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In Geophysics, topographic factors are observations that can be directly measured, but they are often ignored to simplify the model. Studying the coseismic deformation caused by earthquakes helps accurately determine the epicenter's parameterization. It provides a reference for the reasonable layout of coseismic observation stations and GNSS observation stations. After the Mw7.8 earthquake in Nepal in 2015, GCMT, USGS, GFZ, CPPT, and other institutions released their epicenter parameter. However, according to their parameters, the coseismic displacements simulated by the spectral-element method are quite different from the GNSS observations. Firstly, this paper inverts the geometric parameters of the seismogenic fault with Nepal's coseismic GNSS displacement. The spectral-element method determines the source's location and depth under the heterogeneous terrain and outputs the source parameters. Among the results of many studies, the surface source is more consistent with the generation mechanism of large earthquakes. Secondly, this paper calculates the fault slip distribution of this earthquake using SDM (Steepest Descent Method) based on GNSS and InSAR data, which is divided into 1500 subfaults, and the moment tensor of each subfault is calculated. This paper investigates the distribution characteristics of the coseismic deformation field of the 2015 Mw 7.8 earthquake in Nepal under three different models. The results show that the influence of topographic factors is ~ 20%, and the influence of heterogeneous factors is ~ 10%. This paper concludes that the influence of topographic factors is much more significant than that of heterogeneous factors, and the influence of both should be addressed in coseismic deformation calculations. [ABSTRACT FROM AUTHOR]

The establishment of a unified earthquake catalog is a basic requirement for attaining a detailed seismological analysis and an improved seismic hazard assessment. Accordingly, the current research paper aims to present a reliable instrumental unified earthquake catalog for the northern part of Algeria. This unified catalog is compiled using regional empirical relationships derived from converting different magnitude scales to an advanced physical-based moment magnitude scale suggested in the recent literature and denoted by Mwg. The regression methodology used in this study is called the New General Orthogonal Regression approach (N.GOR), which was selected since it is the most trustworthy procedure for scaling the magnitudes to Mwg. To highlight the significance of using the N.GOR, the obtained outcomes of the scaling relations were compared with those issued from the conventional general orthogonal regression (GOR) method, which is deemed to be the most dependable methodology used worldwide for magnitude conversion problems. The unified earthquake catalog was assembled from 1954 to 2022. Reliably converting the original magnitudes into homogenized moment magnitude leads to a complete and consistent unified earthquake catalog. Indeed, the unified moment magnitude catalog presented in this paper could provide reliable data for studying earthquakes distribution and the assessment of seismic hazards in the north of Algeria. [ABSTRACT FROM AUTHOR]

Large parts of Asia, Europe, and the eastern USA have high population concentrations in moderate seismic regions (MSR), where very large earthquakes are rare. With rampant construction in the cities located in MSRs, a relatively moderate earthquake can turn into a catastrophe. Limiting the collapse has been the conventional performance objective for regions with high seismicity. However, this does not necessarily translate into a more desirable target of life-safety under design basis earthquake in MSRs. The present paper investigates the seismic performance of non-ductile reinforced concrete (RC) buildings that were common before the advent of modern design standards, and are found in very large numbers. An analytical model capturing the shear failure is employed using a drift-based limit state material. The results show that a hybrid index captures moderate damage more accurately than the prevalent drift-based index. The paper further shows that while a generic ground motion suite accurately estimates the median fragility, it fails to capture the uncertainty. A 7-story non-ductile RC archetype building was found to be at a collapse prevention risk of 2 × 10–4. The seismic risk deaggregation reveals that seismic risk consistency can be enhanced by explicit specification of the seismic forces for retrofitting. The study shows that the stringent seismic risk targets can be met by non-ductile buildings in MSR, provided they are designed or retrofitted with constraints on strong column weak beam factors. The study will facilitate in developing a scheme for prioritizing and devising the retrofit of pre-modern code and non-ductile deficient buildings. [ABSTRACT FROM AUTHOR]

In this paper, a scalable end-to-end tree boosting system called XGBoost has been applied for predicting the magnitude of an earthquake from the early part of earthquake waveform data. This model uses the features extracted from the early P wave phase of the records as an input. The model's effectiveness has been verified by using data on earthquakes occurring in the Eurasian plate of Japan Islands from 1996 to 2021. Feature engineering has given 29 new features identified from the early P wave phase of the record, which show a high correlation with the magnitude of an earthquake. The comparison of predicted and actual magnitude shows that a trained XGboost model, which uses a single input record for magnitude prediction, gives an average prediction error of 0.004 ± 0.57 for earthquakes in the test dataset. In contrast, the average prediction error of –1.1 ± 0.80 and –0.65 ± 0.69 has been obtained for the magnitude estimated from conventional τc and Pd methods using the same test dataset. It is further seen that the average predicted magnitude of a single earthquake of magnitude 4.5 and 6.1 (MJMA) obtained by using multiple nearfield records using XGBoost model is 4.58 ± 0.33 and 6.32 ± 0.29, which is close to the actual magnitude of the earthquake. The results presented in this paper clearly show that the structured data can be effectively used by complex machine learning or deep learning models to predict earthquake magnitude from single or multiple records. [ABSTRACT FROM AUTHOR]

Slip-buckling failure is a common occurrence in bedding rock slopes, and it can be triggered by long-term gravitational stress, earthquakes, top loading and intense rainfall. In this paper, an analytical solution is proposed to address the slip-buckling failure of bedding rock slopes under the influences of top loading and earthquakes based on mechanical analysis and energy equilibrium theory. The rock layers of bedding slopes are treated as inclined plate beams with hinge support at the slope top and fixed support at the slope toe. The equation for the deflection curve of each rock column of the bedding rock slope under earthquake and top loading can be derived by analysing the forces acting on each rock layer. According to the energy equilibrium theory, the deformation energy of the rock column equals the work done by external forces, from which the critical length of a slope rock layer for slip-buckling failure can be determined. The location of the toe of the rupture surface, where slip-buckling failure occurs, corresponds to the point of maximum deflection on the deflection curve of the rock layer. Clearly, the location of the toe of the rupture surface is where the first derivative of the deflection curve equation equals zero. This approach has been applied to the Hejia landslide and Tangjiashan earthquake-triggered landslide, and the calculation results are in good agreement with the field investigation results. [ABSTRACT FROM AUTHOR]

The clipping of near-field seismic waveforms caused by instrument limitations results in the waste of lots of waveforms and hinders the effective advancement of seismic research projects like source parameter inversion, near-fault ground motion characteristics, and earthquake early warning (EEW). In this paper, we propose to use the cubic spline interpolation method to restore the clipping waveform to solve the near-field data loss. We evaluate the recoverability of seismic waveforms with different clipped levels through artificial clipping experiments and compare the recovery waveforms with the projection onto convex sets (POCS) method. The results show that the restoration deviation of the cubic spline interpolation method is less than 1% at the clipped point, for the records whose clipped amplitude does not exceed 50% of the peak. In addition, the restored phase feature of the cubic spline interpolation is closer to the real waveform than the POCS method. To verify the performance of this method in the realistic earthquake, we apply it to the Barkam Mw 5.9 earthquake. The results show that the peak ratio of the restored clipping records to the measured non-clipping records is close to 1, and the relative error of the response spectrum is less than 0.1. Finally, we apply this method to successfully restore about 60% of near-field clipped records from the 2022 Lushan Mw 5.8 earthquake, which provided more data support for the study of the near-field ground motion. [ABSTRACT FROM AUTHOR]

