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To overcome the reliance on large samples and high-quality data in existing evaluation methods, while also improving evaluation efficiency and accuracy, this paper proposes a method for rapid landslide hazard assessment. This method utilizes existing research findings and specific analytical techniques for the study area to conduct rapid assessments. Taking the landslide in Yongxing Town, Mingshan Area, Ya'an City, Sichuan Province as an example, the Analytic Hierarchy Process (AHP) is combined with the Information Value (IV) method, Certainty Factor (CF) method, and Frequency Ratio (FR) method from previous studies, The AHP-IV and AHP-FR methods assess the study area as a moderately hazardous zone, while the AHP-CF method assesses it as a slightly hazardous zone. Affected by the strong 2013 Lushan earthquake, the landslide in the study area caused permanent damage. Field investigation results show that the landslide hazard in the study area is moderate, and the AHP-IV and AHP-FR methods are more consistent with the actual field results. The AHP-CF method, due to not considering the water system factor and having certain errors in its discrimination method, leans towards a safer assessment, The results of the three evaluation methods are somewhat consistent. [ABSTRACT FROM AUTHOR]

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Numerous scholars have used traditional thermal anomaly extraction methods and time series prediction models to study seismic anomalies based on longwave infrared radiation data. This paper selected bidirectional long short-term memory (BILSTM) as the research algorithm after analyzing and comparing the prediction performance of five time series prediction models. Based on the outgoing longwave radiation (OLR) data, the time series prediction model was used to predict the infrared longwave radiation values in the spatial area of 5° × 5° at the epicenter for 30 days before the earthquake. The confidence interval was used as the evaluation criterion to extract anomalies. The examples of earthquakes selected for study were the Yangbi Ms6.4-magnitude earthquake in Yunnan on 21 May 2021 and the Luding Ms6.8-magnitude earthquake in Sichuan on 5 September 2022. The results showed that the observed values of the Yangbi earthquake 15 to 16 days before the earthquake (5 May to 6 May) exceeded the prediction confidence interval over a wide area and to a large extent. This indicates a strong and concentrated OLR anomaly before the Yangbi earthquake. The observations at 27 days (9 August), 18 days (18 August), and 8 days (28 August) before the Luding earthquake exceeded the prediction confidence interval in a local area and by a large extent, indicating a strong and scattered OLR anomaly before the Luding earthquake. Overall, the method used in this paper extracts anomalies in both spatial and temporal dimensions and is an effective method for extracting infrared longwave radiation anomalies. [ABSTRACT FROM AUTHOR]

One of the primary tasks for effective disaster relief after a catastrophic earthquake is robust communication. In this paper, we propose a simple logistic method based on two-parameter sets of geology and building structure for the failure prediction of the base stations in post-earthquake. Using the post-earthquake base station data in Sichuan, China, the prediction results are 96.7% and 90% for the two-parameter sets and all parameter sets, respectively, and 93.3% for the neural network method sets. The results show that the two-parameter method outweighs the whole parameter set logistic method and the neural network prediction and can effectively improve the accuracy of the prediction. The weight parameters of two-parameter set by the actual field data significantly show that the failure of base stations after earthquake is mainly due to the geological differences where the base stations are located. It can be envisioned that if the geological distribution between the earthquake source and the base station is parameterized, the multi-parameter sets logistic method can not only effectively solve the failure prediction after earthquakes and the evaluation of communication base stations under complex conditions, but also provide site selection evaluation for the construction of civil buildings and power grid towers in earthquake-prone areas. [ABSTRACT FROM AUTHOR]

Several possible lithosphere–atmosphere–ionosphere coupling mechanisms before earthquake occurrence are presented in the literature. They are described by several models with different interaction channels (e.g., electromagnetic, mechanics, chemical, thermal), sometimes in conflict with each other. In this paper, we search for anomalies six months before the Lushan (China) 2013 earthquake in the three geo-layers looking for a possible view of the couplings and testing if one or another is more reliable to describe the observations. The Lushan earthquake occurred in China's Sichuan province on 20 April 2013, with a magnitude of Mw = 6.7. Despite the moderate magnitude of the event, it caused concern because its source was localized on the southwest side of the same fault that produced the catastrophic Wenchuan event in 2008. This paper applies a geophysical multi-layer approach to search for possible pre-earthquake anomalies in the lithosphere, atmosphere, and ionosphere. In detail, six main increases in the accumulated seismic stress were depicted. Anomalous geomagnetic pulsations were recorded in the Chengdu observatory, sometimes following the increased stress. Atmosphere status and composition were found to be anomalous in several periods before the earthquake, and, spatially, the anomalies seem to appear firstly far from the upcoming earthquakes and later approaching the Longmenshan fault where the Lushan earthquakes nucleated. The Formosat-3 data identified interesting anomalies in the altitude or electron content of the ionospheric F2 peak in correspondence with seismic and atmospheric anomalies 130 days before the earthquake. In addition, the total electron content showed high anomalous values from 12 to 6 days before the earthquake. We compared the anomalies and tried to explain their correspondences in different geo-layers by the lithosphere–atmosphere–ionosphere coupling models. In particular, we identified three possible couplings with different mechanisms: a first, about 130 days before the earthquake, with a fast (order of one day) propagation delay; a second, about 40 days before the earthquake occurrence, with a propagation delay of few days and a third from 2.5 weeks until one week before the event. Such evidence suggests that the geo-layers could interact with different channels (pure electromagnetic or a chain of physical-chemical processes) with specific propagation delays. Such results support the understanding of the preparation for medium and large earthquakes globally, which is necessary (although not sufficient) knowledge in order to mitigate their impact on human life. [ABSTRACT FROM AUTHOR]

A World Natural Heritage Site, Jiuzhaigou, is the first nature reserve in China whose primary purpose is to protect natural scenery. On August 8, 2017, a Ms 7.0 earthquake caused many unstable slopes in Jiuzhaigou, Sichuan Province, China. In the extreme storm conditions that follow, the unstable slopes tend to develop into potential landslides, which can cause many casualties and property losses in scenic areas. Sentinel-1A ascending orbit data were obtained in this paper to establish a SAR database. The large-scale deformation rate map of the study area was obtained using a small baseline set InSAR technology. The potential landslides in the deformation area are preliminarily confirmed with remote sensing interpretation. The field verification is further carried out by studying the deformation information of the characteristic points on the potential landslides. The results show that 13 deformation zones were preliminarily identified, and three typical deformation zones were selected for coupling verification and identified as potential landslides. At the same time, further analysis shows that the four potential landslides have been in continuous linear deformation for a long time since the earthquake, posing a severe threat to the safety of local people's lives and property. The research results provide a reference for the early identification and warning of potential landslides in earthquake-prone regions. [ABSTRACT FROM AUTHOR]

The rapid and accurate extraction of wide-area coseismic landslide locations is critical in earthquake emergencies. At present, the extraction of coseismic landslides is mainly based on post-earthquake site investigation or the interpretation of human–computer interactions based on remote sensing images. However, the identification efficiency is low, which seriously delays the earthquake emergency response. On the basis of the available multisource and multiscale remote sensing data, numerous studies have been carried out on the methods of coseismic landslide extraction, such as pixel analysis, object-oriented analysis, change detection, and machine learning. However, the effectiveness of coseismic landslide extraction was low in wide areas with complex topographic and geomorphic backgrounds. Therefore, this paper offers a comprehensive study of the factors influencing coseismic landslides and researches rapid and accurate wide-area coseismic landslide extraction methods with multisource remote sensing and geoscience technology. These techniques include digital elevation modeling (DEM) and its derived slopes and aspects. An embedded multichannel spectral–topographic feature fusion model for coseismic landslide extraction based on DeepLab V3+ is proposed, and a knowledge-enhanced deep learning information extraction method integrating geological knowledge is formed. Using the Jiuzhaigou Ms7.0 earthquake (seismic intensity VIII) in Sichuan Province, China, a comparison of landslide extraction models and strategies is carried out. The results show that the model proposed in this paper achieves the best balance in the accuracy and efficiency of wide-area extractions. Using multiple feature data of coseismic landslides, the problem of mixed pixels is solved. The rate of the misidentification of landslides as clouds, snow, buildings, and roads is significantly lower than in other methods. The identified landslide boundaries are smoother and more accurate, and the connectivity is better. Compared with other methods, ours can more accurately eliminate landslides not triggered by the Jiuzhaigou earthquake. While using the image block strategy to ensure extraction efficiency, it also improves the extraction accuracy of wide-area coseismic landslides in complex backgrounds. [ABSTRACT FROM AUTHOR]

