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Evaluating the seismic vulnerability of facades of historic masonry buildings is essential not only for their significant historical and heritage value, but also to evaluate the safety of this type of construction. This work applies a simplified methodology to assess the seismic vulnerability of the facade of masonry buildings in the historic center of Morelia, Michoacán, México. The historic center of Morelia was declared a World Cultural Heritage Site by UNESCO in 1991. On the facades, there is ornamentation with sculptural and vegetal decorative elements. The methodology involved conducting visual inspections to identify the location, type of structure, construction materials, doors, windows, balconies, cornices, ironwork, pediments, niches, and sculptures, among other characteristic elements of colonial architecture. The seismic demands were determined specifically for the city's historic center based on a recent seismic hazard assessment of Morelia. Based on the methodology and the compiled database, characterized vulnerability indices were defined for the different damage scenarios that buildings may present. Results indicate that earthquakes with intensities greater than VIII on the Modified Mercalli scale risk collapsing heritage masonry buildings' facades. [ABSTRACT FROM AUTHOR]

The Central Apennine Fault System (CAFS) characterizes an active tectonic region of significant importance, witnessing numerous destructive seismic events over the last millennia. Although numerous studies have underscored the role of Coulomb stress transfer (CST) in initiating some of the most catastrophic earthquakes, investigations focusing on its specific influence within the CAFS are limited. This research delves into a thorough examination of the effects of CST on both historical and instrumental seismic events of significant magnitude associated with the CAFS. We selected nine seismic events for the CST investigation, dating from 1279 CE to present. Beyond analyzing the static stress transfer for each individual seismic event, the cumulative CST of recent instrumental earthquakes was also examined to provide a comprehensive overview of the current stress scenario. Leveraging an innovative approach, faults were modeled adopting a variable strike three‐dimensional elliptical shape, ensuring enhanced calculation accuracy. Significant findings emerge from the analysis: CST has played a pivotal role in either activating or inhibiting the faults of the CAFS over the centuries. Several examined instances showcase fault reactivation following increased transferred stress within relatively short time frames, while others highlight the inhibitory effect of stress shadows. Examining the differences in seismic moment release across three seismicity windows (the first one between 1300 and 1400, the second around 1700, and the last one from 1979 to 2016) reveals distinct periods of higher seismicity in the past millennium. The latter shows the lowest cumulative seismic moment, suggesting a potential seismic gap equivalent to a Mw 6.67 earthquake. Deepening our understanding of CST illuminates the role of fault interactions in past earthquake occurrences, offering valuable insights into forecasting potential future seismic sequences. This awareness is vital in crafting targeted seismic risk mitigation strategies, thereby safeguarding local communities from the profound consequences of earthquakes. Plain Language Summary: Over the last millennium, the Central Apennine Fault System (CAFS) in Italy generated devastating earthquakes. This research delves into how Coulomb stress transfer (CST) has influenced the occurrence of these earthquakes, either activating or inhibiting faults as demonstrated by numerous CST studies on major earthquakes worldwide (e.g., the San Andreas Fault, Japanese megathrusts, North Anatolian Fault). By analyzing nine seismic events from 1279 CE to the present, we found that the static stress transferred among faults played a pivotal role. Utilizing an innovative 3D model to represent the faults, we gained a better understanding of how they interact with each other and how stress is distributed in the surrounding crust. Some earthquakes increased stress on certain faults, leading to their reactivation within relatively short periods, while others created "stress shadows" that calmed seismic activity. This knowledge not only helps us understand past earthquakes, but also which faults are currently more prone to causing earthquakes, thus improving seismic risk mitigation strategies to protect local communities. This study sheds light on the complex interactions among faults in the central Apennines, offering valuable insights that can assist in planning and preventing future seismic disasters. Key Points: Historical and instrumental seismicity: analysis of the seismic events in the Central Apennine Fault System (CAFS) over the past millenniumThe Coulomb stress transfer (CST) analysis demonstrates the key role of static stress transfer in fault activation and inhibition in central ItalyInnovative 3D model enhances CST accuracy in CAFS, revealing complex fault interactions and stress dynamics [ABSTRACT FROM AUTHOR]

Due to continued continental convergence of Indian–Eurasian plates, the Himalayan region witnessed several high-magnitude earthquakes and is prone to major seismic events in future as well. Most of the countries with seismically active faults examine paleo seismic data in site specific as well as regional seismic hazard analyses. Hence, it is of great concern to find evidence for prehistoric earthquakes following the morphotectonic route and establish the recurrence intervals of potential earthquakes by characterising and dating large prehistoric events. The present study discusses the paleo seismicity and induced deformational features in the Trans-Yamuna region of the outer Northwest Himalaya by interpreting soft sediment deformation and paleo-liquefaction features. We targeted two sites along the Trans-Yamuna active fault system, which are located in the Sirmurital and Bharli villages; both of these locations are close to Doon Valley along the Main Boundary Thrust. Temporal distribution of paleo-liquefaction features evident major seismic events likely to occur during 16th and 19th centuries, which clearly indicates reactivation of faults in this hinterland region that could experience major rupture during the recurrence of large magnitude earthquake and therefore, constructional activities are a matter of great concern to design structures accordingly. [ABSTRACT FROM AUTHOR]

Abstract Accurately imaging seismogenic structures is crucial for seismic hazard assessment. This is especially important around the deformation front (DF) region off SW Taiwan, where seismic potential is high but the fault structure and seismic activity are still poorly understood. Here, we present a comprehensive delineation of seismogenic structures along the onshore and offshore DF of SW Taiwan, utilizing hypocenter relocations and first-motion focal mechanism solutions from January 1991 to March 2019. Five distinctive seismogenic structures are delineated. Particularly, the energetic seismic activity initialled after the 2017 Mw5.3 Tainan earthquake and migrated northeastward along the western side of the DF. The offshore trace of the DF could serve as a boundary delimiting the seismic activity driven by the flexural stress of the subducted Eurasia Plate to the west of the DF. This observation could constrain the magnitude estimation of future earthquakes offshore SW Taiwan. Meanwhile, the areas with higher seismic moment release are located near the DF rather than known faults, indicating that the DF may dominate the seismic moment release. However, further study is warranted into the intricate relationship among seismic strain variation, the structure of DF, and seismic activity to further understand the seismic potential. Our first-motion focal mechanism solutions show that several earthquakes in SW Taiwan were characterized by P-axis orientations parallel to the strike of the Taiwan orogeny. Those events are preferably explained by the lateral compression induced by the ongoing collision between the Eurasia and Philippine Sea plates.