We studied the earthquake detection capacity of DONET (Dense Oceanfloor Network system for Earthquakes and Tsunamis) operating in the Nankai Trough, a target region monitored for future megathrust earthquakes. The focus of this paper was to evaluate the impact on this capacity from the malfunction of parts of the network. For this purpose, the completeness magnitude, above which all earthquakes are considered to be detected by a seismic network, was used. Then, a catalog that includes events observed by DONET was used. We found spatiotemporal variability of completeness magnitude, ranging from values below 1 in one of the areas where stations are densely deployed to values above 2 at the periphery and outside of the DONET area. We conducted a simulation computation for cases of malfunction of densely distributed stations. The results showed that completeness estimates in the area near the malfunctioning stations were about 1 magnitude larger. This implies that malfunction repair and/or replacement with new stations would be desirable because they pronouncedly affect earthquake monitoring. We then demonstrated an example of how to use the information of completeness magnitude as prior knowledge to compute the b value of the Gutenberg-Richter distribution. The result indicates the b value as a proxy that can help to image stress heterogeneity when there is a magnitude-6 class slow slip event on the Nankai Trough plate boundary. [ABSTRACT FROM AUTHOR]

In this paper, the dynamic response of two 21-story buildings was studied to assess the influence of higher modes in their structural performance. While the first building was structured with ductile moment-resisting steel frames and exhibits a global shear-dominated lateral deformation, the second one uses ductile concentrically braced steel frames and has a global bending-type response. Buildings were virtually located in a soft-soil condition of the lake-bed zone in Mexico City. Nonlinear pushover and dynamic analyses were performed through OpenSees on a detailed 3D-model with plasticity spread along the elements. For this purpose, a set of accelerograms recorded during the Mexico Earthquake of September 19, 2017, were selected, and adjusted to represent the actual seismic hazard at the site. A frequency-domain system identification technique was applied to identify the dynamic characteristics of buildings through a moving-window Fourier analysis, that allows for the estimation of the contribution of higher-modes to their overall nonlinear dynamic response. A ratio of the elastic spectral pseudo-accelerations corresponding to the first two vibration modes is proposed to quantitatively anticipate cases and conditions for which the second mode adversely affects the structural performance of upper stories. The discussion includes a comparative study from the lateral global response of the analyzed models. [ABSTRACT FROM AUTHOR]

The Bucaramanga seismic nest has the highest concentration in volume of intermediate depth seismic events with light and moderate magnitudes (Mb > 4.8) worldwide. Despite the nest depth (Zhypo ≥ 100 km), these events play a crucial role in the seismic hazard assessment for several cities in northern South America (NoSAm), particularly those situated close to their epicenters. Moreover, these earthquakes are widely felt across the country, even hundreds of kilometers away from the nest. This paper assesses the performance of commonly used subduction intraslab Ground Motion Models (GMMs) in predicting the updated nest database gathered and processed by the Colombian Geological Survey. This analysis confirms the necessity of a partially non-ergodic ground motion model for estimating the spectral accelerations produced by Bucaramanga nest earthquakes in northern South America. The GMM presented herein is the first model developed specifically for seismic nests in the region and is conceived as a regionalization of the recent NGA-Sub Abrahamson and Gülerce (Earthq Spectra 38(4):2638−2681, 2022) GMM. Additionally, we provide estimates of the variance components at both the earthquake and station levels and compare the developed GMM with the spectral accelerations recorded for typical earthquakes, for the highest magnitude earthquake in the database, and for a recent Bucaramanga nest earthquake having a moment magnitude over 5. [ABSTRACT FROM AUTHOR]

This paper presents the results of a study carried out to develop a multi-severity casualty approach for predicting the number of fatalities and two levels of injuries resulting from an earthquake. The two levels of injuries are severity 1, which do not require hospitalization, and severity 2, which do require hospitalization. The method provides a probability distribution of casualty, which can assist policymakers and disaster management authorities in developing emergency response plans. The proposed approach takes into account two main sources of uncertainty: variations in ground motion values (by generating thousands of shaking maps considering the spatial correlation of intra-event uncertainty) and uncertainty in casualty rates (by using the fuzzy set theorem and random sampling). As a case study, the proposed method was applied to the Mosha fault seismic scenario (7.4 Mw) in Tehran, Iran. The results indicated that 200,300 people may lose their lives in that seismic scenario. Additionally, the number of injuries with severity 1 and severity 2 are estimated to be about 420,600 and 232,980, respectively. These numbers exceed the healthcare capacity in Tehran. The estimated number of fatalities was then compared with the results of some existing empirical models in the literature. This comparison revealed that the empirical models underestimate the number of fatalities due to various reasons, such as a lack of strong earthquakes in urban areas to be included in empirical models. Thus, the proposed approach has several advantages for estimating casualties in urban fabrics. [ABSTRACT FROM AUTHOR]

Various geometric and mechanical conditions for soil–foundation interfaces affect the superstructure and foundation responses against earthquake. As one of these conditions, 2D asymmetry of soil around the embedded rigid foundation is emphasized in the present paper. Accordingly, a reduced-scaled embedded foundation bearing SDOF superstructure is considered under slow lateral cyclic and dynamic shake table tests in design and service levels at 1 g state, and the system response is compared to those of systems containing surface and embedded foundations with symmetric condition. Test results show the asymmetry in the moment–rotation response curve for system with asymmetric soil condition in static state. While for dynamic response, the behavior under harmonic excitation with the design amplitude level is close to one of system with surface foundation. In addition, the foundation moment capacity of nonlinear dynamic response can be estimated properly through theoretical expression for foundation with asymmetric condition. Moreover, the rocking behavior in two-way excitation causes significant loss of superstructure response relative to the foundation in all three cases. [ABSTRACT FROM AUTHOR]

Remote reconnaissance missions are promising solutions for the assessment of earthquake-induced structural damage and cascading geological hazards. Space-borne remote sensing can complement in-field missions when safety and accessibility concerns limit post-earthquake operations on the ground. However, the implementation of remote sensing techniques in post-disaster missions is limited by the lack of methods that combine different techniques and integrate them with field survey data. This paper presents a new approach for rapid post-earthquake building damage assessment and landslide mapping, based on Synthetic Aperture Radar (SAR) data. The proposed texture-based building damage classification approach exploits very high resolution post-earthquake SAR data integrated with building survey data. For landslide mapping, a backscatter intensity-based landslide detection approach, which also includes the separation between landslides and flooded areas, is combined with optical-based manual inventories. The approach was implemented during the joint Structural Extreme Event Reconnaissance, GeoHazards International and Earthquake Engineering Field Investigation Team mission that followed the 2021 Haiti Earthquake and Tropical Cyclone Grace. [ABSTRACT FROM AUTHOR]

Abstract—This paper analyzes the use of the automated aftershock hazards assessment system (AFCAST) through the example of a series of aftershocks of the Mw 7.8 earthquake in Turkey of February 6, 2023 (the Pazarcik earthquake). The paper presents automated estimates of the aftershock activity area, the magnitude of the strongest aftershock, and the duration of the hazardous period, yielded using data on the main shock and on the first aftershocks. [ABSTRACT FROM AUTHOR]

