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Timely estimation of earthquake magnitude plays a crucial role in the early warning systems for earthquakes. Despite the inherent danger associated with earthquake energy, earthquake research necessitates extensive parameter estimation and predictive techniques to account for uncertain trends in earthquake waveforms when determining earthquake magnitudes using a single station. This study introduces an effective solution to tackle the issue through the automatic magnitude deep network (AMagDN) model. The proposed model includes long short-term memory (LSTM), a bidirectional LSTM, an autocorrelation attention mechanism, and a machine learning block that can capture detailed information from the seismic waveform recorded during an earthquake. The unique feature of this model is the use of multivariate time series waveforms derived from recorded accelerograms specifically tailored to their energy significance with magnitude and seven fusion tabular parameters involving source and geospatial features. The proposed model's training, validation and testing are done using independent 15014, 1287 and 3448 records maintained by the Kyoshin network, Japan, for moderate to great impact earthquakes between 5.5 and 8.0 ( M JMA ). A comparative study shows that the proposed model outperforms recent state-of-the-art models and common linear relations, reducing mean absolute prediction error by 40% from the second-best model. The multi-stations data are also used for successfully forecasting the magnitudes of two significant earthquakes of 7.7 and 7.3 magnitude ( M JMA ) using the proposed model. The reliable prediction capabilities of the proposed model for both single and multi-station data clearly demonstrate its utility in reducing earthquake hazards. [ABSTRACT FROM AUTHOR]

The presence of "ill-posed samples" specifically in low-volume datasets leads to accuracy decrement in the learning procedure and the generalization of neural networks. Such samples can be caused by various reasons such as noise contamination, corrupted sensors, or even, the complex distribution of physical properties governing the problem. The peak ground acceleration (PGA) datasets are definitely among the last mentioned. Focusing on speed and accuracy, a method for calculating earthquake magnitude based on the PGA data recorded at a single station along with hypocentral information has been presented in this research. Here, after training a deep neural network, the regression errors of the training data samples are clustered into two groups, namely well and ill posed using the grey wolf optimization algorithm. Instead of being removed, the data samples with low learning rates are then modified using samples selected from the other cluster in a fusional form. Then, two separate models are used and trained independently for the clusters. Next, in addition to the routine procedure of network generalization, every new sample is first checked whether is more likely to belong to which group of the clustered data, and after processing, the corresponding trained model is used. The results of the experiments show that using the proposed method results in magnitude calculation with an error order of less than 0.212 units of moment magnitude with a probability of more than 99.7%, which is superior to the conventional methods some of which were reviewed in this research. [ABSTRACT FROM AUTHOR]

Predicting ionospheric Total Electron Content (TEC) variations associated with seismic activity is crucial for mitigating potential disruptions in communication networks, particularly during earthquakes. This research investigates applying two modelling techniques, Autoregressive Moving Average (ARMA) and Cokriging (CoK) based models to forecast ionospheric TEC changes linked to seismic events in Indonesia. The study focuses on two significant earthquakes: the December 2004 Sumatra earthquake and the August 2012 Sulawesi earthquake. GPS TEC data from a BAKO station near Indonesia and solar and geomagnetic data were utilized to assess the causes of TEC variations. The December 2004 Sumatra earthquake, registering a magnitude of 9.1-9.3, exhibited notable TEC variations 5 days before the event. Analysis revealed that the TEC variations were weakly linked to solar and geomagnetic activities. Both ARMA and CoK models were employed to predict TEC variations during the Earthquakes. The ARMA model demonstrated a maximum TEC prediction of 50.92 TECU and a Root Mean Square Error (RMSE) value of 6.15, while the CoK model predicted a maximum TEC of 50.68 TECU with an RMSE value of 6.14. The August 2012 Sulawesi earthquake having a magnitude of 6.6, revealed TEC anomalies 6 days before the event. For both the Sumatra and Sulawesi earthquakes, the GPS TEC variations showed weak associations with solar and geomagnetic activities but stronger correlations with the earthquake-induced electric field for the considered two stations. The ARMA model predicted a maximum TEC of 54.43 TECU with an RMSE of 3.05, while the CoK model predicted a maximum TEC of 52.90 TECU with an RMSE of 7.35. Evaluation metrics including RMSE, Mean Absolute Deviation (MAD), Relative Error, and Normalized RMSE (NRMSE) were employed to assess the accuracy and reliability of the prediction models. The results indicated that while both models captured the general trend in TEC variations, nuances emerged in their responses to seismic events. The ARMA model demonstrated heightened sensitivity to seismic disturbances, particularly evident on the day of the earthquake, whereas the CoK model exhibited more consistent performance across preand postearthquake periods. [ABSTRACT FROM AUTHOR]

We compare Fourier Amplitude Spectra of Fault Normal (FN) and Fault Parallel (FP) seismograms at near‐fault sites for seven strike‐slip earthquakes with moment magnitudes Mw ≥ 6. For all events we find large FN/FP ratios at low frequencies consistent with near‐fault S‐wave radiation patterns for strike‐slip earthquakes. However, the difference diminishes with increasing frequency and FN/FP is about 1 above a transition frequency. The results may reflect small tensile/isotropic components in the earthquake rupture zones that homogenize the high‐frequency radiation in different directions at near‐fault sites. The FN/FP ratios at low frequencies and transition frequencies above which FN ∼ FP vary among the analyzed earthquakes and have no clear correlation with the magnitudes. The lack of correlation may signify a characteristic scale (e.g., process zone size, duration of source time function) controlling the isotropic radiation, and/or wave propagation and other effects that mask the source effects. Plain Language Summary: Earthquake source processes have significant impacts on many topics including generation of frictional heat on the fault and seismic ground motion away from the fault. The classical model with pure shear motion predicts that strike‐slip earthquakes should produce considerably larger fault‐normal motion close to the fault than fault‐parallel motion. Analyzing near‐fault seismic waveforms generated by seven moderate to large earthquakes, we find that larger fault‐normal motion is observed only for relatively low frequencies, and that above a transition frequency the fault‐normal and fault‐parallel motions are very similar. The observations may reflect local dilatational processes in the earthquake rupture zones that modify the directional dependence of the high‐frequency seismic radiation. The transition frequencies do not show clear scaling with the size of earthquakes, which suggests a process with a characteristic length and/or time scale, or a mixture of multiple effects. The results highlight the need to further improve our understanding of earthquake source processes with detailed near‐fault data. Key Points: Near‐fault seismograms of Mw ≥ 6 strike‐slip events show significantly larger fault‐normal than fault‐parallel motion at low frequenciesThe near‐fault seismic motions have similar amplitudes in different directions above certain transition frequenciesThe isotropic high‐frequency radiation suggests that local dilatational processes accompany the overall shear motion in the rupture zones [ABSTRACT FROM AUTHOR]

Earthquake magnitude prediction is an exceptionally challenging task that has been explored through various machine learning approaches. However, the development of prediction models is hindered by redundant features and time series properties. The Elite Genetic Algorithm (EGA) excels in searching for optimal feature subsets; while, Long Short-Term Memory (LSTM) is specialized in processing time series and complex data. Hence, we introduce an EGA feature selection and LSTM model (EGA-LSTM) for time series earthquake prediction. Initially, acoustic and electromagnetic data from our developed AETA system are fused and preprocessed using a roulette-based EGA to search strong correlation indicators. Subsequently, LSTM is employed to perform magnitude prediction with the selected features. Specially, the Root Mean Square Error (RMSE) of LSTM and the ratio of selected features are chosen as fitness components of EGA. Finally, we evaluate the proposed EGA-LSTM on AETA data from four regions from China, considering the influence of data in different time periods (timePeriod) and fitness function weights ( ω a and ω F ) on prediction results. Furthermore, our proposed approach outperforms state-of-the-art methods in evaluation metrics such as EV, MAE, MSE, RMSE, and R2. Nonparametric tests reveal that EGA-LSTM is significantly different from others and outperforms the standard LSTM. [ABSTRACT FROM AUTHOR]

