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The portal section of mountain tunnels usually suffers severe damage during earthquakes. The purpose of this paper is to investigate the seismic performance of the combined system of anchor rod and isolation layer in the portal section of the mountain tunnel. The numerical model was established based on the actual terrain of the engineering site and included the tunnel pillar portal structure, horizontal seismic wave input, and absorbing boundary conditions. Four cases were considered: without measures, anchor rod, isolation layer, and combination of anchor rod and isolation layer. Comparative analysis of the dynamic response and seismic performance of the structure under seismic action for each case. The results show that: (1) The combination measures reducing the maximum peak acceleration of the tunnel pillar portal and lining to 0.33g and 0.36g, respectively, achieving acceleration reduction rates of 30% and 36.8%; (2) The combination measures increases frictional resistance through anchor rod, providing restraint and support to the surrounding rock, and the isolation layer further mitigates the interaction between the surrounding rock and the lining, reducing the stress on the lining. This synergy reduces the maximum relative displacement of the tunnel portal pillar by 43.7% to 9.4mm, and the lining by 58% to 7.8mm; (3) The combination measures reduce the maximum peak principal stress of the lining to 1.48MPa, achieving a stress reduction rate of 68.23%. Effectively enhancing the seismic performance of the tunnel and reducing damage and failure. [ABSTRACT FROM AUTHOR]

This paper introduces machine learning-based Turkiye-specific ground motion models for the geometric mean horizontal component of peak ground velocity (PGV). PGV is a significant intensity metric to measure and diagnose potential earthquake damage in structures. Reliable prediction of PGV is of essential importance in precise calculations of seismic hazard. The efficiencies, reliabilities, and capabilities of various machine learning algorithms, including Random Forest, Support Vector Machine, Linear Regression, Artificial Neural Network, Gradient Boosting, and Bayesian Ridge Regression, are evaluated and compared. The most recently compiled Turkish strong motion database, which consists of over 950 earthquakes occurring from 1983 to 2023, is used for shaping the models' ability to learn and make accurate predictions. Three feature selection methods- Least Absolute Shrinkage and Selection Operator, Recursive Feature Elimination, and Pearson's Correlation- representing embedded, wrapper, and filter approaches, respectively, are applied to determine the most suitable estimator parameters to predict PGV. Residual analyses and statistical evaluation metrics are employed to measure the performance and effectiveness of the machine learning models. Among the algorithms applied, Gradient Boosting demonstrates exceptional success in predicting PGV, particularly when utilizing all estimator parameters (features) collectively. The Gradient Boosting model exhibits superior predictive capabilities compared to existing ground motion models. It is applicable to shallow crustal strike-slip and normal faulting earthquakes with moment magnitude ranging from 3.5 to 7.8 and Joyner and Boore distance up to 200 km. [ABSTRACT FROM AUTHOR]

Assessing the potential damage caused by earthquakes is crucial for a community's emergency response. In this study, four machine learning (ML) methods—random forest, extremely randomized trees, AdaBoost (AB), and gradient boosting (GB)—were employed to develop prediction models for the damage potential of the mainshock (DIMS) and mainshock–aftershock sequences (DIMA). Building structures were modeled using eight single-degree-of-freedom (SDOF) systems with different hysteretic rules. A set of 662 recorded mainshock-aftershock (MS-AS) ground motions was selected from the PEER database. Seven intensity measures (IMs) were chosen to represent the characteristics of the mainshock and aftershock. The results revealed that the selected ML methods can well predict the structural damage potential of the SDOF systems, except for the AB method. The GB model exhibited the best performance, making it the recommended choice for predicting DIMS and DIMA among the four ML models. Additionally, the impact of input variables in the prediction was investigated using the shapley additive explanations (SHAP) method. The high-correlation variables were sensitive to the structural period (T). At T=1.0 s, the mainshock peak ground velocity (PGVM) and aftershock peak ground displacement (PGDA) significantly influenced the prediction of DIMA. When T increased to 5.0 s, the primary high-correlation factor of the mainshock IMs changed from PGVM to the mainshock peak ground displacement (PGDM); however, the high-correlation variable of the aftershock IMs remained PGDA. The high-correlation factors for DIMS showed trends similar to those of DIMA. Finally, a table summarizing the first and second high-correlation variables for predicting DIMS and DIMA were provided, offering a valuable reference for parameter selection in seismic damage prediction for mainshock–aftershock sequences. [ABSTRACT FROM AUTHOR]

In February 2023, two catastrophic earthquakes in Turkey resulted in over 50,000 fatalities and over 300,000 injuries. This study investigated the psychological effects on firefighters who engage in rescue operations following these earthquakes, focusing on trauma-related symptoms, depression, anxiety, stress, and resilience. The research employed validated psychometric instruments, including the Post-earthquake Trauma Level Determination Scale (PETLDS); Depression, Anxiety, Stress Scale-21 (DASS-21); PTSD Checklist for DSM-5 (PCL-5); and Brief Resilience Scale (BRS), to assess the psychological states of firefighters. The primary goal of this study was to evaluate the psychological impact of earthquakes on firefighters. Specific objectives include quantifying trauma levels; identifying the prevalence of post-traumatic stress disorder (PTSD), depression, anxiety, and stress among firefighters; and investigating the role of psychological resilience in mitigating the effects of disaster-related psychological trauma. This study is also aimed at providing empirical evidence to inform the development of psychological support and intervention strategies for firefighters in the aftermath of these earthquakes. In this study of 223 primarily male firefighters, significant psychological impacts from earthquake trauma were observed. The PETLDS scores indicated high trauma levels in 28 participants and modest levels in 195. Subscales revealed affective responses and cognitive structure were most affected. DASS-21 scores showed higher depression, anxiety, and stress in the high trauma group. PCL-5 and BRS analyses confirmed higher PTSD symptoms and lower resilience in high-trauma individuals. Correlation analysis highlighted strong associations between trauma, psychological distress, and decreased resilience. These findings highlight the necessity for targeted mental health interventions and support mechanisms for firefighters, contribute to the establishment of training programs to enhance psychological resilience among firefighters, and add valuable insights to the field of disaster psychology. [ABSTRACT FROM AUTHOR]

This study quantifies the effects of long-duration earthquakes on the behavior of reinforced concrete (RC) buildings subjected to successive earthquake-tsunamis through the development of fragility surfaces. The suite is comprised of both ductile and nonductile systems, representing a portfolio of RC structures that could be found in a (coastal) community. Previous research has shown that long-duration earthquakes can significantly influence the structural responses and even the collapse behavior of building systems. Earthquakes with large moment magnitudes that produce tsunamis are often long duration events, yet ground motion duration has not been fully considered when generating tsunami fragility curves or successive earthquake-tsunami fragility surfaces. This study incorporates earthquake loading through a nonlinear time history analysis (NLTHA) and subsequent tsunami loading with a nonlinear static procedure. Detailed probabilistic structural models are subjected to both long-duration and regular-duration earthquakes through the NLTHA phase of the successive simulation to explore the possible impact of long-duration earthquakes on earthquake-tsunami fragility surfaces used to represent the behavior of these RC buildings. Results show that failure probabilities from the fragility surfaces are increased by up to 40% in some cases, with low- to mid-rise RC structures (ductile and nonductile; up to 8 stories) being adversely affected by long-duration earthquakes. Furthermore, this study reports the governing parameters of scalar and vector-valued fragility functions in the proposed RC portfolio exposed to long-duration earthquakes and tsunami hazards. These fragility surfaces can be useful in developing community-level models in risk-based or resilience-based decision-support for disaster mitigation. [ABSTRACT FROM AUTHOR]

