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The 2008 Mw 7.9 Wenchuan and 2013 Mw 6.7 Lushan earthquakes ruptured the central and southern segments of the Longmenshan thrust belt on the eastern Tibetan Plateau, respectively. The ∼M 7 Tianquan earthquake in 1327 is also thought to have occurred on the southern segment with effects spatially overlapping those of the Lushan earthquake, but the deformation style and seismogenic mechanism of the segment remain poorly understood. Satellite image interpretation, field investigations, and trenching reveal that the Shuangshi-Dachuan fault (SDF) on the southern segment displaces landforms, dips southeast, and is dominated by thrust motion with a left-lateral strike-slip component. The latest and penultimate events along the fault occurred in 1085–1457 CE and 1215 BCE-104 CE, respectively. Some ancient landslides exits along the fault, and one of them formed close to 703 ± 17 yr BP. The ages of the latest event and of the landslide agree well with the occurrence of the Tianquan earthquake, indicating that the earthquake was most likely generated by the SDF. Magnetotelluric imaging and the aftershock belt of the Lushan earthquake show that the Longmen Shan forms a wedge-shaped high-resistivity body protruding eastward. The SDF corresponds well to the east-dipping upper electrical boundary of the wedge-shaped body and is interpreted as a shallow backthrust; the seismogenic fault of the Lushan earthquake corresponds to the west-dipping lower boundary and is interpreted as a blind thrust fault. The left-lateral slip component of the SDF may be a response to the lateral extension of the weak lower crust. • The Shuangshi-Dachuan fault is a shallow backthrust of the Longmenshan thrust belt. • The Shuangshi-Dachuan fault (SDF) hosted the 1327 Tianquan earthquake. • The 2013 Lushan earthquake occurred on a blind thrust fault located under the SDF. • The SDF and the blind thrust fault correspond to the electrical structure boundary. • The electrical structure boundary had a controlling effect on the earthquakes. [ABSTRACT FROM AUTHOR]

• The Lushan earthquake occurred at the boundary zone between the high- and low-resistivity bodies. • The crustal structure of the southern Longmen Shan thrust belt matches the multiunit combination seismogenic model. • The seismogenic potential of the southern segment of Longmen Shan is weaker than that of the central segment. Since the Ms 7.0 earthquake occurred in Lushan on April 20, 2013, five years after the Wenchuan Ms 8.0 earthquake, the seismogenic potential of southern Longmen Shan has been a considerable concern. Comparative studies of active faults and deep structures of the Lushan and Wenchuan earthquakes are important to evaluate Longmen Shan potential. Terrace measurements, geophysical surveys and borehole drilling reveal that late Quaternary fault activity in the southern segment of the Longmen Shan thrust belt is weaker than that along the central segment. Magnetotelluric data across the southern segment of the Longmen Shan thrust belt show that the central fault and the front-range fault are the electrical boundaries of the crust and that the Longmen Shan thrust belt is a high-resistivity body. The Lushan earthquake occurred at the boundary zone between the high- and low-resistivity bodies, and the crustal structure of the southern Longmen Shan thrust belt matches the multiunit combination seismogenic model, indicating a potential large earthquake in Longmen Shan. Compared to conditions along the central segment, the low-resistivity layer of the upper and lower crust on the western side of the Songpan-Ganzi block develops along the Xianshuihe fault, which may reduce the strain accumulated from the Songpan-Ganzi block to the southern Longmen Shan thrust belt. This interpretation suggests that the main crustal shortening is accommodated by foreland thin fold structures, whereas the structural deformation accommodated by the thrust belt accounts for only a small proportion; thus, the seismogenic potential of southern Longmen Shan is weaker than that of the central segment. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • The viscosities of the middle-lower crust of the Longmenshan Thrust Belt (LTB), China, are studied. • Rheological properties are not the main controlling factor on fault activity of the LTB. • The lower fault activity along the southern LTB may be due to a greater number of structures. Abstract Seven continuous GPS stations are located on the hanging wall of the Longmenshan Thrust Belt, and post-seismic deformation data of the 2013 Lushan earthquake have been recorded for nearly four years following the earthquake. We transform the data from a global reference frame to the South China Block reference frame, and then, the secular motion and post-seismic deformation of the Wenchuan earthquake are excluded using an exponential fit model. Based on our results, the viscosities of the low velocity zone at a depth of ∼25 km and of the middle and lower crust around the Longmenshan Thrust Belt are obtained as 2.75 × 10 17 P a · s and 2.56 × 10 18 P a · s , respectively. The post-seismic rebound, which was observed near the Lushan epicenter, may represent the occurrence of overslip during the earthquake. The more complex structural style may have produced weaker fault activity along the southern segment of the Longmenshan Thrust Belt than along its middle and northern segments. [ABSTRACT FROM AUTHOR]