Background: On September 5, 2022, an Ms 6.8 earthquake occurred in Luding County, Ganzi Tibetan Autonomous Prefecture, Sichuan, China. The casualties and economic losses caused by the earthquake are huge. Most of the landslides triggered by this earthquake are small and medium-sized rock collapses and destructive debris flows, with a small number of large-scale landslides. Results: There are 5007 coseismic landslides in the Luding earthquake VII-degree area and above, with a total area of 17.36 km2. The landslides are generally distributed along the NW-SE direction. The highest landslide area density is 13.8%, and the highest point density of the landslide is 35.73 km2. High-density area is mainly concentrated in the IX-degree area and the northeast side of the seismogenic fault. Coseismic landslides are more likely to develop in the area with the slope more than 40°, the slope direction of 67.5-112.5 degree, and vegetation coverage of 40–50%. More landslides are developed in granite areas and forest areas. The closer distance to active faults, the more the coseismic landslides develop. The correlation between coseismic landslide development and the distance from the active faults is better than that between coseismic landslide development and the distance from the seismogenic faults. Conclusion: The landslide database used in this paper is the most perfect at present, and the research results have also been verified by fieldwork. This is also the first applied study of this landslide inventory, which indirectly confirmed the accuracy of the inventory. The results obtained in the manuscript will provide an important guideline for future disaster prevention and mitigation in southwest China. [ABSTRACT FROM AUTHOR]

In this paper, based on Sina Weibo data, a natural language processing (NLP) analysis method was used to analyze the temporal and spatial sequence characteristics of people's attention and the characteristics of text content with the help of microblogs posted by people within 6 days after the 2022 Lushan M6.1, Maerkang M5.8 and Luding M6.8 earthquakes. Moreover, the same analysis method was used on the content of comments on microblogs posted by official media outlets within 6 days after the earthquakes to analyze the changes in people's sentiments and the differences in the sentiments in various regions, and the influencing factors were also analyzed. The results of this research show the following: In terms of the spatial and temporal distributions, people's attention was affected by the earthquakes themselves and their social impacts, and the first 2 h was often a period of an outbreak of attention, with the publishing areas mainly concentrated in Sichuan and Guangdong. In terms of people's sentiments, the overall microblogging sentiment of the three earthquakes was positive, and the sentiment value of the people in Sichuan was generally low compared with that of the people in the other regions. Not only was the fluctuation in sentiment affected by the influence of the region, but it was also positively related to the sentiment of official microblogs. The results of this research provide reference for guiding people's sentiments after earthquakes in the new media era. [ABSTRACT FROM AUTHOR]

For emergency rescue and damage assessment after an earthquake, quick detection of seismic landslides in the affected areas is crucial. The purpose of this study is to quickly determine the extent and size of post-earthquake seismic landslides using a small amount of post-earthquake seismic landslide imagery data. This information will serve as a foundation for emergency rescue efforts, disaster estimation, and other actions. In this study, Wenchuan County, Sichuan Province, China's 2008 post-quake Unmanned Air Vehicle (UAV) remote sensing images are used as the data source. ResNet-50, ResNet-101, and Swin Transformer are used as the backbone networks of Mask R-CNN to train and identify seismic landslides in post-quake UAV images. The training samples are then augmented by data augmentation methods, and transfer learning methods are used to reduce the training time required and enhance the generalization of the model. Finally, transfer learning was used to apply the model to seismic landslide imagery from Haiti after the earthquake that was not calibrated. With Precision and F1 scores of 0.9328 and 0.9025, respectively, the results demonstrate that Swin Transformer performs better as a backbone network than the original Mask R-CNN, YOLOv5, and Faster R-CNN. In Haiti's post-earthquake images, the improved model performs significantly better than the original model in terms of accuracy and recognition. The model for identifying post-earthquake seismic landslides developed in this paper has good generalizability and transferability as well as good application potential in emergency responses to earthquake disasters, which can offer strong support for post-earthquake emergency rescue and disaster assessment. [ABSTRACT FROM AUTHOR]

The geological activity in Sichuan and Yunnan of China is intense, and large earthquakes such as the Tonghai earthquake in 1970 have caused huge casualties and economic losses. Therefore, it is significant to reduce the long-period earthquake damage of dams and high-rise buildings to reproduce the near-fault long-period ground motion characteristics of the Tonghai earthquake. In this paper, the finite difference method is used to predict the long-period characteristics of the Tonghai Ms 7.8 earthquake. Considering the uncertainty of the initial fracture point, number of asperities, and slip angle, 18 seismic scenarios are established. The predicted results are verified by comparing intensity, attenuation relation and pulse probability distribution. At the same time, based on the velocity pulse recognition method, the pulse probability distribution of the near-field is obtained. We selected six seismic scenarios with high probability from 18 seismic scenarios. Our results show that the spatial distribution and pulse probability distribution of near-field simulated ground motion is significantly affected by the initial rupture positions. After the characteristics of the largest asperity on the fault are determined, the remaining asperities have limited influence on the spatial distribution of simulated ground motion. This study expands the application scope of the finite difference method, which can simulate the seismic intensity characteristics of destructive earthquakes in areas with few seismic records. [ABSTRACT FROM AUTHOR]

This paper presents the investigation results of a base-isolated RC frame-shear wall structure located in Luding County, Sichuan Province, China, which was damaged by a Ms 6.8 earthquake on September 5, 2022. This recently constructed school office building was about 9 km away from the epicenter. The isolation layer of this building consists of 54 rubber bearings and 12 viscous dampers. These viscous dampers or their connections failed during the earthquake, and the limit state included connection breaking or global buckling of the damper. Also, the superstructure suffered some minor damage. To investigate the cause of structural damages, a nonlinear time-history analysis is conducted using the ground motions recorded by four seismic stations close to the building. The onsite investigation and numerical simulation results revealed the possible reasons for the failure. [ABSTRACT FROM AUTHOR]

Slow-moving landslide-prone areas (SLAs) are unstable objects on the terrestrial surface that can collapse rapidly when provoked by earthquakes, leading to infrastructure damage. It is critical to identify SLAs prior to earthquake events and assess their hazard-causing probabilities when triggered. An assessment approach of earthquake-triggered geohazards is proposed in this paper by combining interferometric synthetic aperture radar (InSAR) derived SLAs and geological and geomorphological factors. Taking the Ms6.8 Luding earthquake, which occurred in the Sichuan Province of southwestern China on September 5, 2022, as an example, 1320 scenes of Sentinel-1 SAR data in western Sichuan were processed using the small baseline subset (SBAS) InSAR technique before the earthquake. After the earthquake, hazard probability assessment was performed in real-time by filtering the SLAs using a spatial analysis technique with geological and geomorphological factors, e.g., real-time peak ground acceleration (PGA), slope, distance to fault (DTF), and distance to the river (DTR) data. The results show that 11 SLAs were classified into high-risk zones. As verified by the Luding co-seismic landslide dataset from visual interpretation of optical remote sensing images, 142 coseismic landslides were triggered by the earthquake in these high-risk regions. In these areas, an ancient landslide, with high pre-earthquake displacement rates (−50 mm/year) on the scarp was reactivated under the Luding earthquake forces. This method can provide a scientific tool for disaster mitigation and rapid response emergency management. [ABSTRACT FROM AUTHOR]