Accurately imaging seismogenic structures is crucial for seismic hazard assessment. This is especially important around the deformation front (DF) region off SW Taiwan, where seismic potential is high but the fault structure and seismic activity are still poorly understood. Here, we present a comprehensive delineation of seismogenic structures along the onshore and offshore DF of SW Taiwan, utilizing hypocenter relocations and first-motion focal mechanism solutions from January 1991 to March 2019. Five distinctive seismogenic structures are delineated. Particularly, the energetic seismic activity initialled after the 2017 Mw5.3 Tainan earthquake and migrated northeastward along the western side of the DF. The offshore trace of the DF could serve as a boundary delimiting the seismic activity driven by the flexural stress of the subducted Eurasia Plate to the west of the DF. This observation could constrain the magnitude estimation of future earthquakes offshore SW Taiwan. Meanwhile, the areas with higher seismic moment release are located near the DF rather than known faults, indicating that the DF may dominate the seismic moment release. However, further study is warranted into the intricate relationship among seismic strain variation, the structure of DF, and seismic activity to further understand the seismic potential. Our first-motion focal mechanism solutions show that several earthquakes in SW Taiwan were characterized by P-axis orientations parallel to the strike of the Taiwan orogeny. Those events are preferably explained by the lateral compression induced by the ongoing collision between the Eurasia and Philippine Sea plates. Key Points: The deformation front has high seismic potential but seismogenic structure remains unclear. The deformation front confined seismic activity and released relatively large seismic moments. The role of the deformation front must be considered in seismic hazard assessment. [ABSTRACT FROM AUTHOR]

This study presents a comprehensive seismic hazard assessment for Büyükçekmece, a district in Istanbul, Turkey, situated near the seismically active North Anatolian Fault (NAF). The study utilizes stochastic ground motion simulations with the validated EXSIM algorithm to understand the potential impact of medium to large-magnitude earthquakes (ranging from MW 6.3 to 7.42) on this vulnerable community. The research employs a site-specific approach, considering unique amplification factors for each location. By conducting 50 scenario-based simulations, the study assesses the seismic hazard, highlighting the importance of comprehending variations in ground motion, even when they are small, for a more precise hazard assessment. Furthermore, this study addresses the critical issue of uncertainty, particularly concerning stress parameters and hypocenter locations. The researchers demonstrate that variability in these factors can introduce substantial uncertainty in ground motion predictions. The study provides insights into the range of potential ground motion outcomes through probabilistic assessments involving multiple scenarios and stress drop values. Notably, the results indicate that ground motion levels vary with earthquake magnitudes and underscore the significance of accounting for this variability. This research emphasizes the seismic vulnerability of Büyükçekmece and the importance of accurate ground motion simulations, offering valuable insights for earthquake preparedness and mitigation efforts in the region. [ABSTRACT FROM AUTHOR]

This study provided a comprehensive understanding of the source process of the 1819 M 7.7 Kachchh Indian earthquake using physics‐based dynamic rupture modeling and strong ground motion simulations. We successfully simulated the spontaneous dynamic rupture along a curved non‐planar fault using the 3‐D curved‐grid finite‐difference method (CGFDM). The estimated earthquake magnitude is around 7.6, consistent with previous estimations. Our simulations accurately replicated macroscopic rupture patterns and surface deformation, showing agreement with observed data along the Allah Bund fault (ABF) with a maximum displacement ∼5.5 m at the Earth's surface. The maximum modeled coseismic slip on the fault was approximately 7.5 m. Notably, the ABF exhibited characteristics of a weak barrier (leaky barrier) at the bending part, allowing the rupture to propagate further. Despite limitations in surface deformation calculations, the modeled values aligned with the trend of surface fault slip, with a slight deviation in the epicenter toward the east compared to earlier studies. We observed a homogeneous principal stress oriented N25°E, consistent with the present day Indian plate motion. The estimated horizontal peak ground velocities (PGVh) and the maximum value of Intensity X+ aligns well with observations. Furthermore, conducting thorough case studies on significant earthquakes and potential seismic scenarios in stable continental regions is crucial. Such studies play a vital role in validating and improving dynamic rupture models. When combined with statistical methods, this research holds great promise for advancing seismic hazard assessments, earthquake engineering, and strategies for disaster management. Plain Language Summary: This paper is centered around the simulation of the dynamic rupture of the 1819 M 7.7 Kachchh earthquake in India. We have successfully replicated the earthquake's behavior using a three‐dimensional simulation method. The study's results demonstrate the significant influence of the local tectonic setting and non‐planar fault structure on earthquake generation and rupture progression. Although slight discrepancies exist between the simulation results and actual observations, the simulations capture significant trends and reproduce macroscopic rupture patterns. The estimated magnitude of the earthquake aligns well with previous studies. The study highlights the role of fault bending and its impact on surface deformation, contributing to a better understanding of seismic hazards and providing insights for seismic hazard assessments and earthquake source characterization. This work is valuable for comprehending earthquake sources, particularly from earthquake perspectives in the SCR region and other areas. Key Points: Dynamic rupture simulations of the 1819 Kachchh M 7.7 earthquake replicate co‐seismic fault slip, enhance our knowledge of the earthquake sourceWeak barrier characteristics observed at the bending part of the fault enabled further rupturing, influenced by SH and the nucleation pointContributes to understanding earthquake hazards, enhancing seismic assessment, engineering, and disaster management strategies [ABSTRACT FROM AUTHOR]

Incorporating local site effects into seismic hazard analysis, especially for deep soil sites, is crucial. This study describes probabilistic seismic hazard analysis (PSHA) incorporating site effects for a deep soil site in Pakistan. Bedrock hazard is assessed in FRISK88M using a rigorous logic tree. Equivalent linear site response analysis (SRA) is performed in STRATA and captured the soil variability properties via Monte Carlo simulations. We proposed a hybrid approach in this study which utilizes the outcomes of Random Vibration Theory (RVT) and multiple Time Histories (TH) approach to assess the site-specific amplifications. Incorporating site amplifications transforms rock ground motion models into site-specific then we performed soil PSHA in FRISK88M. The analysis revealed that RVT overpredicts (3–17%) while TH underpredict (1–6%) hazard as compared to the hybrid approach at all return periods. The hybrid approach proposed in this study provides an innovative, effective and reliable estimates. [ABSTRACT FROM AUTHOR]

Ground motion prediction equations (GMPEs) play a key role in seismic hazard assessment (SHA). Considering the seismo-tectonic, geophysical, and geotectonic characteristics of a target region, all the GMPEs may not be suitable in predicting the observed ground motion effectively. With a fairly large number of published GMPEs, the selection and ranking of suitable GMPEs for the design of logic trees in SHA for a particular target region have become a necessity of late. This paper presents a detailed quantitative evaluation of performance of 16 GMPEs against recorded ground motion data in two target regions, characterized by distinct seismo-tectonic, geophysical, and geotectonical nature. The dataset comprises 465 three-component spectral accelerograms corresponding to 122 earthquake events. The suitability of a GMPE is tested by two widely accepted data-driven statistical methods, namely, likelihood (LH) and log-likelihood (LLH) method. Different suites of GMPEs are shown suitable for different periods of interest. The results will be useful to scientists and engineers for microzonation and estimation of seismic design parameters for the design of earthquake-resistant structures in these regions. [ABSTRACT FROM AUTHOR]

