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The Qinzhou fold belt, situated at the contact zone between the Yangtze and Cathaysia blocks in South China, was affected by the 1936 Lingshan M6¾ earthquake and the 1958 Lingshan M5¾ earthquake, both of which occurred within the conjugate structure. Understanding the deep seismogenic setting and causal mechanism of the Lingshan conjugate earthquake is of great significance for assessing the seismic disaster risk in the region. In this study, we utilized 237 magnetotelluric datasets and employed three-dimensional electromagnetic inversion to characterize the deep-seated three-dimensional resistivity structure of the Qinzhou fold belt and the Lingshan seismic zone. The results reveal that: (1) The NE-trending faults within the Qinzhou fold belt and adjacent areas are classified as trans-crustal faults. The faults exhibit crust-mantle ductile shear zones in their deeper sections, which are essential in governing regional tectonic deformation and seismic activity; (2) The electrical structure of the Qinzhou fold belt is in line with the tectonic characteristics of a composite orogenic belt, having experienced several phases of tectonic modification. The southeastern region is being influenced by mantle-derived magmatic activities originating from the Leiqiong area over a significant distance; (3) In the Lingshan seismic zone, the NE-trending Fangcheng-Lingshan fault is a trans-crustal fault and the NW-trending Zhaixu fault is an intra-crustal fault. The electrical structure pattern "two low, one high" in the zone has a significant impact on the deep tectonic framework of the area and influences the deformation behavior of shallow faults; and (4) The seismogenic structure of the 1936 Lingshan M6¾ earthquake was the Fangcheng-Lingshan fault. The earthquake's genesis was influenced by the coupling effect of tectonic stress and deep thermal dynamics. The seismogenic structure of the 1958 Lingshan M5¾ earthquake was the Zhaixu fault. The earthquake's genesis was influenced by tectonic stress and static stress triggering from the 1936 Lingshan M6¾ earthquake. The conjugate rupture mode in the Lingshan seismic zone is influenced by various factors, including differences in physical properties, rheology of deep materials, and the scale and depth of fault development. [ABSTRACT FROM AUTHOR]

North China is one of the high-risk areas for destructive and strong earthquakes in mainland China and has experienced numerous strong historical earthquakes. An earthquake of magnitude MW 5.5 struck Pingyuan County, Dezhou city, in Shandong Province, China, on 6 August 2023. This earthquake was the strongest in the eastern North China Craton since the 1976 Tangshan earthquake. Since the earthquake did not produce surface ruptures, the seismogenic structure for fault responsible for the Pingyuan MW 5.5 earthquake is still unclear. To reveal the subsurface geological structure near the earthquake epicenter, this study used high-resolution two-dimensional (2D) seismic reflection profiles and constructed a three-dimensional (3D) geometric model of the Tuqiao Fault by interpreting the faults in the seismic reflection profiles. This study further combined focal mechanism solutions, aftershock clusters, and other seismological data to discuss the seismogenic fault of the Pingyuan MW 5.5 earthquake. The results show that the Tuqiao Fault is not the seismogenic fault of the MW 5.5 earthquake. The actual seismogenic structure may be related to the NE-oriented high-angle strike-slip blind fault developed in the basement. We further propose three possible fault models for the strong seismogenic structure in North China to discuss the potential seismotectonics in this region. [ABSTRACT FROM AUTHOR]