This study was conducted as a qualitative inquiry to deeply explore the thoughts and experiences of nursing students involved in support activities in disaster areas. It was conducted as a qualitative study. Data for the study were collected through face‐to‐face interviews or video conferencing using a Personal Information Form and a Semi‐Structured Interview Form created by the researcher. Data analysis was conducted using the MAXQDA software.The population of this qualitative study consisted of nursing students actively involved in support activities in 11 provinces affected by the magnitude of 7.7 earthquake centered in Kahramanmaraş/Turkey. The sample of the study comprised nursing students who responded to our call shared with nursing student groups and met the inclusion criteria.Through qualitative analysis, three themes were identified: initial emotions experienced during the earthquake, difficulties faced during the earthquake process, and emotions following the earthquake experience.Students participating in support activities in the earthquake‐affected region provided explanations regarding their emotions, encountered ethical dilemmas, infrastructure issues, as well as deficiencies in organization and education. [ABSTRACT FROM AUTHOR]

The rapid and accurate prediction of earthquake Strong-Shaking Zone (SSZ) is crucial for issuing precise early warnings to regions at high risk of strong ground shaking. Generally, the SSZ is derived from the real-time spatial distribution of observed ground motions. However, during the initial stages of large earthquakes, the SSZ is often underestimated and provide alerts without enough lead-time (the time interval between the alert declaration and the S-wave arrival to the target area). In this study, we propose an innovative approach termed Near-epicenter-based Partial Matching Crossover. Leveraging the characteristic that reliable magnitude estimates for large earthquakes are available earlier than accurate predictions of the peak ground velocity (PGV) distribution, this approach utilizes near-epicenter station data to rapidly estimate the SSZ. It achieves this by matching a segment of the fault, defined by a predetermined length, with the predicted PGV map within a 120 km radius centered at the epicenter. Application of our method to strong motion data from China, Japan and Turkey demonstrates its efficacy in quickly anticipating the post-earthquake intensity distributions for large earthquakes. Specifically, it offers a lead time of 5 s or more for 51.5% (39,354 km2), 43.3% (5772 km2), 31%(47,107 km2) and 75.3% (81,966 km2) of the IMM = V region during the M 8 Wenchuan earthquake, the M 7.3 Kumamoto earthquake, the M 7.8 Syria earthquake and M 7.6 Turkey earthquake, respectively. The presented approach introduces a novel methodology to extend the lead time for earthquake early warnings. [ABSTRACT FROM AUTHOR]

Together with axial and flexural actions, modern-designed reinforced-concrete walls can also be subjected to torsion during rare loading events, such as large-magnitude earthquakes or strong winds. For certain widely used nonplanar open cross-section geometries, this torque is resisted primarily through warping. In some cases, the longitudinal stresses caused by torsional warping can be of the same order of magnitude as those caused by flexure, which postulates a reduction of the in-plane bending moment capacity of the section. This study explores the reduction of bending moment capacity of open reinforced-concrete U-shaped core walls due to the simultaneous application of flexural, axial, and torsional loading. Initial investigations focused on strain gradients through the wall segments of reinforced-concrete U-shaped walls. Using a refined data set from a recent experimental campaign, the commonly assumed linear strain gradient used in the design of reinforced-concrete walls is challenged. Numerical methods that intrinsically rely on the observed strain gradients are then employed to compute, for a range of torque-to-bending-moment ratios, the ultimate bending moment and torque capacities from combined loading scenarios. The numerical results corroborate existing experimental results, indicating a significant reduction (almost half) in ultimate bending moment capacity when a torque equal to approximately 20% of imposed bending is applied. Interaction diagrams between the ultimate torque and bending moment show that it is possible to derive a simple relationship between the two for the purposes of structural design. These results can help formulate guidelines for future international building codes, which in their current form cannot account for the design of open sections governed by warping torsion. [ABSTRACT FROM AUTHOR]

As electric vehicle (EV) adoption increases, transportation services will shift dependence from liquid fuel infrastructure to electric power infrastructure. Since transportation plays a major role in disaster response and recovery, this shift in dependence has important implications for coupling electrical grids and transport resilience. The implications for the electrical grid for southwestern British Columbia, Canada are examined, motivated by this region's high EV adoption rate and the potential for a catastrophic magnitude 9.5 earthquake. A comparison of the resilience of the electrical infrastructure compared to the fuel infrastructure is provided and approaches for increasing resilience in the region for EV power supply are discussed. This paper compiles lessons learned from past large earthquakes in Chile, Japan, and New Zealand with consideration given to successes and failures. While this paper was written with a focus on southwestern British Columbia, many of the suggestions for increasing power system resilience could be applied in other seismically active locations during the transition to EVs. This paper also considers integrated disaster resilience planning for the changing transport landscape from fuel vehicles to EVs. [ABSTRACT FROM AUTHOR]

For the last few decades, for the liquefaction susceptibility assessment of a location, Standard Penetration Test (SPT) based methods have been generally practiced. In this research, the liquefaction potential of Dhaka Metropolitan Development Plan (DMDP) area has been analyzed using three existing Cone Penetration Test (CPT) based methods. CPT (CPTu and SCPT) data have been collected from 546 locations of the DMDP region covering 1530 square kilometer area and have been analyzed to assess the liquefaction potential. Bangladesh is located in the junction of Indian and Eurasian plate, which makes this country vulnerable to earthquakes. A magnitude 7.5 earthquakes and Peak Ground Acceleration (PGA) value of 0.21 g at the surface have been used to evaluate the liquefaction susceptibility of the region using the three CPT-based techniques and another CPT-based technique has been employed to evaluate the liquefaction susceptibility of the region using variable surface PGA based on Modhupur scenario. Liquefaction potential maps have been proposed and compared for these four methods. It has been found that more than 60% of the study area falls within the LPI range which indicates moderate to relatively high liquefaction vulnerability. The liquefaction susceptibility of the three methods has been found to be in agreement and possible reasons of deviation in any particular method have been explained. Also, Ishihara 1985 proposed LPIISH has been estimated and compared with Iwasaki's LPI values. It has been observed that the difference in results using LPI and LPIISH are not significant. The seismic microzonation and liquefaction analyses will help engineers, planners and relevant professionals to get prior idea about the seismic vulnerability of any part of the DMDP region and take measures beforehand to avoid any damaging consequences. [ABSTRACT FROM AUTHOR]

The 2024 Mw 7.5 Noto Peninsula, Japan, earthquake was initiated within the source region of intense swarm activity. To reveal the mainshock early process, we relocated the earthquake hypocenters and found that many key phenomena, including the mainshock initiation, foreshocks, swarm earthquakes, and deep aseismic slip, occurred at parts of a previously unrecognized fault in intricate fault network. This fault is subparallel (several kilometers deeper) to a known active fault, and the mainshock initiation and foreshocks occurred at the front of a 2‐year westward swarm migration. The initiation location coincides with the destination of the upward migration of a deeper earthquake cluster via several smaller faults. Fluid supply, small earthquakes, and aseismic slip on the fault likely triggered the mainshock, leading to the first major rupture at the western region, propagating further to the west and east sides, resulting in an Mw7.5 event, exceeding 100 km in length. Plain Language Summary: In 2024, an earthquake of magnitude 7.5 happened on the Noto Peninsula, Japan. This earthquake started in an area where many small earthquakes occurred. To reveal how this large earthquake occurred, we precisely determined the hypocenters of the mainshock, foreshocks, aftershocks, and swarm earthquakes. We observed that the mainshock initiation, foreshocks, and some aftershocks occurred on the largest fault in the complex network. Aseismic slip also occurred near the deeper extension. This fault is not a previously known active fault, but small earthquakes migrated westward on it for over 2 years, and the mainshock rupture was initiated at the front. Directly below the mainshock initiation area, small earthquakes moved upward through several small faults. Aseismic slip propagation, fluid supply, and small earthquakes likely triggered the mainshock. The initiated mainshock rupture caused the first major slip in the western region, causing considerable uplift there and further propagating to the east and west. Despite the existence of many minor faults, many key phenomena have occurred on this previously unrecognized fault, which plays a vital role in stress release and tectonic processes in this crust. Key Points: The mainshock initiation, foreshocks, and deep aseismic slip occurred on a previously unknown fault deeper than a known active faultMany swarm earthquakes that appeared to have occurred on different faults actually occurred on different parts of the same faultMainshock rupture was initiated in a westward earthquake migration front where fluid was supplied from depth through several small faults [ABSTRACT FROM AUTHOR]