On 20 April 2013, a 7.0 magnitude earthquake, the second worst natural disaster after the Wenchuan earthquake in 2008, struck Ya'an, Sichuan, China. This research studies the post-traumatic stress disorder (PTSD) and post-traumatic growth (PTG) among 2001 adult survivors who experienced the 2013 Lushan earthquake. A cross-sectional study was conducted in the severely affected area of Sichuan. A total of 2300 adult residents participated in the random sampling questionnaire survey eight months after the earthquake, and the sample population was 2001. PTSD was found to be negatively correlated with the survivors' PTG and resilience was positively related to PTG, while the negative effects of PTSD on PTG are weakened by the moderating role of resilience. The results indicate that more attention needs to be paid to strengthening the survivors' resilience as this can reduce their PTSD levels and improve their PTG. This study could support psychological relief workers helping survivors who experienced the earthquake and administrators who encounter similar situations in other countries or regions. [ABSTRACT FROM AUTHOR]

The Longmenshan (LMS) southern section is the front of the eastwards material migration from the Qinghai–Tibet Plateau. To understand whether the 2022 Ms6.1 Lushan earthquake was a strong aftershock of the 2013 Ms7.0 Lushan earthquake and why the aftershocks of the two earthquakes were concentrated relative to the 2008 Wenchuan earthquake, a three-dimensional electrical structural model of the Lushan earthquake region is established based on magnetotelluric (MT) array data. The model shows high-conductor layers (HCL) in the Songpan–Ganzi terrane (SGT) middle crust, Sichuan Basin (SCB) shallow surface, western Sichuan foreland depression (WSCFD) and LMS Moho. The analysis suggests that the HCL in the study area at a depth of 10 km is caused by saline fluids in the fracture zone or porous sedimentary rock voids, while the high-conductor body in the middle and lower crust and upper mantle is caused by partial melting of rocks. The Lushan earthquake area is subject to compressional deformation horizontally as the eastwards migration of Qinghai–Tibet Plateau material is blocked by the SCB and vertically by the upwards extension of high-conductor plastic material at depth. The aftershocks of the Lushan earthquake area are mainly confined within the Baoxing–Zhonglin–Daxing–Lushan high-conductor region, which has noticeable electrical structural differences compared to the overall high-resistivity structure of the LMS southern section; these differences explain why the aftershocks of the two earthquakes did not expand in the northeast and southwest directions of LMS. Because the 2022 and 2013 Lushan earthquakes both occurred in the same high-conductor region in the deep part of the Dachuan–ShuangShi fault to the Danyi blind fault, the 2022 Lushan earthquake was a strong aftershock of the 2013 Lushan earthquake in terms of electrical structural characteristics. • A 3D crust–mantle electrical model at south section of Longmenshan was established. • Aftershocks of Lushan earthquake mainly distributed in the high-conductor region. • 2022 Lushan earthquake was a strong aftershock of the 2013 Lushan earthquake. [ABSTRACT FROM AUTHOR]

The aftershocks of the 2008 Wenchuan and 2013 Lushan earthquakes delineated a prominent 60-km-long “seismic gap.” The uncertainty regarding the near-future seismic potential of this seismic gap has become of increasing importance to both the scientific community and the public. Using paleoseismology, this study investigated the occurrence of the last major event in the seismic gap and then considered the future seismic potential. Based on image interpretation, trench excavation, radiocarbon and optically stimulated luminescence dating, and comparisons with historical earthquake rupture lengths, the most recent paleoearthquake (estimated magnitude: M6.5–7.0) along the Shuangshi–Dachuan Fault (SDF), which is the southern segment of the Longmen Shan Fault, was constrained to 640–1330 CE (very possibly, 876 CE). According to the most recent geological and geophysical findings, we suggest that the seismic gap (i.e., the SDF) could be capable of generating M6.0–7.0 earthquakes, but that the likelihood of such an occurrence in the near future is not very high. [ABSTRACT FROM AUTHOR]