This study aims to assess the tsunami hazard of the maximum possible earthquake along the south coast of China. GPS‐derived surface velocities around the Manila Trench have been used to clarify the active tectonics and estimate the seismic potential of Manila subduction, where catastrophic tsunamis may originate and cause devastating damage to the surrounding area of the South China Sea. Based on the maximum potential earthquake magnitude estimated from the accumulated seismic moment, more than 100,000 possible tsunami scenarios with varying epicenters have been simulated considering the slip heterogeneity. The impact of several uncertain parameters including the release period and release ratio of accumulated seismic moment are investigated, as well as some assumptions in the model of tsunami generation. Although different release conditions for accumulated seismic moment result in a significant impact on the value of tsunami height, similar trend in spatial distribution has been shown. The results show that the tsunami wave height along the south coast of China has an increasing trend from west to east, with the maximum tsunami wave height exceeding 10 m corresponding to the potential earthquake Mw = 9.1 with a 1,000‐year release period. The impact of fault slip heterogeneity on tsunami wave height is significant. Compared to uniform slip, considering stochastic slip will increase the average tsunami wave height by about 15%. Considering locking distribution will increase the average tsunami wave height by about 20%–30% and also increase the maximum tsunami wave height by about 60%–70%. Plain Language Summary: The purpose of this study is to evaluate the tsunami hazard of the maximum possible earthquake along the south coast of China. The Manila Trench is the potential tsunami source. The first problem to be solved in the study is how large the maximum earthquake is in the Manila Trench. Therefore, the study first uses the horizontal velocity data observed by GPS stations to invert the degree of locking on the fault plane. The rate of accumulated energy is estimated based on the degree of fault locking, and then the maximum magnitude of earthquakes that may occur on the fault with different release periods is estimated. The subsequent issue to be solved is how large the tsunami generated by the maximum earthquake is. In order to fully consider the randomness of slip, the study simulated more than 100,000 possible tsunami scenarios for each earthquake magnitude. The results indicate that only considering uniform slip will significantly underestimate the tsunami hazard along the south coast of China. Key Points: Fault locking inverted by GPS‐derived surface velocities is used to estimate the seismic potential and as constraints on stochastic slipTsunami scenarios with varying epicenters and the slip heterogeneity are simulated for each estimated maximum earthquake magnitudeSensitivity analysis has been conducted considering the release period and the release ratio of accumulated seismic moment [ABSTRACT FROM AUTHOR]

The Jiangsu-South Yellow Sea area is located on the East Asian Continental Margin and at the junction of South and North China. It is one of the high seismicity areas in eastern China. To enhance our understanding of the relationship between disastrous earthquakes and the geophysical properties of Earth materials, P- and S-wave travel-time data over the past 20 years are inverted to image the 3D distributions of seismic velocity (VP and Vs) and Poisson's ratio (σ). The results show that the velocity and Poisson's ratio demonstrate congruence with the prominent geological formations present within the study area. Specifically, the velocity models for the upper crust at depths of 5, 10, and 15 km. We found that within the total study area, 70% ± 7.2% of M5+ earthquakes that occurred during the past decades initiated in the VP tomographic edge zones (TEZ). Moreover, the distribution patterns of M5+ earthquakes in the offshore sea region exhibit significant differences when compared to those in the Jiangnan Orogenic Belt. In the offshore sea region, about 66.7% ± 8% of M5+ earthquakes initiated in the velocity and Poisson's ratio TEZ. The presence of comparatively low Vs and high Poisson's ratio anomalies in the Wunansha Uplift suggest the potential existence of fluids. The triggering mechanism for these earthquakes can likely be ascribed to the presence of hydrothermal fluids and the reactivation of preexisting strike-slip faults, influenced by the subduction of the Pacific and Philippine Sea Plates, as well as the collision between the India and Eurasia Plates. In contrast, within the Jiangnan Orogenic Belt, M5+ earthquakes predominantly initiated in the high-velocity and low Poisson's ratio perturbation zones. The primary factor contributing to seismotectonic features disparities are likely the variation in fluid content. We infer the rock matrix in the vicinity of the source region of the Jiangnan Orogenic Belt is presumed to be drier, more brittle, and possess greater mechanical strength. [ABSTRACT FROM AUTHOR]