The interplay between seismic activity and fluid flow is essential during the evolution of hydrothermal systems. Although earthquakes can trigger transient fluid flow and phase changes in dilational jogs, the temporal scale and the geologic conditions that enhance such process are poorly quantified. Here, we use numerical simulations of deformation and fluid flow to constrain the conditions that maximize adiabatic boiling—referred to as flashing—and estimate the extent and duration of such process. We show that there is an optimal geometry for a dilational jog that maximizes co‐seismic flashing within the jog. Fluid flow simulations indicate that the duration, intensity, and propagation of the flashing front are limited and highly dependent on the magnitude of the co‐seismic slip and the initial pressure‐enthalpy conditions. Our results are valuable to better understand the implications of pressure fluctuations during the seismogenic cycle, as well the mineralization processes in the Earth's crust. Plain Language Summary: Earthquakes can strongly affect circulating fluids within the Earth's crust, mainly where faults bend or split into different fault segments and produce dilatant areas. In these areas, earthquakes play an important role in forming ore deposits, because the co‐seismic volume change can produce a pressure drop that drives boiling with gas exsolution and subsequent mineralization. This process, in which boiling is triggered by a pressure drop rather than a temperature rise, is called flash vapourization or flashing. Here, we used a computer code to unravel scenarios where optimal geometry and pressure‐temperature conditions maximize flash vapourization. Furthermore, we found that the duration and extension of the flashing event are limited and highly dependent on the magnitude of the triggering earthquake and the physico‐chemical conditions of the system. Such results are valuable for assessing the implications of pressure fluctuations during the seismogenic cycle and for better understanding mineralization processes in the Earth's crust. Key Points: We use numerical simulations to constrain the intensity and temporal scale of co‐seismic flash vapourization or flashing triggered by earthquakesWe found an optimal geometry of a dilational jog that maximizes co‐seismic flashing within the jogsUnder optimal conditions, the flashing front propagates up to 1 m away from the dilational jog and persists for almost 3 hr [ABSTRACT FROM AUTHOR]

The Late Quaternary activity characteristics of secondary faults located between the main active faults at the boundaries of large basins are of great significance to the overall understanding of regional seismic hazards. The Wulashan Northern Fault (WNF) is located on the northern side of the Ordos Block, within the Northern Margin Fault Basin in North China, between the Sertengshan Piedmont Fault and Daqingshan Piedmont Fault. Current research on the geometry and kinematics of the WNF needs to be improved. In this study, we aimed to determine the shallow structural characteristics and Late Quaternary activity of the WNF using shallow seismic exploration and composite drilling geological cross-sectional analysis. The results indicate that the WNF is not a single surface fault but multiple branches with a northward-dipping stepped surface distribution. The latest activity of the F1 branch with a maximum coseismic vertical dislocation of 0.9 m occurred before 47.08 ± 3.7 ka B.P. The latest and older activities of the branch of F2 with a maximum coseismic vertical dislocation of 0.96 m and 1.15 m occurred before 73.8 ± 2.8 ka B.P. and 91.2 ± 4.4 ka B.P., respectively. According to a series of empirical relationships between length of surface rupture and magnitude, the maximum potential magnitude of the earthquake was determined to be M = 6.5-7.0. We argue that even though the Late Quaternary activity of the WNF was weaker than that of the other boundary faults of the Hetao Basin, the local urban and rural planning and land and resources construction in the Hetao Basin region should pay attention to the seismic risk of the WNF as an independent section in the future for the effect of secular tectonic loading. [ABSTRACT FROM AUTHOR]

Earthquakes begin with abrupt shifts along the faults. These movements release seismic waves that propagate through the Earth, shaking the ground as a result of the stored “elastic strain” energy being released. Property loss and human deaths occur due to improper design of structures under the earthquake loading conditions. It is observed that Peninsular India witnessed steady-to-serious earthquakes in the last 50 years. Amaravati is the prospective capital city of Andhra Pradesh State, which is situated on the Coromandel Coast of Peninsular India. The upcoming capital city, Amaravati, requires an earthquake hazard analysis because important engineering structures and infrastructure systems will be constructed in the near future. In this study, a probabilistic approach is used to assess the earthquake hazard for Amaravati City (latitudes: 16∘24′36′′–16∘35′24′′N and longitudes: 80∘24′25′′–80∘36′18′′E), India. The seismic risks of Amaravati City presented in terms of the configuration of ground motion parameters, peak ground acceleration (PGA), and spectral response acceleration (Sa) at 0.05s and 1s for 2% and 10% Risks of Exceedance in 50 years, are produced. The uncertainties involved in seismic risk prediction are accounted for by selecting different attenuation relations developed for globally shallow crustal intraplate earthquakes with a logic tree approach. Additionally, the seismic risk values are disaggregated for Amaravati City (16∘31′37′′N and 80∘29′46′′E) to understand the individual contributions of seismic sources in terms of earthquake magnitude and site distance. The uniform hazard spectra are developed for the important places of the Amaravati Capital City and are compared with the Indian seismic code [IS 1893 (Part 1): Criteria for earthquake-resistant design of structures — Part 1: General provisions and buildings] for the rocky site. It is found that the estimated PGA values for Amaravati City are higher than the values recommended by IS 1893 (Part 1) for the rocky site. The results of this study will be very helpful for the composition of earthquake-resistant infrastructures in Amaravati City. [ABSTRACT FROM AUTHOR]

Earthquake prediction is the holy grail of seismology and one of humanity's greatest dreams. The Earth's magnetic field appears to be one of the best possible precursors of earthquakes, although the topic is controversial. Recent advancements have made it possible to observe magnetic fields from satellites with great accuracy. We utilize magnetic measurements from Swarm satellites to explore the potential identification of anomalous magnetic signals preceding earthquakes. Focusing on 1077 major earthquakes that occurred in 2014–2023 in the Alpine–Himalayan belt, we apply an automatic algorithm to data recorded 10 days before each earthquake. This analysis reveals clear pre-earthquake anomalies in the magnetic field components. Notably, a robust correlation is established between the duration of these anomalies and the earthquake magnitude, indicating that as the earthquake magnitude increases, so does the duration of the anomaly. Here we show that this method has a great ability to make predictions (high accuracy 79%, precision 88%, F1-score and hit rate 84%), thus becoming the basis for an Operational Earthquake Prediction System (OEPS). [ABSTRACT FROM AUTHOR]

On January 23, 2024, a magnitude 7.1 earthquake occurred in Wushi County, Aksu Prefecture, Xinjiang, China. The epicenter was located at the Maidan Fault, which is known for its left-lateral strike-slip and thrust characteristics within the Tianshan seismic zone. In this study, we used Interferometric Synthetic Aperture Radar (InSAR) and Global Navigation Satellite System (GNSS) observations to investigate the characteristics and mechanisms of both the coseismic and interseismic deformation. The main findings are as follows: 1) The InSAR coseismic deformation displays clear thrust characteristics, with a maximum relative displacement of ∼ 0.8 m along the line of sight, thereby indicating a thrust-type earthquake. 2) The majority of the slip during the earthquake occurred within a 60 km × 40 km area, with depths ranging from 4 to 26 km. The maximum slip of the fault was about 2.3 m, corresponding to a moment magnitude of 7.0. 3) The seismogenic faults primarily exhibit thrust-type movement characteristics during the interseismic period and possess a clearly defined locking state. The earthquake rupture depth aligns with the depth of locking during interseismic periods. 4) The seismogenic structure experienced compressive deformation in a north–south direction prior to the earthquake, with the epicenter located on the surroundings of the high-strain area, as indicated by the GNSS strain rate. [ABSTRACT FROM AUTHOR]

Two shallow earthquakes of moment magnitude 6.2 and 5.8 occurred in the central arm of Sulawesi on 26 July 2021 and 26 August 2021, respectively. The fault responsible for the earthquake had previously only been partially mapped, thus making further analysis of its characteristics crucial for the assessment of seismic hazard. In this study, we exploit data from a regional seismic network, relocate the associated seismicity using the double difference method with an updated velocity model, determine focal mechanisms from full-waveform inversion, and analyze the static stress changes caused by the mainshock. Our relocated hypocenters and focal mechanism solutions reveal two earthquake clusters, one at the Central Balantak Fault that exhibits normal slip on a SE–NW trending rupture, and the other at the West Balantak Fault, which exhibits dextral strike-slip motion on a SE–NW trending rupture. The additional static stress increase transferred by the Mw 6.2 mainshock may have triggered the subsequent Mw 5.8 event. A detailed assessment of previously unmapped faults in Central Sulawesi is essential for a more comprehensive understanding of seismic hazard in the region. [ABSTRACT FROM AUTHOR]