Though there is now a substantial body of research on the relationship between nonprofits and the state, examples from non-Western countries have been lacking in the nonprofit literature in English. This paper attempts to fill this gap using nonprofit cases in three key districts in Fukushima after the Great East Japan Earthquake. By focusing on these cases, this study captures the complex nature of the relationship between the nonprofit sector and state in Japan during a period of increased activity of both the nonprofit sector and the state. The idea of the nonprofit sector, state, and market as relatively separate and with different interests, influences discussions on themes related to the nonprofit sector (e.g., business-like behavior). The study suggests how the Japanese case can contribute in uncovering assumptions that are embedded in the existing understanding of the nonprofit sector, based primarily on Western examples. [ABSTRACT FROM AUTHOR]

Seismic risk estimation for urban building clusters is essential when developing regional seismic resilience models. A masonry structure is a type of building with a large stock, broad applicability, and simplified construction technology. The traditional seismic intensity measures and fuzzy quantification of structural vulnerability levels result in low accuracy in estimating and predicting seismic damage to masonry structure clusters. This paper proposes a method for evaluating bivariate seismic intensity measure. Nonlinear dynamic and spectral analyses were conducted on real acceleration records monitored by ten stations during the Wenchuan earthquake in Sichuan, China, on May 12, 2008. The outdated seismic vulnerability level of masonry structures is updated, and an optimized structural seismic risk model based on the seismic damage database of 2407 masonry structures in Dujiangyan city under the influence of the Wenchuan earthquake is established. An innovative seismic risk membership index algorithm was developed, and a vulnerability curve was generated for masonry structures considering multiple risk membership indices. An improved seismic risk index calculation function is proposed using the proposed updated vulnerability level, and the seismic risk index curve and stripe model of typical urban masonry building clusters are established. According to the field investigation of the actual structures in Dujiangyan city affected by the Wenchuan earthquake, the typical failure features and disaster mechanism of masonry structures are reported and analysed, and measures and methods to improve and enhance the seismic capacity of such buildings are proposed. The developed seismic risk model for urban masonry structures can contribute positively to the development of relatively accurate seismic resilience models for urban buildings and can improve the accuracy of seismic risk estimation for masonry structures. [ABSTRACT FROM AUTHOR]

The regional seismic risk assessment plays an important role in the disaster prevention and mitigation. The accurate time-history analysis for a region provides an important data base for regional seismic risk assessment. However, an accurate calculation method is limited, then, its accuracy still lacks validation. Meanwhile, there is also a lack of risk assessment methods and indicators applicable to the regional accurate time-history analysis, both of which hinder the seismic risk assessment. In this paper, a regional-scale time history analysis-driven method is proposed for the quantitative evaluation of regional seismic damage risk and verified with a real earthquake damage survey. First, the regional time history analysis method is introduced, including the automatic modeling, response calculating, result analysis and 3-D visualization modules. Second, a calculation method for seismic damage degrees (DD) of buildings is introduced. Subsequently, the probabilistic models of each DD under the ground motions with a specific intensity are calculated based on regional-scale nonlinear time history analysis. Next, the concept of the three-level seismic damage risk is offered, then a determining workflow of seismic damage risks is proposed based on the code-abiding three-level design requirement. Afterward, the regional seismic damage index is suggested for the quantitative evaluation of earthquake-induced damage risk. Finally, the actual seismic damage database of 192 buildings in epicenter of Ludian Earthquake is established through on-site investigations, then used to verify the regional simulation's accuracy. Consequently, it could be an aid to accurately present seismic damage distribution assessments and effectively develop seismic risk mitigation strategies. [ABSTRACT FROM AUTHOR]

This paper investigates the inelastic displacement ratios (IDRs) and displacement ductility demands of a wide range of single-degree-of-freedom (SDOF) systems subjected to pulse-like ground motions (GMs) of the 2023 Pazarcık (Kahramanmaraş) earthquake. A set of twenty-seven GMs characterized as pulse-like are utilized in the study. As-recorded velocity time histories of horizontal components are rotated over 90° at a step of 1° to attain the waveform with the largest peak ground velocity (PGV) over all horizontal orientations. Inelastic displacement ratio and displacement ductility spectra are computed through nonlinear response history analysis (RHA). Local amplifications of both spectra are observed at some periods. The results of this study show that large inelastic displacement and ductility demands are imposed on certain reinforced concrete (RC) structures. Finally, predictive models of the mean inelastic displacement ratio and mean ductility demand spectra (DDS) are developed based on the Gauss–Newton algorithm (GNA). The model provides a strong correlation between the computed and the estimated data, and sufficient convergence criteria. The results of this study collectively emphasize the necessity of integrating pulse-like GMs into future revisions of earthquake codes. [ABSTRACT FROM AUTHOR]

The track structure has an effect on the dynamic characteristics of the bridge structure, which makes the seismic response of the bridge structure complicated. In this paper, an assessment method is proposed to evaluate the seismic risk of bridge structure, including over-limit risk and over-limit scale. Based on a newly proposed simplified model with high accuracy and high computational efficiency, a total of 3000 calculation conditions are analyzed and the sample stability of response is validated to ensure the reliability of the seismic risk analysis. The seismic risks in the longitudinal direction of the track-bridge model are compared with that of the trackless model, and the influence of the constraint effect of China Railway Track System II ballastless track structure on the seismic risk of the structure is obtained. The influence of the number of spans and PGA on track constraints is also revealed. The analysis results, based on a large number of samples, show that although track constraints can reduce the seismic risk of some phenomenon, such as girders' collision, the expected enhancement of longitudinal seismic safety of the system cannot be guaranteed in general, especially when the number of spans is large. However, it is noted that the track constraint can effectively control the over-limit scale of the system, which can reduce the expected repair cost after an earthquake. Therefore, it can be considered that the positive effect of the track constraints is more significant in economy than in structural safety when the bridge is subjected to a longitudinal earthquake excitation. [ABSTRACT FROM AUTHOR]

In this paper, the effect of soil–structure interaction (SSI) on the story acceleration response of a high-rise building due to different earthquakes is investigated. To determine the dynamic response of a 40-story building considering SSI, six different foundation soil conditions and ten different earthquake records are considered. The results show that the SSI effect on the story acceleration response of the high-rise building resting on relatively soft soil types is of critical importance. [ABSTRACT FROM AUTHOR]