Only one long-runout rock avalanche was triggered by the 2013 Lushan earthquake in the Tangjia Valley, Tianquan, Sichuan, China. The rock avalanche involved the failure of ~ 530,000 m 3 of sandstone from the source area. The displaced material travelled a horizontal distance of ~ 1600 m with an elevation descent of ~ 480 m, equivalent to a fahrböschung of 16.7°. Based on a detailed field investigation, we introduce basic characteristics of the rock avalanche and find that the rock avalanche resulted in one run-up in the Chunwojian Valley, a superelevation in the Gangoutou Valley, and increase in volume due to the entrainment of path materials. A numerical model (DAN3D) was used to simulate the post-failure behavior of the rock avalanche. By means of trial and error, a combination of the frictional model and Voellmy model is found to provide the best performance in simulating this rock avalanche. The simulation results reveal that of the rock avalanche lasted approximately 160 s and an average velocity of 10 m/s. [ABSTRACT FROM AUTHOR]

Following the devastating 2008 Wenchuan earthquake (Mw = 7.9), the 2013 Lushan strong shock (Mw = 6.6) occurred again on the Longmen Shan thrust fault. Ever since the earthquake occurred, it has been a topic of hot debate on whether it is a strong aftershock of the 2008 Wenchuan earthquake or a new independent one. To this purpose, we investigated the seismogenic fault for the Lushan earthquake, and found that it is situated on the same fault system as that for the Wenchuan earthquake, and the Lushan shock ruptured one of the asperities which were left unbroken in the 2008 Wenchuan earthquake. In addition, we analyzed the statistical properties of the Wenchuan-Lushan earthquake sequence (WLES) using three established empirical laws on aftershocks. The modelling results showed that the WLES, in which the Lushan event is regarded as one of aftershocks of the Wenchuan mainshock, well satisfied three accepted statistical laws, namely the Gutenberg-Richter relation, modified Omori-Utsu law and Båth’s law. At the same time, we observed that the weak and ductile materials between the hypocenters of the Wenchuan and Lushan shocks resulted in seismic gap in between, and the strong materials in the source region and special curved geometry of seismogenic fault for the Lushan event may be responsible for the approximately 5-year delay of the occurrence. In particular, the focal mechanism of the Lushan event, like most of the other strong aftershocks of the Wenchuan mainshock, is nearly thrust-type fault, suggesting the Lushan earthquake, together with other strong aftershocks, is controlled by the same stress environment. Most of all, we noticed that the Lushan event was triggered by the 2008 Wenhcuan main shock. Taken together, it is reasonable to infer that the 2013 Lushan event is a strong aftershock, possibly being the largest one, of the Wenchuan earthquake. Meanwhile, we propose in the paper that it is an important criterion for identification of aftershocks by means of judging whether they are triggered by the main shock or not. Identifying and forecasting strong aftershocks shall be crucial in evaluating the seismic hazard for large earthquakes. [ABSTRACT FROM AUTHOR]

Experimental studies have confirmed that temperature is notably affected by rock deformation; therefore, change in crustal stress should be indicated by measurable changes in bedrock temperature. In this work, we investigated the possibility that the bedrock temperature might be used to explore the state of crustal stress. In situ measurement of bedrock temperature at three stations from 2011 to 2013 was used as the basis for the theoretical analysis of this approach. We began with theoretical analyses of temperature response to change in crustal stress, and of the effect of heat conduction. This allowed distinction between temperature changes produced by crustal stress (stress temperature) from temperature changes caused by conduction from the land surface (conduction temperature). Stress temperature has two properties (synchronous response and a high-frequency feature) that allow it to be distinguished from conduction temperature. The in situ measurements confirmed that apparently synchronous changes in the stress temperature of the bedrock occur and that there exist obvious short-term components of the in situ bedrock temperature, which agrees with theory. On 20 April 2013, an earthquake occurred 95 km away from the stations, fortuitously providing a case study by which to verify our method for obtaining the state of crustal stress using temperature. The results indicated that the level of local or regional seismic activity, representing the level of stress adjustment, largely accords with the stress temperature. This means that the bedrock temperature is a tool that might be applied to understand the state of stress during seismogenic tectonics. Therefore, it is possible to record changes in the state of crustal stress in a typical tectonic position by long-term observation of bedrock temperature. Hereby, the measurement of bedrock temperature has become a new tool for gaining insight into changes in the status of shallow crustal stress. [ABSTRACT FROM AUTHOR]