Tectonic extrusion bypassing the eastern Himalayan syntaxis results in a significant increase in regional stress instability and the associated frequent occurrence of earthquakes in southern Yunnan, China. However, the stress field, and the relationship between the focal mechanism of earthquakes and stress evolution in southern Yunnan, remain enigmatic. In this paper, using a modified grid point test method, we calculated the focal mechanism of ML ≥ 2.5 earthquakes in southern Yunnan (22–25° N, 100–104° E) from January 2009 to June 2023. Utilizing the solutions of historical earthquake focal mechanisms, we obtained the present-day regional tectonic stress field in southern Yunnan via inversion. The results indicate complex and diverse seismic focal mechanisms, and the main types of earthquakes are strike-slip events, followed by normal fault and reverse fault events. The orientations of the maximum and minimum principal stress axes rotate in a clockwise direction from northeast to southwest. The internal stress orientation distribution of the rhombic Sichuan–Yunnan block in the study area is consistent, and the block boundary zone is the site where stress deflection occurs, and the regional tectonic stress field is influenced by the interaction among different blocks. The distribution of R-value in the Lamping–Simao block gradually increases from north to south, indicating that the compressive stress required for material transport becomes relatively small. Combined with the geological and tectonic background of the study area, our results suggest that the speed of block movement gradually decreases from north to south; the distribution of R-value in the South China block is significantly smaller than that of the interior of the Sichuan–Yunnan rhombus, and the proportion of compressive stresses is larger, indicating a stronger extrusion in this region, which may be related to the fact that the Sichuan–Yunnan rhombus is strongly resisted by the South China block in the east. [ABSTRACT FROM AUTHOR]

On 5 September 2022, an Ms6.8 magnitude earthquake occurred in Luding County, Sichuan Province, China. Based on Sentinel-1 SAR images, this paper uses the D-InSAR approach to obtain the displacement field of the earthquake, invert the coseismic sliding distribution, and then calculate the static coulomb stress changes of the coseismic deformation on the aftershock distribution and surrounding faults. Further, the seismic structure is analyzed and discussed. The InSAR coseismic deformation field demonstrates that the maximum LoS displacement of the surface deformation caused by the Luding earthquake is about 15 cm. The Luding Ms 6.8 earthquake is dominated by the Moxi fault, which is a left-lateral strike-slip fault that ruptures along the NNW-SSE trend at about 160.3°, and the dip is 81°. The fault depth is mainly 5~15 km, the maximum sliding amount is about 174.8 cm, and the corresponding depth is 8.5 km. The seismic moment tensor obtained by inversion is 1.06 × 1019 Nm, Mw = 6.65. The Coulomb stress generated by the Luding earthquake on the northern end of the Anninghe fault zone exceeded the trigger threshold. The risk of the Anninghe fault's future earthquake was greater, and continuous monitoring and risk assessment were required. [ABSTRACT FROM AUTHOR]

This paper analyzed the strong motion characteristics based on 86 three-component strong motion records of the MW 6.6 Luding earthquake. Additionally, the factors that influence the variation in ground motion for three earthquakes with similar magnitude in Sichuan Province were investigated. The analysis result indicates a strong correlation between the observed ground motion parameters and the distribution of published Modified Mercalli Intensity. The residual analysis reveals that the spectral accelerations at periods 0.1–10.0 s are amplified to 0.0798–0.3057 times the mean level in the rupture forward direction and weakened to 0.0738–0.2831 times the mean level in the rupture backward direction. The maximum pulse direction recorded by the 51LDJ station is N6°E, aligning with the vertical fault direction. The velocity pulses has distinct bidirectional pulses in the waveforms, with a PGV of 37.0 cm/s. The source effect of the strike-slip MW 6.6 Luding and MW 6.5 Jiuzhaigou earthquakes on ground motion is relatively less significant compared to the average level of mainshocks in southwest China. However, the thrust-fault MW 6.7 Lushan earthquake exhibits a stronger source effect on ground motion during short and medium periods, but a weaker source effect during long periods when compared to the average level. The anelastic attenuation of the Longmenshan, Xianshuihe, and Huya fault zones in Sichuan exhibits significant regional variation and periodic correlation. This phenomenon is closely linked to the regional tectonic background variations and the heterogeneity of crustal structure within the area. [ABSTRACT FROM AUTHOR]

A Mw 6.6 earthquake struck Luding county, in Sichuan province of China on September 5, 2022, causing severe damage of nearby infrastructures. The earthquake indicates an awakening of southeast branch of Xianshuihe fault since the last 1973 Mw 7.6 Luhuo earthquake in Sichuan, thus attracting attention from the public. A physics-based method, combining spectral element method (SEM) and finite element method (FEM), was presented in this paper to investigate the correlation between near-fault motions and response of a road tunnel, which has a closest distance of about 6.0 km to the fault. This method allows to incorporate the rupture details, geological irregularity, 3D velocity structure, as well as the underground tunnel. The ground motions simulated by SEM were validated by comparison to specific station records and empirical ground motion model (GMM), which were subsequently input into the tunnel to obtain its axial deformation and sectional inner forces. Parametric study on tunnel alignment was conducted, and wavelet transformation was used to extract dynamic pulses from the ground motions. The results show that the tunnel response is remarkably affected by dynamic pulse directivity, and the axial forces could be dominated by permanent fault displacement for tunnel of the strike-normal alignment. [ABSTRACT FROM AUTHOR]

In the network‐based on‐site earthquake early warning system (EEWS), the 'blind zone', namely the zone where the issued warning arrives later than the destructive S and surface waves, is one of the challenges affecting its effectiveness. The 'blind zone' is determined by the interstation distance, or equivalently the density of seismic stations, of the network. In this paper, we suggest a practical approach according to which, when in a region a temporary increase of seismic hazard is declared, additional stations are deployed in such a way that the blind zone is temporarily reduced. In the procedure, the time‐dependent neo‐deterministic seismic hazard assessment (TD‐NDSHA) plays a vital role in the identification of the regions potentially exposed to high macroseismic intensities. As a showcase example, we consider the scenario of year 2014 at the Sichuan‐Yunnan border of southwest China. The TD‐NDSHA is based on the standard NDSHA procedure at regional scale (bedrock conditions), with the 'controlling earthquakes' defined on the basis of the Annual Consultation. We show that the 'blind zone' can be reduced in the identified areas of interest (e.g., MMI ≥ VI), by deploying a limited number of additional seismic stations. In the case where false alarms can be tolerated, significant reduction of the 'blind zone' can be implemented by moving from a network‐based EEWS to a single‐sensor‐based EEWS and skipping the process of location and magnitude‐determination/prediction procedures. [ABSTRACT FROM AUTHOR]

On August 20, 2019, at 2 a.m., a disastrous debris flow occurred in Chediguan gully in Yinxing town, China. The debris flow destroyed the drainage groove and the bridge at the exit of the gully. In addition, the debris flow temporarily blocked the Minjiang River during the flood peak, flooding the Taipingyi hydropower station 200 m upstream and leaving two plant workers missing. To further understand the activity of the debris flow after the Wenchuan earthquake, the characteristics of this debris flow event were studied. Eleven years after the Wenchuan earthquake, a disastrous debris flow still occurred in the Chediguan catchment, causing more severe losses than those of earlier debris flows. In this paper, the formation mechanism and dynamic characteristics of this debris flow event are analysed based on a drone survey, high-definition remote sensing interpretations and other means. The catastrophic debris flow event indicates that debris flows in the Wenchuan earthquake area are still active. A large amount of dredging work in the main gully could effectively reduce the debris flow risk in the gully. In addition, it is also important to repair or rebuild damaged mitigation measures and to establish a real-time monitoring and early warning system for the high-risk gully. [ABSTRACT FROM AUTHOR]

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

With the rapid development of network technology, research on the emotional tendencies of online disasters has increasingly played a significant role in responding to disaster public opinion events. This paper collected data from microblogs and selects three relatively large earthquakes that occurred in Sichuan in 2022 as research samples, namely the Lushan earthquake that occurred on June 1, the Malkang earthquake that occurred on June 10, and the Luding earthquake that occurred on September 5. By calling the E-Trans emotional analysis model, the emotional tendency values were obtained. Using Python language and a time–frequency of 15 min, the original content posted by microblog users within 24 h after the earthquake was analyzed for emotional tendencies, and research conclusions were drawn on the characteristics of emotional tendencies in earthquake disasters and related factors. The results show that the emotional tendencies of the three earthquakes conform to the "Three·Three" emotional tendency model for disasters, and the emotional tendency values in the three periods show a significant marginal diminishing effect. Changes in emotional tendencies during earthquake disasters are mainly related to the magnitude of the earthquake, the number of aftershocks, issues that the public is more concerned about on microblogs, and earthquake prevention and mitigation department microblog promotions. This study can provide a reference for post-disaster emergency response and network public opinion guidance for earthquake prevention and mitigation. [ABSTRACT FROM AUTHOR]