Today's earthquakes are the most direct manifestation of the latest tectonic activity and are the most powerful tool to understand the characteristics of nonrigid deformation within a continent. Particularly, the newly formed faults that have been active since the Late Pleistocene are characterized to have low development maturity, poor connectivity in geometric structure, and obvious difference in strike/depth dip in different sections. Therefore, earthquakes can reveal their three-dimensional space changes, especially the characteristics of brittle-ductile transition depth. Earthquakes can also promote the understanding of the preparation and earthquake generation process of newly formed active faults. The newly formed strike-slip active faults in the Bohai Bay Basin have experienced many strong earthquakes, including the Tangshan MS7.8 and the three Ninghe MS≥ 6.2 earthquakes. The crustal brittle-ductile transition depth revealed by these earthquakes has an important practical significance to understanding the seismogenic mechanism and activity of the region. In this paper, the new fault in the Baodi Miaozhuang uplift in the Bohai Bay Basin is taken as the target fault. In addition, the 2012 Baodi MS4.0 and MS3.5 earthquakes in the Baodi uplift and the 1976 Ninghe MS6.2 and MS6.9 and the 1977 Ninghe MS6.2 earthquakes in the Miaozhuang uplift are taken as the research objects. Finally, the CAP method is used to study the source mechanism solution and the source depth of the Baodi MS4.0 and MS3.5 earthquakes based on the waveform data from the Capital Circle Digital Seismic Network. The double difference method is used to locate the source positions of two earthquake sequences by employing the Sp converted wave of near earthquakes to accurately determine the source depth. Moreover, combined with other data, the seismogenic mechanism of earthquakes in this area and the brittle-ductile transition depth of new fractures are discussed. The following results were found. (1) The source properties of the Baodi MS4.0 and MS3.5 earthquakes are not completely consistent with the known faults on the exposed surface of the Baodi Miaozhuang uplift. Combining the research results of the source parameters of the three Ninghe earthquakes having an MS ≥ 6.2, it is inferred that they all occurred in the Baodi-Ninghe deep fault. (2) Based on the models of electrical structure and rheological structure in the focal area, the five significant earthquakes in Baodi Miaozhuang uplift reveal that the brittle-ductile transition depth of the Baodi-Ninghe deep fault is about 15 km. (3) Based on the dynamic evolution process of the Bohai Bay Basin and relevant deep geophysical exploration data, it is hypothesized that the seismic activity in this area is mainly the result of the Baodi-Ninghe deep fault and deep fluid actions. [ABSTRACT FROM AUTHOR]

The dynamic effect is a very important issue widely debated by scholars when studying the genetic and disaster-causing mechanisms of earthquake-triggered landslides. First, the dynamic effect mechanism and phenomena of earthquake-triggered landslides were summarized in this paper. Then, the primary types of dynamic effects were further used to interpret the Mogangling landslide in Moxi Town of Luding County, China. A field investigation, remote sensing, numerical calculation and theoretical analysis were carried out to illustrate the failure mechanism of slope rock masses affected by earthquakes. The interaction between seismic waves and slope rock masses and the induced dynamic effect of slope rock masses were primarily accounted for in the analysis. The slope topography, rock mass weathering and unloading characteristics, river erosion, regional seismogenic structure, and rock mass structure characteristics were also discussed. The results showed that the formation of the Mogangling landslide was mainly related to the high amplification effect of seismic acceleration and back slope effects, interface dynamic stress effects, and double-sided slope effects of seismic waves caused by the catastrophic Ms 7.75 Moxi Earthquake in 1786. The principles for the site and route selection of large-scale infrastructure in the planning stage and the scientific prevention of seismic geological disasters were proposed on the basis of the dynamic effect of earthquake-induced landslides. [ABSTRACT FROM AUTHOR]

On September 5, 2019, a moderate earthquake of Mw5.4 unexpectedly occurred in the apparently quiescent central basin of the South China Sea. We immediately carried out a seismicity monitoring experiment around the epicenter by using broadband ocean bottom seismometers (OBS) for the following three scientific targets. The first is knowing the earthquake seismogenic mechanism, fault structure and further development. The second is finding the role of the residual spreading ridge playing in earthquake processes and further revealing the deep structures of the ridge directional turning area. The third is confirming the existence and significance of the so called "Zhongnan fault". This paper reports the preliminary results of the first phase experiment. Five OBSs were deployed for seismicity monitoring with a duration of 288 days, but only three were recovered. Micro-earthquakes were firstly detected by an automatic seismic phase picking algorithm and then were verified by analyzing their seismic phases and time-frequency characteristics in detail. A total of 21, 68 and 89 micro-earthquakes were picked out from the three OBSs respectively within the distance of 30 km. The dominant frequency of these micro-earthquakes is 12–15 Hz, indicating tectonic fracturing. During the first two months after the mainshock the seismicity was relatively stronger, and micro-earthquakes were still occurring occasionally till the end of observation, indicating the epicenter area is active. We used Match&Locate method to locate 57 micro-earthquakes preliminarily. Their spatial distribution shows that the seismicity is developed mainly along the NE direction roughly parallel to the residual ridge with depth variations between 10–20 km. [ABSTRACT FROM AUTHOR]

In this paper a novel approach named Multi Pier Macro MPM method is proposed for seismic analysis of steel moment frames. Based on the model an arbitrary multi-bay and multi-story moment frame is substituted by a single bay braced frame consists of two piers and two braces at each story. Piers are continuous and braces are pinned to piers. Both piers and braces are 1D truss elements. The axial, flexural and shear stiffness of the moment frame are provided by axial behavior of piers and braces. MPM method was benchmarked against four steel moment frames including two mid-rise and two high-rise buildings. The seismic responses of equivalent braced frames including maximum floor displacements and story drifts was compared with original moment frames responses as exact results, by means of Non-linear Static Procedure NSP and Non-linear Response History Analysis NL-RHA. NL-RHA was performed using twelve ground motion records scaled to Maximum Design Earthquake MDE and Maximum Considered Earthquake MCE hazard intensities. The results proved the simplified braced frame is able to estimate the seismic responses of mid and high-rise moment frame buildings with high accuracy meanwhile the analysis time and computational cost were limited remarkably. [ABSTRACT FROM AUTHOR]

Rapid changes in geotechnical and geological ground conditions lead to significant ground motion variability. This condition mainly occurs at the so-called basin edges, where there is an abrupt transition between soft highly compressible soils and stiffer materials. This problem becomes more relevant in areas where ground subsidence drastically changes the dynamic response of high plasticity clay deposits, such as those found in Mexico City, due to fundamental site period evolution with time. This paper presents site response analyses at an abrupt transition area in the southeast Mexico City region, along the edges of the Xochimilco-Chalco lakes. Considerable damage associated with three-dimensional wave propagation effects was observed in this zone during the September 2017 Puebla-Mexico earthquake. A series of three-dimensional finite difference numerical models of the basin edge were developed to evaluate ground motion variability, considering topographic effects and soil non-linearities. Good agreement between the computed response and the observed damage during the 2017 Puebla-Mexico earthquake reconnaissance was found. In addition, several normal and subduction events with a return period of 250 years were considered to evaluate the effect that frequency content, and strong ground motion duration have on the soil response variability. From the results gathered here, it was established the relevance of accounting for three-dimensional wave propagation fields to assess site effects at basin-edge zones properly and to be able to implement proper risk mitigation measurements at these zones. [ABSTRACT FROM AUTHOR]