Amravati has been designated as the prospective youthful capital of the Indian state of Andhra Pradesh, nestled in the geologically stable southern peninsular region. Following the impactful Bhuj earthquake on 26 January 2001 measuring 7.6 Mw on the Richter scale, which resulted in substantial destruction, there has been a heightened curiosity in seismic microzonation research throughout India, encompassing Andhra Pradesh. This study is specifically cantered on evaluating the seismic activity and microzonation of Amaravati, employing a multifaceted seismic hazard assessment methodology. The exploration encompasses three distinct phases. Firstly, site characterization involves regional geological, geomorphological, and geotechnical analysis. Secondly, local site effects and resonance frequencies are assessed using DEEPSOIL software, providing amplification factors through a one-dimensional linear approach. In the third stage, liquefaction hazard analysis and liquefaction potential index are evaluated using the simplified procedure suggested by Seed and Idriss. Microzonation results are presented through nine themes: which includes geological mapping, geomorphology, geotechnical observations, shear wave velocity distribution, seismotectonic set-up, rock depth, amplification, peak ground acceleration, and liquefaction susceptibility mapping. The thematic mapping divides the Amaravati region into three zones: susceptible, partially susceptible, and not susceptible. This comprehensive study enhances understanding of seismic hazards in the Amaravati capital region, aiding in informed urban planning and disaster mitigation. [ABSTRACT FROM AUTHOR]

When new seismic hazard estimates are published it is natural to compare them to existing results for the same location. This type of comparison routinely indicates differences amongst hazard estimates obtained with the various models. The question that then arises is whether these differences are scientifically significant, given the large epistemic uncertainties inherent in all seismic hazard estimates, or practically important, given the use of hazard models as inputs to risk and engineering calculations. A difference that exceeds a given threshold could mean that building codes may need updating, risk models for insurance purposes may need to be revised, or emergency management procedures revisited. In the current literature there is little guidance on what constitutes a significant or important difference, which can lead to lengthy discussions amongst hazard modellers, end users and stakeholders. This study reviews proposals in the literature on this topic and examines how applicable these proposals are, using, for illustration purposes, several sites and various seismic hazard models for each site, including the two European Seismic Hazard Models of 2013 and 2020. The implications of differences in hazard for risk and engineering purposes are also examined to understand how important such differences are for potential end users of seismic hazard models. Based on this, we discuss the relevance of such methods to determine the scientific significance and practical importance of differences between seismic hazard estimates and identify some open questions. We conclude that there is no universal criterion for assessing differences between seismic hazard results and that the recommended approach depends on the context. Finally, we highlight where additional work is required on this topic and that we encourage further discussion of this topic. [ABSTRACT FROM AUTHOR]

The Sichuan–Yunnan area is one of the most seismically active regions in China. As ground-motion models form a key component of seismic hazard analysis, it is important to select (or develop) appropriate models for this area. The increasing number of digital ground-motion records of earthquakes in this area has allowed the development of local ground motion prediction equations (GMPEs). This study compares and, later, recommends appropriate GMPEs for the Sichuan–Yunnan area. We first evaluate the inherent quality of local GMPEs, with respect to their underlying datasets, the variables used and their functional forms, to determine a set of candidate GMPEs. Then we investigate how well the predictions from the GMPEs match observations computed from strong-motion records of recent earthquakes in this area. The fit between predictions and observations varies significantly amongst the GMPEs. The results suggest that some recent local GMPEs would lead to biased ground-motion estimates due to limitations of their underlying datasets and functional forms. Based on both evaluations of inherent quality and compatibility with observations, only one local GMPE is recommended. A comparison of the predictions from three widely-used non-local GMPEs indicates that ground motions in the Sichuan–Yunnan area appear more variable than those in other regions but that predictions from these non-local GMPEs are generally unbiased. We recommend use of a mixture of robust local and non-local GMPEs within seismic hazard analyses to capture the epistemic uncertainty in ground-motion prediction for this area. [ABSTRACT FROM AUTHOR]

Abstract This study provided a comprehensive understanding of the source process of the 1819 M 7.7 Kachchh Indian earthquake using physics‐based dynamic rupture modeling and strong ground motion simulations. We successfully simulated the spontaneous dynamic rupture along a curved non‐planar fault using the 3‐D curved‐grid finite‐difference method (CGFDM). The estimated earthquake magnitude is around 7.6, consistent with previous estimations. Our simulations accurately replicated macroscopic rupture patterns and surface deformation, showing agreement with observed data along the Allah Bund fault (ABF) with a maximum displacement ∼5.5 m at the Earth's surface. The maximum modeled coseismic slip on the fault was approximately 7.5 m. Notably, the ABF exhibited characteristics of a weak barrier (leaky barrier) at the bending part, allowing the rupture to propagate further. Despite limitations in surface deformation calculations, the modeled values aligned with the trend of surface fault slip, with a slight deviation in the epicenter toward the east compared to earlier studies. We observed a homogeneous principal stress oriented N25°E, consistent with the present day Indian plate motion. The estimated horizontal peak ground velocities (PGVh) and the maximum value of Intensity X+ aligns well with observations. Furthermore, conducting thorough case studies on significant earthquakes and potential seismic scenarios in stable continental regions is crucial. Such studies play a vital role in validating and improving dynamic rupture models. When combined with statistical methods, this research holds great promise for advancing seismic hazard assessments, earthquake engineering, and strategies for disaster management.

This study emphasizes the role of active faults as seismogenic sources in probabilistic seismic hazard assessments (PSHA) in the United Arab Emirates (UAE). An extensive PSHA analysis has been carried out in this study, which incorporates faults alongside area seismic sources within a logic tree-oriented framework. Seismicity is evaluated in terms of spectral acceleration (SA) and Peak ground acceleration (PGA) for return periods of 2,475, 975, and 475 years at 5 % damping. The results are compared with seismic hazard projections derived from previous PSHA studies that utilized only area sources. A key observation is the pronounced impact of the Dibba and Oman range frontal faults on the UAE's northeastern region due to the proximity of the faults. This contributes to higher seismic hazard in this region, with some return periods showing greater hazard levels than those documented in earlier studies. In order to aid seismic hazard design in the UAE, contour maps depicting the SAs at 0.2 and 1.0 s, along with PGA, are developed. The analysis reveals that the highest seismic hazard is predicted along the northeastern borders of the UAE, particularly the coastal area of Ras-Al Khaimah, with a PGA of 0.22 g for a return period of 2,475 years.