The analysis of slope failure modes is essential for understanding slope stability. This study investigated the failure modes and triggering factors of a rock slope using the limit equilibrium method, finite differences method, and exploratory factor analysis. First, the limit equilibrium method was used to identify potential sliding surfaces. Then, the finite differences method was employed to study deformation and failure features in a slope. Stability factors were calculated considering specific conditions such as rainfall, prestressing loss, and earthquakes using the strength reduction method. Finally, exploratory factor analysis was utilized to identify the triggering factors of each failure mode. The results revealed that failure modes were categorized into two types based on the positions of the sliding surface. The main triggering factors for Failure Mode 1 were rainfall and prestress loss, while for Failure Mode 2 they were earthquake loading and prestress loss. This study offers a comprehensive exploration of potential failure modes and their triggering factors from mechanical and statistical perspectives, enriching our understanding of potential failure modes in rock slopes. [ABSTRACT FROM AUTHOR]

The seismic hazard of a fault system is controlled by the maximum possible earthquake magnitude it can host. However, existing methods to estimate maximum magnitudes can result in large uncertainties or ignore their temporal evolution. Here, we show how the maximum possible earthquake magnitude of a fault system can be assessed by combining high-resolution fault coupling maps with a physics-based model from three-dimensional dynamic fracture mechanics confirmed by dynamic rupture simulations. We demonstrate the method on the Anninghe-Zemuhe fault system in southwestern China, where dense near-fault geodetic data has been acquired. Our results show that this fault system currently has the potential to generate Mw7.0 earthquakes with maximum magnitudes increasing to Mw7.3 by 2200. These results are supported by the observed rupture extents and recurrence times of historical earthquakes and the b values of current seismicity. Our work provides a practical way to assess the earthquake potential of natural faults. In this study, the authors show how the maximum possible earthquake magnitude of a fault system can be assessed by combining high-resolution fault coupling maps with a physics-based theoretical model. They demonstrate the method on the Anninghe-Zemuhe fault system in southwestern China. [ABSTRACT FROM AUTHOR]

There is an ongoing discussion about how to forecast the maximum magnitudes of induced earthquakes based on operational parameters, subsurface conditions and physical process understanding. Although the occurrence of damage caused by induced earthquakes is rare, some cases have caused significant economic loss, injuries and even loss of life. We analysed a global compilation of earthquakes induced by hydraulic fracturing, geothermal reservoir stimulation, water disposal, gas storage and reservoir impoundment. Our analysis showed that maximum magnitudes scale with the characteristic length of pressure diffusion in the brittle Earth's crust. We observed an increase in the nucleation potential of larger-magnitude earthquakes with time and explained it by diffusion-controlled growth of the pressure-perturbed part of faults. Numerical and analytical fault size modelling supported our findings. Finally, we derived magnitude scaling laws to manage induced seismic hazard of upcoming energy projects prior to operation. This article is part of the theme issue 'Induced seismicity in coupled subsurface systems'. [ABSTRACT FROM AUTHOR]

In this study, the precursory seismic activity before a major earthquake was investigated by using the Pattern Informatics (PI) algorithm along the Sagaing fault zone (SFZ), Central Myanmar. After improving the earthquake catalog, the completeness of seismicity data with Mw ≥ 3.6 reported during 1980–2020 was used in retrospective testing to find the suitable parameters of the PI algorithm. According to the retrospective test with 6 cases of different forecast period times related to Mw ≥ 5.0 earthquakes, including verification using the relative operating characteristics (ROC) diagram, the characteristic parameters of both time intervals (change time and forecast time window) = 10 years and target forecast earthquake magnitude Mw ≥ 5.0 are suitable parameters for PI investigation along the SFZ. Therefore, these parameters were applied with the most up-to-date seismic dataset to evaluate the prospective areas of upcoming major earthquakes. The results reveal that the Myitkyina and the vicinity of Naypyidaw might be at risk of a major earthquake in the future. Therefore, effective earthquake mitigation plans should be urgently arranged. [ABSTRACT FROM AUTHOR]

Performing stimulation experiments at approximately 1 km depth in the Bedretto Underground Laboratory for Geosciences and Geoenergies necessitates identifying and characterizing the target fault zone for on-fault monitoring of induced fault slip and seismicity, which presents a challenge when attempting to understand seismogenic processes. We discuss the multidisciplinary approach for selecting the target fault zone for experiments planned within the Fault Activation and Earthquake Ruptures (FEAR) project, for which the aim is to induce the fault slip and seismicity for an earthquake magnitude of up to 1.0 while enhancing the monitoring and control of fluid-injection experiments. Structural geological mapping, remote sensing, exploration drilling and borehole logging, ground-penetration radar, and laboratory investigations were employed to identify and characterize the target fault – a ductile–brittle shear zone several meters wide with an intensely fractured volume spanning over 100 m. Its orientation in the in situ stress field favors reactivation in normal to strike-slip regimes. Laboratory tests showed slight velocity strengthening of the fault gouge. The fault's architecture, typical for crystalline environments, poses challenges for fluid flow, necessitating detailed hydraulic and stress characterization before each of the FEAR experiments. This multidisciplinary approach was crucial for managing rock volume heterogeneity and understanding implications for the dense monitoring network. Successfully identifying the fault sets the stage for seismic activation experiments commencing in spring 2024. [ABSTRACT FROM AUTHOR]

Megathrust geometric properties exhibit some of the strongest correlations with maximum earthquake magnitude in global surveys of large subduction zone earthquakes, but the mechanisms through which fault geometry influences subduction earthquake cycle dynamics remain unresolved. Here, we develop 39 models of sequences of earthquakes and aseismic slip (SEAS) on variably‐dipping planar and variably‐curved nonplanar megathrusts using the volumetric, high‐order accurate code tandem to account for fault curvature. We vary the dip, downdip curvature and width of the seismogenic zone to examine how slab geometry mechanically influences megathrust seismic cycles, including the size, variability, and interevent timing of earthquakes. Dip and curvature control characteristic slip styles primarily through their influence on seismogenic zone width: wider seismogenic zones allow shallowly‐dipping megathrusts to host larger earthquakes than steeply‐dipping ones. Under elevated pore pressure and less strongly velocity‐weakening friction, all modeled fault geometries host uniform periodic ruptures. In contrast, shallowly‐dipping and sharply‐curved megathrusts host multi‐period supercycles of slow‐to‐fast, small‐to‐large slip events under higher effective stresses and more strongly velocity‐weakening friction. We discuss how subduction zones' maximum earthquake magnitudes may be primarily controlled by the dip and dimensions of the seismogenic zone, while second‐order effects from structurally‐derived mechanical heterogeneity modulate the recurrence frequency and timing of these events. Our results suggest that enhanced co‐ and interseismic strength and stress variability along the megathrust, such as induced near areas of high or heterogeneous fault curvature, limits how frequently large ruptures occur and may explain curved faults' tendency to host more frequent, smaller earthquakes than flat faults. Plain Language Summary: Subduction zones, where one tectonic plate dives beneath another, generate the largest earthquakes worldwide. Our study investigates how the shape and tilt of these large offshore underground faults, termed "megathrusts," may determine the size of large earthquakes, how often they happen, and how similar or different subsequent events are. By creating computer simulations of earthquakes in subduction zones, we found that the angles and dimensions of the megathrust may set a limit on how big an earthquake can get. We also find that the presence of bends or curves along these faults can make earthquakes more unpredictable, sometimes leading to more variable series of smaller quakes before the biggest one hits. Our findings may help explain why some areas near subduction zones are prone to larger or more frequent earthquakes than others. Understanding these patterns can improve our ability to prepare for these natural disasters, potentially reducing their damaging effects on nearby communities and infrastructure. Key Points: Systematic earthquake cycle simulations reveal how subduction zone geometry controls megathrust earthquake size and timingDip and curvature affect characteristic slip style: periodic uniform ruptures versus supercycles of variably‐sized slow‐to‐fast eventsSeismogenic zone dip and dimensions limit maximum earthquake size; curvature‐linked stress and strength heterogeneity modulates recurrence [ABSTRACT FROM AUTHOR]

