Earthquake Moment Magnitude Research Articles

Chemical release risk assessment in earthquake: Natech event scenario

IntroductionIn recent decades, an increase in natural disasters has led to the Natech events occurrence, which are technological accidents triggered by natural hazards. This study aims to assess the risk of chemical release of the H2S toxic gas following an earthquake from the refinery. MethodThe Natech risk assessment was carried out in potential earthquake risk scenarios via a semi-quantitative method using Rapid-N software. The reference scenario was obtained using the Australian SMUG Model, which has presented precise prioritization. FindingsThe Natech risk assessment has shown 40 possible earthquake risk scenarios from 5 enclosing Faults in Tehran (North Tehran, Mosha, North Ray, South Ray, and Kahrizak) with an extension of more than 15 km. The earthquake moment magnitudes of 7.5, 7.1, 6.5, and 5.9 were obtained on the Richter scale and at two Focal depths of 5 and 10 km. The South-Ray Fault (HSR-1) was selected as the reference scenario with a moment magnitude of 7.5 on the Richter scale at a Focal depth of 5 km and a distance of 5.5 km from the earthquake epicenter. The highest probability of Natech risk has shown the release of H2S toxic gas in an area with a radius of 6.59 km from the studied vessel in atmospheric stability conditions. ConclusionLegislation in line with risk reduction, planning for the transfer of potentially dangerous industries to outside urban areas, monitoring land use laws, and promoting coordination between the government, industries, and people in the management of risks caused by industries containing hazardous substances and processes, assessing the risk of Natech events and their consequences, strengthening risk communication and the installation of early warning systems, and public education to adopt personal and socially safe behaviors when facing natural disasters are recommended.

Liquefaction Potential Index Analysis in Solo – Yogyakarta - NYIA Kulon Progo Toll Road (Section Karanganyar to Klaten Regency) at Central Java

Liquefaction had occurred in Yogyakarta due to an earthquake of moment magnitude, Mw 6.3 on May 27, 2006. This earthquake caused severe damage in several areas in Central Java. The study area in this construction was located mostly in some areas of Central Java Province that had a shallow groundwater table and often occurred earthquakes that might trigger liquefaction. The objective of this study was to analyze liquefaction potential in the construction of Solo – Yogyakarta – NYIA Kulon Progo toll road especially sta. 00+000-07+500 From Colomadu, Karanganyar Regency to Delanggu, Klaten Regency using two scenarios based on the existing earthquake history according to USGS data. That were earthquakes with Mw 6.3 and Mw 5.2 on a total of 47 boreholes. This study used data from Standard Penetration Tests (SPT) and laboratory tests. The liquefaction potential analysis used the simplified procedure and Liquefaction Potential Index method. Based on liquefaction potential analysis, an earthquake of Mw 5.2 has a very low liquefaction potential compared to an earthquake of Mw 6.3. According to analysis results and hazards caused, an earthquake with Mw 6.3 is recommended to be used as a basis for mitigation against liquefaction planning.

Uncertainties in Broadband Determination of the High-Frequency Spectral Decay, Kappa, in Eastern Canada

ABSTRACT Kappa (the high-frequency spectral decay slope at near-source distances; often referred to as κ0) is determined at 25 seismograph stations in Eastern Canada using broadband ground-motion modeling approaches. The database comprises Fourier spectra (effective amplitude spectrum for the horizontal component and the vertical component, 0.8–40 Hz) computed from 3318 earthquakes of moment magnitude M 1.5–5 recorded on stations within 150 km. Average kappa values for bedrock sites, having shear-wave velocities from 850 to 2400 m/s, are highly variable, ranging from −29 to +21 ms (horizontal) and −28 to +11 ms (vertical), but appear on average to be near-zero. The values obtained are sensitive to methodology, especially the necessary adjustments to the spectra to account for site amplification effects. Kappa values do not appear to correlate well with site parameters such as rock shear-wave velocity, average shear-wave velocity in the upper 30 m, primary wave velocity, site class, type and age of rock, or instrument housing. This lack of correlation may reflect the noted sensitivities to methodological factors. We conclude that kappa values in rock environments are not reliably estimated from such proxies and should be determined from recorded ground motions at a given location. On average, there is little evidence of significant high-frequency attenuation on rock sites beyond that already accounted for in ground-motion modeling by the empirical parameterization of regional Q-related path effects.