The 2008 Wenchuan earthquake (Mw7.9) occurred in the Longmen Shan fault zone. The stress change and crustal deformation during the accumulation period is computed using 3D finite element modelling assuming visco-elastic rheology. Our results support that the eastward movement of the Tibetan Plateau resulting from the India-Eurasia collision is obstructed at the Longmen Shan fault zone by the strong Yangtze craton. In response, the Tibetan ductile crust thickens and accumulates at the contact between the Tibetan Plateau and the Sichuan Basin. This process implies a strong uplift with the rate of about 1.8 mm/a of the upper crust and induces a stress concentration nearly at the bottom of the Longmen Shan fault zone. We believe that the stress concentration in the Longmen Shan fault zone provides a very important geodynamic background of the 2008 Wenchuan earthquake. Using numerical experiments we find that the key factor controlling this stress concentration process is the large viscosity contrast in the middle and lower crusts between the Tibetan Plateau and the Sichuan Basin. The results show that large viscosity contrast in the middle and lower crusts accelerates the stress concentration in the Longmen Shan fault zone. Fast moving lower crustal flow accelerates this stress accumulation process. During the inter-seismic period, spatially the maximum stress accumulation rate of the eastern margin of the Tibetan Plateau is located nearly at the bottom of the brittle upper crust of the Longmen Shan fault zone. The spatial distribution of the stress accumulation along the strike of the Longmen Shan fault zone is as follows: the normal stress decreases while the shear stress increases from southwest to northeast along the Longmen Shan fault zone. This stress distribution explains the thrust motion in the SW and strike-slip motion in the NE during the 2008 Wenchuan earthquake. [ABSTRACT FROM AUTHOR]

Livelihood plays an indispensable role in sustainable community development. Previous studies of sustainable livelihood have focused on the factors that contribute to the vulnerability or resilience of livelihood, but there is limited understanding of the factors that determine people's livelihood restoration after a major disaster. By using a mixed method, combined interviews with questionnaires, this research has quantified the critical factors that influence the livelihood recovery of local communities affected by the Lushan earthquake in 2013, China. The statistical analysis shows that the most highly ranked top four factors are access to income generation assets, external housing recovery support, the level of community participation in decision making, and availability of family support. Factor analysis further suggested that the 16 critical factors identified fall into four categories, namely: 1) government policies; 2) access to resources; 3) social cohesion; 4) individual characteristics. For livelihood recovery to be embedded in the long-term sustainable development of earthquake-affected communities in Lushan, it is important to address the sustainable development through a proper knowledge transfer process including training, education, and more novel community services. • We proposed a study to identify critical factors affecting livelihood recovery following the 2013 Lushan earthquake. • We capture the perspectives of communities impacted by the 2013 Lushan earthquake in China. • Several critical factors are identified and four clusters of them are grouped using Principal Component Analysis. • Recommendations based on the results are provided in order to improve livelihood status in the affecting area. [ABSTRACT FROM AUTHOR]

In China, numerous subsurface, surface water well and spring parameters are being monitored through a large network of stations distributed in China sponsored by China Earthquake Administration (CEA). All the data from these network is managed by China Earthquake Network Center (CENC). In this paper, we have used numerous data (water radon, gas radon, water level, water temperature) available through CENC for the period 2002–2014 and studied the behavior and characteristics of water 222 radon [Rn(w)]. The observed parameters were also complemented by rainfall data retrieved from Tropical Rainfall Measuring Mission (TRMM) satellite. Our detailed analysis shows pronounced changes in the observed parameters (especially water and gas radon) prior to the earthquake. The changes in water radon, ground water level and rainfall showing characteristics behavior for Wenchuan and Lushan earthquakes. The long term data analysis of water radon and water level at various locations around epicenters of two major earthquakes along Longmenshan fault show a positive and negative relation of water radon and water level prior to these earthquakes. It is difficult to find any trend of water radon and changes in water radon pattern with these two earthquakes that could prove as a reliable precursor of earthquakes. Changes in the water radon concentrations from one location to other may be associated with the changes in ground water regime and geological settings in the epicentral and surrounding regions. [ABSTRACT FROM AUTHOR]