The Jiaodong Peninsula in the eastern North China Craton is well-known for world-class deposits and as the only known late Mesozoic giant gold province located within a Precambrian metamorphic terrane. Here we synthesize deep seismic reflection data from the Jiaodong Peninsula, and on conjunction with existing interpretations of magnetotelluric data. We provide a new interpretation that offers insights into the possible crust-mantle interaction and deep ore-forming processes in this supergiant gold province. Six high-yield NNE-trending gold mineralized fault zones that span approximately 420 km across strike are identified: Sanshandao, Jiaojia, Zhaoping, Qixia, Guoji, and Muru. We identify distinct features in the coupled crust and lithospheric mantle beneath the Jiaodong gold province including a metamorphic core complex (MCC) and detachment fault systems at shallow crustal levels, a mid-crustal detachment belt (MCDB), a low-angle reverse fault in the lower crust, a reflection-transparent region and crust-mantle transition zone (CMT), as well as a deeper Moho discontinuity. Our study also reveals clear detachment or absence of the Moho and CMT beneath the Tan-Lu and Wulian-Yantai fault zones, the presence of weak wave impedance, or reflection-transparent regions in the deep parts of the high-angle faults, such as the Tan-Lu and Wulian-Yantai faults, and that in the core of the Linglong MCC. These are interpreted as zones formed through the homogenization of crustal materials as a result of the upward migration of heat, magmas, and fluids from the lithospheric mantle to the middle and upper crust. Important auriferous fluid pathways from the Moho include reverse faults at lower crustal levels, the MCDB, and detachment fault systems at upper crustal levels. The fluid pathway systems played a crucial controlling role in the intensity of formation of gold deposits. The CMT and MCDB are thicker, and the mineralization intensity and known gold resources are greater, where they are closer to the mantle-derived melt and fluid pathway. We propose a new two-stage model to explain the origin of the giant Jiaodong gold deposits which is based on the crust-mantle interaction as indicated by seismic reflection and magnetotelluric profiles, combined with existing experimental petrology and thermodynamic simulations, as well as information on mineralization and tectonothermal events based on isotope data. We envisage that the subduction-collision at ∼250–220 Ma between the Yangtze and North China cratons resulted in the formation of enriched lithospheric mantle that served as one of the important sources of auriferous fluids. At ∼120 Ma, asthenosphere upwelling, which induced metasomatism and partial melting in the overlying enriched lithospheric mantle, resulted in the activation, migration and concentration of gold, generating one of the world's giant gold fields. [ABSTRACT FROM AUTHOR]

The Puer Basin region, where Yangtze continental block and the Tethyan orogen collide, provides a favorable area for studying the processes of magmatic evolution, intracontinental earthquakes and hydrothermal systems. Focused on these issues, we have acquired a three-dimensional electrical model of the Puer Basin in southern Yunnan, using broadband magnetotelluric data extending from 320 to 0.001 Hz along eight profiles covering the Puer Basin. The complex subsurface model is filled with zones of fluid-filled fracture, partial melt networks, regional faults, and cold plutons. There are two highly conductive zones (3–10 Ωm) beneath the Puer Basin from 10 km to 35 km in depth. The estimated melt fractions are in the range of 4–26 vol%, which is required to account for the observed high conductivities in the crust based on the formulation of the multiple conduction models and resistivity from the three-dimensional magnetotelluric inversion. The partial melt in the middle and lower crust may have been derived from either magma intrusion of the mantle sources or the dehydration processes in the slab subducting of Yangtze continental block beneath the Tethyan orogen in southern Yunnan. Based on the three-dimensional electrical model, integrating with crustal anisotropy, thermal structure, potential field and seismic survey results, we have a more comprehensive understanding of the mechanism of the hydrothermal system, seismotectonics, and deep seismogenic background. • We have obtained a three-dimensional electrical model of the Puer Basin in southern Yunnan. • 3D electrical model reveals two magma chambers in mid-lower crust in the Puer Basin. • Seismicity and hydrothermal activity appears to be controlled by the conductive zones in mid-lower crust. [ABSTRACT FROM AUTHOR]

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]

• We determined crustal and upper mantle P-wave tomography of East China. • Two types of large earthquakes occurred in the central-south Tanlu Fault. • High-V bodies account for the 1668 Tancheng earthquakes. • Low-V zone between 35 and 200 km affects earthquakes under the Subei-Yellow Sea Basin. The Tanlu Fault is a significant fault in East China that has been associated with numerous destructive earthquakes in its central-south segment. However, the mechanisms behind these earthquakes remain unclear. This study aims to shed light on the seismic velocity structures of the crust and upper mantle under East China and their influence on the region's seismotectonics. Our findings reveal that the upper mantle structures play a crucial role in regional seismotectonics. The 1668 Tancheng earthquake (M 8.5) is located above remarkable upper-mantle high-velocity bodies on both sides of the Tanlu Fault. Thus, it was likely produced by the interaction between the North China and Yangtze plates, with the lithospheric mantle significantly affecting the plate interaction. Another group of earthquakes of magnitude M 5–6 is located in the Subei–Yellow Sea Basin (SYSB). We have imaged a low-velocity body in the upper mantle, which is believed to represent hot and buoyant materials under the SYSB. This anonymous body may reduce the vertical stress in the crust and provide fluids to fault planes, thereby facilitating moderate-to-large earthquakes in the crust. These new findings provide valuable insight into the seismotectonics of East China, particularly the role of the upper mantle structures in shaping the region's seismic activity. [ABSTRACT FROM AUTHOR]