Three-dimensional coseismic displacements and slip distribution of the 2021 Mw 7.4 maduo earthquake: Synergy of SAR, InSAR and optical images

On 21 May 2021, an earthquake of moment magnitude (Mw) 7.4 occurred near Maduo county in Qinghai Province China. This is the first major earthquake that occurred in the interior of the Bayan Har block in the Tibetan Plateau over the past 70 decades. Focusing on this event, we conducted a study on three-dimensional (3D) coseismic displacement reconstruction and its tectonic implication. We acquired both Synthetic Aperture Radar (SAR) and optical imaging satellite imagery, including SAR images from Sentinel-1 and Advanced Land Observation Satellite-2 (ALOS-2) as well as the multi-spectrum images from the Sentinel-2 (S2) satellite. We applied the Interferometric SAR (InSAR) and pixel-offset tracking (POT) techniques to coseismic SAR data pairs and reconstructed two dimensional displacements. With the constructed displacement fields in multiple viewing directions, we resolved the 3D coseismic displacements (north-south, east-west, and up components) by integrating the regional strain model with variance components estimation (SM-VCE). We recommend using the standard deviation value at each grid cell, which can be calculated in the resampling, as the initial weight. Based on the resolved 3D coseismic displacements, we further estimated the dip angles for the two segments (F4 and F5) in the east of the rupture zone. The associated moment magnitude is about Mw7.4, which corresponds to the released energy of ∼ 1.74×1020 Nm.

The Importance of Assessing the Geological Site Effects of Ancient Earthquakes from the Archaeoseismological Point of View

Earthquakes have and continue to, occur worldwide, though some places are affected more than others by earthquake-induced ground shaking and the same earthquake can cause more damage in one area than in nearby locations due to site-specific geological site conditions, also known as local site effects. Depending on the chronology of the earthquakes, various disciplines of seismology include instrumental and historical seismology, archaeoseismology, palaeoseismology and neotectonics, each focusing on using specific sources of information to evaluate recent or ancient earthquakes. Past earthquakes are investigated to expand the pre-instrumental and instrumental earthquake catalog and better evaluate a region’s seismic hazard. Archaeoseismology offers a way to achieve these goals because it links how ancient civilizations and their environment might have interacted and responded to past earthquake-induced ground motion and soil amplification. Hence, archaeoseismology explores pre-instrumental (past) earthquakes that might have affected sites of human occupation and their nearby settings, which have left their co-seismic marks in ancient manufactured constructions exhumed by archaeological excavations. However, archaeoseismological observations are often made on a limited epicentral area, poorly constrained dated earthquakes and occasionally on unclear evidence of earthquake damage. Archaeological excavations or field investigations often underestimate the critical role that an archaeological site’s ancient geological site conditions might have played in causing co-seismic structural damage to ancient anthropogenic structures. Nevertheless, the archaeological community might document and inaccurately diagnose structural damage by ancient earthquake shaking to structures and even estimate the size of past earthquakes giving little or no consideration to the role of geological site effects in addressing the causative earthquake. This mixture of factors frequently leads to imprecise estimates of the size of ancient earthquakes and unlikely earthquake environmental impacts, leaving unexplained the location and the moment magnitude of the causative earthquake. Hence, it is essential not to rely solely on earthquake intensities based on archaeologically documented co-seismic damage without assessing the nature of the observed structural damage and the contribution of the geological site effects. This paper explains the geological site effects concept to archaeologists unfamiliar with the notion. It clarifies its role in assessing ground shaking, soil amplification and earthquake intensity by past earthquakes and how and why the geological site effects can be estimated when a site is thought to have been struck by an earthquake. Hence, the geological site effects must be considered when archaeological excavations describe and interpret destruction layers. Conversely, engineers and seismologists dealing with seismic hazard risk assessment must pay close attention to archaeological investigations assessing earthquake intensities and locations based on field evidence of damage to structures attributed to past earthquakes, because the geological site effects might have been factored in inaccurately or not at all.