The devastating 2008 Mw7.9 Wenchuan and 2013 Mw6.6 Lushan earthquakes occurred in the Longmen Shan (LMS) fault zone, the eastern margin of the Tibetan Plateau. Seismology investigation reveals that earthquakes of Ms > 5.0 are frequently recorded in the eastern Tibetan Plateau, however rare earthquake of Ms > 5.0 and only a few earthquakes of 3.0 < Ms < 5.0 have been recorded in the Sichuan Basin. This study investigates the relation between the crustal rheology and the earthquake activity across the eastern margin of the Tibetan Plateau through 3D numerical experiments assuming visco-elasticity rheology. We setup several finite element lithospheric models based on different rheological structure. The interseismic stress accumulation processes in the models are simulated with boundary conditions of steady compressional deformation rate constrained by GPS observations. The results show that the crustal stress accumulation process across the eastern margin of the Tibetan Plateau is significantly controlled by the regional crustal rheology, which presents large horizontal viscosity variation in the lower crusts between the Tibetan Plateau and the Sichuan Basin. The stress accumulation rate in the upper crust of the eastern Tibetan Plateau is much higher than the Sichuan Basin. This stress spatial distribution explains the seismology observation that earthquakes are densely recorded in the eastern Tibetan Plateau, whereas rarely in the Sichuan Basin. The stress concentration nearly at the bottom of the entire LMS fault zone is thought to be responsible for the generation of the 2008 Mw7.9 Wenchuan and 2013 Mw6.6 Lushan earthquakes. There is a high possibility of future earthquakes in the seismic gaps at the southwest segment of the LMS fault zone, where it was stress accumulated but did not rupture during the last two events of the 2008 Wenchuan and 2013 Lushan earthquakes. [ABSTRACT FROM AUTHOR]

The 20 April 2013 Lushan earthquake with a magnitude of M s 7.0 induced widespread landsliding along the southern segment of the Longmen Shan fault zone. This paper presents a preliminary analysis of the characteristics of these co-seismic landslides triggered in an area of 13,323 km 2 . A total of 3810 individual landslide points were identified through an intensive field investigation and from digital aerial photographs taken after the Lushan earthquake. To facilitate the more detailed analysis on the areal frequency of co-seismic landslides as polygons, we selected an area of 732 km 2 around the epicenter that had the highest density of co-seismic landslides. The sizes of the landslides are, in general, much smaller than those that were triggered by the 2008 Wenchuan earthquake. The most common types of landslides in the study area were rock falls and shallow, disrupted landslides from steep slopes, which typically involved the top few meters of weathered bedrock and colluvium. In this study, the relation between the landslide distribution and five main factors was analyzed: fault proximity, epicenter proximity, peak ground acceleration (PGA), slope angle, and lithology. Our study results show that the landslide concentration tends to decrease with distance from the seismogenic fault, and the highest landslide concentration is located within a distance of 5 km. Regarding the distance to the epicenter, the largest landslide density is found at a distance between 5 and 10 km. The landslide concentration also increases with increasing slope angle until a maximum for the slope class 45°–55°. In addition, results show that slopes consisting of deeply weathered and fractured sandstones and mudstones were the most susceptible to co-seismic landslides. In this study, we found that the location of the hanging wall and the footwall of the fault did not seem to have an important effect on the landslide distribution. This is in contradiction to what has been reported in other earthquake areas such as the Wenchuan area. [ABSTRACT FROM AUTHOR]

A thrust earthquake of Mw6.6 occurred on April 20, 2013, near Lushan County in the southern Longmen Shan at the east margin of Tibetan Plateau. This earthquake did not produce a surface rupture zone, and the Late Quaternary activities of the outcropped faults in the earthquake area were not obvious, which increased the difficulty of studying the seismogenic structure. This article took as the research target the middle reach of the Qingyijiang River which traverses the earthquake area, by surveying, correlating the fluvial terraces, studied quantitatively the Late Quaternary tectonic deformation, and further discussed the seismotectonics. The longitudinal profile of river terraces along the middle reach of the Qingyijiang River reveals that the principal deformation style in the Late Quaternary was anticline-type folding. The folding is a typical fault-bend fold involving the basement, which is controlled by the newest flat–ramp–flat structure possibly formed in the Pliocene or the Early Pleistocene. Across the fold, the average shortening rate in the Late Quaternary is ~ 0.6–1.3 mm/yr, about one third of the crustal shortening rate by GPS data across the Longmen Shan fold-and-thrust belt and its foreland. The foreland thin-skinned structure developed in the Cretaceous to Paleogene strata in the earthquake area was passively involved into the fault-bend folding in the Late Quaternary, which commend the thrust ramp developing in a piggyback style. The newest ramp appears to have controlled the rupture and the surface deformation of the 2013 Lushan earthquake. In the process of thrust sheet sliding toward foreland along the flat–ramp–flat detachment, the ramp acts as a locking structure where earthquake ruptures. The coseismic surface deformation seems to be passive folding of the thrust sheet climbing the ramp. [ABSTRACT FROM AUTHOR]