Liquefaction occurs when the ground experiences intense shaking due to seismic activities, causing water-saturated soils or loosely packed sediments near the surface to weaken and behave like a liquid. The present paper has reviewed and investigated the liquefaction around tunnels due to any seismic event that may occur during the tunnel's lifetime. To effectively prevent soil liquefaction around the tunnel, it is crucial to analyze both the acceleration response of the tunnel and the soil motion that results from liquefaction. This paper examines the geotechnical engineering aspects of such liquefactions and discusses analytic techniques to mitigate their effects. Also, the response of tunnel displacement under different magnitudes of earthquakes has been discussed. Different mitigation methods are explored in response to the damages caused by the liquefaction of soil due to earthquakes. Case studies of this problem that occurred in different nations were analyzed as well, amidst which are tunnel disasters in Turkey, Syria, China, Italy, Japan, India, and the USA. These instances demonstrate the terrible repercussions of liquefaction, such as building collapse, road network destruction, and surface and subsurface structure deterioration. By reviewing these instances, major patterns and trends in liquefaction-induced damages emerge, giving valuable insights for future mitigation and engineering practices. This review serves as a valuable resource for engineers and researchers involved in tunnel design, construction, and maintenance. This review paper addresses the dangers associated with liquefaction in soils and highlights the need for robust design considerations and appropriate construction techniques to mitigate potential damages. [ABSTRACT FROM AUTHOR]

Different catalogues of earthquakes are available for the Indian region besides regional catalogues for the Gujarat region. The limitations of these and other historical catalogues have been discussed in this paper for earthquake hazards and other studies. Keeping in view that these historical catalogues have been successful in explaining the recent occurrence of a few earthquakes like Coimbatore (1900), Hyderabad (1983), Bangaluru (1985) and Jabalpur (1997), the study has been extended to the Gujarat region. In this paper, therefore, an attempt has been made to correlate the historical data of the felt earthquakes in the Gujarat region from all the available sources with instrumental data to examine the recurrence of the earthquakes. It has been found that in addition to the seismically active Kutch region and Narmada and Cambay rifts, there is a tendency for earthquakes to recur in many districts of Gujarat for which felt data from historical times is available. The seismicity map prepared by the Institute of Seismological Research (ISR), Gandhinagar based on the Seismic Telemetry (2006–2020) shows scattered seismicity over the whole of Gujarat region besides active seismicity in the Kutch region. This data when combined with that from the catalogue prepared by the National Centre of Seismology provides greater confidence for earthquake hazard studies It has also been found that the coastal regions of Saurashtra and south Gujarat are more prone to swarm types of earthquakes. [ABSTRACT FROM AUTHOR]

This paper is focused on study of the geomagnetic field variation response caused by a series of earthquakes with magnitudes of Mw = 7.5–7.8 in Turkey on February 6, 2023. The initial data include high-precision observations of the geomagnetic field with a one-second sampling rate recorded at magnetic observatories in Russia and neighboring countries from middle to high latitudes. The paper analyzes the morphology of the geomagnetic signal, its amplitude-frequency characteristics, pulses in the rate of change and delays of the geomagnetic field response to earthquakes with magnitudes Mw = 7–8 depending on the distance to the source. The results suggest that the geomagnetic effect is detected best in the rate of change recordings, reaching anomalous amplitudes of 10 nT/s. The signal delay ranges from 221 to 592 s depending on the magnetic field component and the distance to the epicenter, which is in the range from 765 to 2650 km for the selected observatories. [ABSTRACT FROM AUTHOR]

Abstract—Based on the long-term observations of the wells on the Petropavlovsk-Kamchatsky Test Site, the Kamchatka Peninsula, the paper analyzes manifestations of three main types of seismohydrogeological effects—hydrogeological precursors, coseismic pressure jumps and postseismic effects of the vibrational impact of seismic waves in measurements of the pressure and chemical composition of groundwater, depending on the earthquake parameters (magnitude, epicentre distance, intensity of seismic impact in the observation areas). The paper presents data on the earthquakes that were preceded by hydrogeological precursors in several (n = 2–4) wells. It is discussed whether it is possible to use hydrogeological precursors to predict strong earthquakes in Kamchatka. The authors also discuss the results of their experimental use in a real-time environment with weekly reports on the current observational data for the Kamchatka Branch of the Russian Expert Council. By the example of water level observations in YUZ-5 Well, the authors analyzed coseismic jumps in the groundwater pressure due to rupture formation in the sources of local Mw > 6.0 earthquakes and four types of effects of the vibrational impact of seismic waves during local and distant Mw = 6.8–9.3 earthquakes at epicentral distances from 80 to 14600 km; the study demonstrates that such effects depend on the earthquake parameters and the intensity of seismic impact in the well area. [ABSTRACT FROM AUTHOR]

According to B.L. Berry's 'harmonic model,' any natural or social process is a superposition of several cosmic rhythms. The author assumes that stability of these rhythms allows prediction of earth phenomena over an unlimited time. We show that the statistical criteria supposedly substantiating the harmonic model were applied incorrectly. The initial data for the analysis were biased and selected incompetently; the adequacy of the methods used was not verified. Predictions of natural catastrophes (earthquakes, weather anomalies, etc.) and various social events according to Berry's model are unsatisfactory. Statistics do not confirm that these predictions are at least slightly better than random guessing. Berry's model is unacceptable; it is untenable both in detail and in general. [ABSTRACT FROM AUTHOR]

On 30 October 2020 at 11:51 UT, a magnitude 7.0 earthquake occurred in the Dodecanese sea (37.84°N, 26.81°E, 10 km depth) and generated a tsunami with an observed run-up of more than 1 m on the Turkish coasts. Both the earthquake and the tsunami produced acoustic and gravity waves that propagated upward, triggering co-seismic and co-tsunamic ionospheric disturbances. This paper presents a multi-instrumental study of the ionospheric impact of the earthquake and related tsunami based on ionosonde data, ground-based Global Navigation Satellite Systems (GNSS) data and data from DORIS beacons received by Jason3 in the Mediterranean region. Our study focuses on the Total Electron Content to describe the propagation of co-seismic and co-tsunami ionospheric disturbances (CSID, CTID), possibly related to gravity waves triggered by the earthquake and tsunami. We use simultaneous vertical ionosonde soundings to study the interactions between the upper and lower atmosphere, highlighting the detection of acoustic waves generated by the seismic Rayleigh waves reaching the ionosonde locations and propagating vertically up to the ionosphere. The results of this study provide a detailed picture of the Lithosphere-Atmosphere–Ionosphere coupling in the scarcely investigated Mediterranean region and for a relatively weak earthquake. [ABSTRACT FROM AUTHOR]

Barcelona is in an area of low- to medium-seismicity and its earthquake vulnerability and risk has been assessed in different studies over the last 20 years. Most of these works have developed vulnerability models for the representative building classes of the city, trying to capture their main characteristics, and have been mostly represented through fragility curves. However, due to the lack of data for historical earthquake losses in the city, it has not been possible to validate, nor calibrate, any of these vulnerability models. In the absence of earthquake loss data, the objective of this paper is to compare the earthquake risk results of Barcelona, using common hazard and exposure datasets and different sets of vulnerability functions from previous studies to see how they rank compared with other locations with similar studies but more complete historical loss data. The results show large differences between the analysed vulnerability datasets, with some results that in our view tend to overestimate earthquake risk in Barcelona, and also allow identifying critical aspects that require future research. [ABSTRACT FROM AUTHOR]