Evaluating the seismic vulnerability of facades of historic masonry buildings is essential not only for their significant historical and heritage value, but also to evaluate the safety of this type of construction. This work applies a simplified methodology to assess the seismic vulnerability of the facade of masonry buildings in the historic center of Morelia, Michoacán, México. The historic center of Morelia was declared a World Cultural Heritage Site by UNESCO in 1991. On the facades, there is ornamentation with sculptural and vegetal decorative elements. The methodology involved conducting visual inspections to identify the location, type of structure, construction materials, doors, windows, balconies, cornices, ironwork, pediments, niches, and sculptures, among other characteristic elements of colonial architecture. The seismic demands were determined specifically for the city’s historic center based on a recent seismic hazard assessment of Morelia. Based on the methodology and the compiled database, characterized vulnerability indices were defined for the different damage scenarios that buildings may present. Results indicate that earthquakes with intensities greater than VIII on the Modified Mercalli scale risk collapsing heritage masonry buildings’ facades.

Simulated ground motions have the potential to advance seismic hazard assessments and structural response analyses, particularly for conditions with limited recorded ground motions such as large magnitude earthquakes at short source-to-site distances. However, rigorous validation of simulated ground motions is needed for hazard analysts, practicing engineers, or regulatory bodies to be confident in their use. A decade ago, validation exercises were mainly limited to comparisons of simulated-to-observed waveforms and median values of spectral accelerations for selected earthquakes. The Southern California Earthquake Center (SCEC) Ground Motion Simulation Validation (GMSV) group was formed to increase coordination between simulation modelers and research engineers with the aim of devising and applying more effective methods for simulation validation. Here, we summarize what has been learned in over a decade of GMSV activities, principally reflecting the views of the SCEC research community but also extending our findings and suggestions for a path forward to broader United States and worldwide simulation validation efforts. We categorize different validation methods according to their approach and the metrics considered. Two general approaches are to compare validation metrics from simulations to those from historical records or to those from semi-empirical models. Validation metrics are categorized into ground motion characteristics and structural responses. We discuss example validation studies that have been impactful in the past decade and suggest future research directions. Key lessons learned are that validation is application-specific, our outreach and dissemination need improvement, and much validation-related research remains unexplored. [ABSTRACT FROM AUTHOR]

Deep-learning (DL) pickers have demonstrated superior performance in seismic phase picking compared to traditional pickers. DL pickers are extremely effective in processing large amounts of seismic data. Nevertheless, they encounter challenges when handling seismograms from different tectonic environments or source types, and even a slight change in the input waveform can considerably affect their consistency. Here, we fine-tuned a self-trained deep neural network picker using a small amount of local seismic data (26,875 three-component seismograms) recorded by regional seismic networks in South Korea. The self-trained model was developed using publicly available waveform datasets, comprising over two million three-component seismograms. The results revealed that the Korean-fine-tuned phase picker (KFpicker) effectively enhanced picking quality, even when applied to data that were not used during the fine-tuning process. When compared to the performance of the pre-trained model, this improvement was consistently observed regardless of variations in the positions of seismic phases in the input waveform, Furthermore, when the KFpicker predicted the phases for overlapping input windows and used the median value of probabilities as a threshold for phase detection, a considerable decrease was observed in the number of false picks. These findings indicate that fine-tuning a deep neural network using a small amount of local data can improve earthquake detection in the region of interest, while careful data augmentation can enhance the robustness of DL pickers against variations in the input window. The application of KFpicker to the 2016 Gyeongju earthquake sequence yielded approximately twice as many earthquakes compared to previous studies. Consequently, detailed and instantaneous statistical parameters of seismicity can be evaluated, making it possible to assess seismic hazard during an earthquake sequence. [ABSTRACT FROM AUTHOR]

If coseismic deformation of the earthquake region can be obtained in a short time, it is important for timely evaluate the disaster and cooperate with the development of earthquake relief work. Space geodesy technology has the advantages of high monitoring accuracy and high spatial resolution, and has been widely used in seismic deformation monitoring related fields. The coseismic deformation obtained by processing space geodetic data can intuitively show the surface deformation caused by the earthquake and provide a reference for judging the disaster situation. However due to the lag of data acquisition, it is often impossible to provide coseismic deformation map in a short time after the earthquake. In this paper, using the near real-time focal mechanism solutions of the USGS NEIC, seismic elastic dislocation model and seismic empirical formula, a seismic deformation simulation application based on Android smartphone (namely Codefmap APP) is developed based on Java and Python language. The program has the functions of earthquake catalog query at any time in the world, actively obtaining USGS NEIC source parameters, displaying epicenter position and automatically calculating coseismic deformation. For important events, the deformation simulation results can be given within one day, especially for blind earthquakes. It can provide a reference basis for determining potentially dangerous areas and early earthquake relief to a certain extent.

Greece is located in one of the most seismically active regions in Europe. Many seismic hazard studies have been performed for various sites around Greece, at a regional or local scale. However, the latest national seismic hazard map, currently used for the seismic design of buildings and infrastructure, was published in 2000 and has not been updated since then. In light of recent advances in seismic source and ground motion modeling, the present study focuses on a comparative Probabilistic Seismic Hazard Assessment (PSHA) for the region of East Macedonia and Thrace (EMTH), located in Northern Greece. Various seismic source models are implemented and compared against an updated earthquake catalog to form the necessary source model logic tree. The ground motion logic tree is composed of Ground Motion Prediction Equations (GMPEs), which have been proven suitable for implementation in Greece. PSHA results are presented for the most important cities of East Macedonia and Thrace in a comparative way, which highlights the variability of the seismic hazard among the various seismic source models. An updated seismic hazard map of the study area is proposed, and a comparative disaggregation analysis is performed to estimate the earthquake scenarios with the largest contribution to the seismic hazard.

The micro-seismic hazard assessment (micro-SHA) of the Bhuj city (highest seismic zone V) has been accomplished considering seismotectonic as well as shallow subsurface modeling through geophysical (multi-channel analysis of surface waves (MASW) survey at 19 sites) and geotechnical parameters from 28 boreholes distributed in the entire Bhuj city. The average shear wave velocity through the MASW survey at 30 m depth (VS30) is estimated in the range of 400–915 m/s (NEHRP C-type and B-type soil classes). Seismotectonically justified a total of 54 scenario-earthquakes (SEQs) along all major faults have been considered to evaluate the strong ground motion at generic soil level having a shear wave velocity of 760 m/s and depth of 12–28 m. The surface level strong motion (SM) has been estimated through ground response analysis preparing soil models along all boreholes. The PGA at the surface in Bhuj city has been estimated in the range of 528 cm/s2 to 1020 cm/s2; highest in the central-western part of the Bhuj city where clay with high plasticity is present. The mean-spectral acceleration over the study area for 0.2 s (corresponding to 1-2 story), 0.55 s (4-5 story), 1sec (high rise) and 1.25 s period (large structures) are prepared at the surface from all scenario earthquakes. The amplification of SM in the Bhuj city is computed in the range of 1.7–3.7.