Due to China's exposure and susceptibility to natural hazards, it is important for governments and aid agencies to have tools that enable effective post-disaster livelihood recovery in creating self-sufficiency for the affected population. This paper introduces a framework of critical components that constitute a successful livelihood recovery by studying the perceptions and perspectives of those affected by the 2013 Lushan earthquake in Sichuan Province. A mixed method, namely a pilot study, questionnaire survey and interviews, was used. While the populations surveyed valued the employment benefits of creating new market and economic sectors in areas where rural farming was predominant prior to the earthquake, they considered that recovery of their housing was most essential for livelihood diversification. External assistance was also regarded highly in assisting with livelihood recovery, in which family ties and social connections seemed to have played a larger role than that of government agencies and NGOs. Lastly, the results highlighted that a goal of livelihood recovery cannot be achieved without individual well-being being considered, in relation to people's perceptions about quality of life and their physical and mental health. This paper aims to assist the Chinese policy makers and practitioners in disaster recovery in setting an agenda of preparing for livelihood recovery in peace times, or of post-disaster recovery planning should a disaster event occurs so that the economic impact and livelihood burdens of those affected can be effectively mitigated. [ABSTRACT FROM AUTHOR]

The effect of soil parameters on basin amplification effect has been widely investigated, especially for the small and medium-sized basins under plane wave incidence or point source ruptures. However, the sensitivities of seismic amplification effect of large-scale basins with respect to soil parameters during great earthquakes with tremendous rupture faults have obtained relatively less attention. In this paper, based on the established three-dimensional Sichuan basin model, the effects of four material parameters of the basin sediments, including the shear wave velocity, Poisson's ratio, and the shear quality factor of the Quaternary sediment, as well as the velocity of the rock above the basin crystalline basement (which will be referred as SVQS, PRQS, QFQS, and VCBR, respectively), on the long-period wave amplification patterns of the Sichuan basin during the great Wenchuan earthquake are investigated by using the spectral element method and parallel computing technique. The results show the following: (1) SVQS has the greatest influence on the basin horizontal component ground motions, while the vertical component is comparably insensitive to it. (2) PRQS demonstrates comparable effects on the horizontal and vertical basin ground motions. With the increase of PRQS, the amplitudes and regions of the strong shakings both become smaller. However, the influence of PRQS is less significant compared with SVQS and VCBR. (3) QFQS mainly affects the relatively high-frequency motions inside the basin, and the low-frequency motions are generally insensitive to it. With the reduction of QFQS, the amplitudes and regions of the basin strong ground motions turn a little smaller, but the distribution features are generally unchanged. (4) Effects of VCBR on the horizontal and vertical component basin ground motions are opposite. With the growth of VCBR, the amplitudes and areas of strong horizontal motions increase consequently, but they decrease for the vertical component. [ABSTRACT FROM AUTHOR]

The Wenchuan earthquake occurred in Sichuan Province, China, on May 12, 2008, and caused a large number of secondary geological disasters such as collapses, debris flows, and landslides, as well as extensive damage to local vegetation. The earthquake had an impact on the regional climate, seriously affecting the sustainable development of the regional environment and economy. In this study, the normalized difference vegetation index (NDVI) was used to characterize the vegetation status, which was calculated from images acquired by the MODIS sensor. Based on the vegetation cover and precipitation of the area affected by the Wenchuan earthquake over about 70 years, in this paper we analyze the characteristics of vegetation changes and their impact on the climate after the earthquake. The results revealed that the above secondary geological disasters caused by the earthquake destroyed vegetation. After the earthquake, NDVI decreased from 0.394 in 2007 to 0.383 on July 1, 2008, and then increased year by year to 0.413 in 2015, except in 2010. During the two years after the earthquake, several large-scale debris flows occurred in this area, damaging the surface vegetation, so the vegetation coverage was low in 2010. The change of the land cover has an indirect impact on the local precipitation. The annual and seasonal (except winter) precipitation trended downward from 1948 to 2018, with an annual average decrease of 1.6069 mm, but trended upward from 2008 to 2018, with an annual average increase of 14.012 mm, after the Wenchuan earthquake, indicating the recovery of vegetation. The increased vegetation promoted regional precipitation, but the interaction mechanism between the vegetation cover and the precipitation is complex. The effect of the vegetation differs in different regions and cannot be generalized. This study provides theoretical support for vegetation restoration and environmental management in areas with strong earthquakes. [ABSTRACT FROM AUTHOR]

In its one hundred years of existence, the Communist Party of China has experimented with how to connect its narratives of legitimacy to people's affects. In this essay, I trace the conceptualization of gratitude, from its repudiation in the Mao era as a vestige of feudalism and imperialism to its return in the reform era as a re-verticalization of Party sovereignty. The paper addresses four examples of gratitude work: Politburo Standing Committee member Wang Yang's short-lived critique of gratitude in the name of a different conception of popular sovereignty; the celebration of the tenth anniversary of the Sichuan earthquake as a day of gratitude; the detention of Uyghurs in Xinjiang who are taught to be grateful to the Communist Party in a campaign of religious de-radicalization; and the refusal of gratitude in quarantined Wuhan during the COVID-19 pandemic. In these cases, the Communist Party's sovereignty stands at the threshold between bio- and necro-politics, promising life and salvation in the midst of death and destruction. [ABSTRACT FROM AUTHOR]

Maoxian Country in Sichuan Province, China is a quake-prone mountainous area. Within 300 km of it, there have been more than ten strong earthquakes higher than Ms6.0 on record. The nearest one is the Diexi Earthquake of 1933, 8.7 km from Maoxian County. A catastrophic scale landslide, the Xinmo landslide, took place on the steep cataclinal slope of Xinmo Village on June 24, 2017. Shear failure happened to the phyllite layer of rich fissures during the landslide. In this paper, shaking table tests have been conducted on the Xinmo landslide as a prototype, and a non-contact deformation measurement based on the digital image correlation (DIC) technique has been made to analyze the dynamic response and deformation of the slope under accumulated seismic actions. As the results, stress amplification is found at the end of joints on the potential slide face. Failure starting from the middle of the potential slide face in the beginning extends upwards and downwards along the face, and leads to a steep tension crack on the top of the slope and a buckling failure of radial-arc cracks at the foot. A semi-steep radial crack in buckling part has a shear failure. The tensile stress amplification on the discontinuous face contributes to the failure accumulation of it and asymptotic failure of the slope. It proposed that the closure and downward displacement of tensile crack on the top of slope, buckling phenomenon at the foot of slope and shear failure of semi-steep crack are all the bad omens of landsliding. [ABSTRACT FROM AUTHOR]

China is one of the countries most affected by earthquakes. Improving public cognition and response to earthquake disaster (EDCR) is an effective means to reduce seismic risk and losses. The 2013 Lushan earthquake area was also stricken by the 2008 Wenchuan earthquake. Most of the residents in this area have been affected by both earthquakes, which provides a rare opportunity to gain insight into the interaction between public's EDCR and their earthquake disaster experience. Using a questionnaire survey on over 200 local residents selected by stratified sampling method, this paper investigates the public's cognition and response capability with regard to earthquake disaster in the 2013 Mw6.6 Lushan earthquake area, Sichuan Province, China, with a particular emphasis on exploration on the relationship between people's earthquake disaster experience and their disaster cognition and response behaviors. The results show that the overall EDCR level of local residents is moderate—their average cognition and response score for earthquake disaster is only 0.60. The number of earthquakes experienced, education, and family income level are the three most important factors that significantly impact an individual's overall EDCR capability. Those who have experienced more earthquakes better adapt to the impacts of disaster. Especially, the experience learned from the 2008 Mw7.9 Wenchuan earthquake played a positive role in the cognition and response of the public to the 2013 Lushan earthquake. In addition, people with higher education could master more knowledge of earthquake disaster and better control their emotions. Similarly, respondents with a higher family income had more resources and ways to engage in more reasonable response behaviors to manage disaster effects. Based on these findings, it is suggested that local policy-makers implement targeted earthquake disaster education and knowledge dissemination strategies, especially develop and expand various experiential learning modes (e.g., emergency exercise/drilling, situational learning, virtual reality, scenario approach, safety/disaster experience center, participatory activities) for the local public and beyond to more effectively strengthen their cognition of disaster and response capability. [ABSTRACT FROM AUTHOR]