This present research conducted an experimental study on the influence of different earthquake damages on the seismic performances of aged reinforced concrete (RC) beam-column joints retrofitted with basalt fiber-reinforced polymer (BFRP) sheets under cyclic loadings. Six beam-column joints included one benchmark specimen, one uncorroded specimen retrofitted with BFRP sheets, and four earthquake-damaged corroded specimens with the corrosion rates of 0% and 9% retrofitted with BFRP sheets. Test results demonstrated that the seismic performances of earthquake-damaged corroded specimens effectually improved after retrofitting with BFRP sheets, and the retrofitting effectiveness was significantly affected by the earthquake-damaged levels. The bucking of stirrups, spalling and crushing of concrete of retrofitted specimens were effectually postponed, while the ductility of corroded and uncorroded specimens under the earthquake damages increased after retrofitting with BFRP sheets. The total cumulative energy dissipation and final stiffness of retrofitted specimens considerably improved with the maximum increase of 22.3% and 14.3% comparing to those of benchmark specimen, respectively. Besides, the models for predicting the shear strength of RC beam-column joint cores considering the influences of earthquake damage, reinforcement corrosion, and FRP retrofitting were proposed. [ABSTRACT FROM AUTHOR]

Recently, Egypt had seismic activity. These seismic events have affected the stability of minarets, especially historical ones. Weight is one of the minaret's main stability factors. The main objective of the current research is to perform a three-dimensional (3D) assessment of an existing minaret, determine its accurate spatial model, document its current condition, examine its stability in the event of earthquakes, and identify the requisite measures to safeguard the minaret from any potential damage. The masonry to construct the minaret was used by extracting and examining specimens of this substance to determine its physical characteristics. The current work created three-dimensional models of the Abou-Ghanam El-Bialy minaret using a terrestrial laser scanner (TLS) to document its current condition, as well as minaret was subjected to a free vibration analysis using 3D finite element modeling. Finally, the minaret's seismic behavior was assessed utilizing mode forms, base responses, and normal stresses. The surveying method effectively documented the Minarets' existing case. The 3D seismic analysis showed that the minaret responded dynamically to earthquake loading, with mode shapes, base reactions, and normal stresses being crucial characteristics. Based on these data, we may suggest procedures to protect the minaret during seismic events. [ABSTRACT FROM AUTHOR]

In the southern Sichuan Basin of China (SSBC), hydraulic fracturing (HF) production of shale gas and surface buildings have been seriously affected by some medium scale (local magnitude ML > 4.0) earthquake events. In this study, focusing on relocated hypocenters in SSBC from January 2016 to May 2017, the Density-Based Spatial Clustering of Applications with Noise algorithm was introduced to divide it into four seismic regions. The temporal evolution of seismicity parameters, detailed views of potential faults near injection wells and spatial migration of seismic activity in each region were obtained. Moreover, the statistical correlation between seismicity and engineering disturbance was calculated by adopting epidemic type aftershock sequence model (ETAS); the relationship between corner frequency, stress drop and seismic moment of each region were analyzed, and the spatial distribution of the stress drop, the relationship with the focal mechanism solutions (ML > 3.5) and the fault slip-tendency under the regional stress pattern were discussed. The results show that the seismic diffusion rate of each region can be well described by the square root envelope (0.3–0.8 m2/s) and seismicity has a strong cluster mode (triggered events) and a weak background mode (independent events). Most (more than 97.5%) of the stress drops are in the range of 0.1–10 MPa, and the high stress drops is mainly located in the YS108 shale block; under the current regional stress pattern, the faults in region YS108 are unfavorablely oriented, while those in the south of N201 are favorablely oriented, with a high sliding trend. This knowledge may provide time to take mitigating actions to reduce the potential for damaging earthquakes. Highlights: Spatial clustering in SSBC based on DBSCAN algorithm and the relocated hypocenters associated with hydraulic fracturing, and the spatiotemporal migration characteristics are analyzed. Focal mechanisms indicate different fault planes, matching well with relocated hypocenters Statistical relationship between source parameters (corner frequency, stress drop, seismic moment, etc.) and regional variations Discuss the slip-tendency of potential faults in various regions under inversion of current stress pattern [ABSTRACT FROM AUTHOR]

The Sichuan-Yunnan block is a tectonically active region in China, with frequent large earthquakes occurring in and around it. Despite most earthquakes being concentrated along boundary faults, intraplate faults also have the potential to generate damaging earthquakes. Remote sensing makes it possible to identify these potential earthquake source faults. During an active fault investigation in the Liangshan area, a distinct lithological boundary named Caimashui fault was found. The geometric distribution and kinematic parameter of the fault is crucial for assessing seismic hazards and understanding the deformation pattern within the Sichuan-Yunnan block. The Caimashui fault is mapped with remote sensing interpretation, a field survey, and UAV measurement. Through trenching and Quaternary dating, the Late Quaternary active characteristics of the fault are studied. The fault is a Holocene active dextral strike-slip fault with a reverse component, exhibiting a dextral strike-slip rate of ~0.70 ± 0.11 mm/a. Paleoseismic investigation shows that the last surface rupture event of the Caimashui fault occurred later than 4150 ± 30a BP, with a magnitude of M ≥ 7.0. The fault may act as a secondary splitting fault, absorbing the deformation caused by various sinistral strike-slip rates of the boundary faults and the potential energy from the counterclockwise rotation of the Central Yunnan micro-block. [ABSTRACT FROM AUTHOR]

In Almaty, the largest city in Kazakhstan lying on a high seismic region, many residential buildings constructed during the Soviet Union are still in service. These buildings were not properly designed against earthquakes and special seismic detailing was not well considered according to the local design code. Therefore, this paper presents an analytical seismic assessment of two typical reinforced concrete moment frame residential structures constructed in this era, representing 812 buildings with almost identical construction materials, geometries, and structural details. Two-dimensional nonlinear models were developed for these buildings in each orthogonal direction based on the structural details collected from a Kazakh government agency. Incremental dynamic analyses were then performed using 24 historical strong ground motions with fault characteristics similar to those in the Almaty region. Structural global and local seismic responses were investigated. A new approach was proposed to define structural global inter-story drift limits at different damage states based on local seismic demands considering uncertainties of earthquakes and structural nonlinear dynamic responses. Based on these inter-story drift limits, the structural fragility curves were then developed to identify the damage probability of these buildings, which were further used to roughly estimate repair costs at different earthquake intensity levels. It has been found that these buildings are vulnerable to destructive earthquakes due to poor structural details. They possess a high probability of incurring extensive damage (high repair cost) or even collapsing (irreparable) at the earthquake intensity level, with a return period of 475 years or 2475 years, respectively. [ABSTRACT FROM AUTHOR]