The primary objective of our study was to investigate both the negative and positive psychological changes following the Lushan earthquake, and to explore the factors associated with psychological changes. Multi-stage random sampling was used to select respondents from Lushan County, Sichuan Province, China. A simplified Chinese version of the short form of Changes in Outlook Questionnaire (CiOQ-S) was used to assess psychological changes in earthquake survivors. Descriptive statistics, t -tests, ANOVA and stepwise linear regression analysis were used for data analysis. A total of 4972 respondents were investigated in the cross-sectional study. The mean scores of the positive and negative psychological changes were 26.61 and 8.12, respectively. The factors associated with positive psychological changes included ethnic minority, high level of education, high household income, not injured in the earthquake, not trapped during the earthquake, and having experienced the Wenchuan earthquake. The factors associated with negative psychological changes included female gender, ethnic minority, low household income, history of diseases, injured during the earthquake, and trapped during the earthquake. The current analysis helps expand our knowledge of the negative and positive psychological changes that may occur following an earthquake experience. [ABSTRACT FROM AUTHOR]

Abstract: On 20th April, 2013, a large earthquake (Lushan 6.6) occurred in Sichuan, China, in the same fault zone as the devastating 7.9 Wenchuan earthquake. The two earthquakes have similar focal mechanisms and both caused large hydrological changes in the region. The similarity of focal mechanisms, fault zone geology and the abundance of hydrological responses provide a rare opportunity for testing proposed mechanisms for hydrological responses to earthquakes. Using data from wells installed in hard rocks, we find that both the magnitude and the sign of water level changes are inconsistent with those predicted by the coseismic strain hypothesis in the near-field and in the intermediate-field. Instead, permeability change may be the dominant mechanism for the coseismic changes in water level. We also find that the minimum seismic energy required to trigger liquefaction for the Wenchuan earthquake is only 1/20 of that for the Lushan earthquake, suggesting either that the occurrence of liquefaction is more sensitive to low seismic frequencies or that the Wenchuan earthquake changed the sensitivity of unconsolidated materials, and properties had not completely recovered during the 5-year interval between the two earthquakes. [Copyright &y& Elsevier]

Abstract: The 2013 Mw 6.6 Lushan earthquake occurred in the Longmen Shan fold-and-thrust belt, Sichuan Province, China, near the five-year anniversary of the devastating 2008 Mw 7.8 Wenchuan earthquake. To define the fault that generated the 2013 earthquake and its relationship with the Beichuan fault, which ruptured in the Wenchuan earthquake, we construct several cross sections and a 3D structural model. The sections and models reveal that the main-shock of the Lushan earthquake occurred on a portion of the Range Front blind thrust (RFBT) and that the structural geometry of this fault varies along strike. The Lushan main-shock occurred at a location along the strike of the fault where the geologic shortening and total fault slip are greatest. A lateral ramp of the RFBT appears to coincide with the northern limit of aftershocks from the Lushan earthquake, leading to a 75 km seismic gap between the Wenchuan earthquake and the 2013 earthquake sequence. Although both the Wenchuan and Lushan earthquakes occurred within the Longmen Shan fold-and-thrust belt, different faults generated the two events. Based on this structural characterization and analysis of the aftershocks of the Wenchuan and Lushan earthquakes, we suggest that the Lushan earthquake may have been triggered by the 2008 rupture but is best considered as an independent event rather than an aftershock of the Wenchuan earthquake. The RFBT that generated the Lushan earthquake is linked to a detachment that extends into the Sichuan basin along the Triassic evaporite layer. The coulomb stress change simulation suggests that other faults linked to this detachment may have been loaded by the 2008 and 2013 earthquake, posing the risk of future earthquakes along the Longmen Shan and in the densely populated Sichuan basin. [Copyright &y& Elsevier]

Highlights: [•] 1-Hz and 50-Hz GPS data from several near-field stations were processed. [•] Dynamic displacements and coseismic permanent offsets were retrieved. [•] P wave arrival was detected with the 1-Hz GPS sites. [•] The advantages of 50-Hz GPS measurements were verified. [ABSTRACT FROM AUTHOR]