The MS8.0 earthquake that occurred in Wenchuan, Sichuan in 2008 provides an important case for the study of operational earthquake forecasting and short-term aftershock forecasting of major disaster-inducing earthquakes in China. This paper focuses on the comparative study of the applicability of the epidemic-type aftershock sequence (ETAS) model, the Reasenberg–Jones (R–J) model and the Omi–R–J model, which are widely adopted internationally for short-term aftershock forecasting and seismic hazard mitigation strategy research. We compare the stability of model parameters and aftershock occurrence rate forecasting, and evaluate the effectiveness of forecasting using the N-test and T-test with multiple time windows. The results show that the sequence parameters of the ETAS model, the R–J model and the Omi–R–J model tend to stabilize after 15.50, 15.50 and 6.00 days following the earthquake respectively, and the attenuation of the Wenchuan MS8.0 earthquake is rather normal. Compared to the ETAS model and the R–J model, the Omi–R–J model obtain steadier model parameters in a shorter time with significantly smaller parameters pORJ, cORJ, bORJ and standard deviations. Among the three models, the overall aftershock occurrence rate forecasted by the R–J model is the highest, followed by the Omi–R–J model, while that of the ETAS model is the lowest. N-test results show overall forecasting effectiveness of 93.8, 80.7 and 97.7% for the ETAS, R–J and Omi–R–J models, respectively, with the ETAS and Omi–R–J models superior to the R–J model, and the Omi–R–J model slightly better than the ETAS model. The overall "information gain per earthquake" calculation results show that the ETAS model is superior to the Omi–R–J and R–J models, while the Omi–R–J model is better than the R–J model; thus the combined use of the ETAS and Omi–R–J models by focusing on their respective strengths might ensure optimal performance. These "maneuverable" forecasting approaches to short-term aftershock model forecasting will play a vital role in efficient post-disaster relief, emergency management decision-making and post-disaster reconstruction. [ABSTRACT FROM AUTHOR]

The earthquake and its secondary geological disasters have some long-term effects on vegetation recovery, and the spatiotemporal differentiation of vegetation coverage in earthquake-stricken areas are often not valued by researchers. Beichuan County in Sichuan Province is the worst-hit area during Wenchuan earthquake, tracking the vegetation coverage in this disaster area can provide feedback for post-earthquake ecological restoration. Based on remote sensing (RS) and Geographic information system (GIS), this paper relies on dimidiate pixel model (DPM) and vegetation coverage transfer matrix to explore the vegetation coverage of the earthquake worst-hit area. The results show that the overall level of vegetation coverage in Beichuan county is high, and earthquakes are dominant in the areas with high vegetation coverage. Besides, earthquake can do most severe damages to the areas with high vegetation coverage, followed by medium damage impacting to the areas with medium vegetation coverage, but the damage of other areas are relatively small. From 2007 to 2020, the average vegetation coverage in Beichuan County decreased from 0.835 in 2007 to 0.755 in 2008, then gradually recovered to 0.826 in 2020, experiencing a sharp decline and then a steady increase. The recovery of vegetation coverage is improved over time, but the spatiotemporal differences of the recovery process are obvious. Elevation has the largest driving force on vegetation coverage (q = 0.569, p less than 0.001), followed by temperature and rainfall; the interaction between factors has a significant increasement in the spatial differentiation of vegetation coverage, indicating that vegetation coverage is a combination result of multiple factors. The research findings can help construct the scientific management of the eco-environment in the disaster area, it can also help builda medium to long-term ecological restoration plan according to the variation in vegetation coverage. [ABSTRACT FROM AUTHOR]

Research in the field of earthquake prediction has a long history, but the inadequacies of traditional approaches to the study of seismic threats have become increasingly evident. Remote sensing and Earth observation technology, an emerging method that can rapidly capture information concerning anomalies associated with seismic activity across a wide geographic area, has for some time been believed to be the key to overcoming the bottleneck in earthquake prediction studies. However, a multi-parametric method appears to be the most promising approach for increasing the reliability and precision of short-term seismic hazard forecasting, and thermal infrared (TIR) anomalies are important earthquake precursors. While several studies have investigated the correlation among TIR anomalies identified by the robust satellite techniques (RSTs) methodology and single earthquakes, few studies have extracted TIR anomalies over a long period within a large study area. Moreover, statistical analyses are required to determine whether TIR anomalies are precursors to earthquakes. In this paper, RST data analysis and the Robust Estimator of TIR Anomalies (RETIRA) index were used to extract the TIR anomalies from 2002 to 2018 in the Sichuan region using Moderate Resolution Imaging Spectroradiometer (MODIS) land surface temperature (LST) data, while the earthquake catalog was used to ascertain the correlation between TIR anomalies and earthquake occurrences. Most TIR anomalies corresponded to earthquakes, and statistical methods were used to verify the correlation between the extracted TIR anomalies and earthquakes. This is the first time that the ability to predict earthquakes has been evaluated based on the positive predictive value (PPV), false discovery rate (FDR), true-positive rate (TPR), and false-negative rate (FNR). The statistical results indicate that the prediction potential of RSTs with use of MODIS is limited with regard to the Sichuan region. [ABSTRACT FROM AUTHOR]

Seismic landslides are the most common and highly destructive earthquake-triggered geological hazards. They are large in scale and occur simultaneously in many places. Therefore, obtaining landslide information quickly after an earthquake is the key to disaster mitigation and relief. The survey results show that most of the landslide-information extraction methods involve too much manual participation, resulting in a low degree of automation and the inability to provide effective information for earthquake rescue in time. In order to solve the abovementioned problems and improve the efficiency of landslide identification, this paper proposes an automatic landslide identification method named improved U-Net model. The intelligent extraction of post-earthquake landslide information is realized through the automatic extraction of hierarchical features. The main innovations of this paper include the following: (1) On the basis of the three RGB bands, three new bands, DSM, slope, and aspect, with spatial information are added, and the number of feature parameters of the training samples is increased. (2) The U-Net model structure is rebuilt by adding residual learning units during the up-sampling and down-sampling processes, to solve the problem that the traditional U-Net model cannot fully extract the characteristics of the six-channel landslide for its shallow structure. At the end of the paper, the new method is used in Jiuzhaigou County, Sichuan Province, China. The results show that the accuracy of the new method is 91.3%, which is 13.8% higher than the traditional U-Net model. It is proved that the new method is effective and feasible for the automatic extraction of post-earthquake landslides. [ABSTRACT FROM AUTHOR]

In recent years, the rapid expansion and development of the shale gas industry in the Sichuan Basin has coincided with a series of unexpected moderate-sized earthquakes. Given that the Sichuan Basin is situated within a stable interior block, the focal mechanism of the 2019 earthquake sequence (ML4.7, ML5.4, and ML5.2) in the Weiyuan-Rongxian area remains a subject of debate. In this study, we propose a joint InSAR- and PCA- based inversion method utilizing the distributed Mogi model to investigate the spatial-temporal characteristics of a gas reservoir and evaluate the induced Coulomb stress change. The surface deformation derived from Sentinel-1 data between 2015 and 2021 was consistent with the spatial distribution of production wells, and it correlated with the temporal changes in reservoir volume associated with the shale gas operating process. The Coulomb stress loading on the regional faults suggests that human activities associated with shale gas operation likely triggered the three moderate earthquakes. Furthermore, our results indicate Coulomb stress loadings of 10 kPa, 15 kPa, 5 kPa, 3 kPa, and 87 kPa on the Dongxingchang fault, Gaoqiao fault, Dayaokou fault, Niujingao fault, and Lijiachang fold, respectively. Consequently, fluid injection and extraction during shale gas development could be contributing to the elevated seismic activity in the Weiyuan-Rongxian area. [ABSTRACT FROM AUTHOR]