Deep-learning (DL) pickers have demonstrated superior performance in seismic phase picking compared to traditional pickers. DL pickers are extremely effective in processing large amounts of seismic data. Nevertheless, they encounter challenges when handling seismograms from different tectonic environments or source types, and even a slight change in the input waveform can considerably affect their consistency. Here, we fine-tuned a self-trained deep neural network picker using a small amount of local seismic data (26,875 three-component seismograms) recorded by regional seismic networks in South Korea. The self-trained model was developed using publicly available waveform datasets, comprising over two million three-component seismograms. The results revealed that the Korean-fine-tuned phase picker (KFpicker) effectively enhanced picking quality, even when applied to data that were not used during the fine-tuning process. When compared to the performance of the pre-trained model, this improvement was consistently observed regardless of variations in the positions of seismic phases in the input waveform, Furthermore, when the KFpicker predicted the phases for overlapping input windows and used the median value of probabilities as a threshold for phase detection, a considerable decrease was observed in the number of false picks. These findings indicate that fine-tuning a deep neural network using a small amount of local data can improve earthquake detection in the region of interest, while careful data augmentation can enhance the robustness of DL pickers against variations in the input window. The application of KFpicker to the 2016 Gyeongju earthquake sequence yielded approximately twice as many earthquakes compared to previous studies. Consequently, detailed and instantaneous statistical parameters of seismicity can be evaluated, making it possible to assess seismic hazard during an earthquake sequence.

A modified version of a seismic risk assessment method is presented that generalises original risk analytical processes, constructs interrelationships among hazard variables in pre-assign weight-based formats, and establishes priorities to address potentially vulnerable dams. The concerned parameter values contained in each component are labelled based on adjusted grading standards, respecting the regional difference in hydraulic structure attributes and safety acceptability ranges. The cascade dams in Dadu River, China, are selected to test the applicability of the proposed method. We systematically investigate potential seismic hazards to demonstrate the implications of earthquake on dam safety. The results indicate that the adapted parameter ranges correspond with the physical aspects of the dams and potential social-economic consequences in seismic-prone regions. Correspondingly, the hazard recognition levels accommodate their local near-source earthquake conditions. Moreover, the investigation guides local emergency services with warnings of potential dam damages and ensuing floods when encountering critical earthquake shaking. [ABSTRACT FROM AUTHOR]

Despite recent international efforts toward a risk‐conscious approach to advancing seismic design, Japan, a country very prone to earthquakes, remains conservative regarding the consideration of risk‐based seismic hazards in developing seismic designs. This article attempts to interpret the reasons. First, the evolution of Japanese seismic design codes and specifications is introduced, noting that the design seismic loads have remained essentially the same since the revisions implemented in 1981. Second, Japanese efforts in providing and renewing seismic hazard maps are briefly introduced and discussed. The maps have been developed using the data recorded by Japanese strong motion networks. Some unique challenges in preparing seismic hazard maps for the territory of Japan are presented, in light of the observations of actual earthquakes in the past three decades. On many occasions, the damage disclosed in modern buildings remained limited even when the recorded ground motions significantly exceeded the design earthquake level. An inherent conservatism is embedded in the performance criteria imposed on structural systems and elements. Third, political‐legal and sociocultural aspects are discussed. Centralized operation is commonly exercised in Japan for post‐disaster relief efforts, and the general public also values "equality" for such support. The factors naturally encourage cautiousness for the revision of relevant seismic codes and specifications. [ABSTRACT FROM AUTHOR]

Probabilistic seismic hazard analysis (PSHA) has become a fundamental tool in assessing seismic hazards and for estimating seismic design and seismic safety evaluation of ground motions. This report describes a study to test and verify the numerical approaches and software used in PSHA on Semnan, one of the important cities of Iran country. The geological and seismological data are integrated into a probabilistic seismic hazard model for the region. Historical and instrumental earthquake data, geology, tectonics, fault activity, and seismic source models associated with seismic events are taken into account. A probabilistic approach within a logic-tree framework is used to calculate seismic hazard for Semnan. The results were also displayed in terms of uniform hazard spectra for rock sites for return periods of 100, 475 and 2475 years, which is deemed appropriate for structural design standards in the Iran building code. As the results of this study have been displayed on the map for different return periods and different natural periods, it can provide the basis for the preparation of new seismic risk maps. [ABSTRACT FROM AUTHOR]

The assessment of seismic risk and the prevention of earthquake occurrences during reservoir operation present significant challenges in terms of accurate determination. This study aims to address this issue by developing a numerical model. The primary objective is to estimate the vulnerability of different fault types to reservoir impoundment. This model integrates essential parameters such as fault dip and the relative orientation between the reservoir and potential earthquakes, and it is structured within a risk framework using polar coordinates. Through comprehensive computations, we evaluate the alterations in elastic stress and fluid pore pressure resulting from water impoundment. This is achieved by employing a fully coupled two-dimensional poroelastic approach. Furthermore, our model incorporates relevant seismic data to enhance its accuracy. The findings of our study underscore that the critical factor lies in the fault's precise positioning with respect to the reservoir. The risk associated with a fault is contingent upon both its location and its orientation, emphasizing the importance of these factors in determining hazardous zones. [ABSTRACT FROM AUTHOR]

Greece is located in one of the most seismically active regions in Europe. Many seismic hazard studies have been performed for various sites around Greece, at a regional or local scale. However, the latest national seismic hazard map, currently used for the seismic design of buildings and infrastructure, was published in 2000 and has not been updated since then. In light of recent advances in seismic source and ground motion modeling, the present study focuses on a comparative Probabilistic Seismic Hazard Assessment (PSHA) for the region of East Macedonia and Thrace (EMTH), located in Northern Greece. Various seismic source models are implemented and compared against an updated earthquake catalog to form the necessary source model logic tree. The ground motion logic tree is composed of Ground Motion Prediction Equations (GMPEs), which have been proven suitable for implementation in Greece. PSHA results are presented for the most important cities of East Macedonia and Thrace in a comparative way, which highlights the variability of the seismic hazard among the various seismic source models. An updated seismic hazard map of the study area is proposed, and a comparative disaggregation analysis is performed to estimate the earthquake scenarios with the largest contribution to the seismic hazard. [ABSTRACT FROM AUTHOR]

In this research work, we present the evolution of Coulomb failure stress (CFS) in the Sulaiman Lobe and its implications for seismic hazard assessment. The Chaman transform fault, ~1,000 km long, is the major active fault that marks the western boundary between Pakistan and Afghanistan on the Indian Plate. To date, few studies have been conducted to unveil the interactions among earthquakes and the implications of these interactions for seismic hazard assessment in the region. We thoroughly investigated the published and online catalog to construct a sequence of major earthquakes that occurred in this region during the past. The final earthquake sequence was composed of 15 earthquakes of Mw ≥ 6.0, beginning with the 1888 earthquake. We used the stress-triggering theory to numerically simulate the evolution of CFS caused by these earthquakes. The numerical results revealed that 8 out of 15 earthquakes were triggered by the preceding earthquakes. The earthquakes in 1908, 1910, 1935, 1966, and 1997 were rather independent earthquakes in this sequence. Although the epicenters of the 1975a and 1975b earthquakes were in the stress shadow zone, the partial rupture segments of both these earthquakes were in high-CFS regions. The CFS induced by the 1935 earthquake was notable, as it later triggered the 2008 doublet. Moreover, our results revealed that the northern segment of the Chaman Fault, the southern segment of the Ghazaband Fault, and the northwestern segment of the Urghargai Fault demonstrated a high change in CFS that could trigger seismicity in these regions. The necessary arrangements must therefore be made to mitigate any possible seismic hazards in the region.