Irregular rupture process of the 2022 Taitung, Taiwan, earthquake sequence

In September 2022, two destructive earthquakes of moment magnitude (Mw) 6.6 (foreshock) and 7.1 (mainshock) occurred in Taitung County, south-eastern Taiwan. To understand their complex rupture processes, we analysed these earthquakes using the Potency Density Tensor Inversion method, which can stably estimate the rupture propagation process, including fault geometry, without overfitting the data. The analyses revealed that the major rupture of the foreshock propagated towards shallow depth, in a south–southwest direction, following an initial rupture that propagated towards the deeper part of the fault. The mainshock, with its epicentre on the north–northeast side of that of the foreshock, consists of two distinct episodes. During the first episode (0–10 s), the initial rupture propagated north–northeast, through a deep path, followed by the main rupture that propagated bilaterally in a north–northeast and south–southwest direction. The second rupture episode (10–16 s) started near the hypocentre of the mainshock, and the rupture propagated towards the shallow side of the fault. The results suggest that the stress concentration from both the foreshock and mainshock’s first rupture episode may have caused the second rupture episode in the high fracture surface energy area between the foreshock and the first rupture episode of the mainshock. The irregular rupture process of the foreshock and mainshock may reflect the heterogeneity of stress and structure in the source region.

Numerical static-load test and earthquake simulation of a cable stayed bridge

A bridge is an essential component of transportation networks and plays a crucial role in the operation of infrastructure, so maintaining this structure to guarantee the regular operation of bridges in a healthy condition is needed. The establishment of a bridge model numerically is a critical step of the bridge evaluation because many cases of the bridge test can be done numerically. The generated results can then be verified and adjusted with the real or full-scale test. This research aims to establish a numerical model of a cable-stayed bridge and perform numerical bridge tests and earthquake simulations. The targeted bridge is located in Taiwan, and it consists of four spans with three pylons. Static load tests are performed using a truck load set applied at each mid-span. Bridge displacement due to the truckloads is the primary concern of the static load test. Besides, dynamic bridge simulation under earthquake excitation is also simulated. On 18 September 2022, a destructive earthquake of moment magnitude (Mw) 7.1 occurred in Taitung County, southeastern Taiwan. Some infrastructures like bridges and buildings were damaged and even collapsed due to this earthquake. The bridge is simulated using the earthquake history record of the earthquake. The bridge's dynamical system properties are first outputted to see the bridge's natural frequencies and mode shapes. Displacement and stress history responses due to the earthquake excitation at some critical points are also evaluated. The simulation results can be a reference for real bridge testing.

Real‐Time Seismogeodetic Earthquake Magnitude Estimates for Local Tsunami Warnings

AbstractWe estimate a seismogeodetic earthquake moment magnitude using unclipped, broadband velocity and displacement waveforms from collocated Global Navigation Satellite Systems and seismic stations located within 800 km epicentral distance for nine 7.2 < < 9.1 earthquakes. We consider the vertical component of seismogeodetic displacement as an approximate source time function and integrate the associated time series to obtain the seismic moment. By continuing to integrate vertical displacement beyond the initial P‐waves, we obtain rapid estimates of that are within 0.2 magnitude units for 8 thrust faulting events and within 0.3 units for the single normal faulting event. Because our estimates of the seismic moment are based on the maximum value of integrated displacement, no regression against other source parameters, or distance, is necessary. Our new method shows promise for integration into earthquake and local tsunami early warning systems, including tsunami earthquakes characterized by relatively slow moment release over a longer rupture time, and earthquakes with complex source time functions.