On 5 September 2022 (BJT), Luding, located in southwestern Sichuan Province, China, experienced an MS 6.8 earthquake. This earthquake occurred within the historical rupture zone of the 1786 MS 7.75 event, part of the southern section of the Xianshui He Fault belt. Given the average 155-year recurrence interval for strong earthquakes in this area, the 236 years since the last event made this earthquake somewhat expected. However, prior to this event, we did not detect any anomalies indicating low surface b-values, which are often indicative of a high-stress state in the source area before strong earthquakes, as highlighted by numerous studies. Our research focused on the northern section of the eastern boundary of the Sichuan–Yunnan sub-block, encompassing the Xianshui He, Anning He, Zemu He, and Daliang Shan fault belts. We meticulously located earthquakes of ML ≥ 1.5 from 2009 to May 2022. The catalog was divided into two periods: 2009–2014 and 2015–May 2022. Using an AIC-constraint method, we analyzed the changes in b-values (Δb) in the latter period compared to the former. Our findings revealed a significant abnormal Δb zone (Δb < −0.3), with a radius of approximately 50 km, when ΔAIC ≥ 2 was selected. Intriguingly, the epicenter of the recent Luding MS 6.8 earthquake fell within this abnormal zone. Furthermore, we calculated the b-value cross-section for the southern section of the Xianshui He fault belt using a directory of precisely located small earthquakes. This revealed that the location, scale, and shape of the abnormally low-b-value area corresponded with the large displacement co-seismic area of the main earthquake, affirming the b-value's effectiveness in identifying asperities. The b-value's temporal evolution prior to the mainshock exhibited a nearly decade-long continuous decrease, signifying a long-term stress-loading process akin to that observed before many strong earthquakes. The b-value anomalies observed from different profiles before the Luding earthquake underline the necessity of a comprehensive, multi-dimensional analysis of such anomalies. Finally, our analysis indicates that nine earthquakes with MS ≥ 6.5, including the Luding MS 6.8 event, have contributed to increased Coulomb Failure Stress change (ΔCFS) in the Daofu (DF)–Kangding (KD) section of the Xianshui He fault belt and the northern section of the Anning He fault belt south of Shimian (SM), with amplitudes surpassing the 0.01 MPa threshold. This suggests the potential for strong earthquakes in these zones. [ABSTRACT FROM AUTHOR]

On September 5, 2022, a strong earthquake with a magnitude of MS6.8 struck Luding County in Sichuan Province, China, triggering thousands of landslides along the Dadu River in the northwest-southeast (NW-SE) direction. We investigated the reactivation characteristics of historical landslides within the epicentral area of the Luding earthquake to identify the initiation mechanism of earthquake-induced landslides. Records of the two newly triggered and historical landslides were analyzed using manual and threshold methods; the spatial distribution of landslides was assessed in relation to topographical and geological factors using remote sensing images. This study sheds light on the spatial distribution patterns of landslides, especially those that occur above historical landslide areas. Our results revealed a similarity in the spatial distribution trends between historical landslides and new ones induced by earthquakes. These landslides tend to be concentrated within a range of 0.2 km from the river and 2 km from the fault. Notably, both rivers and faults predominantly influenced the reactivation of historical landslides. Remarkably, the reactivated landslides are characterized by their small to medium size and are predominantly situated in historical landslide zones. The number of reactivated landslides surpassed that of previously documented historical landslides within the study area. We provide insights into the critical factors responsible for historical landslides during the 2022 Luding earthquake, thereby enhancing our understanding of the potential implications for future co-seismic hazard assessments and mitigation strategies. [ABSTRACT FROM AUTHOR]

Smartphone location data provide the most direct field disaster distribution data with low cost and high coverage. The large-scale continuous sampling of mobile device location data provides a new way to estimate the distribution of disasters with high temporal–spatial resolution. On September 5, 2022, a magnitude 6.8 earthquake struck Luding County, Sichuan Province, China. We quantitatively analyzed the Ms 6.8 earthquake from both temporal and geographic dimensions by combining 1,806,100 smartphone location records and 4,856 spatial grid locations collected through communication big data with the smartphone data under 24-hour continuous positioning. In this study, the deviation of multidimensional mobile terminal location data is estimated, and a methodology to estimate the distribution of out-of-service communication base stations in the disaster area by excluding micro error data users is explored. Finally, the mathematical relationship between the seismic intensity and the corresponding out-of-service rate of communication base stations is established, which provides a new technical concept and means for the rapid assessment of post-earthquake disaster distribution. [ABSTRACT FROM AUTHOR]

The Sichuan-Tibet traffic corridor (STTC) is a critical transportation route in China that spans the western Sichuan Basin and the Tibetan Plateau. This area has a complex geological history and presents challenges for infrastructure construction due to its high seismic intensity and extreme elevation. Recent research has made advancements in addressing these challenges and supporting infrastructure development and mineral resource exploitation. The second volume of this Research Topic focuses on active faults, magmatic-hydrothermal activities, and the tectonic evolution history of the Tibetan Plateau within the STTC. Additionally, it explores the diverse range of mineral resources in the area. The findings from these studies will contribute to further geological investigations and resource assessments in the STTC. [Extracted from the article]

The development of machine learning technology enables more robust real-time earthquake monitoring through automated implementations. However, the application of machine learning to earthquake location problems faces challenges in regions with limited available training data. To address the issues of sparse event distribution and inaccurate ground truth in historical seismic datasets, we expand the training dataset by using a large number of synthetic envelopes that closely resemble real data and build an earthquake location model named ENVloc. We propose an envelope-based machine learning workflow for simultaneously determining earthquake location and origin time. The method eliminates the need for phase picking and avoids the accumulation of location errors resulting from inaccurate picking results. In practical application, ENVloc is applied to several data intercepted at different starting points. We take the starting point of the time window corresponding to the highest prediction probability value as the origin time and save the predicted result as the earthquake location. We apply ENVloc to observed data acquired in the southern Sichuan Basin, China, between September 2018 and March 2019. The results show that the average difference with the catalog in latitude, longitude, depth, and origin time is 0.02°, 0.02°, 2 km, and 1.25 s, respectively. These suggest that our envelope-based method provides an efficient and robust way to locate earthquakes without phase picking, and can be used in earthquake monitoring in near-real time. [ABSTRACT FROM AUTHOR]

A magnitude 6.8 strike-slip earthquake (EQ) struck Luding, Sichuan Province, China, on 5 September 2022, resulting in significant damage to nearby Ganzi Prefecture and the city of Ya'an. In this research, the near-surface atmospheric electric field (AEF) recorded at four sites 15 d before the Luding EQ was analyzed and differentiated, and multisource auxiliary data including precipitation, cloud base height, and low cloud cover were used at the same time. Nine possible seismic AEF anomalies at four sites were obtained preliminarily. Accordingly, microwave brightness temperature (MBT) data, which are very sensitive to the surface dielectrics and are closely related to the air ionization, together with surface soil moisture, lithology, and a 3D-simulated crustal stress field, were jointly analyzed to confirm the seismic relations of the obtained negative AEF anomalies. The geophysical environment for crustal high-stress concentration, positive charge carrier transfer, and surface accumulation was demonstrated to exist and to meet the conditions necessary to generate local negative AEF anomalies. Furthermore, to deal with the spatial disparities in sites and regions with potential atmospheric ionization, near-surface wind field data were employed to scrutinize the reliability of the AEF anomalies by comprehensively analyzing the spatial relationships among surface charges accumulation areas, wind direction and speed, and the AEF sites. Finally, four negative AEF anomalies were deemed to be closely related to the Luding EQ, and the remaining five possible anomalies were ruled out. A possible mechanism of negative AEF anomalies before the Luding EQ is proposed: positive charge carriers were generated from the underground high-stress concentration areas and then transferred to and accumulated on the ground surface to ionize the surface air, thus disturbing the AEF above the ground. This study presents a method for identifying and analyzing seismic AEF anomalies and is also beneficial for the examination of the pre-earthquake coupling process between the coversphere and the atmosphere. [ABSTRACT FROM AUTHOR]