Recent geodetic and seismological observations of two major earthquakes in southeastern Türkiye in February 2023 have revealed complex rupture initiation, propagation, and segmentation along the East Anatolian Fault Zone (EAFZ) and surrounding regions. However, the role of upper crust structures along the EAFZ in determining the diverse rupture processes of this earthquake doublet remains unclear. To further investigate this, we employed double-difference location and seismic tomography techniques to determine high-resolution seismic velocities (VP, VS) and Poisson's ratio (σ) structures using a multi-parameter joint tomographic algorithm. Our dataset includes 100,833 high-quality source-receiver travel-time pairs of P- and S-waves. We find that the unique rupture processes of this earthquake doublet were primarily influenced by contrasting crustal seismic structures and localized geological settings. The Mw7.8 mainshock was initiated within a transitional edge zone characterized by a rigid part (asperity) of the seismogenic zone with sharp contrast variations in rock strength ranging from low to high along the EAFZ. In comparison, the Mw7.6 rupture originated in a ductile belt featuring fluid saturation with low-VP, low-VS, and high-σ values that extended parallel to the Çardak Fault. The pronounced contrast structures observed along the former rupture can be attributed to the oblique collision system between the weakened section of the east Anatolian plateau and the brittle Arabian platform, while the latter rupture was initiated within the ductile structure associated with fluid intrusion caused by the northward subduction of the Cyprus slab and subsequent detachment. Furthermore, the occurrence of the first earthquake (E1) serves to alleviate shear stress on the second earthquake (E2) fault, potentially impeding the initiation of an E2 rupture. On the contrary, this event also significantly reduces the normal stress acting on the E2 fault due to a double left-lateral strike-slip system within a triangular region. This reduction not only results in a decrease of fault friction force and an increase in rock porosity but also induces lower strain drops and the redistribution of Coulomb stress, thereby contributing to the initiation of the E2 event. The proposed rupture pattern exceeds the conventional model that governs individual earthquake ruptures, offering new insights for mitigating potential seismic disasters in Türkiye. The lessons learned from this doublet event can contribute to reevaluating the ongoing risk of damaging earthquakes in China's South-North Seismic Zone or other regions worldwide with comparable geological conditions. [ABSTRACT FROM AUTHOR]

Functional recovery is a new, nonstandardized building design objective, intended to improve a building's capacity to maintain or rapidly restore basic intended functions after a natural hazard event. Current building seismic design standards, which target life-safety performance objectives, provide limited requirements to ensure buildings maintain, or rapidly recover, function after earthquakes. Therefore, the expected functional recovery performance that is provided by current building codes is unclear. To provide clear and systematic insights to inform the development of prescriptive and performance-based design standards, this study documents the functional recovery performance for a set of 60 reinforced concrete archetype buildings. The results indicate that the estimated functional recovery time for reinforced concrete buildings designed to life-safety standards may approach 1 year, on average, for design-level earthquakes. Additionally, while increased strength and stiffness requirements significantly reduce the likelihood of a building being marked as unsafe due to structural damage, additional design provisions for nonstructural components are required to ensure a high confidence of rapid recovery. The findings from this study clarify the expected post-earthquake recovery of modern reinforced concrete buildings and identify key trends in underlying damage and response mechanisms required to improve future building performance. [ABSTRACT FROM AUTHOR]

The buildings in various geographical conditions are strengthened due to different reasons, such as earthquakes, fire, or deterioration. One of the important issues is that comfort levels are ensured, and energy consumption is kept at a minimum in educational buildings where renovation and strengthening work is being carried out. In this study, in terms of energy consumption and acoustic comfort, a method is proposed to examine a building damaged in an earthquake and then strengthened. The method has also been created and implemented to provide control and improvement suggestions in terms of thermal and acoustic conditions in strengthening projects of buildings. As a case study, the pre- and post-reinforcement situation of an educational building in a temperate humid climate has been evaluated. In addition, different glazing scenarios that reduce energy consumption while increasing facade noise reduction have been developed and analyzed. The results showed that while sufficient noise reduction is achieved in the building envelope, there is a 15.9% reduction in the total energy consumption of the building. The optimum scenario decreased total energy consumption by 19.4 % in B113 and 26 % in B114 and increased the facade noise reduction levels by 14.2 dB in B113 and 15 dB in B114. The proposed method and the findings will contribute to the design process of newly designed, renovated, and strengthened buildings in terms of energy efficiency and indoor acoustical comfort. [ABSTRACT FROM AUTHOR]

In Japan, a country prone to earthquakes, numerous damaging earthquakes have been recorded throughout history, often accompanied by descriptions of mysterious earthquake lights (EQL), which may involve various mechanisms. In this article, the possible mechanisms for different types of EQL in 11 cases are reviewed among 21 selected earthquakes. These involve preseismic physicochemical variations in the geological structure of the fault in the lithosphere, which contains deep Earth gases such as radon, methane, and others, as a primary factor for EQL generation. Additionally, various seismic, atmospheric, hydrospheric, and ionospheric variations interact with each other, resulting in the visualization of characteristic anomalous phenomena, such as glowing or shining ground, mountains, offshore areas, and skies of various colors. These phenomena appear momentarily but can sometimes last for extended periods. Because EQL often appear just before an earthquake, their study might be significant for earthquake prediction. Additionally, EQL involving methane flames in the ground is an important research topic as it relates to public safety. Was what they witnessed paranormal? [ABSTRACT FROM AUTHOR]

Earthquakes have serious destructive effects on building structures, and effective seismic design is the key to building design. In order to reduce the damage of earthquakes to building structures, seismic design of buildings is based on improved viscous dampers. First, the displacement seismic design was studied and a displacement-based structural seismic model was constructed. In addition, analyzing traditional viscous dampers, an improved viscous damper is adopted based on it. Through equivalent damping expression, a displacement seismic model based on the improved viscous damper is constructed. Finally, two targets, frequent and rare earthquakes, were selected for experimental analysis. In frequent earthquake experiments, the improved viscous damper structure increased the shock absorption rate by 35.65 % compared to the no-structure design. In the shear force comparison, the maximum shear force of the improved viscous damper structure in the HB wave X direction is 2186 KN, which is the smallest shear force among the three structural designs. In a rare earthquake experiment, the maximum value of the floor shear force in the X-direction of the Humbolt bay wave of the proposed improved viscous damper structure was 8696 KN. Compared with other structures, the floor shear force was the smallest. In the comparison of floor displacements, the maximum inter-story displacement in the Humbolt bay wave Y-direction of the proposed improved viscous damper structure is 162 mm, which is the smallest inter-story displacement compared with other structures. In addition, the structure apex displacement was also compared. The structure apex displacement value of the improved viscous damper structure was lower than that of other structures and was in the slight damage range. The overall seismic effect was significantly better than other structural designs. The research content is conducive to optimizing the application effect of viscous dampers and provides technical reference for the seismic design of building structures. [ABSTRACT FROM AUTHOR]

Zhuanyao dwellings faced significant seismic risks in rural regions of China. Therefore, a shaking-table test was performed to explore the seismic performance of Zhuanyaos and validate the finite-element simulation results. The results showed that the damage to the pier and roof levels of Zhuanyaos was more severe after earthquakes, resulting in a noteworthy increase in the displacement responses of these two levels compared to that of the vault level. The damage to the front structure (Yaolian) and mid-pier of the Zhuanyao were more severe than the damage to the back wall and side pier, respectively, which caused a significant reduction in acceleration responses of Yaolian and mid-pier. Following the crack development, dynamic response, and field investigation, three typical collapse modes of Zhuanyaos were presented. Subsequently, the parametric analysis was conducted using a verified finite-element simulation method. The results show that using the catenary arch can reduce earthquake damage in Zhuanyaos. Increasing the width of the middle pier can improve the seismic performance of Zhuanyaos to a certain extent; however, it may exacerbate local damage to the structure. Besides, the high seismic vulnerability of Zhuanyaos stemming from an increasing thickness of overlying soil cannot be ignored. [ABSTRACT FROM AUTHOR]