Obtaining geological and landform dislocation features, as well as the measured stratigraphic activity age, provides direct evidence to evaluate fault activity, which is more difficult to do in areas with low tectonic activity, such as eastern and central China. A detailed investigation of the fault activity, trenching, drilling joint geological profile, geological survey, and chronological analysis were used to obtain the spatial geometry, fault kinematics, and activity chronology of the Jiulong fault. The conclusions are as follows: (1) The Jiulong fault was a fracture zone composed of four branch faults, with a width of around 30–40 m and good extendibility, while the maximum surface rupture length was 373 m. (2) The Jiulong fault has many strata dislocations, and the dislocation distance decreased from bottom to top, demonstrating synsedimentary structure characteristics, with a maximum stratigraphic dislocation distance of 18.2 m. (3) Preliminary analysis suggested the Jiulong fault as a secondary fracture of the Xiangfan-Guangji fault zone and provided evidence of the southeastward extension of the Xiangfan-Guangji fault. A preliminary hypothesis purported the Xiangfan-Guangji fault as the seismogenic fault of the Ms 5.0 magnitude earthquake in 1911. (4) According to OSL and ESR dating analyses, the upper breakpoint of the Jiulong fault cuts into the Late Pleistocene Xingang Formation (Qp3x) strata, and the latest active age of the Jiulong fault was 57.6 ka. The chronology analysis confirmed an active fault from the Late Pleistocene and identified a weak tectonic in Jiujiang Province, which represents the largest active fault outcrop uncovered in the area so far. This study provides evidence and research materials for the evaluation of fault activity and seismic stability in this region. [ABSTRACT FROM AUTHOR]

On February 6, 2023, two separate destructive earthquakes with magnitudes of 7.7 and 7.5 occurred in Kahramanmaraş, Türkiye. More than 50,000 people lost their lives, and over 100,000 were reported injured. In this study, patients referred to hospitals with burn diagnosis and management of burn wounds following the disaster were evaluated. Information on burn injury admissions related to the earthquake was collected from all burn facilities in the country within 15 days after the earthquake. The patients' demographics, being under rubble, rescue times, burn causes, grafting procedures, and deaths were recorded. Following the earthquake, burn victims were transferred to the 13 Burn Treatment Centers located in 10 provinces. A total of 191 patients were burned. Among the burn patients, 101 (52.9%) were rescued from the rubble 2–60 h after the earthquake. Eight patients who were hospitalized at the burn centers died. Scalding and flame burns were the most common etiologies. Burned total body surface area, concomitant crush injury, hospitalization, and mortality was higher among the patients trapped under rubble (p < 0.001, p < 0.001, p < 0.001, and p < 0.001, respectively). Victims who stayed longer time under the rubble required significantly more grafting procedures (p < 0.001). In a literature review, it was observed that there are a limited number of publications reporting earthquake-related burns. In the February, 6 Türkiye earthquake, flame burns were seen due to small fires that occurred in collapsed buildings during the earthquake. And also contact burns and hot liquid burns were seen in earthquake victims trapped under rubble. Bursting hot water pipes, overturned stoves, contact with hot central heating radiators, and heated construction irons caused scalding and contact burns. It is believed that prolonged entrapment may cause delays in burn treatment or lead to deeper burns due to prolonged contact with the burning agent, increasing hospitalization rates. This earthquake once again drew attention to burn injuries that could occur during and after earthquakes, including those that may occur under rubble. • During high magnitude of earthquakes burn injuries could also occur. • Trapped under rubble may result with deeper burn wounds • Being under rubble increase need of grafting for treatment of burns [ABSTRACT FROM AUTHOR]

SUMMARY: Microseismic monitoring is an important technique to obtain detailed knowledge of in-situ fracture size and orientation during stimulation to maximize fluid flow throughout the rock volume and optimize production. Furthermore, considering that the frequency of earthquake magnitudes empirically follows a power law (i.e. Gutenberg–Richter), the accuracy of microseismic event magnitude distributions is potentially crucial for seismic risk management. In this study, we analyse microseismicity observed during four hydraulic fracture treatments of the legacy Cotton Valley experiment in 1997 at the Carthage gas field of East Texas, where fractures were activated at the base of the sand-shale Upper Cotton Valley formation. We perform waveform cross-correlation to detect similar event clusters, measure relative amplitude from aligned waveform pairs with a principal component analysis, then measure precise relative magnitudes. The new magnitudes significantly reduce the deviations between magnitude differences and relative amplitudes of event pairs. This subsequently reduces the magnitude differences between clusters located at different depths. Reduction in magnitude differences between clusters suggests that some attenuation-related biases could be effectively mitigated with relative magnitude measurements. The maximum likelihood method is applied to understand the magnitude frequency distributions and quantify the seismogenic index of the clusters. Statistical analyses with new magnitudes suggest that fractures that are more favourably oriented for shear failure have lower b-value and higher seismogenic index, suggesting higher potential for relatively larger earthquakes, rather than fractures subparallel to maximum horizontal principal stress orientation. [ABSTRACT FROM AUTHOR]

In this study, a TEC variation window value was selected based on the wavelet power spectrum method to analyze the seismic–ionospheric coupling relationship. In the full-time domain, a 27-day periodicity of the wavelet power spectrum was obtained that passed the 95% significance test. The sliding interquartile range method was used to analyze earthquakes above Mw6.5 in Japan from 2011 to 2022, excluding the hybrid effects between earthquakes close to one another. The sunspot number (SSN), 10.7 cm radio flux (F10.7), total solar irradiance (TSI), solar wind velocity (Vsw), geomagnetic activity index in the equatorial region (DST), and global geomagnetic activity index (KP) were used as indices representing solar and geomagnetic activity. After removing solar and geomagnetic interference from ionospheric anomaly changes using the sliding interquartile range method, the TEC anomaly changes before the earthquake were verified as being caused by the earthquake and analyzed. The statistical analysis of ionospheric total electron content (TEC) anomalies showed that earthquake magnitude was positively correlated with the amplitude of TEC anomalies but not linearly. The occurrence time of ionospheric anomalies lagged behind to some extent with the increase in earthquake magnitude. Additionally, abnormal changes on the 29th day (15 February 2022) before the 20th earthquake did not conform to previous research rules. According to the lithosphere–atmosphere–ionospheric coupling (LAIC) mechanism and global ionospheric map (GIM) studies, the TEC anomaly was consistent with the vertical projection of the epicenter with obvious regularity. The results show that these TEC anomalies may be related to earthquakes. [ABSTRACT FROM AUTHOR]

From a tectonic perspective, Türkiye is a geographical region known for its high seismic activity, with some of the most active faults in the world. On February 6, 2023, two consecutive earthquakes with magnitudes of Mw 7.7 and Mw 7.6 struck Kahramanmaraş within a remarkably short time span of 9 h. This event stands out as a rare and unprecedented tectonic occurrence in terms of seismicity and tectonic activity over the past 100 years. The impact of these two major earthquakes on the region's reinforced concrete structures was significant, resulting in severe damage and the collapse of numerous buildings. It is of utmost importance to investigate and examine the design flaws and underlying factors that contributed to the damage observed in the reinforced concrete structures affected by these earthquakes. Such research will not only contribute to the improvement of structural design, seismic regulations, and quality control measures during construction but also enhance our understanding of earthquake engineering. In this study, an in-depth field investigation was conducted on reinforced concrete structures in Hatay, one of the regions most affected by the Kahramanmaraş earthquakes. The damages occurring in the buildings were documented through a detailed field survey and analyzed. A total of 540 reinforced concrete structures in the Hatay region were extensively examined, and the damages that occurred in these structures were photographed and interpreted to understand their underlying causes. Subsequently, based on the findings from the field investigation, a structural model was designed that incorporated the most significant design and construction errors responsible for the damages observed in the 540 examined structures. The devised model was subjected to static push-over analysis and nonlinear dynamic analysis using the SAP2000 finite element software, and the results obtained were interpreted. [ABSTRACT FROM AUTHOR]