[Display omitted] • The Menyuan earthquake is a conjugated type of rupturing event with a seismic gap. • The Menyuan earthquake is related to complicated stress loading and fluid effects. • There exists some relationship among the three Menyuan mainshocks. On 8 January 2022, an earthquake with Ms 6.9 struck Menyuan County, Qinghai Province, China, which provides an opportunity to investigate the seismotectonics of the Qilian-Haiyuan fault in northeast Tibet. We collect seismic observation data from China Seismic Network Center from 8 January to 6 February 2022 around the 2022 Menyuan mainshock. The double-difference relocation algorithm is applied to relocate 904 earthquakes, and 820 high-precision hypocenter locations are obtained. The mainshock epicenter was located at 10.2 km depth in the Tuolaishan fault. The aftershock sequence extended towards nearly E-W along the Tuolaishan fault and NW-SE along the Lenglongling fault, parts of the Qilian-Haiyuan fault, but there were fewer aftershocks at the beginning of the rupture near the intersection between the Lenglongling and Tuolaishan faults, suggesting a conjugated type of rupturing with a seismic gap. Integrating with focal mechanism solutions of mainshock and one large aftershock, we suggest that the rupture is a left-lateral strike-slip event with a high dip. The stress change around the faults intersection. The 1986 Ms 6.4 earthquake may trigger the 2016 Ms 6.4 earthquake, and then the extrusion stress could transfer to around the 2022 Ms 6.9 earthquake source area due to the Indo-Eurasian collision. Previous tomographic models revealed low-velocity anomalies under the Menyuan earthquakes, reflecting that fluids could decrease friction coefficient and normal stress on the fault planes and further promote the generation of these earthquakes. These fluids could be contained in the lower crustal flow and mantle upwelling flow under northeast Tibet. [ABSTRACT FROM AUTHOR]

Eastern China comprises a complex amalgamation of geotectonic blocks of different ages and undergone significant modification of lithosphere during the Meso-Cenozoic time. To better characterize its deep structure, we conducted H – κ stacking of receiver functions using teleseismic data collected from 1143 broadband stations and produced a unified and detailed map of Moho depth and average Poisson’s ratio ( σ ) of eastern China. A coexistence of modified and preserved crust with generally in Airy-type isostatic equilibrium was revealed in eastern China, which correlates well with regional geological and tectonic features. Crust is obviously thicker to the west of the North–South Gravity Lineament but exhibits complex variations in σ with an overall felsic to intermediate bulk crustal composition. Moho depth and σ values show striking differences as compared to the surrounding areas in the rifts and tectonic boundary zones, where earthquakes usually occur. Systematic comparison of Moho depth and σ values demonstrated that there are both similarities and differences in the crustal structure among the Northeast China, North China Craton, South China, and the Qinling-Dabie Orogen as well as different areas within these blocks, which may result from their different evolutionary histories and strong tectonic-magma events since the Mesozoic. Using new data from dense temporary arrays, we observed a change of Moho depth by ∼3 km and of σ by ∼0.04 beneath the Tanlu Fault Zone and an alteration of Moho depth by ∼5 km and of σ by ∼0.05 beneath the Xuefeng Mountains. In addition, striking E–W difference in crustal structure occur across the Xuefeng Mountains: to the east, the Moho depth is overall <35 km and σ has values of <0.26; to the west, the Moho depth is generally >40 km and σ shows complex and large-range variation with values between 0.22 and 0.32. These, together with waveform inversion of receiver functions and SKS shear-wave splitting measurements, suggest that the Tanlu Fault Zone is at least a crustal-scale fault and the Xuefeng Mountains may be a deep tectonic boundary between the eastern Yangtze Craton and western Cathaysia Block. [ABSTRACT FROM AUTHOR]