TFCGAN: Nonstationary Ground-Motion Simulation in the Time–Frequency Domain Using Conditional Generative Adversarial Network (CGAN) and Phase Retrieval Methods

ABSTRACTDespite the exponential growth of the amount of ground-motion data, ground-motion records are not always available for all distances, magnitudes, and site conditions cases. Given the importance of using time histories for earthquake engineering (e.g., nonlinear dynamic analysis), simulations of time histories are therefore required. In this study, we present a model for simulating nonstationary ground-motion recordings, which combines a conditional generative adversarial network to predict the amplitude part of the time–frequency representation (TFR) of ground-motion recordings and a phase retrieval method. This model simulates the amplitude and frequency contents of ground-motion data in the TFR as a function of earthquake moment magnitude, source to site distance, site average shear-wave velocity, and a random vector called a latent space. After generating the phaseless amplitude of the TFR, the phase of the TFR is estimated by minimizing all differences between the observed and reconstructed spectrograms. The simulated accelerograms produced by the proposed method show similar characteristics to conventional ground-motion models in terms of their mean values and standard deviations for peak ground accelerations and Fourier amplitude spectral values.

Comparison of SPT and Vs-based Liquefaction Assessment on Young Volcanic Sediment: A Case Study in Bantul District of Yogyakarta, Indonesia

On May 26, 2006, an earthquake of moment magnitude (Mw) 6.3 occurred in Yogyakarta. The damages found in Bantul were predicted to be caused by liquefaction. Moreover, liquefaction symptoms were found, such as a sand boil and lateral spreading. It inferred that the damage was controlled by the amplification factors from young volcanic sediments that are redeposited and altered volcaniclastics from the active Mount Merapi. This study compared subsurface conditions based on two field investigation methods (SPT and Shear Wave Velocity) and determined the liquefaction potential by considering groundwater and the region's seismicity. Several equations to represent the N-SPT and Vs data were also analyzed to obtain the most fitted equation. As a result, several equations used in this study were inadequate to properly correlate N-SPT and Vs. A comparison of safety factor values indicated that the liquefaction potential in the studied area on the Vs-based method is lower than the result from the SPT-based method

Sensitivity analysis of input ground motion on surface motion parameters in high seismic regions: a case of Bhutan Himalaya

Abstract. Historical earthquakes demonstrate that strong motion characteristics and local soil condition, when coupled, significantly influence seismic site response. Interestingly, most of the Himalayan earthquakes depicted anomalous behavior per the site conditions historically. Being one of the most active seismic regions on earth, the eastern fringe of the Himalaya has observed many devastating earthquakes together with non-uniform damage scenarios. To quantify such anomalies, we evaluate surface motion parameters for a soft soil deposit located in the city of Phuentsholing in western Bhutan. Using one-dimensional site response analysis, the sensitivity of ground motion variation is estimated. This study accounts for the earthquakes of moment magnitudes 6.6 to 7.5 with a wide variation in peak ground acceleration (PGA). To dissect the characteristics of six inputted ground motions on eight local ground conditions, a sensitivity analysis is performed statistically. The statistical correlation of the response datasets and the linear regression model of the bedrock outcrop and the surface motion spectral acceleration along the stratified depth are examined to quantify the variation in surface motion parameters. The results highlight that the strong motions with PGA greater than 0.34 g demonstrate greater sensitivity, leading to some anomalies in response parameters, especially amplification. Similar results were obtained for the low PGA range (<0.1 g).