The process of choosing ground motions typically relies on assembling a collection of ground motions that match a desired spectrum. This selection process is guided by specific seismological criteria, including factors like earthquake magnitude, distance from the epicenter, site soil type, and the range of spectral periods that need to fit with the target spectrum. The selection algorithm and the available dataset of waveforms obviously play significant roles in this process. In many engineering and site response applications, it is essential that the input ground motion is representative for the shaking at the free surface of the Earth, and at times also a specific soil type may be required. However, real waveform databases often lack sufficient and/or consistent metadata related to the installation type and soil characterization of recording stations, as well as to the earthquake seismological parameters. This deficiency can lead to the selection of inappropriate waveforms, such as those recorded by stations situated within manmade structures (buildings, bridges, dams) or on a soil type different than the intended one. To address this issue, our approach for creating an appropriate waveform database applicable to Switzerland starts with the computation of seismic hazard disaggregation for return periods of 475 and 975 years. This computation helps identifying the magnitude-distance scenarios most relevant for the five seismic hazard zones defined in the Swiss building code. Once these magnitude-distance ranges are identified, we adhere to established standards regarding the quality control of three-component waveforms and their associated metadata. We assemble a database of waveforms by collating and homogenizing data from available global databases. In the interest of comprehensiveness, we also incorporate data obtained from 3D physics-based numerical simulations of strong-motion near the seismic source. Finally, we employ an algorithm that integrates the Eurocode 8 waveform selection criteria. This algorithm allows us to select and scale waveforms suitable for microzonation and structural analysis studies within each of Switzerland's five seismic hazard zones. Selecting waveforms compatible with the target design spectra proves to be challenging due to the stringent criteria imposed by Eurocode 8. This challenge arises from the scarcity of recorded waveforms with verified metadata and precise site characterization in the desired magnitude-distance ranges. [ABSTRACT FROM AUTHOR]

In Iceland, the most seismically active region in Northern Europe, large earthquakes up to ~ M w 7 repeatedly take place in the two transform zones of the country. Of the two, only the South Iceland Seismic Zone (SISZ) in southwest Iceland is on land and with a large part of the country's population either collocated or in close proximity to it. Strong earthquake occurrence in the SISZ takes place on a bookshelf fault system, an array of short, vertical, and dextral strike-slip faults oriented perpendicular to the overall transform motion. Importantly, this system has recently been shown to be continuous further towards the west along the entire Reykjanes Peninsula Oblique Rift (RPOR), making the bookshelf fault system approximately twice as long as previously thought. Moreover, a systematic spatial variation of maximum earthquake magnitudes characterizes the SISZ-RPOR system, from ~ M w 7 down to ~ M w 5.5 from eastern SISZ to western RPOR, respectively, indicates a subzonation of the seismic region. The above has not been taken into account in past probabilistic seismic hazard assessments (PSHA) and poses a challenge as the historical earthquake catalogue precludes reliable estimates of seismicity parameters for individual subzones of the SISZ-RPOR system. In this study, we address this issue using a recently developed physics-based finite-fault model of the SISZ-RPOR bookshelf fault system, and quantitatively estimate the time-independent magnitude-frequency distributions (MFDs, of the Gutenberg-Richter type) for each subzone. We establish zone-specific distributions representative of long-term fault slip rates and derive the seismicity parameter estimates corresponding to the 2.5, 50, and 97.5 percentiles of fault slip rates along the SISZ-RPOR as predicted by the physics-based model. We present new and quantitative estimates of subzone MFDs and show that the model effectively explains the historical earthquake catalogues. The results of this study not only enable the efficient yet physically realistic and consistent revision of conventional time-independent PSHA for southwest Iceland using e.g., empirical ground motion models, but also a more comprehensive physics-based PSHA from finite-fault rupture modeling and advanced seismic ground motion simulation techniques. [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]

In 2022, four earthquakes with MS ≥6.0 including the Menyuan MS 6.9 and Luding MS 6.8 earthquakes occurred in the NorthSouth Seismic Zone (NSSZ), which demonstrated high and strong seismicity. Pattern Informatics (PI) method, as an effective long and medium term earthquake forecasting method, has been applied to the strong earthquake forecasting in Chinese mainland and results have shown the positive performance. The earthquake catalog with magnitude above MS 3.0 since 1970 provided by China Earthquake Networks Center was employed in this study and the Receiver Operating Characteristic (ROC) method was applied to test the forecasting efficiency of the PI method in each selected region related to the North-South Seismic Zone systematically. Based on this, we selected the area with the best ROC testing result and analyzed the evolution process of the PI hotspot map reflecting the small seismic activity pattern prior to the Menyuan MS 6.9 and Luding MS 6.8 earthquakes. A “forward” forecast for the area was carried out to assess seismic risk. The study shows the following. 1) PI forecasting has higher forecasting efficiency in the selected study region where the difference of seismicity in any place of the region is smaller. 2) In areas with smaller differences of seismicity, the activity pattern of small earthquakes prior to the Menyuan MS 6.9 and Luding MS 6.8 earthquakes can be obtained by analyzing the spatio-temporal evolution process of the PI hotspot map. 3) The hotspot evolution in and around the southern Tazang fault in the study area is similar to that prior to the strong earthquakes, which suggests the possible seismic hazard in the future. This study could provide some ideas to the seismic hazard assessment in other regions with high seismicity, such as Japan, California, Turkey, and Indonesia. [ABSTRACT FROM AUTHOR]

On October 7, 2021, a magnitude 5.9 earthquake struck the Harnai (Baluchistan) region of Pakistan, causing several fatalities and injuries within the epicentral area. First-order tectonic deformation in this region is caused by the convergence of the Indian Plate with respect to the Eurasian Plate. The Katwaz Block hinders the motion of the Indian Plate, resulting in the formation of strike-slip faults. In this study, the P-wave first-motion polarity technique was used to determine the mainshock faulting style. Cyclic scanning of the polarity solutions was applied to determine the most suitable focal mechanism solution among the available solutions generated by the FOCMEC (focal mechanism) software. The nodal planes correspond to different faulting styles (i.e., thrust and strike-slip faulting). A nodal plane oriented in the NW-SE direction corresponded to a strike-slip mechanism, which was considered to be the fault plane. Tectonically, this earthquake was associated with the Harnai-Karahi strike-slip fault zone owing to the fault strike and direction of slip. The apparent stress drop, fault length, and moment magnitude of the Harnai earthquake were 35.4 bar, 6.1 km, and 5.9, respectively. A lower b-value for the Gutenberg-Richter law was observed prior to the earthquake. Higher α- than b-values (α > b) indicate that this earthquake was governed by large events as opposed to small-magnitude events. The Harnai sequence had a decay exponent close to unity, lasted for 145 days, and produced few aftershocks. The study will help the future hazard mitigation in the region. [ABSTRACT FROM AUTHOR]

Knowledge regarding earthquake hazards and seismicity is crucial for crisis management, and the occurrence of foreshocks, seismic activity patterns, and spatiotemporal variations in seismic activity have been studied. Furthermore, the estimation of the region-time-length (RTL) parameter has been proposed to detect seismic quiescence before the occurrence of a large earthquake. In addition, the time-to-failure method has been used to estimate the time occurrence of large earthquakes. Hence, in this study, to gain deeper insight into seismic activity in the southern Zagros region, we utilized the RTL algorithm to identify the quiescence and activation phases leading to the Fin doublet earthquakes. Temporal variations in the RTL parameter showed two significant anomalies. One corresponded to the occurrence time of the first earthquake (2017-12-12); the other anomaly was associated with the occurrence time of the second event (2021-11-14). Based on a negative value of the RTL parameter observed in the vicinity of the Fin epicenters (2021), seismic quiescence (a decrease in seismicity compared to the preceding background rate) was identified. The spatial distribution of the RTL prognostic parameters confirms the appearance of seismic quiescence surrounding the epicenter of the Fin doublet earthquakes (2021). The time-to-failure method was designed using precursory events that describe the acceleration of the seismic energy release before the mainshock. Using the time-to-failure method for the earthquake catalog, it was possible to estimate both the magnitude and time of failure of the Fin doublet. Hence, the time-tofailure technique can be a useful supplementary method to the RTL algorithm for determining the characteristics of impending earthquakes. [ABSTRACT FROM AUTHOR]