On April 20, 2013, a Mw 6.6 earthquake struck Lushan County of Sichuan Province, China, about 80 km southwest of the epicenter of the 12 May 2008 Wenchuan Mw 7.9 event. It triggered a large number of landslides in a broad area, causing causality and injuries and damages to roads, drains, dwellings, and infrastructures. Field investigations of coseismic landslides provide a basis for better understanding and illustrating the spatial distributions and hazards related to the Lushan earthquake-triggered landslides. Therefore, this paper presents results of field investigations of the Lushan earthquake-triggered landslides, which can be classified into two main categories of disrupted landslides and coherent landslides, and constitutes seven types. The disrupted landslides include five types: rock falls, rock slides, rock avalanches, soil falls, and soil slides; and the coherent landslides have two types: soil slumps and slow earth flows. All of the seven types of landslides can be observed in many field photos, aerial photographs, and/or satellite images. Among them, seven typical large-scale landslides, distributed in a northeast trending line consistent with the Shuangshi-Dachuan fault, which is presumably related with the earthquake, are described in detail. We prepared an original, emergency-based coseismic landslide inventory map based on visual interpretation of available post-earthquake aerial photographs and pre-earthquake satellite images, combined with results from emergency-based field investigations. The original inventory map registered 3884 landslides. Later, 11,761 more landslides were identified by much more careful and time-consuming visual interpretation based on the same aerial photographs and satellite images. Subsequently, all the 15,645 coseismic landslides were correlated with six common landslide impact factors, including elevation, slope angle, slope aspect, topographic position, stratum/lithology, and peak ground accumulation (PGA). These observational and compiled coseismic landslide data allow us to make subsequent compiling of a detailed and completed landslide inventory by visual interpretation of remote sensing images as well as further studies of landslides induced by the Lushan earthquake. [ABSTRACT FROM AUTHOR]

This paper summarizes the Ms 6.0 earthquake disaster that occurred in Changning, Sichuan Province, China, on 17 June 2019. Additionally, a description of the disaster emergency response is provided. As determined by on-site investigation and analysis, the direct causes of earthquake casualties are summarized. Among them, 66 % of the casualties can be attributed to substandard seismic protection, 25 % to improper earthquake risk avoidance, 6 % to earthquake-induced geological disasters, and 3 % to pre-existing diseases exacerbated by the earthquake. Responding to the causes of these four casualty types, we summarize 4 lessons, which are to build in accordance with seismic protection requirements; strengthen publicity and education awareness of earthquake emergency evacuation and training for the population; investigate and evaluate potential geological disaster sources in the stricken area, along with conducting prevention and control; establish cooperation with health organizations, focusing on people who are older or have serious illnesses and conducting earthquake evacuation training and psychological counselling. [ABSTRACT FROM AUTHOR]

The increased seismic activity of the last ~10 years in Changning county of Sichuan Province comprised just small (mostly ML < 5.0) injection‐induced earthquakes. The MW 5.7 earthquake on June 17, 2019, is the largest event ever reported there. Moment tensor of the mainshock was remarkably dominated by a compensated linear vector dipole. We resolve its fine structure showing it was a doublet, allowing approximation by a thrust‐ and strike‐slip subevent. The mainshock nucleated as thrust faulting, which (together with the largest aftershocks) can be linked with previously known reverse faults, favorably oriented to regional stress field. Contrarily, the strike‐slip segment of the mainshock, less favorably oriented, was probably facilitated by elevated pore pressure due to previous injections. Shallow active strike‐slip faulting, not yet mapped in the region, is a new feature, important for future hazard assessment. Plain Language Summary: Changning county in Sichuan Basin belongs to major salt‐producing resources, with water injection wells drilled to ~3‐km depths. Enhanced occurrence of small earthquakes was observed in the last ~10 years. However, on June 17, 2019, a damaging earthquake struck the region. Seismic agencies reported diverse focal mechanisms and pointed to departures from shear faulting, typical for tectonic events. To understand these enigmatic features, we modeled records from 12 broadband seismic stations, adding over 100 first‐motion polarities. We found that the earthquake was very shallow (~4 km) and consisted of two shear events: the initial thrust faulting and the following strike‐slip faulting along an SE‐NW trending near‐vertical plane, aligned with aftershocks. The initial episode was "normal," expected on existing faults and supported by tectonic stresses of the region. Contrarily, the significant strike‐slip faulting appears to be rather "abnormal," probably facilitated by the initial shock and by elevated pressure of underground fluids. The 2019 earthquake provided a rare opportunity to illuminate interplay between long‐lasting water injections, tectonic stress, complexity of existing faults, and their dynamic interactions. That is how seismology aims at making industrial activities sustainable and safe. Key Points: This is the so‐far largest earthquake in a salt‐mining area where seismicity has been increased in previous 10 years by injection‐induced eventsMainshock nucleated as a thrust, then rupturing a previously unknown strike‐slip fault, suboptimally oriented to regional stress fieldThe complex nature of the event explains its small double‐couple component and diversity of focal mechanisms across reporting agencies [ABSTRACT FROM AUTHOR]

On 1 June 2022, a magnitude 6.1 earthquake struck the southern segment of the Longmenshan fault zone on the eastern edge of the Tibetan Plateau, once again causing casualties and economic losses. Understanding the deep-seated dynamic mechanisms that lead to seismic events in the Lushan earthquake area and assessing the potential hazards in seismic gap areas are of significant importance. In this study, we utilized 118 magnetotelluric datasets collected from the Lushan earthquake area and employed three-dimensional electromagnetic inversion with topographic considerations to characterize the deep-seated three-dimensional resistivity structure of the Lushan earthquake area. The results reveal that the Shuangshi–Dachuan fault in the Lushan earthquake area can be divided into two relatively low-resistivity zones: a western zone dipping southeastward and an eastern zone with a steeper slightly northwestern dip. These two zones intersect at a depth of approximately 20 km, forming an extensional pattern resembling a "Y" shape. The epicenters of both the 2013 and 2022 Lushan earthquakes are primarily located in the upper constricted portion of the pocket-like low-resistivity body at depth. The distribution of seismic aftershocks is confined within the region enclosed by the high-resistivity body, following the pattern of the Y-shaped low-resistivity zone. [ABSTRACT FROM AUTHOR]

By deploying a magnetic monitoring network in the earthquake-prone areas of Sichuan, China, and conducting long-term observations, processing, and analysis of real-time geomagnetic data, it can be observed that the pre-earthquake geomagnetic anomalies are highly correlated with the occurrence time of earthquakes. We propose a novel algorithm that obtains a new quantity by accumulating geomagnetic anomaly energy to eliminate external environmental interference and take its gradient as a measure for predicting the occurrence time of an earthquake. Through observations of a large amount of geomagnetic data, it is confirmed that the proposed method can be used to predict the occurrence time of earthquakes with about 75% to 85% accuracy. Conclusions: The geomagnetic anomaly phenomenon can be accurately observed and recorded before an impending earthquake, and it has been confirmed by data that using this observation makes imminent earthquake prediction a practical prediction method. [ABSTRACT FROM AUTHOR]

Monitoring seismicity in real time provides significant benefits for timely earthquake warning and analyses. In this study, we propose an automatic workflow based on machine learning (ML) to monitor seismicity in the southern Sichuan Basin of China. This workflow includes coherent event detection, phase picking, and earthquake location using three-component data from a seismic network. By combining PhaseNet, we develop an ML-based earthquake location model called PhaseLoc, to conduct real-time monitoring of the local seismicity. The approach allows us to use synthetic samples covering the entire study area to train PhaseLoc, addressing the problems of insufficient data samples, imbalanced data distribution, and unreliable labels when training with observed data. We apply the trained model to observed data recorded in the southern Sichuan Basin, China, between September 2018 and March 2019. The results show that the average differences in latitude, longitude, and depth are 5.7 km, 6.1 km, and 2 km, respectively, compared to the reference catalog. PhaseLoc combines all available phase information to make fast and reliable predictions, even if only a few phases are detected and picked. The proposed workflow may help real-time seismic monitoring in other regions as well. [ABSTRACT FROM AUTHOR]

An Mw 6.8 earthquake occurred in Luding County, Ganzi Tibetan Autonomous Prefecture, Sichuan Province, on 5 September 2022. This seismic event triggered numerous coseismic geohazards in the seismic zone. In this study, the ascending- and descending-track synthetic aperture radar (SAR) images observed by the Sentinel-1A satellite are utilized to extract the coseismic surface deformation of the Luding earthquake. Subsequently, a faulting model is estimated based on the elastic dislocation theory, under the constraint of the InSAR observation. Additionally, the POT technique was employed to detect coseismic geohazards. High-spatial-resolution optical remote sensing images served to validate the reliability of the detection results. The coseismic interferometric synthetic aperture radar (InSAR) deformation field indicated a maximum deformation of ~190 mm and ~140 mm along the ascending and descending tracks, respectively. The estimated best-fitting faulting model suggests that the optimal seismogenic fault strike and dip angles are 169.3° and 70°, respectively. The fault slip predominantly exhibits left-lateral strike-slip characteristics and is concentrated at depths of 3–12 km. The estimated maximum fault slip was 2.67 m, occurring at a depth of 7 km. The pixel offset tracking (POT) result derived from the pre- and post-earthquake SAR images found a total of 245 medium- to large-scale coseismic geohazards, with a verification rate from optical images exceeding 64%. The distribution of these geohazards is notably dense within the significant fault rupture segment. Geohazards on the fault hanging wall are densely packed, whereas landslides along the Dadu River's fault footwall are also notably frequent. [ABSTRACT FROM AUTHOR]