When traversing through an active strike-slip fault, buried pipelines may be subjected to permanent ground deformation (PGD), causing large strains in the pipeline during an earthquake. The presence of bends near the fault-crossing zones may further increase the strain in the pipe. Moreover, it is well acknowledged that bends are the most vulnerable location to earthquake damage, mainly when compressive strain develops due to PGD. Hence, most design guidelines recommend constructing pipelines without field bends, elbows, and flanges crossing the fault zone. However, it is not always possible to provide only a straight segment of the pipeline, especially for blind faults where the location of the faults is unknown. Hence, the present study aims to investigate the response of buried continuous steel pipelines with field bends subjected to strike-slip faulting by conducting an extensive parametric study. A three-dimensional pipe-soil interaction model is developed in a finite element framework for this study. The pipeline response in terms of its maximum von-Mises stress and maximum longitudinal stress and strain due to fault crossing is studied for various influencing parameters such as pipe bend angle, soil strength, pipe burial depth, and distance of the fault trace from the bend. Based on the results obtained, suitable relationships in terms of modification factors over the response of a straight pipeline as a function of a few critical parameters are determined using regression analyses. It is concluded that providing bends to the pipeline can significantly affect its structural response when subjected to fault displacement when the fault trace is close to the pipe bend. The primary outcome of this investigation would be to suggest a simplified methodology to estimate the response of pipelines having field bends while crossing fault lines from the response of straight pipelines in a similar scenario. [ABSTRACT FROM AUTHOR]

The original single component of seismic data served as the foundation for the majority of previous investigations on the impact of pulse-like ground motion on the dynamic response of structures. The seismic responses of significant infrastructure are less studied when multicomponent motion is taken into account as seismic excitation. As velocity pulses may cause considerable damage to long-period structures, it is of great significance to understand the seismic responses of gravity dams under near-fault pulse-like ground motions for mitigating structural damage. In this study, a unique evaluation approach is suggested for examining the dynamic responses of gravity dams using the combined ground motion of the horizontal and vertical components. Furthermore, the seismic responses of the dam body under rotated and scaled multipulse excitations are investigated. We employed continuous wavelet transform to choose 16 near-fault pulse-like ground motions from actual seismic events with similar amplitude as seismic excitation signals in order to simulate the earthquake damage to the Koyna Dam using the finite-element approach. The displacement, principal stress, and damage fractures of the gravity dam are used to quantify the impact of the pulse intensity variation. The analysis results demonstrate that the structure has remarkable seismic response owing to the presence of large pulse records. The large residual and peak displacements are mainly caused by the velocity pulses and the sensitivity of the upper part of the dam neck to the horizontal relative displacement is significantly higher than that of the lower part. Although the mean intensity parameter of the rotated records with velocity pulse is smaller than that of the Koyna nonpulse, the former increases the mean damage to the dam by 41%. Compared with the rotated records, the scaled records may overestimate the damage of pulse-like motions to the structure, and the stronger pulses are likely to cause severe penetration cracks around the dam neck. The seismic response spectra reveal the potential effects of multicomponent pulse-like motions on the gravity dam and emphasize the significance of considering the combined motion for seismic design. [ABSTRACT FROM AUTHOR]

The museum system is exposed to a high risk of seismic hazards. However, it is difficult to carry out seismic hazard prevention to protect cultural relics in collections due to the lack of real data and diverse types of seismic hazards. To address this problem, we developed a deep-learning-based multi-source feature-fusion method to assess the data on seismic damage caused by collected cultural relics. Firstly, a multi-source data-processing strategy was developed according to the needs of seismic impact analysis of the cultural relics in the collection, and a seismic event-ontology model of cultural relics was constructed. Additionally, a seismic damage data-classification acquisition method and empirical calculation model were designed. Secondly, we proposed a deep learning-based multi-source feature-fusion matching method for cultural relics. By constructing a damage state assessment model of cultural relics using superpixel map convolutional fusion and an automatic data-matching model, the quality and processing efficiency of seismic damage data of the cultural relics in the collection were improved. Finally, we formed a dataset oriented to the seismic damage risk analysis of the cultural relics in the collection. The experimental results show that the accuracy of this method reaches 93.6%, and the accuracy of cultural relics label matching is as high as 82.6% compared with many kinds of earthquake damage state assessment models. This method can provide more accurate and efficient data support, along with a scientific basis for subsequent research on the impact analysis of seismic damage to cultural relics in collections. [ABSTRACT FROM AUTHOR]

Earthquakes are one of the most dangerous natural disasters that have constantly threatened humanity in the last decade. Therefore, it is extremely important to take preventive measures against earthquakes. Time estimation in these dangerous events is becoming more specific, especially in order to minimize the damage caused by earthquakes. In this study, a hybrid deep learning model is proposed to predict the time of the next earthquake to potentially occur. The developed CNN+GRU model was compared with RF, ARIMA, CNN and GRU. These models were tested using an earthquake dataset. Experimental results show that the CNN+GRU model performs better than others according to MSE, RMSE, MAE and MAPE metrics. This study highlights the importance of predicting earthquakes, providing a way to help take more effective precautions against earthquakes and potentially minimize loss of life and material damage. This study should be considered an important step in the methods used to predict future earthquakes and supports efforts to reduce earthquake risks. [ABSTRACT FROM AUTHOR]

The single-station microtremor method is one of the fastest, most reliable, and cheapest methods used to identify dynamic soil properties. This study utilizes 49 single-station microtremor measurements to identify the dynamic soil properties of the Hilalkent quarter of the Yakutiye district in Erzurum. Soil dominant frequency and the amplification factor were calculated by using the Nakamura horizontal/vertical spectral ratio (H/V) method. While the soil dominant frequency values varied between 0.4 Hz and 10 Hz, the soil amplification factor changed between 1 and 10. Higher H/V values were acquired with lower frequency values. The vulnerability index (Kg) and shear strain parameters that are utilized to estimate the damage that may be caused by an earthquake were mapped. Especially in the west side of the study area, higher Kg values were observed. The shear strain map was created with 0.25 g, 0.50 g and 0.75 g bedrock accelerations, and soil types that lost elasticity during an earthquake were identified. The average shear wave velocity for the first 30 m (Vs30) was calculated. Finally, it was observed that the western part of the study area, which resulted in a higher period and higher H/V, higher Kg and lower Vs30 values, presents a higher risk of damage during an earthquake. [ABSTRACT FROM AUTHOR]

Quickly and accurately assessing the damage level of buildings is a challenging task for post-disaster emergency response. Most of the existing research mainly adopts semantic segmentation and object detection methods, which have yielded good results. However, for high-resolution Unmanned Aerial Vehicle (UAV) imagery, these methods may result in the problem of various damage categories within a building and fail to accurately extract building edges, thus hindering post-disaster rescue and fine-grained assessment. To address this issue, we proposed an improved instance segmentation model that enhances classification accuracy by incorporating a Mixed Local Channel Attention (MLCA) mechanism in the backbone and improving small object segmentation accuracy by refining the Neck part. The method was tested on the Yangbi earthquake UVA images. The experimental results indicated that the modified model outperformed the original model by 1.07% and 1.11% in the two mean Average Precision (mAP) evaluation metrics,   m A P b b o x 50 and m A P s e g 50 , respectively. Importantly, the classification accuracy of the intact category was improved by 2.73% and 2.73%, respectively, while the collapse category saw an improvement of 2.58% and 2.14%. In addition, the proposed method was also compared with state-of-the-art instance segmentation models, e.g., Mask-R-CNN and YOLO V9-Seg. The results demonstrated that the proposed model exhibits advantages in both accuracy and efficiency. Specifically, the efficiency of the proposed model is three times faster than other models with similar accuracy. The proposed method can provide a valuable solution for fine-grained building damage evaluation. [ABSTRACT FROM AUTHOR]