On February 6, 2023, two catastrophic earthquakes occurred on the East Anatolian Fault. The earthquakes had magnitudes of Mw = 7.7 and 7.6 and struck Kahramanmaraş-Pazarcık and Kahramanmaraş-Elbistan, respectively. The Kahramanmaraş-Pazarcık earthquake was triggered at 04:17 local time on the Dead Sea Fault (a branch of the East Anatolian Fault). The last earthquake on the addressed fault occurred about 500 years ago. The recorded peak ground acceleration (PGA) at the Pazarcık station reached 2.05g. In addition, the Pazarcık earthquake triggered two independent earthquakes, the Nurdağı and Islahiye earthquakes, which occurred 10 min later than the Pazarcık earthquake. However, the last earthquake, with its epicenter in Kahramanmaraş-Elbistan, struck at 13:24 local time. The recorded PGA for the Elbistan earthquake is 0.68g. This study aims to present the fault rupture mechanism of the February 6, 2023, Kahramanmaraş earthquakes, earthquake characteristics, and to evaluate the performance of masonry dwellings during the Kahramanmaraş earthquake doublet, which affected 10 provinces and numerous towns and villages. This paper also aims to illustrate the damage and failure mechanisms of the masonry dwellings, despite unexpectedly high accelerations that exceeded the design spectrum in the field, specifically in Kahramanmaraş, Gaziantep, Hatay, and Malatya, according to the current earthquake code in use. [ABSTRACT FROM AUTHOR]

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Different risk management activities, such as land-use planning, preparedness, and emergency response, utilize scenarios of earthquake events. A systematic selection of such scenarios should aim at finding those that are representative of a certain severity, which can be measured by consequences to the exposed assets. For this reason, defining a representative scenario as the most likely one leading to a loss with a specific return period, e.g., the 100-year loss, has been proposed. We adopt this definition and develop enhanced algorithms for determining such scenarios for multiple return periods. With this approach, we identify representative earthquake scenarios for the return periods of 50, 100, 500, and 1000 years in the Chilean communes of Valparaíso and Viña del Mar, based on a synthetic earthquake catalog of 20 000 scenarios on the subduction zone with a magnitude of Mw≥5.0. We separately consider the residential-building stock and the electrical-power network and identify and compare earthquake scenarios that are representative of these systems. Because the representative earthquake scenarios are defined in terms of the annual loss exceedance rates, they vary in function of the exposed system. The identified representative scenarios for the building stock have epicenters located not further than 30 km from the two communes, with magnitudes ranging between 6.0 and 7.0. The epicenter locations of the earthquake scenarios representative of the electrical-power network are more spread out but not further than 100 km away from the two communes, with magnitudes ranging between 7.0 and 9.0. For risk management activities, we recommend considering the identified scenarios together with historical events. [ABSTRACT FROM AUTHOR]

The occurrence of a series of earthquakes of different magnitudes or multiple mainshocks has been reported recently. This leads to the liquefaction of sand due to excess pore pressure generation under undrained loading conditions, which alters the stable structure of the soil to an unstable form. The response of saturated sandy deposits under these conditions is rarely experimented by researchers and the present study highlights this issue. Here six shake table test results are analyzed to understand the initiation of liquefaction in the sand at varying base accelerations (0.15 g, 0.2 g and 0.3 g) at continuous and series of identical shaking events. Multiple shaking events were provided to simulate earthquakes at closely spaced time intervals. The surface settlements and response of excess pore water pressure at various depths within a saturated sand bed due to these shaking events are investigated. The results showed that the soil layer near the surface of the soil is most likely to be liquefied. Also, the re-liquefaction resistance of the sand remains constant for the first few shakings, but the dissipation time of excess pore water pressure decreases with increasing density. [ABSTRACT FROM AUTHOR]

A microgravity investigation was conducted along the axis of the Derbendikhan rockfill dam in Iraq. The dam lies in an earthquake-prone area within the High Folded Zone of the Western Zagros Fold-Thrust Belt. The goal of the survey was to evaluate the expected subsurface damage that could threaten the stability of the dam due to the effects of a 7.3 magnitude earthquake and future earthquakes that cause foundation cracking and landslides. The survey consists of 324 microgravity stations distributed on four profiles. Residual gravity anomalies were obtained by removing the regional effect of a 5-m upward continuation filter. Several negative and positive anomalies are distinguishable in a residual anomalies map that reflects the subsurface heterogeneity within the clay material that makes up the dam. The results reveal that there are no recognizable indications regarding the evolution of subsurface channels after the earthquake was given. Furthermore, two prominent anomalies appear close to the right bank at roughly 21 m in depth. These positive and negative anomalies suggest that high- and low-density zones coincide with different degrees of compressional stresses caused by the earthquake. Twodimensional modeling indicates several low (less compacted) and high (more compacted) density areas that warrant further investigation in terms of material strength. The results can be used as a guide for a drilling program to examine the sources of the anomalies. [ABSTRACT FROM AUTHOR]

Based on U‐Pb dating of zircon crystals and petrographic analysis, this study provides new insights into the paleogeographic and accretion evolution along SW Japan. Our data are consistent with an older submarine fan identified from drilling in the Shikoku Basin (Kyushu Fan ∼14.7–12.2 Ma), having a mixed sand provenance from the paleo‐Yangtze/Yellow rivers and the Shimanto Belt, and the younger Zenisu Fan (∼9.2–7.6 Ma), which is mainly sourced from the Shimanto Belt and the Izu‐Bonin/Honshu arc collision. Our results are in agreement with the hypothesis of very oblique subduction or strike‐slip motion between the northern Shikoku Basin and mainland Honshu from ∼12.2 to 9.2 Ma, after which essentially orthogonal subduction occurred after ∼8 Ma. The two main sandbodies drilled at IODP Site C0002 within the inner Nankai Accretionary Prism have similar petrographic signatures to those of the Zenisu and Kyushu submarine fans in the Shikoku Basin. The incorporation of the Shikoku Basin deposits most likely resulted from the seaward propagation of in‐sequence thrusts forming an outer accretionary wedge. The incorporation of the Kyushu Fan into the inner accretionary prism implies that the décollement was located in the hemipelagic interval beneath the Kyushu Fan at least until ∼2 Ma, whereas it is now located in the hemipelagic intervals below the Zenisu Fan. Such shifts in décollement location are most likely related to changes in physical properties of the hemipelagic interval due to significant compaction and diagenesis during subduction. Plain Language Summary: Sediment inputs exert a first‐order influence over the tectonic behavior of subduction zones. Based on U/Pb dating of zircon and petrographic analyses, this study focuses on the provenance, transport and accretion of sediments along SW Japan where a large‐magnitude earthquake occurred. U/Pb dating of zircon from sand sampled in the Shikoku Basin and in the frontal Nankai accretionary prism indicates a significant sediment input from SE China and from the Shimanto Belt from ∼14.7 to ∼8 Ma. The youngest submarine fan of the Shikoku Basin was mainly sourced from the Shimanto Belt and the Izu‐Bonin/Honshu arc collision. This agrees with the hypothesis of a very oblique subduction or strike‐slip motion of the Philippines Sea Plate between ∼12.2 and 9.2 Ma, after which orthogonal subduction occurred after ∼8 Ma. The deformed submarine fans observed in the accretionary prism show similar petrographic signatures to sandbodies of the Shikoku Basin located on the incoming plate. This indicates that the Shikoku Basin deposits were incorporated by seaward propagation of thrusts, likely after resurgence of orthogonal subduction ∼8 Ma. To our knowledge, this is the first time that any study has correlated stratigraphy on a subducting oceanic plate to the internal stratigraphy of a linked accretionary prism. Key Points: Contrasting sediment sources between the Shikoku Basin fans indicate strike‐slip motion/oblique subduction of the Philippine Sea PlateSimilar petrographic signature between accreted materials of the inner Nankai accretionary prism and submarine fans of the Shikoku BasinChanges in décollement location between ∼6 and ∼2 Ma, likely related to changes in physical properties of hemipelagic intervals [ABSTRACT FROM AUTHOR]

Circular crack models with a constant rupture velocity struggle to effectively model both the amplitude and duration of first P-wave pulses generated by small magnitude seismic events. Assuming a constant rupture velocity is unphysical, necessitating a deceleration phase in the rupture velocity to uphold the causality of the healing process. Moreover, a comprehensive failure model might encompass an initial nucleation phase, typically characterized by an increase of the initial rupture velocity. Studies have demonstrated that quasi-dynamic circular crack models featuring variable rupture velocities can accurately model the shape of the observed first P-wave pulse. Based on these principles, an Empirical Green's function (EGF) approach was previously formulated to estimate the source parameters of small magnitude earthquakes, called MAIN. In addition to determine the source radius and stress drop, this method also enables the inference of the temporal evolution of rupture velocity. However, this method encounters difficulties when the noise-to-signal ratio in the recordings of smaller earthquakes used as EGF exceeds 5%, a common situation when employing regional-scale recordings of small-magnitude earthquakes as EGF. Through synthetic tests, we demonstrated that, in such instances, the problem of this technique is that the alignment between the onset of P waves of EGF and MAIN is not rightly recovered after the initial inversion step. Consequently, a novel inversion method has been developed to address this issue, enabling the identification of the optimal alignment of P-wave arrivals in EGF and MAIN across all stations. A Bayesian statistical approach is proposed to meticulously investigate the solutions of model parameters and their correlations. Using the new technique on a small magnitude earthquake (ML = 3.3) occurred in Central Italy enabled us to identify the most likely rupture models and examine the issue of correlation among model parameters. Application of Occam's Razor Principle suggests that, for the investigated event, a circular crack model should be favored over a heterogeneous rupture model. [ABSTRACT FROM AUTHOR]