Current earthquake catalogs provide high‐precision depth values that contain valuable information. Thus, we extend the spatiotemporal Epidemic Type Aftershock Sequence model to 3D by considering hypocentral instead of epicentral distances. To explore the most appropriate parametric form of the spatial kernel, we first examine different triggering functions for the depth difference of the aftershock‐mainshock pairs identified by the Nearest‐Neighbor method, showing that a magnitude‐dependent power‐law kernel fits best the earthquakes data in Southern California. Therefore, we incorporate the corresponding kernel into the 3D‐ETAS model with space‐dependent background activity, where we additionally allow for depth‐dependent aftershock productivity. The application to Southern California shows that the model fits the data well. We also find that the aftershock productivity strongly depends on depth, similar to the seismic moment released by the mainshocks, which may be related to depth‐dependent seismic coupling. Plain Language Summary: Seismicity models are an important backbone of seismic hazard analysis. So far, standard seismicity models are mostly restricted to epicenter information, neglecting earthquake depths because of historically large uncertainties. However, earthquake catalogs with high‐precision depth values are nowadays available, enabling us to develop new statistical models, including hypocentral information. We first show that a power‐law kernel best describes Southern California's hypocenter distribution of aftershocks. Thus, we incorporate it in our new seismicity model, which also considers a depth‐varying background activity and aftershock potential. Our model consistently describes the observed earthquake occurrence and reveals a significant depth‐dependent variation of the aftershock potential in Southern California. Key Points: We extend 2D Epidemic Type Aftershock Sequence (ETAS) model to 3D to make use of high‐precision hypocenter informationMagnitude‐dependent spatial power‐law kernels with hypocentral distances best fit observed dataOur 3D‐ETAS model application reveals depth‐dependent aftershock productivity in Southern California [ABSTRACT FROM AUTHOR]

The Húsavík‐Flatey Fault Zone (HFFZ) is the largest strike‐slip fault in Iceland and poses a high seismic risk to coastal communities. To investigate physics‐based constraints on earthquake hazards, we construct three fault system models of varying geometric complexity and model 79 3‐D multi‐fault dynamic rupture scenarios in the HFFZ. By assuming a simple regional prestress and varying hypocenter locations, we analyze the rupture dynamics, fault interactions, and the associated ground motions up to 2.5 Hz. All models account for regional seismotectonics, topo‐bathymetry, 3‐D subsurface velocity, viscoelastic attenuation, and off‐fault plasticity, and we explore the effect of fault roughness. The rupture scenarios obey earthquake scaling relations and predict magnitudes comparable to those of historical events. We show how fault system geometry and segmentation, hypocenter location, and prestress can affect the potential for rupture cascading, leading to varying slip distributions across different portions of the fault system. Our earthquake scenarios yield spatially heterogeneous near‐field ground motions modulated by geometric complexities, topography, and rupture directivity, particularly in the near‐field. The average ground motion attenuation characteristics of dynamic rupture scenarios of comparable magnitudes and mean stress drop are independent of variations in source complexity, magnitude‐consistent and in good agreement with the latest regional empirical ground motion models. However, physics‐based ground motion variability changes considerably with fault‐distance and increases for unilateral compared to bilateral ruptures. Systematic variations in physics‐based near‐fault ground motions provide important insights into the mechanics and potential earthquake hazard of large strike‐slip fault systems, such as the HFFZ. Plain Language Summary: The Húsavík‐Flatey Fault Zone (HFFZ) is the largest strike‐slip fault in Iceland, located in the Tjörnes Fracture Zone in Northern Iceland where the largest earthquakes in Iceland have occurred. At present the seismogenic potential of HFFZ suggests that an earthquake of magnitude ∼7 is possible, which poses a high earthquake hazard in the region. In this study, we generate a set of plausible earthquake rupture scenarios on the HFFZ that account for multi‐physics, regional geology and topo‐bathymetry. We simulate the corresponding seismic ground motions by exploring various assumptions, for example, in terms of slipping fault geometry and hypocenter locations. Our simulated scenarios have comparable magnitudes with historic events. The physics‐based ground motion scaling conforms to new empirical ground motion models, but shows varying ground motion variability with distance. Our study provides an overview of multiple rupture scenarios on the HFFZ and suggests that an ensemble of physics‐based dynamic rupture scenarios can complement classical seismic hazard assessment methods to better characterize the hazard in tectonically and seismically complex regions, especially in data‐scarce regions. Key Points: Observational constrained dynamic rupture scenarios of the Húsavík‐Flatey Fault Zone match expected regional earthquake scaling and magnitudesSegmented fault geometry, hypocenter location, fault prestress and roughness affect rupture dynamics and ground motionsOur physics‐based scenarios show magnitude‐consistent average attenuation relationships and match empirical ground motion models [ABSTRACT FROM AUTHOR]

The present work develops a comprehensive probabilistic seismic hazard study for Lebanon, a country prone to a high seismic hazard since it is located along the Levant fault system. The historical seismicity has documented devastating earthquakes which have struck this area. Contrarily, the instrumental period is typical of a low-to-moderate seismicity region. The source model built is made of a smoothed seismicity earthquake forecast based on the Lebanese instrumental catalog, combined with a fault model including major and best-characterized faults in the area. Earthquake frequencies on faults are inferred from geological as well as geodetic slip rates. Uncertainties at every step are tracked and a sensitivity study is led to identify which parameters and decisions most influence hazard estimates. The results demonstrate that the choice of the recurrence model, exponential or characteristic, impacts the most the hazard, followed by the uncertainty on the slip rate, on the maximum magnitude that may break faults, and on the minimum magnitude applied to faults. At return periods larger than or equal to 475 years, the hazard in Lebanon is fully controlled by the sources on faults, and the off-fault model has a negligible contribution. We establish a source model logic tree populated with the key parameters, and combine this logic tree with three ground-motion models (GMMs) potentially adapted to the Levant region. A specific study is led in Beirut, located on the hanging-wall of the Mount Lebanon fault to understand where the contributions come from in terms of magnitudes, distances and sources. Running hazard calculations based on the logic tree, distributions of hazard estimates are obtained for selected sites, as well as seismic hazard maps at the scale of the country. Considering the PGA at 475 years of return period, mean hazard values found are larger than 0.3 g for sites within a distance of 20–30 km from the main strand of the Levant Fault, as well as in the coastal region in-between Saida and Tripoli (≥ 0.4 g considering the 84th percentile). The study provides detailed information on the hazard levels to expect in Lebanon, with the associated uncertainties, constituting a solid basis that may help taking decisions in the perspective of future updates of the Lebanese building code. [ABSTRACT FROM AUTHOR]