Liquefaction resistance evaluation of soils using artificial neural network for Dhaka City, Bangladesh

Soil liquefaction resistance evaluation is an important site investigation for seismically active areas. To minimize the loss of life and property, liquefaction hazard analysis is a prerequisite for seismic risk management. Liquefaction potential index (LPI) is widely used to determine the severity of liquefaction quantitatively and spatially. LPI is estimated from the factor of safety of liquefaction that is the ratio of cyclic resistance ratio (CRR) to cyclic stress ratio calculated applying simplified procedure. Artificial neural network (ANN) algorithm has been used in the present study to predict CRR directly from the normalized standard penetration test blow count (SPT-N) and near-surface shear wave velocity (Vs) data of Dhaka City. It is observed that ANN models have generated accurate CRR data. Three liquefaction hazard zones are identified in Dhaka City on the basis of the cumulative frequency (CF) distribution of the LPI of each geological unit. The liquefaction hazard maps have been prepared for the city using the liquefaction potential index (LPI) and its cumulative frequency (CF) distribution of each liquefaction hazard zone. The CF distribution of the SPT-N based LPI indicates that 15%, 53%, and 69% of areas, whereas the CF distribution of the Vs based LPI indicates that 11%, 48%, and 62% of areas of Zone 1, 2, and 3, respectively, show surface manifestation of liquefaction for an earthquake of moment magnitude, Mw 7.5 with a peak horizontal ground acceleration of 0.15 g.

Reviewing the progress of reconstruction five years after the 2015 Gorkha earthquake, Nepal

ABSTRACT An earthquake of moment magnitude (M w) 7.8, the largest in the last 80 years, struck central Nepal on April 25, 2015. Named the Gorkha earthquake, it wreaked havoc on the country’s central region, affecting 32 of 77 districts. The earthquake impacted nearly a million private houses, thousands of educational infrastructures, hundreds of health facilities, myriad cultural heritages and many other infrastructures. The National Reconstruction Authority (NRA) was established to lead the post-earthquake recovery and reconstruction and complete it within five years. This paper presents details of the earthquake’s effects, the early response and the status of the post-earthquake reconstruction progress five years after the earthquake. Official reports from Nepalese government institutions, national and international authorities, government databases and research papers on the Gorkha earthquake were reviewed. The numbers of various infrastructures reconstructed and under construction each year after the earthquake and the reconstruction processes adopted are presented. The results show that 67% of private houses, 74% of educational institutions and 58% of health facilities were reconstructed in the five years.

Investigating Stress Transfer Between the Tuz Gölü Fault Zone and Hasan Dağ Volcano (Turkey)

Faulting, magmatism and volcanism are intrinsically linked by plate tectonics. Fault slip imparts stress changes to the surrounding crust and other faults and fractures. Volcano-tectonic hazard assessment in areas with long recurrence intervals of volcanic and tectonic activity requires an assessment of current stress levels. Here we investigate stress transfer between the Akhisar-Kiliç fault segment (AKFS) of the seismically active Tuz Gölü fault zone in the Central Anatolian Volcanic Province and the active Hasan Dağ volcanic complex. Current stress accumulation by protracted gradual slip on the AKFS since its most recent rupture (5.45 ka±0.16 BP) is quantified using the Coulomb Failure Stress change (ΔCFS). We calculate currently accrued ΔCFS magnitudes of between 2.5±0.2 and 15±0.5 MPa on the fault plane for published lower and upper-bound estimates of right-lateral slip rates, respectively. These changes are sufficient to promote failure of the segment. The M5.1 September 20, 2020 earthquake SW of Hasan Dağ occurred in a volume predicted by this study to have undergone fault unclamping by gradual slip along the AKFS. We also show that gradual slip of the AKFS contributes to the progressive unclamping of fractures and transtensional opening of potential magma pathways oriented perpendicularly to the AKFS both above and below Hasan Dağ’s magma reservoir, while pathways oriented parallel to the AKFS are being clamped. Earthquake moment magnitudes of between Mw5.94 and Mw6.76 due to hypothetical partial or complete rupture of the segment exacerbate these trends. The spatial pattern of Coulomb failure stress changes on Hasan Dağ’s magma reservoir is predominantly controlled by the location of rupture relative to the reservoir with the magnitude of the earthquake playing a subordinate role. We explore implications of our findings for the assessment of interconnected seismo-volcanic hazards and associated risks.