Assessing the actual seismic economic losses of regional building portfolios is essential to quantify the seismic resilience of urban and rural areas. Various building clusters indicate different damage levels under real earthquakes of different intensities, which directly leads to apparent anomalies in the actual economic losses of various building portfolios. This paper proposes an economic loss assessment model for large-scale regional building portfolios, considering the damage probability matrices. The traditional empirical vulnerability quantification method is optimized and updated by combining the analysis methods of probability risk, reliability, macroseismic intensity, and instrument intensity. Five typical building sample sets (total survey area: 56,937.1893 × 104 m2) of 57 typical cataclysmic earthquakes that occurred in Yunnan Province, China, from 1993 to 2022 are collected and processed, and an updated fragility dataset is established. The calculation model considering empirical structural vulnerability and economic loss quantitative parameters is innovatively developed. Combined with the quantitative approaches of the multidimensional nonlinear fitting model and the established regional empirical structural vulnerability database, the seismic loss evaluation model of large-scale regional structures is established. Ultimately, the earthquake loss point cloud and matrix of typical building portfolios in the large-scale zone are developed using cloud analysis and the proposed seismic loss evaluation model. [ABSTRACT FROM AUTHOR]

In this paper, the optimal design of multiple tuned mass dampers (MTMDs) is performed to mitigate the seismic response of structures when considering the earthquake excitation as a random process. Frequency-domain analysis of the structure is performed according to random vibration theory in order to establish a new optimization problem in terms of the parameters of tuned mass dampers (TMDs) as design variables. In this regard, a semi-analytical formulation is developed for the random earthquake response of structures equipped with tuned mass dampers, which is highly efficient for each objective function evaluation needed for optimal design. Hence, the present formulation renders an effective optimization problem for the rapid design of MTMDs under earthquake loading. Minimization of the maximum standard deviation of structural response is proposed as an objective function, while some constraints are defined for the parameters and response of TMDs. Five well-known metaheuristic methods including particle swarm optimization, whale optimization algorithm, grey wolf optimizer, water evaporation optimization, and bat algorithm are employed for solving the proposed optimization problem. A comprehensive design example is considered based on a ten-story building frame, which demonstrates the efficiency and capability of the proposed random vibration-based problem for optimal design of MTMDs. The optimized TMDs are also verified with response history analysis in the time domain using several seismic ground motions. [ABSTRACT FROM AUTHOR]

This paper continues a series of publications on the modification of the Map of Expected Earthquakes (MEE), a method of medium-term earthquake forecasting. It is devoted to the calculation and analysis of retrospective statistical characteristics of dynamic and quasi-stationary prognostic indicators in the Kamchatka region used at this stage in the modernized MEE method. In our calculations we used the regional catalog of earthquakes in Kamchatka over the period from 1962 to 2020. The object of the forecast were earthquakes with Kforecast ≥ 13.5. The slope of the recurrence frequency graph γ with an efficiency value of Jt = 10.7 and JS = 11.3 appeared as one of the most effective precursors for the Kamchatka region, both in time and area. The next most effective (in terms of time) precursor was the number of earthquakes Neq in quiescence form with Jt = 5.8. In terms of area, the most effective precursor is the released seismic energy E2/3, also in quiescence form with JS = 14.7. The value of unconditional probability P(D1) of the occurrence of a strong earthquake was calculated based on a set of dynamic indicators, which turned out to be equal to 0.09. A map of the stationary conditional probability of a strong earthquake has been constructed that takes into account the stationary prognostic indicator "presence of faults in a cell" with values of 0.01 (in the cells where there are no faults) and 0.13 (in the cells where there are). As part of the next stage of work, it is planned to continue expanding the functionality of the algorithm for the medium-term forecast of the MEE. The ultimate goal of modernization is the development of a digital problem-oriented system for medium-term earthquake forecasting using a set of prognostic indicators. [ABSTRACT FROM AUTHOR]

In this paper we consider four moderate earthquakes that occurred on November 9, 2011; September 5, 2015; March 16, 2018; and October 10, 2019, in the southern basin of Baikal Lake near the Goloustnaya River delta. Seismotectonically, the earthquake sources are confined to the southwestern part of the Olkhon graben. The earthquake focal mechanisms allow us to suggest the activity of local submeridional faults, feathering the structures of the general northeast strike. For two seismic events, the following parameters were determined: scalar seismic moment M0 = 4.0 × 1015 N m, moment magnitude Mw = 4.4, and source depth h = 12 km for the September 5, 2015 earthquake and M0 = 2.2 × 1015 N m, Mw = 4.2, and h = 7 km for the March 16, 2018 earthquake. None of the seismic events was followed by noticeable aftershock activity. In 2011–2019, these earthquakes caused a noticeable macroseismic effect within the Irkutsk agglomeration, as well as a rather wide public response. Macroseismic data were collected mainly using an online survey system; the number of responses received within the first day after an earthquake varies from 127 to 341. The maximum intensity, IV–V, was observed for the November 9, 2011 earthquake in the settlement of Bolshoye Goloustnoye. The results can be used for assessing the seismic hazard in the Southern Baikal region. [ABSTRACT FROM AUTHOR]

In this paper we attempt to determine the sources of original information on earthquakes among newspapers published in Russia in 1809–1819. It is revealed that the information presented in periodicals was not used to the full extent in compiling the main historical catalogs of earthquakes in Russia. Paradoxically, instead of the original reports from Russian newspapers, often greatly abridged and distorted information was cited from translated versions and European newspapers, as well as from descriptive catalogs of earthquakes compiled in Paris and London. It is shown that in Russia there were several communication channels for transmitting messages from distant localities to the center. Not all incoming information was published; some of it ended up in the archives, usually as reports to the authorities. Some information remained in personal correspondence. Therefore, research on historical seismicity cannot be limited to searching for information in newspapers. [ABSTRACT FROM AUTHOR]

Earthquake indicators provide a huge advantage in the preparation for the calamity and its aftermaths. Total electron content (TEC) is an ionospheric measurement that varies before the possible happenstance of an earthquake. In this research paper, ordinary kriging based surrogate model (OKSM) which is used for forecasting ionospheric TEC variation is adapted as an earthquake indicators in low-latitude and mid-latitude regions. Seven International GNSS Service (IGS) stations from the mid-latitude and low-latitude region are chosen for observation. The stations are from different countries such as Indonesia (BAKO), Ecuador (RIOP), Greece (ORID), Cyprus (NICO), Hawaii (HNLC) and Italy (MATE & MAT1). The OKSM prediction program is performed with previous 2 months of TEC data from the observed date and its accompanying solar parameters such as Planetary K and A index (Kp & Ap), Radio Flux at 10.7 cm (F10.7) and disturbance storm time (DST) index acquired from OMNIWEB data servers. The performance of the model is evaluated using statistical metrics such as root mean square error (RMSE), normalized – RMSE (NRMSE), mean absolute error (MAE), Pearson's correlation coefficient (PCC) and chi-squared goodness of fit test. The evaluation of the prediction model on the same date shows that the performance deviation of OKSM is in the range of 2–5 TECU and also establishes the fact that the prediction capability of the OKSM is accurate. Application of the OKSM constructed with previous days data collected from high earthquake prone areas by omitting effects of solar storms and solar activities will act as a highly economical and simple early warning indicator of an earthquake. [ABSTRACT FROM AUTHOR]