We analyze two high-quality Southern Californian earthquake catalogues, one with focal mechanisms, to statistically model and test for dependencies of the earthquake-size distribution, the b values, on both faulting style and depth. In our null hypothesis, b is assumed constant. We then develop and calibrate one model based only on faulting style, another based only on depth dependence and two models that assume a simultaneous dependence on both parameters. We develop a new maximum-likelihood estimator corrected for the degrees of freedom to assess models' performances. Our results show that all models significantly reject the null hypothesis. The best performing is the one that simultaneously takes account of depth and faulting style. Our results suggest that differential stress variations in the Earth's crust systematically influence b values and that this variability should be considered for contemporary seismic hazard studies.

Different nonergodic Ground-Motion Models based on spatially varying coefficient models are compared for ground-motion data in Italy. The models are based different methodologies: Multi-source geographically weighted regression (Caramenti et al. 2022), and Bayesian hierarchical models estimated with the integrated nested Laplace approximation (Rue et al. 2009). The different models are compared in terms of their predictive performance, their spatial coefficients, and their predictions. Models that include spatial terms perform slightly better than a simple base model that includes only event and station terms, in terms of out-of sample error based on cross-validation. The Bayesian spatial models have slightly lower generalization error, which can be attributed to the fact that they can include random effects for events and stations. The different methodologies give rise to different dependencies of the spatially varying terms on event and station locations, leading to between-model uncertainty in their predictions, which should be accommodated in a nonergodic seismic hazard assessment. [ABSTRACT FROM AUTHOR]

The demarcation of seismic area source zones plays a pivotal role in probabilistic seismic hazard assessment (PSHA). In this study, we developed five distinct seismotectonic area source models, integrating large and small areas based on geological, tectonic, and seismological data. Logic tree methodology is utilized in FRISK88M for PSHA. Analysis revealed higher hazards in models with larger area sources compared to those with smaller ones. Hazard deaggregation of seismotectonic model-5 (SM5) is examined and sensitivity analysis of various logic tree nodes is investigated in terms of percent deviation w.r.t mean hazard at various spectral and return periods. The findings underscore that recurrence methods fall into "insensitive level" (≤5%), source mechanism and a-value distribution belong to "low sensitive level" (>5–15%), magnitude distribution lies in "medium sensitive level" (>15–25%), b-value distribution belongs to "high sensitive level" (>25–35%), and ground motion prediction equations (GMPEs) and depth distribution falls into "very high sensitive level" (>35%) in relation to seismic hazard. • Developed seismotectonic models using geological, tectonics and seismological data. • Performed PSHA using FRISK88M by applying a logic tree. • Effect of small and large area source zones on PSHA. • Sensitivity analysis of logic tree nodes at various spectral and return periods. • Sensitivity level classes of logic tree nodes by % deviation w.r.t mean hazard. [ABSTRACT FROM AUTHOR]

The assessment of seismic risk and the prevention of earthquake occurrences during reservoir operation present significant challenges in terms of accurate determination. This study aims to address this issue by developing a numerical model. The primary objective is to estimate the vulnerability of different fault types to reservoir impoundment. This model integrates essential parameters such as fault dip and the relative orientation between the reservoir and potential earthquakes, and it is structured within a risk framework using polar coordinates. Through comprehensive computations, we evaluate the alterations in elastic stress and fluid pore pressure resulting from water impoundment. This is achieved by employing a fully coupled two-dimensional poroelastic approach. Furthermore, our model incorporates relevant seismic data to enhance its accuracy. The findings of our study underscore that the critical factor lies in the fault’s precise positioning with respect to the reservoir. The risk associated with a fault is contingent upon both its location and its orientation, emphasizing the importance of these factors in determining hazardous zones.

This article aims to provide an overview of successive seismic zonations in mainland France and probabilistic seismic hazard studies performed over the previous ${\approx }$30 years. A short presentation is given on the engineering and regulatory framework that shapes the background of seismic zonation and hazard studies, followed by a scientific overview of published probabilistic seismic hazard estimations. The components of these past PSHA studies are summarized (seismic source models, ground-motion models, management of uncertainties). The evolution of hazard estimates with time is displayed for a set of representative cities. Finally, three generations of official seismic zonation maps in France are presented (1967, 1986, 2004), and the evolution of methods and results is highlighted. This review shows that the academic community has previously had little involvement in this topic. As current zonation relies on outdated models, there is an opportunity for scientific and engineering communities to efficiently work together to build the next generation of probabilistic seismic hazard models for France.

The SISFRANCE database aims to collect and interpret archives relating the historical seismicity in metropolitan France. The database presently contains some 12,500 documents that allow to define 108,832 macroseismic data points, for a total of 6427 events, of which 5743 can be qualified as real earthquakes. Although half of these events are and will probably remain poorly known, completing our knowledge of historical earthquakes remains a fundamental element for the definition of seismic hazard and the understanding of seismicity in France and low to moderate seismicity regions in general. The first aim of this paper is to explain the state of the art of the database and remind end users how the limits introduced by the necessary interpretation of archival data are translated into quality factors that should be carefully considered when using such data for seismotectonic and seismic hazard purposes.Originally built as part of the necessary datasets to define the seismic hazard for nuclear facilities, the SISFRANCE database is the result of 40 years of work within a consortium bringing together the French civil nuclear operator (EDF), the French geological survey (BRGM), and the French institute of nuclear safety (IRSN). SISFRANCE is also the heir to archival research carried out since the second half of the 19th century, thus constituting the richest collection of data related to historical seismicity in France. The second aim of this paper is to explain to end users the current state of archival research within the SISFRANCE consortium, present avenues for future research strategies, and list potential improvements of the database structure.Archival research within the SISFRANCE consortium, no longer carried out by a dedicated historian since 2018, is presently being pursued by engaging individual researchers or academics, focusing research on specific archives and regions, as well as by developing data-mining techniques to exploit the increasing wealth of accessible numerical archives. Given the new impetus of French governmental research agencies that encourage transdisciplinarity research, SISFRANCE is also pursuing the idea of further engaging the academic community of historians and seismologists, presently greatly underrepresented in the field of historical seismicity in spite of the importance of this data, fundamental for any seismotectonic and seismic hazard study in France.