The aim of this study was to develop an innovative deep learning based intelligent software (DamageNet) and its mobile applications to classify seismic damage of Reinforced Concrete (RC) elements. Images of 2455 damaged elements that have been exposed to different destructive earthquakes were collected from the "datacenterhub" database. The DamageNet algorithm has been compared with the pretrained convolutional neural networks (CNN) algorithms (VGG16, ResNet-50, MobileNetV2 and EfficientNet) according to performance metrics. With the other models, a maximum test success of 89% was achieved, while with DamageNet a test success of 92% was achieved in damage classification. The mobile application developed based on the DamageNet model was tested in the field after the earthquakes (Mw:7.7 and Mw:7.6) in Kahramanmaraş/Turkey and classification success of 88% was obtained. [ABSTRACT FROM AUTHOR]

Understanding the behavior of structures during earthquakes is crucial for ensuring safety. Despite their significant impact on buildings, infill walls are often overlooked in seismic assessments, contributing to the complexity of a structure. Because of their intricate nature and modeling difficulties, infill walls are frequently excluded from seismic models. However, given the prevalence of reinforced concrete buildings with various infill wall materials in earthquake-prone areas, it is essential to incorporate infill walls for a more realistic evaluation of seismic behavior. This study scrutinizes a building that sustained damage in the Izmir earthquake in Turkey. The building was represented in four distinct models using the SAP2000 V24 finite element program: without infill walls, with porotherm clay blocks, burnt clay brick, and autoclaved aerated concrete blocks. Real parameters of the building were utilized in the modeling process. Upon comparing the results of the time history analysis, it was observed that the presence of infill walls had a positive impact on various building properties, including period, ground floor shear force, column bearing capacity, and inter-story drift ratio. Additionally, infill walls increased base shear forces on the ground floors and the overall base shear force. Notably, similar outcomes were obtained with porotherm clay blocks and burnt clay brick as infill wall types, while autoclaved aerated concrete blocks exhibited lower stiffness than other infill wall models. [ABSTRACT FROM AUTHOR]

Indonesia is located in one of the most seismically active regions in the world and often experiences damaging earthquakes. In the past the housing sector has sustained higher earthquake related damage and losses than other sectors. This is often attributed to the fact that the most common houses in Indonesia are non-engineered, built with poor quality workmanship, poor quality materials and without resilient seismic design features. However little effort has been made to quantify how fragile Indonesian houses are, or how their fragility may vary according to the population density or relative wealth of a region. It is not possible to derive empirical fragility functions for Indonesia due to insufficient damage data. The aim of this study is to determine whether existing earthquake fragility functions can be applied to common house types in Indonesia. Scenario damage analyses simulating the 2006 Yogyakarta and 2009 Padang events were undertaken several times testing different fragility functions. The simulated damage results were then compared to the damage observed post event to determine whether an accurate damage prediction could be achieved. It was found that the common house types in Yogyakarta and Central Java vary according to age of construction, location and relative wealth of a region and can be reasonably well represented by existing fragility functions. However, the houses in Padang and surrounding West Sumatra did not vary in a predictable manner and are more fragile than anticipated. Therefore, the fragility of the most common house types in Indonesia differs between Central Java and West Sumatra. This has important implications for seismic damage and risk assessment undertaken in Indonesia. [ABSTRACT FROM AUTHOR]

Understanding the generation of damaging, high‐frequency ground motions during earthquakes is essential both for fundamental science and for effective hazard preparation. Various theories exist regarding the origin of high‐frequency ground motions, including the standard paradigm linked to slip heterogeneity on the rupture plane, and alternative perspectives associated with fault complexity. To assess these competing hypotheses, we measure ground motion amplitudes in different frequency bands for 3 ≤ M ≤ 5.8 earthquakes in Southern California and compare them to empirical ground motion models. We utilize a Bayesian inference technique called the Integrated Nested Laplace Approximation (INLA) to identify earthquake source regions that produce higher or lower ground motions than expected. Our analysis reveals a strong correlation between fault complexity measurements and the high‐frequency ground motion event terms identified by INLA. These findings suggest that earthquakes on complex faults (or fault networks) lead to stronger‐than‐expected ground motions at high frequencies. Plain Language Summary: An important and unresolved question in earthquake science is how damaging, rapid ground shaking is generated during an earthquake. Various ideas currently exist to explain the cause of such ground motions, with the standard view attributing strong ground motion to frictional variations on the fault plane that ruptures during an earthquake. However, recent studies have also indicated that geometric complexities within fault networks may likewise influence the strong ground shaking. To help resolve this conundrum, we analyzed the ground motions produced by earthquakes in Southern California to assess the dependence of these ground motions to the complex fault networks on which the earthquakes occur. Our findings indicate that complex fault network systems have a substantial influence on how damaging earthquake ground shaking could be. These results have broad implications for our understanding of the physics of earthquakes and have important implications for earthquake hazards. Key Points: We investigate the influence of fault network complexity on the high‐frequency ground motions of earthquakes in CaliforniaWe observe a strong correlation between fault complexity and residual ground motions at high frequenciesThe correlation is frequency‐dependent, with stronger correlations observed at frequencies above 2 Hz [ABSTRACT FROM AUTHOR]

Damage zones are common around faults, but their effects on earthquake mechanics are still incompletely understood. Here, we investigate how damage affects rupture patterns, source time functions (STF) and ground motions in 2D fully‐dynamic cycle models. We find that back‐propagating rupture fronts emerge in large faults and can be triggered by residual stresses left by previous ruptures or by damage‐induced pulse‐to‐crack transitions. Damage‐induced back‐propagating fronts are modulated by slip rate oscillations, amplify high‐frequency radiation, and sharpen the multiple peaks in STF even in the absence of frictional heterogeneity or fault segmentation. Near‐field ground motion is predominantly controlled by stress heterogeneity left by prior seismicity, and further amplified within the damage zone by trapped waves and outside it by secondary rupture fronts. This study refines our knowledge on damage zone effects on earthquake rupture and identifies their potentially observable signatures in the near and far field. Plain Language Summary: Faults are surrounded by layers of fractured rocks, known as damage zones, which can affect earthquakes and related hazards, but in ways that are still not well understood. Here, by running computer simulations, we investigate how damage zones influence earthquake ruptures and consequent ground motions. Our models fully account for seismic wave effects, produce multiple earthquake cycles, and span a large range of fault lengths and damage zone properties that are representative of natural faults. We identify characteristic patterns of earthquake rupture produced by damage zones: back‐propagating fronts that re‐rupture the fault, and oscillatory fault motions that affect ground shaking amplitude and frequency content. We identify which of these effects might be observable in seismograms recorded near and far from the fault. Overall, our computational study highlights significant effects of damage zones on earthquakes and on the shaking they produce. These results can guide us to better interpret earthquake source and ground motion observations, and to predict the potential characteristics of future events. Key Points: Reduction of nucleation size and pulse‐crack transitions are two distinct damage zone effects that induce back‐propagating rupture frontsDamage effects can enhance high‐frequency radiation and complexity of source time functions, potentially observable in the far fieldBack‐propagating fronts have potential signatures in near‐field seismograms and can affect peak ground motions [ABSTRACT FROM AUTHOR]