The 2008 8.0 Ms Wenchuan earthquake caused serious ecological degradation in the northwest of China's Sichuan Province. Elucidating landscape fragmentation and spatial pattern of post-earthquake landscape is of great interest in order to improve ecological restoration and predict the spatial distribution of damaged ecosystems in earthquake-affected areas. We used four real-time remote sensing images to analyze the landscape pattern characteristics and spatial autocorrelation of the Longxi River Basin before and after the Wenchuan earthquake during the period from 2005 to 2015. In the study period, the degree of landscape fragmentation increased 1 year after the earthquake in 2009 but decreased in 2011 and 2015. The spatial distribution of forest, farmland, and shrub-grassland had significantly positive spatial correlation and the characteristics of spatial aggregation from 2005 to 2015. Construction land had no significant spatial correlation before the earthquake in 2005, but significantly positive spatial correlation after the earthquake, while traffic land had no significant spatial correlation across the study period. Unlike the other landscape types, geological disasters changed from a significantly negative spatial correlation before the earthquake to a significantly positive spatial correlation after the earthquake. However, the positive autocorrelation of all landscape types decreased with the increase of space distance, but in different distance-decay rates. The High-high spatial aggregation areas of geological disasters and construction land clustered gradually upstream of the basin and distributed in Longchi town, respectively; those of farmland distributed in the southeast of the basin increased in 2009 but then decreased, while those of forests had the opposite pattern as the dominant landscape type after the earthquake. Our results elucidated the spatial structure and distribution features of the Longxi River Basin to give a theoretical foundation for assessing the effects of ecological restoration and reconstruction management in earthquake-affected areas. [ABSTRACT FROM AUTHOR]

Although many geophysical models have been proposed in the Longmenshan fault zone (LFZ) and its surrounding areas, the deep structure of the seismic gap and its constraint of the Wenchuan and Lushan earthquakes remain uncertain. Based on the compiled aeromagnetic data and Bouguer gravity data, we have tried to create a more detailed and reasonable magnetic and density model using 2D forward modeling and 3D inversion and made the deep structure of the LFZ visible. The research shows that structure is heterogenous across the LFZ. The earthquake epicenters are located in regions with high-magnetic anomalies and gravity gradients that are associated with rigid blocks that were likely to accumulate stress. However, the seismic gap shows low-magnetic anomalies and transition of gravity anomalies related to a weak zone. The Sichuan Basin has two NE-trending banded high-magnetic blocks extending beneath the LFZ that firmly support the idea that the crust of the Sichuan Basin has subducted downward the LFZ. More importantly, the basement subducts to approximately 33 km west of the Wenchuan–Maoxian fault, with a low dip angle beneath the middle segment of the LFZ, whereas the distance decreases to approximately 17 and 19 km under the southern segment. Thus, the crust of the Sichuan Basin beneath the middle segment extends farther than that beneath the southern segment, with the seismic gap as the transition zone. Therefore, we propose that the structural heterogeneity of the basement on the western margin of the Sichuan Basin may be the main reason for the different focal mechanisms and geodynamics of the Wenchuan and Lushan earthquakes. [ABSTRACT FROM AUTHOR]

The purpose of this work is to carry out seismically induced landslide probabilistic hazard mapping for future seismic scenarios of Aba Prefecture and Chengdu Plain region, Sichuan Province, China. Nine earthquake events that occurred in the regions and neighboring areas are selected, which include a total of 251,260 landslide records. This work used 12 influencing factors including elevation, slope, aspect, relief, topographic wetness index (TWI), topographic position index (TPI), peak ground motion, distance to active faults, vegetation coverage, distance to roads, lithology, and annual rainfall to establish the LR model. Based on the probabilistic seismic hazard analysis (PSHA) method, the distribution of predicted seismic motion under four earthquake scenarios is calculated including frequent, occasional, rare, and very rare earthquake occurrence. Using the PGA distribution of the four scenarios as input peak ground motion parameters, we calculated the occurrence probability of coseismic landslides in the entire Aba Prefecture and Chengdu Plain region under the action of different ground motions. The result shows that the high-hazard areas are mainly concentrated in the Longmenshan fault zone, and the southern area of Kangding is also a potential high-hazard area for landsliding. Meanwhile, as the probability of exceedance decreases, the probability of corresponding earthquake-induced landslides hazard probability and the area of high-hazard regions also significantly increase. Especially, the Pengguan complex rock mass in the southwest of the Longmenshan fault zone is the potential high-hazard area for coseismic landslides. Highlights: Establishing a coseismic landslides evaluation model suitable for Aba Prefecture and Chengdu Plain region. Calculating the occurrence probability of coseismic landslides under different peak ground motions. [ABSTRACT FROM AUTHOR]

For the low accuracy of earthquake prediction caused by the lack of large earthquake data, this paper proposed an earthquake prediction method based on negative selection. In this method, it used the variable real valued negative selection algorithm to generate mature detectors which were used to predict whether an earthquake occured. Due to the absence of nonself data sets in the negative selection training, it could be reduced the impact of lacking large earthquake data on the training effect. It used the historical earthquake data of Sichuan province to predict whether the magnitude 5.0 and above earthquakes occurred in Sichuan within one month. Compared with the traditional machine learning algorithm, the results show that the negative selection has better prediction effect. [ABSTRACT FROM AUTHOR]

• Abrupt high δ13C -CO2-DIC in the hot springs occurred before earthquakes. • The carbon isotopic spikes are caused by fractionation due to tectonic activity. • The δ13C -CO2-DIC of hot springs changed markedly before and after the earthquakes. • The elevated carbon isotopic levels may be a signal for the subsequent earthquakes. Geothermal springs are controlled by deep faults, which are the major causes of earthquakes. A series of geochemical indicators of hot springs, such as carbon dioxide content (CO 2), carbon isotope and noble gas isotope etc., have been used for earthquake monitoring and early warning at home and abroad. Given that previous studies have failed to establish an inevitable link between the carbon isotopic variations of hot springs and seismic activities, in this study, mass spectrometry techniques were used to analyze the carbon isotopes of gaseous CO 2 and noble gas isotope in hot springs, thermal water, and newly formed travertines from western Sichuan before and after an Ms 4.8 earthquake (i.e., 7.14 earthquake). The results showed that the carbon isotope level of the hot spring system increased significantly before the earthquake, i.e., δ13C CO2 = -2‰ to 3.3‰, δ13C DIC = 2.2‰ to 6.6‰ (DIC = dissolved inorganic carbon in geothermal water), R/R A = 0.90–1.83, and δ13C travertine = 1.76‰ to 5.75‰. These indicators decreased markedly 1 week after the earthquake, whereas the helium isotope ratio of R/R A did not exhibit a noticeable change (δ13C CO2 = -3.9‰ to 0.4‰, δ13C DIC = 1.6‰ to 4.1‰, R/R A = 0.68–1.87). Combined with previous thermodynamic calculation and experimental results on carbon isotope fractionation of the CO 2 –calcium carbonate system, we suggest that the high carbon isotope characteristics of hot springs are caused by carbon isotope fractionation following the release of CO 2 from fault carbonate decomposition owing to tectonic activity, not by a mixture of different carbon sources. A high carbon isotopic delivery path in geothermal water, from released CO 2 to DIC and then to travertine, was observed. The new mechanism proposed in this paper reveals the intrinsic relations between the changes of the hot spring geochemical properties and deep tectonic activities, and the variations of these geochemical parameters before and after earthquakes may assist in capturing seismic precursors. A post-peak earthquake warning model has thus been preliminarily proposed, however, long-term monitoring data are required to reduce some uncertainties. [ABSTRACT FROM AUTHOR]