The M 6.5 earthquake that occurred in the Monte Cristo Range near Mina, Nevada on 15 May 2020 was exceptionally well-recorded with both seismic and geodetic instrumentation. The arid nature of the region also facilitated detailed ground mapping of the surface rupture. Here we integrate several independent data sets to illustrate the educational and research opportunities afforded by these rich data sets. We construct a series of models for slip at depth that are consistent with the satellite-derived geodetic data, the distribution of aftershocks, and the mapped surface rupture. We also show that the modelled depth of maximum slip is in good agreement with heat flow and laboratory data on quartz rheology defining the depth of the brittle-ductile transition. The Monte Cristo Range earthquake also suggests new approaches to seismic hazard assessment may be required for earthquakes in rapidly evolving tectonic regions such as the Walker Lane and Eastern California shear zone. [ABSTRACT FROM AUTHOR]

Abstract The results of seismic risk assessment of spatially distributed infrastructure systems are significantly influenced by spatial correlation of earthquake intensity measures (IM). The assumption of isotropy is a basis for most of the existing correlation models of earthquake IMs. In this study, the isotropy assumption of intra-event residuals of peak ground velocity (PGV) and peak ground displacement (PGD) is investigated by implementing a nonparametric statistical test. Using recorded IMs of 9 earthquakes, it is concluded that there is not sufficient evidence to support the assumption of isotropy in general, and the set of intra-event residuals of PGV and PGD should be considered as the realization of anisotropic random fields. Investigations show that the anisotropy properties of intra-event residuals of PGV and PGD are related to anisotropy properties of local soil characteristics indicated by average shear wave velocity of soil profile from the 30 m depth to the surface (V s30 ). Finally, predictive models are proposed based on obtained results in order to simulate the correlated univariate random fields of PGV and PGD considering anisotropy.

In the present study, probabilistic seismic hazard assessment (PSHA) and disaggregation of seismic hazard in Golestan and adjacent areas have been conducted. The study area includes Golestan province and surrounding areas to about 150 km away from the geographical borders of the province. For this purpose, at the first stage, geological and seismotectonic studies, including the tectonic features, faults dimensions, and faults mechanism in the study area have been studied. The seismicity parameters including b-value, annual mean occurrence rate (λ) and maximum possible magnitude (Mmax) of the study area are evaluated based on the uniform catalog containing historical and instrumental earthquakes from 400 BC to the end of 2021 AD with magnitudes ranging from 3.5 to 7.5 on the Mw scale. Based on the geological and seismological information of the study area, 21 areal seismic source zones have been identified. Using the spatial distribution function, the annual mean occurrence rate of earthquakes of each seismic source has been determined in different magnitude intervals. The latest three local ground motion prediction equation models of the Iranian plateau, have been employed to assess the peak ground acceleration (PGA) and spectral acceleration (SA) in periods of 0.2, 1, and 2 seconds for return periods of 50, 475 and 2475 years. A three branches logic tree with the same weight has been used to apply the GMPEs. The GMPEs are specific to Iran and used for the first time in the study area. The entire study area is divided into points that are 5 km apart. Subsequently, the PGA and SA have been calculated for each point with the OpenQuake software package. The results are presented in the form of seismic hazard zoning maps in Golestan province and spectral acceleration curves for Gorgan city. The calculations are on the bedrock site condition according to the Iranian code of practice for seismic resistant design on building (Standard No. 2800 4th edition). In order to determine the most effective seismic source in the PGA of the Gorgan, the disaggregation of PSHA has been conducted on the parameters of distance, magnitude, the number of standard deviations (ε), and latitude and longitude. The most probable scenario of maximum acceleration in Gorgan has been introduced. The results show that some areas of the Gorgan, Kord-Kouy, Agh-Ghala and Ali-Abad in southwest and Maraveh-Tapeh in northeast of the province can be affected by more ground acceleration than other areas so that the maximum ground acceleration in these areas for the return period of 475 years is 0.21g to 0.25g. The disaggregation of PSHA for Gorgan city shows that the Caspian and North Alborz faults have the most substantial contribution in the PGAs of Gorgan. [ABSTRACT FROM AUTHOR]

West-Africa is a region of low-to-moderate seismicity, with only a few known earthquakes of moment magnitude greater than 5, notably the 1939 Mw 6.4 Accra (Ghana) earthquake. An effort has been made to perform a seismic hazard assessment for the region enclosed within latitudes 2°N and 16°N and longitudes 18°W and 15°E using a probabilistic approach within a logic-tree framework. Ground-motion scaling relationships are selected to account for epistemic uncertainty. The compiled catalogue from 1615 to 2018 and homogenised to moment magnitude (Mw). We present hazard result values on rock site conditions, in terms of seismic hazard curves, peak ground acceleration and uniform hazard spectra, for the study region and four selected cities. We estimate the maximum PGAs of 10%, and 2%, chances over 50 years at 0.10 and 0.26 g respectively, in Accra. Finally, a deaggregation of the Accra site was carried out to identify the dominant earthquake scenario for the chosen site for a 475-year return period. Results showed that the prevalent scenario characterised by seismic events between magnitudes 5.5-6.0 and at a distance less than 60 km. Findings from these assessments will help to contribute to the safe development of the region. [ABSTRACT FROM AUTHOR]

The heavily populated Cebu Island is cut by the Central Cebu Fault System (CCFS). While the CCFS has not produced any MW > 5.0 earthquakes in the past century, recent strong earthquakes in the adjacent islands have brought attention to the seismic hazards in the region. Fault properties such as strike, dip, slip direction, and surface trace length were determined based on literature review, fieldwork, and analysis of geomorphic features. Empirical relations were utilized to estimate down-dip width and magnitude. The gathered data were used to create a three-dimensional model of the four major faults in the CCFS: Balamban Fault, Central Highland Fault, Uling-Masaba Fault, and Lutac-Jaclupan Fault. The 3D model was used to generate peak ground acceleration maps of central Cebu, should an earthquake occur along any of the major faults. Site corrections were made based on the seismic velocity of the upper 30 m of the subsurface. The major faults are estimated to be capable of generating MW 6.4 to 7.1 earthquakes. Worst-case scenarios in densely populated areas show 0.40 to 0.70 g of PGA, suggesting the potential for severe damage in central Cebu. We explored the advantages of using raster mathematics in a GIS platform for calculating and presenting ground motion. These advantages include rapid calculations for tens of millions of points, reducing the effects of interpolation artifacts in final map products. This study emphasizes the importance of detailed structural, geological, and geomorphological data in modeling seismic hazards. Further investigations on the seismogenesis of the CCFS segments are recommended.