Phenological and seismological impacts on airborne pollen types: A case study of Olea pollen in the Region of Murcia, Mediterranean Spanish climate

The rationale of this paper was to investigate whether earthquakes impact airborne pollen concentrations, considering some meteorological parameters. Atmospheric pollen concentrations in the Region of Murcia Aerobiological Network (Spain) were studied in relation to the occurrence of earthquakes of moment magnitude (up to Mw = 5.1) and intensity (intensity up to grade VII on the European Macroseismic Scale). In this study, a decade (2010–2019) was considered across the cities of the network. Earthquakes were detected in 12 out of 1535 days in the Olea Main Pollen Season in Cartagena, 49 out of 1481 days in the Olea Main Pollen Season in Lorca, and 39 out of 1441 days in the Olea Main Pollen Season in Murcia. The Olea pollen grains in this network were attributed to the species Olea europaea, i.e., the olive tree, a taxon that appears widely in the Mediterranean basin, in both cultivated and wild subspecies. Differences between the Olea concentration on days with and without earthquakes were only found in Lorca (Kruskal-Wallis: p-value = 0.026). The low frequency and intensity of the earthquakes explained these results. The most catastrophic earthquake felt in Lorca on May 11th, 2011 (IVII, Mw = 5.1, 9 casualties) did not result in clear variations in pollen concentrations, while meteorology (e.g., African Dust Outbreak) might have conditioned these pollen concentrations. The research should be broadened to other active seismological areas to reinforce the hypothesis of seismological impact on airborne pollen concentrations.

Landslides triggered by the 2018 Mw 7.5 Palu supershear earthquake in Indonesia

On September 28th, 2018, a supershear earthquake of moment magnitude (Mw) 7.5 struck the Palu area in central Sulawesi, Indonesia. To gain insight into landslides triggered by the Palu earthquake, a detailed landslide interpretation project was carried out in the meizoseismal area. To establish a co-seismic landslide inventory, we collected high-resolution images, including Worldview pre- and post- earthquake images, Sentinel pre- and post- earthquake images and Google Earth pre- and post- earthquake images. The results show that the Palu event triggered at least 7063 co-seismic landslides, including 8 flowslides. The total landslide area is 29.7 km2, with the highest density being 96 landslides/km2. The rock type (Kambuno granite) is a dominant factor influencing the landslide distribution; the average landslide H/L (H is the fall height and L is the horizontal length of an entire landslide) is 0.56. The flowslides that occurred in the Palu Basin are seismic liquefaction-induced landslides that failed along very gentle slopes (generally, slopes that are <3°) and traveled hundreds to thousands of meters, and the average H/L was 0.021.

Seismicity Patterns Prior to the Thessaly (Mw6.3) Strong Earthquake on 3 March 2021 in Terms of Multiresolution Wavelets and Natural Time Analysis

On 3 March 2021, a strong, shallow earthquake of moment magnitude, Mw6.3, occurred in northern Thessaly (Central Greece). To investigate possible complex correlations in the evolution of seismicity in the broader area of Central Greece before the Mw6.3 event, we apply the methods of multiresolution wavelet analysis (MRWA) and natural time (NT) analysis. The description of seismicity evolution by critical parameters defined by NT analysis, integrated with the results of MRWA as the initiation point for the NT analysis, forms a new framework that may possibly lead to new universal principles that describe the generation processes of strong earthquakes. In the present work, we investigate this new framework in the seismicity prior to the Mw6.3 Thessaly earthquake. Initially, we apply MRWA to the interevent time series of the successive regional earthquakes in order to investigate the approach of the regional seismicity at critical stages and to define the starting point of the natural time domain. Then, we apply the NT analysis, showing that the regional seismicity approached criticality a few days before the occurrence of the Mw6.3 earthquake, when the κ1 natural time parameter reached the critical value of κ1 = 0.070.

Tsunami inundation maps for the northwest of Peninsular Malaysia and demarcation of affected electrical assets.