Applying machine learning to continuous acoustic emissions, signals previously deemed noise, from laboratory faults and slowly slipping subduction‐zone faults, demonstrates hidden signatures are emitted that describe physical details, including fault displacement and friction. However, no evidence currently exists to demonstrate that similar hidden signals occur during seismogenic stick‐slip on earthquake faults—the damaging earthquakes of most societal interest. We show that continuous seismic emissions emitted during the 2018 multi‐month caldera collapse sequence at the Kı̄lauea volcano in Hawai'i contain hidden signatures characterizing the earthquake cycle. Multi‐spectral data features extracted from 30 s intervals of the continuous seismic emission are used to train a gradient boosted tree regression model to predict the GNSS‐derived contemporaneous surface displacement and time‐to‐failure of the upcoming collapse event. This striking result suggests that at least some faults emit such signals and provide a potential path to characterizing the instantaneous and future behavior of earthquake faults. Plain Language Summary: Applications of machine learning have revealed that continuous acoustic emissions from laboratory earthquake experiments contain continuous, hidden signatures that describe the fault slip. In these laboratory studies, the acoustic emissions signals that were previously deemed to be dominantly noise, are found to be rich with details that can describe physical properties such as the fault displacement, friction, and fault thickness. By applying similar machine learning approaches, it was discovered that signatures of surface displacement exist in the seismic emissions from slowly slipping subduction zone faults. However, there has yet to be similar evidence observed during seismogenic stick‐slip on earthquake faults–the damaging earthquakes of most societal interest. Here we study a repeating caldera collapse sequence with short enough repeat times to mimic the experiments performed in the laboratory. We find that seismic emissions from seismogenic fault slip associated with the 2018 caldera collapse at the Kı̄lauea volcano in Hawai'i, also contain hidden signatures informing of instantaneous surface displacement associated with fault slip at depth, as well as time‐to‐failure of the upcoming slip event. These observations suggest that at least some seismogenic faults emit such signals, and provide a potential path to characterizing the instantaneous and future behavior of earthquake faults. Key Points: Features extracted from 30 s of continuous seismic waveforms contain information about contemporaneous GNSS ground displacementsA gradient boosted tree model predicts GNSS ground displacements and timing of the next caldera collapse eventThe observations suggest some seismogenic faults emit precursory signals, providing a potential path to characterize behavior of faults [ABSTRACT FROM AUTHOR]

In past, the 2004 Indian Ocean earthquake and the 2011 Great East Japan earthquake had caused collapse of many breakwaters due to failure of their foundations. The seismic behaviour of rubble mound (RM) breakwater is not well understood may be due to limited number of research works done in the area. Therefore, in the present study, a series of shaking table tests were conducted for RM breakwater in order to determine the exact reasons and mechanisms of failure of the breakwater during an earthquake. In addition, a novel countermeasure technique was developed to mitigate the earthquake-induced damage of RM breakwater. The countermeasure model dealt with geobags as armour units on the both sides instead of conventional armours to increase the stability. The developed model has geogrid and sheet piles in seabed foundation soils of the breakwater. The effectiveness of countermeasure model was examined by comparing with conventional RM breakwater model considering parameters like settlement, horizontal displacement, acceleration-time histories, excess pore water pressure and deformation patterns. Numerical analyses were done to elucidate the failure mechanisms. Overall, the developed model was found to be resilient breakwater against the earthquakes; and the technique could be adopted in practical use on the real ground. • Seismic responses of RM breakwater and foundation soils is studied. • A new countermeasure technique has developed to mitigate earthquake induced damage of RM breakwater. • The geobags on the outer slopes of breakwater has reduced the lateral movement of breakwater and the geogrids placed in the breakwater restricted vertical movement of the same during the earthquake loadings. • The utilization of sheet piles has restricted the lateral flow of foundation soils during the mainshock. • The developed countermeasure is found to be resilient against the earthquake. [ABSTRACT FROM AUTHOR]

A rapid and accurate estimate of earthquake damage is a key component in a successful earthquake early warning (EEW) system. The cumulative absolute velocity (CAV) is an important and widely used parameter to measure ground motion intensity, but it cannot be correctly estimated via the traditional approach with the limited information available in typical EEW systems. Therefore, current EEW systems cannot effectively use CAV to predict earthquake damage. Herein, a CAV prediction model (DLcav) based on convolutional neural networks was proposed for EEW systems. DLcav is an end‐to‐end solution to continuously predict CAV using arriving seismic waves of increasing length and supplemented with additional auxiliary information. The effectiveness of DLcav to predict CAV was tested based on Japanese ground motion records, and the generalization ability of DLcav was assessed using the ground motion records from Chile. The results demonstrate that DLcav can rapidly predict CAV with good accuracy, which will help better estimate earthquake damage in EEW systems. [ABSTRACT FROM AUTHOR]

Earthquakes are hazardous natural disasters, and they may cause severe damage and losses where they occur. In addition to their devastating effects, they may trigger following disasters like tsunamis and fires. Post-earthquake fires are known as the most dangerous secondary disasters and generally cause much more damage than the damage caused by the earthquake itself. The difficulty in determining and responding to ignition sources, the lack of equipment and workforce, and obstacles like collapsed buildings that block the ways to reach fires may cause catastrophic disasters after an earthquake. In recent years, Unmanned Aerial Vehicle technologies (UAVs) have shown promising performance in post-disaster response operations. Parallel to technological improvements, they have been used for many purposes, like fire-fighting, victim location detection, base station support, and material distribution in disaster areas. To manage a possible response and improve the performance of UAVs in post-earthquake fire areas, it is crucial to be prepared in advance. This study proposes an artificial neural network-based clustering approach for unmanned aerial vehicle use in post-earthquake fire areas. After conducting a detailed literature review covering post-earthquake fires, usage of UAVs in disasters, and some aspects of Self Organizing Maps, the methodology used for clustering the neighborhoods regarding their post-earthquake fire risk similarities is introduced. A real-life application is carried out to identify and cluster the regions and provide preliminary information to the decision-makers on possible interventions. Neighborhoods of Tuzla district, one of the riskiest districts in terms of post-earthquake fires in Istanbul, are clustered with Self-Organizing Maps (SOM). In a possible post-earthquake fire disaster, the Tuzla district can be divided into three areas, and UAVs can be organized more efficiently and quickly based on this cluster information. The results of this real-life application can guide decision-makers by showing which regions have similarities for UAV response in possible post-earthquake fires and where they can be intervened together. The authorities can benefit from the findings of this study while preparing disaster plans, intervention actions, and post-disaster humanitarian activities. [ABSTRACT FROM AUTHOR]

During the last decades, liquefaction damages induced by earthquakes have underlined the importance of identifying effective soil improvement techniques for mitigation purposes. Vibratory methods, such as rammed aggregate piers, are commonly used to densify sands and silty sands, erroneously neglecting the influence of the lateral stress. This paper presents the results of a series of liquefaction mitigation case studies carried out using rammed aggregate piers in Christchurch (New Zealand), Boca de Briceño (Ecuador), and Bondeno (Italy) following the 2010–2011 Canterbury seismic sequence, the 2016 Muisne earthquake, and the 2012 Emilia seismic sequence, respectively. The availability of coupled piezocone and seismic dilatometer tests before and after treatment enabled a geotechnical characterization of the three sandy sites to be made, along with estimating the at-rest lateral earth pressure coefficient, and comparing the effectiveness of the treatment at the trial sites. Finally, the paper proposes an updated procedure for liquefaction assessment that takes into account both the increase in soil density and lateral stress produced by ground improvement. [ABSTRACT FROM AUTHOR]