This paper reports the obtained analysis data on the focal mechanisms and general distribution of earthquake epicenters in the Laptev Sea region. The principal stress axes directions were calculated by the formal stress inversion method for four groups of event clusters with known focal mechanisms. The distributions of the earthquake epicenters and crust thickness were compared. According to the seismological data, the extension axis of the Gakkel Ridge on the Laptev Sea shelf currently continues in the vicinity of the group of extension detachments located along the eastern boundary of the Anisin, Zarya, and Belkovskii–Svyatonosskii rift chains. The more ancient extension axis located along the group of detachments marking the eastern boundary of the Ust'-Lena and Omoloi rift systems and continuing the Gakkel Ridge axis is currently much less active. It carries residual stresses near its intersection with the Khatanga–Lomonosov fault zone in the northwestern parts of the shelf area and with the Lena–Taimyr zone of boundary uplifts, in the southwestern part. The axes oriented along the Olenyok and Bykovskii channels and the Siberian Platform boundary form extension conditions in the eastern part and strike–slip conditions in the western part of the Lena delta area. [ABSTRACT FROM AUTHOR]

This paper describes the behavior of several seismic precursors prior to the 2016–2019 activation in an area of a complex geodynamic setting at the boundary of the Pacific, North American, and Eurasian plates. We used an integrated approach to combine identified precursors with a view to getting more accurate locations of possible rupture zones of future large earthquakes. The precursors include quiescence based on the RTL parameter and the "Z-function", variations in the slope of the earthquake recurrence graph (γ-value), and the areas of seismic ruptures dS. For the first time in Kamchatka, we analyze anomalies in the parameter dS interpreted as seismic activations to show the presence of a precursory component before the onset of the foreshock activation. Examples include increases in the values of that parameter before events that were the largest for the areas where they occurred: the Near-Islands Aleutian earthquake of July 17, 2017, Mw = 7.8 and the Uglovoe Podnyatie earthquake of December 20, 2018, Mw = 7.3. The overall extent of the anomalous area, which still exists and includes consecutive quiescence and foreshock phases, is ~900 km, which creates conditions for possible occurrence of a new great earthquake in the junction zone of the three plates with a magnitude that can exceed whatever has been recorded in the region so far. [ABSTRACT FROM AUTHOR]

This paper reports results from an analysis of swarm seismic events that were recorded in 2018 in the area of the Elbrus Volcanic Center (EVC) by the North Caucasus Seismological Network of the Federal Research Center, Geophysical Survey, Russian Academy of Sciences (FRC GS RAS). The standard location procedure was used to find the hypocenters of recorded events in the EVC area. In the LOS program package, a complex combined location algorithm, methods for minimizing the time residuals at the source, and search over a grid with several trial depth values, were used to relocate the hypocenters of seismic events in swarm sequences. This approach enhances location reliability due to incorporation of the uncertainties related to erroneous onset identification and insignificant deviations of travel times that depend on the earth velocity model used here. A study of earthquake mechanisms for the larger earthquakes has determined the type of slip in agreement with the kinematics in the Elbrus–Mineralnye Vody normal-oblique fault zone. Correlation analysis of waveforms on the vertical component that have been filtered in the frequency range 1‒10 Hz, which includes P and S waves, at the nearest station shows a high agreement among the data under analysis (the correlation coefficient is R ≥ 0.85), thus indicating a high probability of all events having similar sources and propagation paths of seismic waves. Comparison of power spectral densities for individual earthquakes in the swarm sequences also demonstrates a high similarity. [ABSTRACT FROM AUTHOR]

The Chuya earthquake of 2003 exerted an appreciable influence on the seismicity of the entire Altai. This paper presents data on variations in the Altai seismicity from 2003 to 2021. It is shown that earthquakes of the first half-year after the major earthquake of 2003 had their rupture zones in the epicentral zone, while the other Altai structures were aseismic. After 2009 we saw changes both in the near zone that encompasses geological structures that were adjacent to the epicenter (with distances of 60‒80 km from the mainshock epicenter), such as the Aigulak, Kurai, South Chuisky and North Chuisky mountain ranges, and in the far zone at distances of 250‒450 km from the epicenter and in different directions from it. The Aigulak earthquake of 2019 gave rise to an aftershock process that displaced the center of Altai seismicity to the eponymous mountain range. There are no data on large earthquakes during the historical period for many Altai structures which have been activated following the Chuya earthquake, either from seismological or from paleo-geological evidence. One could explain the evolution of seismicity around the rupture zone of the Chuya earthquake in space, and with time delays of some years, invoking the influence of a large earthquake on a medium involving plasticity. We know of nonlinear models that hold promise for future research concerning the influence of large earthquakes on the evolution of seismicity in geological media. [ABSTRACT FROM AUTHOR]

We use a method based on Uniform Hazard Spectrum (UHS) to compile seismic microzonation maps for the broader area of Novi Sad, a city in Serbia. The maps are intended for use in the performance-based design (PBD) of earthquake-resistant structures. At present, PBD requires the use of two sets of spectral amplitudes, one in which the structure remains linear and the other in which it may respond nonlinearly. These PBD requirements cannot be met by using only one (same) fixed-shape spectrum and scaling by peak ground acceleration alone for varying probabilities of exceedance. The alternative we present in this paper is based on UHS and describes a combined contribution from (a) seismic excitation by local earthquakes, for which region-specific attenuation equations are used, and (b) seismic excitation by large, distant earthquakes, for which different attenuation equations are used. Our maps also take into account the influences of site geology and site soil conditions in a balanced manner. [ABSTRACT FROM AUTHOR]

With the increase in the pace of development, the demand for tunnels has increased in recent years. Analysing the stability of a tunnel in a fractured rock mass is a very challenging and cumbersome activity. The tunnel stability depends on the strength of the rock, joints bolt strength, in-situ stresses, and their orientation. This paper focuses on constructing tunnels in fractured/jointed rock mass. Three different software namely Rocscience Phase2 (finite element based), FLAC3D (finite volume based) and PFC3D (distinct element based), were used to analyse the performance and stability under static and dynamic loading conditions. The geomaterial properties used for the analysis were taken from data obtained after laboratory testing and based on available literature. The effect of joint orientation and bolt length was analysed using Phase 2 assuming plain strain conditions. The effect of earthquake and performance of fully grouted, energy absorbing and deformation-controlled bolts under seismic loading conditions were compared using FLAC3D. While the 3D distinct element analysis of geometry was performed using PFC3D to evaluate the effect of joints and their orientation. The performance of the different types of bolts was also analysed numerically. The behaviour of bolts can be customised using the 'fish'function. The results indicate that analysis must incorporate the fusion of various numerical simulation techniques like finite element-, finite volume- and distinct element-based methods for more reliable results. [ABSTRACT FROM AUTHOR]

In this paper, we present the first results of complex geological and geophysical studies of active tectonics in the northeast of Taymyr that were carried out during the expedition of the Northern Fleet and the Russian Geographical Society in 2020. At the foot of the Byrranga Mountains, a wide zone of active fault-folded tectonic deformations was identified and studied. The general kinematics of displacements is reverse-thrust with signs of shear. The structural style of young tectonic deformations bears a direct resemblance to well-studied structural analogues of the Central Asian seismic belt. The Taymyr seismotectonic zone reveals both spatial and genetic isolation. It has an individual model of the Late Cenozoic geodynamic evolution and modern seismotectonic regime, which differs sharply from the Laptev Sea rift zone adjacent to the east. A complex of geological and geophysical methods showed the high efficiency of application in the Arctic to identify young fault-fold structures, which are potential sources of strong earthquakes. [ABSTRACT FROM AUTHOR]

