a computational domain for deterministic earthquake scenario modeling in a 2-dimensional cross-section. A

M_{w}

9.0 megathrust, a

M_{w}

6.5 crustal thrust and a

M_{w}

7.0 intraslab earthquake are chosen as scenario events that pose credible threats to Jakarta, and the interactions with the basin of seismic waves generated by these events were simulated. The highest long-period PGVs amplifications are recorded at sites near the middle of the basin and near its southern edge, with maximum amplifications of PGV in the horizontal component of 726% for the crustal, 1500% for the megathrust and 1125% for the deep intraslab earthquake scenario, respectively. We find that the levels of response spectral acceleration fall below those of the 2012 Indonesian building Codes’s design response spectra for short periods (<1 s), but closely approach or may even exceed these levels for longer periods. Full article

(This article belongs to the Special Issue Site-Specific Seismic Hazard Analysis: New Perspectives, Open Issues and Challenges)

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24 pages, 48589 KiB

Open AccessArticle

Probabilistic Estimates of Ground Motion in the Los Angeles Basin from Scenario Earthquakes on the San Andreas Fault

by Ramses Mourhatch and Swaminathan Krishnan

Geosciences 2018, 8(4), 126; https://doi.org/10.3390/geosciences8040126 - 6 Apr 2018

Cited by 4 | Viewed by 5210

Abstract

Kinematic source inversions of past earthquakes in the magnitude range of 6–8 are used to simulate 60 scenario earthquakes on the San Andreas fault. The unilateral rupture scenario earthquakes are hypothetically located at 6 locations spread out uniformly along the southern section of the fault, each associated with two hypocenters and rupture directions. Probabilities of occurrence over the next 30 years are assigned to each of these earthquakes by mapping the probabilities of 10,445 plausible earthquakes postulated for this section of the fault by the Uniform California Earthquake Rupture Forecast. Three-component broadband ground motion histories are computed at 636 sites in the greater Los Angeles metropolitan area by superposing short-period (0.2–2.0 s) empirical Green’s function synthetics on top of long-period (>2.0 s) spectral element synthetics. The earthquake probabilities and the computed ground motions are combined to develop probabilistic estimates of ground shaking in the region from San Andreas fault earthquakes over the next 30 years. The results could be useful in city planning, emergency management, and building code enhancement. Full article

(This article belongs to the Special Issue Site-Specific Seismic Hazard Analysis: New Perspectives, Open Issues and Challenges)

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21 pages, 7036 KiB

Open AccessArticle

Ambient Vibrations Measurements and 1D Site Response Modelling as a Tool for Soil and Building Properties Investigation

by Sebastiano Imposa, Giuseppe Lombardo, Francesco Panzera and Sabrina Grassi

Geosciences 2018, 8(3), 87; https://doi.org/10.3390/geosciences8030087 - 6 Mar 2018

Cited by 16 | Viewed by 4753

Abstract

The safety of historic buildings heritage is an important task that becomes more substantial when the buildings are directed to educational purposes. The present study aims at evaluating the dynamic features of the Benedettini complex, an historic monastery located in downtown Catania, which is at present the headquarters of the humanistic studies department of the University of Catania. Both the building’s complex response to a seismic input and the soil-to-structure interaction were investigated using ambient noise recordings. The results point out a multiple dynamic behaviour of the monastery structure that shows several oscillation modes, whereas the identification of a single natural frequency can be observed in some sites where the structure can more freely oscillate. This observation is also confirmed by the variability of computed damping values that appear linked to the different rigidity of the structure, as a function of the either the longitudinal or transversal orientation of the investigated structural elements. Moreover, the comparison between the building’s fundamental period and spectral ratios frequencies, which were obtained from free field ambient noise measurements located outside the monastery, outline the presence of potential resonance effects between the site and structure during a seismic event. Numerical modelling of the local seismic response confirms the obtained experimental site frequencies, setting into evidence that higher amplification factors are reached in the same frequency range characterizing the building. Full article

(This article belongs to the Special Issue Site-Specific Seismic Hazard Analysis: New Perspectives, Open Issues and Challenges)

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