Assessment of existing reinforced concrete (RC) structures after an earthquake is a challenging task that must somehow relate qualitative and quantitative observations in the plastic hinge regions and the associated residual deformation capacity of damaged structures. Having an estimate available for the remaining drift capacity will result in more economical and informed decisions regarding demolition or strengthening options. This study aims to develop a practical methodology to estimate the maximum drift demand of an RC column based on the residual crack width. For this purpose, fiber-based frame elements are used to model the RC column considering appropriately concrete behavior in compression and tension stiffening effects. Afterwards, the accuracy and reliability of the proposed methodology are demonstrated by validating the computational approach with two cyclic experimental results from literature and new test data for a one-bay one-story RC frame conducted within the course of this study. A comprehensive parametric study is performed for RC columns with different axial loads, longitudinal and transverse reinforcement ratios, and ground motions to exhibit the stochastic behavior. The study identifies the axial load ratio as the predominant parameter. Key findings include strong correlations between maximum drift ratios and total residual crack widths, as well as maximum compressive strains, with regression analysis yielding equations for accurate drift ratio estimation. Simple predictive models are proposed to estimate the maximum deformation demands based on observed residual crack widths. Residual cracking exceeding 5 mm poses significant risk for the columns with axial load ratios above 0.4, with 90% probability of exceedance 2% drift ratio. [ABSTRACT FROM AUTHOR]

The New Zealand Community Fault Model (NZ CFM) is a publicly available representation of New Zealand fault zones that have the potential to produce damaging earthquakes. Compiled through collaborative engagement between New Zealand earthquake-science experts, this first edition (version 1.0) of the NZ CFM builds upon previous compilations of earthquake-source active fault models with the addition of new and modified information. Developed primarily to support an update of the New Zealand National Seismic Hazard Model, the NZ CFM comprises two principal components. The first dataset is a two-dimensional map representation of the surface traces of 880 generalised fault zones. Each fault zone is assigned specific geometric and kinematic attributes, including uncertainties, supplemented with a subjective quality ranking focused primarily on the confidence in assigned slip rates. The second component is a three-dimensional representation of the fault zones as triangulated mesh surfaces that are projected down-dip from the two-dimensional mapped traces to a geophysically-defined maximum fault rupture depth. This article summarises the compilation and parameterisation of the NZ CFM, along with background on its relation to predecessor datasets, and forward applications to probabilistic seismic hazard assessment and physics-based earthquake models currently being developed for Aotearoa New Zealand. [ABSTRACT FROM AUTHOR]

Earthquakes with magnitudes of 6–7 have been reported even in various active tectonic settings where fault deformation topography have not been detected. Therefore, delineating concealed active faults generating such earthquakes is necessary to reduce earthquake damage; however, few studies exist to provide its clues regarding such faults. The 1984 Western Nagano Earthquake in Japan was a main shock with a magnitude of Mj 6.8 and a depth of 2 km at the source. Solid bedrocks are well‐exposed in the earthquake source region; however, no surface rupture have been identified, and the active fault is known to be concealed. In this study, we collected data on striations observed in fractures by geological survey around the source area of the 1984 Western Nagano Earthquake. Using the collected data, the multiple inverse method was used to estimate the stresses that affected the striation formation. Consequently, stresses similar to acting faults in this area were detected in minor faults around the known concealed active fault. This suggests that the minor faults might be part of the damage zone that has been developed around the concealed active fault. Some minor faults were recognized in Quaternary volcanic rocks, confirming that they experienced displacements recently. This study indicates the possibility of detecting concealed active faults in the bedrock by geological survey. Plain Language Summary: The activity of active faults causes earthquakes. Therefore, it is crucial to understand the distribution of active faults to prepare for earthquakes in advance. However, earthquakes can also occur where active faults have not been recognized. In this case, the active fault cannot be recognized on the surface but might be concealed. In this study, we collected data on many slip marks on fractures in the bedrock where a concealed active fault has been inferred and estimated the stress required to form the slip marks to examine whether a clue to the existence of a concealed active fault can be obtained from a surface approach. Consequently, similar stresses to currently acting faults in this area were obtained in the area directly above the concealed active fault. This discovery shows that there are many recently moved slip marks directly above the concealed active fault, which might be related to the activity of the fault. This result indicates the possibility of recognizing the concealed active fault from surface approaches. Key Points: We collected minor faults‐slip data around the 1984 Western Nagano Earthquake region, and conducted a multiple inverse methodAs results, the minor faults were active in the recent stress are concentrated just above the concealed active faultIt shows the possibility of understanding the existence of the concealed active fault by using our method even in no active fault areas [ABSTRACT FROM AUTHOR]

The Jishishan Ms 6.2 earthquake occurred at 23:59 on December 18, 2023 in Gansu Province, China. We conducted a field survey to assess the hazards and damages caused by the earthquake and its associated geo-activities. Subsequently, we organized a seminar to discuss the possible causes of the destruction of a prehistoric site—Lajia Settlement—dated back to four thousand years B.P. and located only several kilometers away from the epicenter of the Jishishan earthquake. The Jishishan earthquake was unique for its hazard and disaster process, which featured ground shaking and a series of complex geological and geomorphological activities: sediment and soil spray piles, liquefaction, collapse, landslide, and mudflow along water channels. We define this phenomenon as the Jishishan earthquake ripple hazard (JERH). The most recent evidence from the JERH suggests that a prehistoric earthquake similar to the JERH, instead of riverine floods or earthquake-induced landslide dam outburst flood, as previously hypothesized, destroyed the Lajia Settlement. [ABSTRACT FROM AUTHOR]

Rapid and accurate structural damage assessment after an earthquake is important for e0cient emergency management. The widespread application of surveillance cameras provides a new possibility for improving the e0ciency of assessment. However, it is still challenging to directly assess the structural seismic damage based on videos captured by indoor surveillance cameras during earthquakes. In this study, we elaborate on the concept of estimating the structural natural frequency based on the relative pixel displacement of inter-stories. Furthermore, we propose a strategy for post-earthquake structural damage assessment that integrates the computer vision and time-frequency analysis. *is approach aims to navigate the di0culties inherent in earthquake damage assessment and improve emergency responses. The relative pixel displacement between the camera and the 5xed features on the 6oor is extracted from videos by using the Harris corner detection and Kanade--Lucas--Tomasi algorithms. The structural natural frequency is estimated using the synchroextracting transform-enhanced empirical wavelet transform. The natural frequency shift-related seismic damage index is de5ned and calculated for damage assessment. A shake table experiment of a smallscale steel model is conducted to verify the accuracy and feasibility of the approach, and the practicality of the proposed approach is further veri5ed by utilizing the data from a full-scale reinforced concrete benchmark model experiment.Theresults demonstrate that the approach can accurately and e0ciently evaluate the structural damage after an earthquake based on the video captured by surveillance cameras during the earthquake. The error of the acquired damage index is less than 0.1. We will apply more advanced algorithms in the future to alleviate this problem. [ABSTRACT FROM AUTHOR]

The damage assessment of numerous buildings after the earthquake is still a challenge by traditional methods as it requires a significant amount of time and resources for carrying out building-by-building seismic damage assessment. This study presents the machine learning (ML)-based damage assessment of buildings after an earthquake. The applicability of the machine learning model will be limited considering only structural properties or ground motion characteristics. Thus, in this study, the applicability of different machine learning techniques is explored using real-world earthquake damage datasets considering both the structural properties and ground motion characteristics. Initially, the entire dataset is used to train the ML models to classify the building's damage into five categories ranging from null to slight damage to collapse. Later, the dataset is divided into three traffic light damage tags: green, yellow, and red. The performance of the ML model to classify the building's damage into three damage tags is found better than that of classifying it into five damage categories. This research aims to be beneficial in planning and decision-making for emergency response and recovery following an earthquake. [ABSTRACT FROM AUTHOR]