On January 8, 2022, an M6.9 earthquake occurred in Menyuan, Qinghai, which caused surface damage. In this paper, the line-of-sight (LOS) coseismic surface deformation field is obtained by the interferometric synthetic aperture radar (InSAR) of the Sentinel-1 satellite. Constrained by the InSAR surface deformation field, a Bayesian method based on sequential Monte Carlo sampling was used to invert the geometric parameters of seismogenic faults and the distribution of fault slip. Moment magnitude of the model is Mw6.6. The earthquake was determined to occur at a left-lateral strike-slip fault. Based on the historical strong earthquake dislocation model, the PSGRN/PSCMP program was used to calculate the Coulomb stress change at the epicenter of the 2022 Menyuan M6.9 earthquake caused by the surrounding historical strong earthquakes. The results show that the occurrence of the Gulang M8 earthquake in 1927, the Menyuan Mw5.7 in 1986 and the Menyuan Mw5.9 earthquake in 2016 caused a significant increase in Coulomb stress at the epicenter of the 2022 Menyuan earthquake. The coseismic and post-seismic Coulomb stress increases were greater than 0.01 MPa. Combined analysis of this result with regional tectonic stress, allows us to conclude that the 2022 Menyuan M6.9 earthquake occurred on the dynamic background of the continuous extrusion of the Indian plate towards the Eurasian plate, and the regional historical strong earthquake activity played a significant role in promoting it. The research results provide a theoretical basis for understanding the seismogenic background and dynamic mechanism of the 2022 Menyuan earthquake. [ABSTRACT FROM AUTHOR]

In this paper, we determine the location of the hypocenter and the magnitude of the earthquake of September 11/23, 1888 based on macroseismic data published in the Russian periodic in Russian, Armenian, and Georgian languages. Calculations showed that the magnitude of the earthquake was previously significantly underestimated, due to which it was not included in the catalog of strong earthquakes in the Caucasus test region (Shebalin and Tatevossian, 1997). The accuracy of the location of the hypocenter makes it possible to identify the active fault, with which the source of the 1888 earthquake is associated. The earthquake with Mw = 6.6 that occurred almost 100 years later confirms the long-term activity of the Western branch of the East Anatolian fault zone. [ABSTRACT FROM AUTHOR]

In this paper, we kinematically analyze the movements of plates and blocks of the region of southeastern Turkey, where strong earthquakes occurred on February 6, 2023, based on a homogeneous database of displacement velocities of GNSS permanent monitoring stations. Along the East Anatolian fault zone from 2008 to 2018, the Arabian Plate was established to shift relative to the Anatolian Plate, which corresponds to a left shift (without a normal component) at a rate from 1 cm/yr in the eastern part to 0.8 cm/yr in the western part. Along the Chardak fault, displacements corresponding to the left shift occurred at a rate of less than 0.7 cm/year. The revealed kinematics is confirmed by focal mechanisms and cosesismic displacements of the studied earthquakes. The M7.5 earthquake that occurred directly on the Chardak fault is not an aftershock of the M7.8 earthquake, but is a relatively independent event. An analysis of the seismic regime shows that the stresses on the East Anatolian fault after the main M7.8 event are relieved by the first large latitudinal fault zone (the Chardak fault). The results of our study suggest that the counterclockwise rotation of the Anatolian and Arabian plates associated with the opening of the Red Sea Rift is most likely decisive for the general kinematics of the plates in the region. [ABSTRACT FROM AUTHOR]

Static and dynamic frictional properties of rock discontinuities are of great importance in the evaluation of the initiation of failure and post-failure motions of rock engineering structures as well as the rupture and strong motions induced by earthquake faults in earthquake science. Nevertheless, experiments on static and dynamic frictional properties of rock discontinuities are very rare. In this study, the authors describe tilting and stick–slip experiments on various natural rock discontinuities and saw-cut surfaces to determine their static and dynamic frictional properties. Furthermore, these experimental results are compared with each other to discuss the static and dynamic frictional properties of rock discontinuities from tilting and stick–slip tests. Experimental results show that peak (static) friction angle for discontinuity surfaces obtained from tilting tests and stick–slip experiments are very close to each other. Highlights: In this paper, it is demonstrated that the static and dynamic frictional properties of rock discontinuities can be determined from tilting and stick-slip tests. Experimental results confirm that peak (static) friction angle for discontinuity surfaces obtained from tilting tests are very close to those obtained from stick-slip experiments. The experimental results could be useful for researchers dealing with the estimation of post-failure motions of failed bodies in Rock Mechanics and Rock Engineering as well as strong motion simulations in Earthquake Science and Engineering. [ABSTRACT FROM AUTHOR]

The existence of several magnitude scales in the compiled earthquake catalogs of a specific region has made the development of regional relations connecting magnitude scales a necessity, especially for creating a homogeneous seismic catalog in which all magnitudes should be converted to a preferred magnitude scale. To consistently estimate all magnitude ranges and avoid the saturation problem for large earthquakes, the preference is always given to the moment magnitude Mw scale, wherein the most complete and reliable catalog used worldwide is the Global Centroid Moment Tensor (GCMT). However, to our knowledge, no study has yielded regional (in Algeria) relationships for converting different magnitudes to the moment magnitude (Mw,GCMT). The main reason is typically due to the lack of data pairs of different magnitude scales with Mw (GCMT). To overcome this issue, in this research paper, the moment magnitudes data used for northern Algeria (the area bounded by 32° to 39° N and 3° W to 10° E) have been taken principally from the GCMT catalog and enhanced with the European–Mediterranean Regional Centroid Moment Tensor catalogs RCMT and ZUR-CMT. Regarding this latter, it has been demonstrated in the literature that for the Mediterranean regions, a minor correction should be addressed before merging its data with the GCMT and RCMT catalogs, which are perfectly correlated. To accomplish this task, the magnitude scales tested against Mw are the surface wave magnitude, MS, and the body wave magnitude mb issued from the international seismological sources of ISC and NEIC for the same boundaries. As long as the earthquake magnitudes, in general, are affected by errors of comparable size, the best and most reliable regression method that considers the errors in both dependent and independent variables for linear conversion problems is the General Orthogonal Regression, which is adopted and applied herein to develop the regional relations. [ABSTRACT FROM AUTHOR]

Predicting individual large earthquakes (EQs)' locations, magnitudes, and timing remains unreachable. The author's prior study shows that individual large EQs have unique signatures obtained from multi-layered data transformations. Via spatio-temporal convolutions, decades-long EQ catalog data are transformed into pseudo-physics quantities (e.g., energy, power, vorticity, and Laplacian), which turn into surface-like information via Gauss curvatures. Using these new features, a rule-learning machine learning approach unravels promising prediction rules. This paper suggests further data transformation via Fourier transformation (FT). Results show that FT-based new feature can help sharpen the prediction rules. Feasibility tests of large EQs ( M ≥ 6.5) over the past 40 years in the western U.S. show promise, shedding light on data-driven prediction of individual large EQs. The handshake among ML methods, Fourier, and Gauss may help answer the long-standing enigma of seismogenesis. [ABSTRACT FROM AUTHOR]