Due to the influence of sampling strategy, the resulting probability of landslides using logistic regression (LR) can deviate considerably from the actual areal percentage of coseismic landslides. This study used the landslides data of the 2013 Lushan, China earthquake to further address this issue. Based on the Bayesian theory, we proposed a sampling method that selects the sliding samples and non-sliding samples based on the ratio of the stable area to the landslide area. Using this method, we tested 15 values of sampling intensities (1, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 200, 500, 1000, and 2000 grid cell km−2) and 12 values of non-sliding/sliding sample ratios (1, 5, 10, 25, 50, 75, 100, 125, 150, 175, 200, and 228) for the analysis of the LR model. Ten factors were considered in this analysis, including elevation, slope gradient, aspect, the topographic wetness index (TWI), peak ground acceleration (PGA), distance to the epicenter, distance to rivers, distance to roads, lithology, and annual precipitation. In terms of these 15 sampling intensities and 12 sample ratios, the samples were trained 200 and 150 times, respectively using the LR model, yielding 4800 predicted pictures of potential landslides in the study area. The results show that different sampling intensities have a certain effect on the total predicted landslide area – the higher the intensity of the samples, the more stable the prediction results. Especially when the sampling intensity reaches 1000 grid cell km−2, the total area of the predictive model is about 17.1 km2, which is close to the real area with 17.16 km2, with a difference within 2%. Different ratios of non-slide/slide sample greatly affect the occurrence probability of coseismic landslides. When the ratio is 1:1, the predicted landslide area (A p) is between 1265 and 1290 km2, with an average of 1280 km2, which is 75 times the actual landslide area. The functional relationship between the ratio of predicted area to real area (R pa) and the ratio of non-sliding samples to sliding samples (R ns) is R pa = 99.156 R ns − 0.826. It implies that the non-slide/slide sample ratio determined by the ratio of stable area to the landslide area permits us to construct real probability models to predict the areal percentages of landslides, and based on such models, the predicted probability is largely consistent with the actual areal percentage of coseismic landslides. • Real occurrence probability modeling of co-seismic landslides • The effect of sampling intensity on the resulting probability of landslides • The non-slide/slide sample ratio greatly influences landslide probability [ABSTRACT FROM AUTHOR]

• The 2008 M w 7.9 Wenchuan earthquake decoupled most of the Longmenshan Fault Zone (LFZ). • Subsequent coupling & relocking is analysed using GPS & cross-fault levelling data. • The northeastern section of the LFZ has recovered coupled state. • Part of the middle section of the LFZ began relocking after the Lushan earthquake. • Strong coupling & high seismic risk continue in two aftershock gaps of the LFZ. The analysis of post-seismic fault relocking and healing is crucial for predicting future seismic risk in seismogenic regions. In this study, we investigated the dynamic characteristics of the coupling fraction and relocking process of the Longmenshan Fault Zone (LFZ) following the 2008 M w 7.9 Wenchuan earthquake. Analysis was performed using Global Positioning System (GPS) velocity data for the periods 2009–2011, 2011–2013, 2013–2015, and 2015–2018, combined with cross-fault levelling data from 2008 to 2017. The results show that following short-term creep caused by the Wenchuan earthquake, the northeastern section of the LFZ rapidly began relocking process, and that today, the fault plane is close to being fully coupled; following the subsequent 2013 M w 6.6 Lushan earthquake, coupling fraction along part of the middle section of the LFZ, southwest of the Wenchuan earthquake source, gradually increased, which are basically consistent with fault healing results indicated by permeability and seismic wave velocity. The Wenchuan earthquake also accelerated strain accumulation rates and enhanced coupling along the southwestern section of the LFZ. Following the Lushan earthquake, only local areas of the southwestern section were decoupled, limiting the release of accumulated strain energy. The aftershock gap between the Wenchuan and Lushan earthquakes, and the aftershock gap southwest of the Lushan earthquake remain strongly coupled and continue to accumulate strain energy; as such, seismic risk remains high in these two segments. [ABSTRACT FROM AUTHOR]