The massive destruction and loss caused by the 2004 Sumatra-Andaman tsunami were attributed to the lack of knowledge on tsunami and low regional detection and communication systems for early warning in that region. This study aimed to identify locations at risk of impending tsunami from Andaman Sea for the safety of community and proper development planning at the coastal areas by providing an updated and revised inundation maps. The last study on this area was conducted several years ago which open the possibility to new findings. Generated by tsunami simulation models, the maps illustrate the extent and level of inundation to which the coastal community and infrastructure would be subjected. As a result of coastal changes and availability of better topographic data, the existing inundation maps for the coastal areas of northwest Peninsular Malaysia at risk to impending tsunami from the Andaman Sea are revised. This paper documented the computational setup leading to the generation of the revised inundation maps. The tsunami simulation model TUNA was used to simulate the generation, propagation, and subsequent run-up and inundation of tsunamis triggered by earthquakes of moment magnitudes (Mw) 8.5, 9.0, and 9.25 along the Sunda Trench. From the simulations, it was found that at Mw 9.25, Balik Pulau, Pulau Pinang would be subjected to inundation of as far as 3.47km with 5.40-m-deep inundation at the highest section.

Social vulnerability to seismic-tsunami hazards in district Gwadar, Balochistan, Pakistan

Social vulnerability illuminates differences in human capacity to prepare for, respond to, and recover from disasters. It varies over space and time and among social groups, largely due to variations in socioeconomic and demographic features. The Makran Subduction Zone is one of the known active seismic sources that can generate devastating shaking and tsunami disasters in District Gwadar, Pakistan, such as a large earthquake of moment magnitude 8.1 in 1945. This study presents the first social vulnerability index study for District Gwadar in relation to imminent earthquake-tsunami hazards and shows how SoVI concepts and indicators are adopted. SoVI follows a place-based framework that was originally adopted in developing social vulnerability index for the USA. To assess social vulnerability to earthquakes and tsunamis in Gwadar, we evaluate a social vulnerability index at village level. Using a principal component analysis, 16 village-level indicators are condensed to five factors that explain 64.2% of the variance in the data. Although different factors contribute to the social vulnerability in each village, the overall results confirm the social and economic disparities among villages and reflect differential vulnerability to natural hazards at local to regional scales. Finally, a map of social vulnerability index is compared with seismic-tsunami hazard maps to identify the communities living in risky zones. The approaches and results presented in this study will help emergency managers to identify community sub-groups that are more susceptible to disaster risks and to develop effective risk reduction strategies that are tailored to local conditions.

Inversion for the static friction coefficient of seismogenic faults: Application to induced seismicity of the Basel Enhanced Geothermal System, Switzerland

The static coefficient of friction describes the strength of faults and is considered to vary in nature between typical laboratory values measured on a large variety of rocks (0.6-0.85) and very low values for fault rocks containing talc, chlorite and kaolinite (<0.3). The effective frictional strength of a seismically active fault is the result of a combination of frictional properties of the fault rocks and the prevailing pore fluid pressures, which can reach supra-hydrostatic values permitting unfavourably oriented faults to slip. Here, we present an iterative inversion procedure to obtain the average static friction coefficient of a population of seismic faults, provided that stress tensor, geometry of faults and fluid pressures are adequately constrained. The application to a dataset of 48 seismically activated faults (earthquake moment magnitude, MW≤3.0) by fluid injection in crystalline basement in the Basel Enhanced Geothermal System (Switzerland) yields an average coefficient of friction of 0.66±0.11. The inversion results, which are well constrained by high-quality focal mechanisms and robust above-hydrostatic fluid pressure estimations, have uncertainty primarily dependent on the principal stress and fault plane orientations. Values of the friction coefficient in crystalline rocks in the continental basement are compatible with experimentally determined values but require supra-hydrostatic fluid pressures. A comprehensive characterization of all the frictional parameters should be required to better assess rheological and stability fault models, both for natural and human induced earthquakes.