The traditional approach for estimating the b-value of the Gutenberg–Richter law, which is posited to inversely correlate with differential stress, has historically relied on the maximum likelihood technique, utilizing data from earthquakes exceeding a magnitude cutoff, Mc. This traditional approach is significantly influenced by the value of Mc, leading to extensive research focused on methods for determining Mc with greater accuracy. However, a recent study introduced a novel method based on the frequency distribution of magnitude difference, termed the b-positive method. This innovative method could enable more robust b-value estimations, even in scenarios where Mc may vary spatially and temporally. Our study concentrated on analyzing aftershocks, related to 25 magnitude-7 class earthquakes surrounding the Japanese archipelago. We estimated the b-values using both the goodness-of-fit test for Mc, a traditional approach, and the b-positive method. The aftershock data were examined over two distinct time frames: the initial 10 days following each mainshock and an extended period of 1000 days. Our findings indicated that the estimates produced by the b-positive method showed negligible variation between the 10-day and 1000-day aftershock periods (correlation coefficient of 0.95), whereas the traditional approach tended to yield lower b-values for the 10-day aftershocks compared to those from the 1000-day period. Variations in b-values, when analyzed using the traditional approach, could be inaccurately ascribed to temporal fluctuations in differential stress that may not actually be present. The b-positive method offers a vital solution to prevent these erroneous interpretations, serving as an essential alternative. [ABSTRACT FROM AUTHOR]

New Makran simulations imply two generalized zones of mid-field tsunami hazard in greater Karachi. The simulations presuppose seven megathrust ruptures that strike east-west, range in area from 100 × 150 km to 355 × 800 km, and lie west of the city by no less than 100 km. The assumed seismic slip is uniform across each rupture area. The smallest rupture approximates the 1945 Makran earthquake of magnitude 8.1, while the largest corresponds to a previously conjectured giant Makran earthquake of magnitude 9.2. None of the sources include a complication in 1945: late-arriving waves from submarine slides or splay faulting. Consequently, the first simulated wave is the largest in each of the seven scenarios. And because the sources are to the west, the simulated waves are higher, and arrive sooner, at Karachi Port (1.5 hr) than 30 km farther east at Port Qasim (nearly 3 hr). These combinations of height and arrival time can be generalized as properties of two hazard zones: a western one that includes Karachi Port, and an eastern one that includes Port Qasim. The simulated flooding extends farthest inland into low-lying residential areas of the western zone. Neither hazard zone is near-field or far-field. That is, neither is near enough to the fault ruptures for felt seismic shaking to dependably warn of a fast-arriving tsunami, yet neither is distant enough to receive more than three hours of advance notice through tsunami warning systems. Our simulations are intended to support emergency management in this mid-field setting. [ABSTRACT FROM AUTHOR]

Objective: On February 6, 2023, two earthquakes of magnitude 7.8 and 7.6 occurred in Kahramanmaras, affecting south and central Türkiye as well as north and west Syria. The objective of this study is to present the clinical and radiological findings of chest trauma patients in a significant disaster like an earthquake. It aims to contribute to early diagnosis and intervention in multidisciplinary treatment approaches, thereby reducing mortality and morbidity rates. Materials and Methods: This study was a cross-sectional type registry research. A total of 6,500 patients who presented to Kayseri City Hospital due to the earthquake between February 6, 2023 and February 20, 2023 were retrospectively reviewed through medical hospital records. Of these, 150 patients with blunt or penetrating chest trauma were included in the study. Results: Among the 6,500 patients screened, chest trauma was identified in 150 cases. The average age was 45.1 years. Of the patients, 40.0% arrived at the hospital within 0-1 days, while 10.7% arrived after 6 or more days, with the longest duration being 11 days. While 30.7% of patients had no rib fractures, 31.3% had fractures on the right side, 10.7% had bilateral fractures, and 23.3% had 5 or more rib fractures. Complications occurred in 61.3% of cases, 69.3% received medical treatment, and 26.7% underwent tube thoracostomy. The patients' hospital stays ranged from 0 to 162 days, with an average of 18 days and a median of 11.5 days. Conclusion: Türkiye and its surrounding regions are prone to frequent earthquakes, and similar events are expected in the future. A multidisciplinary patient approach, starting from the emergency department, plays a crucial role, with thoracic surgery being an integral part of this approach. [ABSTRACT FROM AUTHOR]

Earthquakes with moment magnitude (M w) ranging from 6.5 to 7.0 have been observed to generate sufficiently strong acoustic waves (AWs) in the upper atmosphere. These AWs are detectable in Global Navigation Satellite System satellite signals-based total electron content (TEC) observations in the ionosphere at altitudes ∼250–300 km. However, the specific earthquake source parameters that influence the detectability and characteristics of AWs are not comprehensively understood. Here, we extend our approach of coupled earthquake-atmosphere dynamics modelling by combing dynamic rupture and seismic wave propagation simulations with 2-D and 3-D atmospheric numerical models, to investigate how the characteristics of earthquakes impact the generation and propagation of AWs. We developed a set of idealized dynamic rupture models varying faulting types and fault sizes, hypocentral depths and stress drops. We focus on earthquakes of M w 6.0–6.5, which are considered the smallest detectable with TEC, and find that the resulting AWs undergo non-linear evolution and form acoustic shock N waves reaching thermosphere at ∼90–140 km. The results reveal that the magnitude of the earthquakes is not the sole or primary factor determining the amplitudes of AWs in the upper atmosphere. Instead, various earthquake source characteristics, including the direction of rupture propagation, the polarity of seismic wave imprints on the surface, earthquake mechanism, stress drop and radiated energy, significantly influence the amplitudes and periods of AWs. The simulation results are also compared with observed TEC fluctuations from AWs generated by the 2023 M w 6.2 Suzu (Japan) earthquake, finding preliminary agreement in terms of model-predicted signal periods and amplitudes. Understanding these nuanced relationships between earthquake source parameters and AW characteristics is essential for refining our ability to detect and interpret AW signals in the ionosphere. [ABSTRACT FROM AUTHOR]

The Lacq area in southwest France has been associated with continuous moderate induced seismic activity since 1969. However, the mechanisms driving this induced seismicity are not fully understood: reservoir depletion has been proposed as the main factor, and more recently wastewater injection has been suggested to play a more important role. The interpretation of these mechanisms relies heavily on the quality of earthquake locations, which we prove to be weak due to a lack of local instrumentation for several years. In order to provide the most complete and reliable induced event catalogue for the studies of the Lacq induced seismicity mechanisms and seismic hazard, we made an exhaustive compilation, analysis and improvement of all available catalogues. We also provided new earthquake detections and relocations in a 3-D velocity model from past and present temporary deployments never used for studying the Lacq area. Important remaining location uncertainties lead us to also carefully sort the events according to their location confidence, defining 3 classes of events (unconstrained location, location constrained within 2–3 km and 1–2 km, respectively). This new harmonized catalogue and the identification of well-constrained events, covering 50 yr of induced seismicity, allow us to propose that wastewater injection is almost certainly the main mechanism driving the seismicity, with (i) most of the constrained events located within the reservoir boundaries and (ii) the released seismic energy variations following variations in injection operations at different scales. In particular, we have also highlighted a change in the injection–seismicity relationship around 2010–2013. From 2013, despite lower injection volumes, seismicity remained persistent and some clusters of earthquakes were detected predominantly in spring, summer and early autumn, except in winter periods. From 2016, we observed a strong temporal relationship between days with higher rate/volume injections (approximately above 400 m3 d−1) and both clustered events and higher magnitude earthquakes (greater than 2.4). [ABSTRACT FROM AUTHOR]