Housing reconstruction is critical following natural disasters, especially in rural areas of developing countries. Concentrated rural settlement (CRS) is an important method adopted by local governments in China to promote post-disaster rural housing recovery. However, the effectiveness and selection of CRS approaches under different situations often puzzles local governments, even though various approaches to CRS development have been available since the Wenchuan Earthquake on May 12, 2008. This study therefore compares three approaches to developing CRS (unified planning/unified reconstruction, unified planning/joint reconstruction, and unified planning/self-reconstruction), based on three case studies in Lushan County of Ya'an City in Sichuan Province of China. The factors considered include the triggering event, participants, process, and outcome. Research information and data were collected using interviews, a questionnaire survey, and content analysis. The comparison reveals a transformation from a government-led pattern to a resident-led pattern in the rural housing reconstruction after the Lushan Earthquake. When comparing the effectiveness of these three approaches, each approach must be considered according to its prerequisites to ensure the sustainability of reconstruction. Based on the comparative analysis, the study also offers a map for future initiatives, providing valuable insights for local governments to develop sustainable CRS in post-disaster reconstruction. [ABSTRACT FROM AUTHOR]

To enhance the timeliness and accuracy of spatial prediction of co-seismic landslides, this paper proposes a prediction strategy in three phases: emergency response, mid-term resettlement and later reconstruction in the affected area. Taking the Lushan Ms 7.0 earthquake of 2013 as an example, it is stated as follows: In the emergency response phase, combining with topographic and geological data of the study area, the rapid assessment is conducted by the Newmark method without co-seismic landslide data. In the temporary resettlement phase with partial landslide data available, considering 10 factors including elevation, slope gradient, slope direction, topographic wetness index (TWI), peak ground acceleration (PGA), distances to the epicenter, distances to rivers, distances to roads, lithology and annual precipitation, a logistic regression (LR) model is established, and the spatial prediction of landslides is made. In the reconstruction phase with a complete landslide inventory, the incomplete data is replaced and the latest assessment is conducted based on the LR model. The accuracies of three phases are tested by using complete landslide data. The results show that the area under curve (AUC) values of the three stages is 0.59, 0.84 and 0.87, respectively. Such results can meet the requirement of spatial prediction of seismic landslides in each stage of disaster reduction. [ABSTRACT FROM AUTHOR]

• A 3D fault morphology model of the RFBR was constructed for the southern LMS. • The geometrical irregularity of the RFBR induced segmentation of thrusting. • Fractured duplex over the geometrical bump contributed to the presence of seismic gap. A 3D fault morphology model has been constructed from seismic profiles covering the piedmont of the southern Longmen Shan (LMS), eastern margin of the Tibetan Plateau. It reveals a spatial correlation between an ∼3.5 km-high geometrical bump on the range front blind ramp (RFBR) and the gap between the 2008 M w 7.9 Wenchuan and 2013 M w 6.6 Lushan earthquakes. Sandbox modeling is then used to probe the effects of the geometrical irregularity of the RFBR on fault behaviors and the LMS range front deformation. Sand wedges are designed to thrust over artificial blind ramps, analogous to the thrusting of the LMS orogenic wedge toward the Sichuan Basin through the RFBR. The experiments reproduce the first-order deformation features presented in the southern LMS range front, confirming that along-strike geometrical variations of the RFBR have induced the segmentation of both fault motion and the range front deformation. Their results also suggest that the gap between the Wenchuan and Lushan earthquakes is located directly within the structural transition zone originating from the geometrical bump on the RFBR. Additionally, there is a duplex structure occurring in the hanging wall of the geometrical bump, which localizes significant shear strain with progressive shortening and represents a fracture zone corresponding to the observed geophysical anomaly (low seismic velocity) underneath the seismic gap. It is likely that this fractured body protected the gap from the ruptures of the Wenchuan and Lushan earthquakes. [ABSTRACT FROM AUTHOR]

The spatial interrelatedness of business recovery after a disaster is an issue that is often overlooked in disaster-related studies. The current study explores the spatial correlation of business operating status and its variability over time by using Moran's I, spatial Tobit model and LISA cluster map techniques. Field investigation data are collected from 951 retail businesses in Lushan Old County, China in the following periods after the 2013 Lushan earthquake: from 0 to 3 months, 0 to 1 year, 0 to 2 years, 0 to 3 years, and 0 to 4 years. Results show that the operating status of businesses had a significant positive global spatial dependence, which exhibited an inverted "U" trend with the change in time in the aftermath of the Lushan earthquake. The local spatial correlation of business operating status varies in different street regions. Eventually, an increasing number of business districts gradually turned into poorly operated or recovered regions after the earthquake. Findings of this study provide a new insight into the analysis of business recovery after a disaster. Moreover, results can be regarded as a solid theoretical foundation in formulating a contrapuntal strategy for post-disaster business restoration in different regions. [ABSTRACT FROM AUTHOR]