The Nankai trough has repeatedly experienced large megathrust earthquakes at intervals of 100–200 years. The inland region of southwest (SW) Japan has a seismically active period from 50 years before to 10 years after megathrust earthquakes. To assess the activities of inland earthquakes after megathrust earthquakes, we need to quantitatively evaluate the postseismic stress accumulation on the inland source faults considering plausible viscoelastic relaxation. Recent studies have shown the importance of low-viscosity layers along the lithosphere-asthenosphere boundary (LAB layer) in postseismic deformation. In the present study, we focus on the most recent ruptures, the 1944 M7.9 Tonankai and the 1946 M8.0 Nankai earthquakes, estimating the 4-year stress change on the source faults in SW Japan in a forward modeling approach. The 1944–1946 megathrust rupture sequence was followed by severe ~ M7 inland earthquakes, such as the 1945 M6.8 Mikawa and 1948 M7.1 Fukui earthquakes. For stress calculation, we used a highly detailed finite element model incorporating the actual topography and the plausible viscoelastic underground structure from past studies. The calculated inland stress field shows the dominance of the coseismic change during the 1944 and 1946 earthquakes and little contribution from viscoelastic relaxation. In contrast, viscoelastic relaxation has a significant effect on stress in the slab, indicating the importance of quantifying the viscosity of the LAB layer. Based on the calculated stress, we evaluated the change in the Coulomb failure stress (ΔCFS) on each source fault. The ΔCFS is generally positive on the strike-slip faults east of 135°E due to the 1944 rupture. In contrast, the ΔCFS on the faults west of 135°E, including the Median Tectonic Line segments, became positive due to the 1946 rupture. The occurrence of the damaging earthquakes in 1945 and 1948 can be explained by the calculated ΔCFS. The ΔCFS on the recent earthquake faults of the recent damaging earthquakes such as the 2016 M7.2 Kumamoto earthquake is generally negative, suggesting the delay in stress accumulation. The ΔCFS on the source faults of the intra-slab earthquakes differ significantly as large as tens of kilopascals depending on the viscosity of the LAB layer. [ABSTRACT FROM AUTHOR]

In the 2016 Kumamoto Earthquake, the main shock, which occurred in the midnight of 16th of April 2016, caused the significant damage in the earthquake affected areas. The initial response by clinical engineers were conducted based on the disaster response manual in the hospital. While the manual was effective in clarifying the roles of the staff in the acute phase of emergencies, the manual did not prioritize the order in the damage assessment and recovery works of the medical devices. In addition, the manual did not cover the reporting system between the disaster response headquarters and the clinical engineers. Based on these experiences in the 2016 Kumamoto Earthquake, the Business Continuity Plan (BCP) was drafted to establish the reporting system in emergency response and prioritize the damage assessment and response of medical devices. In addition, the disaster response drills were conducted based on the BCP to share the experiences on the Kumamoto Earthquake among the clinical engineers. [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]

Seismic risk assessment of building portfolios has been traditionally performed using empirical ground motion models, and scalar fragility and vulnerability functions. The advent of machine learning algorithms in earthquake engineering and ground motion modelling has demonstrated promising advantages. The aim of the present study is to explore the benefits of employing artificial neural networks (ANNs) in earthquake scenarios for spatially-distributed building portfolios. To this end, several recent major seismic events in the Balkan region were selected to assess damage and economic losses, considering different modelling approaches. For the assessment of the seismic demand, the ANN developed in the companion study and common ground motion models for Europe were adopted. For the vulnerability component, recent ANN models and existing scalar fragility and vulnerability functions for the Balkans were used. The estimates of all modelling cases were compared against the aggregated damage and economic loss data observed in the aftermath of these events. The findings of this study suggest that overall, the ANNs led to damage and economic loss estimates closer to the observations. [ABSTRACT FROM AUTHOR]

The calculation of the spatial distribution of ground motion is one of the most important steps in earthquake scenarios. The advancements in machine learning algorithms and the release of new ground motion data can enable improvements in the reliability and accuracy of this component. We developed an artificial neural network (ANN) ground motion model using a compiled database from two subsets with measured Vs30 from the Pan-European strong motion database and the NGA-West2 database. The ANN model employs five input parameters: moment magnitude (Mw), hypocentral depth, Joyner–Boore distance (Rjb), shear wave velocity in the top 30 m (Vs30), and faulting type. The outputs of the ANN are the RotD50 horizontal components of common intensity measures used in seismic risk assessment: PGA, PGD, PGV, Arias Intensity, and 5% damped spectral acceleration at 27 periods from 0.01 to 4.0 s. A mixed-effects modelling approach was followed to train the ANN and partition the ground motion variability into between-event and between-site terms. The input parameter scaling relationships were studied and demonstrated physically sound trends of the ground motion with respect to Mw scaling, distance attenuation, and site amplification. The predicted median response spectra for several combinations of Mw and Rjb were compared to common ground motion models for Europe, and the results are discussed. The developed ANN is used in a companion study to calculate the hazard footprints for several historical earthquakes in the Balkan region. [ABSTRACT FROM AUTHOR]

Probabilistic seismic hazard assessments (PSHAs) provide the scientific basis for building codes to reduce damage from earthquakes. Despite their substantial impact, little is known about how well PSHA predicts actual shaking. Recent PSHA for California, Japan, Italy, Nepal, and France appear to consistently overpredict historically observed earthquake shaking intensities. Numerical simulations show that observed shaking is equally likely to be above or below predictions. This result from independently developed models and datasets in different countries and tectonic settings indicates possible systematic bias in the hazard models, the observations, or both. Analysis of possible causes shows that much of the discrepancy is due to a subtle and rarely considered issue: the conversion equations used in comparing the models--which forecast shaking as peak ground acceleration or velocity--and observations--parameterizations of qualitative shaking reports. Historical shaking reports fill a crucial data gap, but more research is warranted on how qualitative observations relate to instrumental shaking measures for earthquakes. [ABSTRACT FROM AUTHOR]

Fusion-based imaging using ground-penetrating radar (GPR) and ultrasonic echo array (UEA) was employed to track damage progression in the columns of two full-scale reinforced concrete (RC) bridge column-footing subassembly laboratory specimens. The specimens had different lap-splice detailing and were subjected to reverse-cyclic lateral loading simulating a subduction zone earthquake. GPR and UEA scans were performed on the east and west faces of the columns at select ductility levels. Reconstructed images were obtained using the extended total focusing method (XTFM) and fused using a wavelet-based technique. Composite images of each column's interior were created by merging the images from both sides. A quantitative analysis based on the structural similarity (SSIM) index accurately captured damage progression. A backwall analysis using the amplitude of the backwall reflector was also performed. Changes as early as in the first measurement (μ = 0.5 displacement ductility level) could be detected. Damage variation along the column height was observed, consistent with greater damage at the base. The proposed analyses distinguished the structural behavior differences between the two specimens. In summary, the SSIM metric provides a valuable tool for detecting changes, while the backwall analysis offers simple yet informative insights into damage progression and distribution in full-scale RC members. [ABSTRACT FROM AUTHOR]