Abstract: Field investigations show that the Wenchuan earthquake on the 12th of May 2008 ruptured two NW-dipping imbricate reverse faults along the Longmen Shan fault zone. The length of the Beichuan–Yingxiu Fault reaches nearly 240km. Southeast of this fault, a smaller displacement occurred along the Guanxian–Jiangyou Fault, which has a length of about 70km. A NW-striking left-lateral reverse fault, the Xiaoyudong Fault, was clearly observed between these two main surface ruptures. This co-seismic surface rupture pattern is one of the most complicated patterns of recent great earthquakes. In order to clarify how rupture progressed northward during the Wenchuan earthquake, we conducted a detailed investigation including rupture tracing, displacement measurement, fault kinematic estimation, and stress analysis of the Xiaoyudong area. Our results show that the Xiaoyudong Fault is not a simple tear fault. In contrast, it is an independent active fault located on the northern boundary of the Xiaoyudong salient. The Xiaoyudong salient is an independent topographic highland occupying a surface area of approximately 100km2. From a stratigraphic point of view, this highland is a little older than the adjacent area. The s-shape stream north of the Xiaoyudong salient indicates that the Xiaoyudong Fault is still active. The Xiaoyudong salient plays an important role in controlling fault propagation and stress delivery. When the Wenchuan earthquake occurred in the south of the Xiaoyudong salient, this salient partially impeded the northward propagating rupture and dispersed it into two branches to the north. The rupture distribution north of Xiaoyudong would be significantly different without this salient. The existence of the Xiaoyudong salient and the rupture pattern of the Wenchuan earthquake also prove that the multi-segment rupturing model is a better approximation than a single-segment model for estimating the maximum magnitude of the paleo-earthquake of the Longmen Shan fault zone. [Copyright &y& Elsevier]

Abstract: The 3-D geometry of the seismicity in Hindu Kush–Pamir–western China region has been defined by seismic records for 1975–1999 from the National Earthquake Information Center, the U.S. Geological Survey, and over 16,000 relocated earthquakes since 1975 recorded by the Xinjiang seismic network of China. The results show that most M s ≥ 5.0 hypocenters in the area are confined to a major intracontinental seismic shear zone (MSSZ). The MSSZ, which dips southwards in Pamir has a north-dipping counterpart in the Hindu Kush to the west; the two tectonic realms are separated by the sinistral Chaman transform fault of the India–Asia collisional zone. We demonstrate that the MSSZ constitutes the upper boundary of a south-dipping, actively subducting Pamir continental plate. Three seismic concentrations are recognized just above the Pamir MSSZ at depths between 45–65 km, 95–120 km, and 180–220 km, suggesting different structural relationships where each occurs. Results from focal mechanism solutions in all three seismological concentrations show orientations of the principal maximum stress to be nearly horizontal in an NNW–SSE direction. The south-dipping Pamir subduction slab is wedge-shaped with a wide upper top and a narrow deeper bottom; the slab has a gentle angle of dip in the upper part and steeper dips in the lower part below an elbow depth of ca. 80–120 km. Most of the deformation related to the earthquakes occurs within the hanging wall of the subducting Pamir slab. Published geologic data and repeated GPS measurements in the Pamir document a broad supra-subduction, upper crustal zone of evolving antithetic (i.e. north-dipping) back-thrusts that contribute to north-south crustal shortening and are responsible for exhumation of some ultrahigh-pressure rocks formed during earlier Tethyan plate convergence. An alternating occurrence in activity of Pamir and Chaman seismic zones indicates that there is interaction between strike-slip movement of the Chaman transform fault system and deep-subduction of the Pamir earthquake zone. Pamir subduction-related seismicity becomes shallower in depth with increasing distance east of the transform fault. Therefore, sinistral movement of the Chaman transform fault appears to be influencing continental deep-subduction in the Pamir region and may provide an explanation for the unusual south-dipping geometry of the intracontinental Pamir plate. [Copyright &y& Elsevier]

We performed a numerical simulation of seismic activity along the Xianshuihe fault, a highly active strike-slip fault approximately 350 km long, located along the eastern margin area of the Tibetan plateau, southwestern China. Historical earthquake data over the last 300 yr indicate repeated periods of seismic activity, and migration of large earthquakes along the fault during active seismic periods. To understand the characteristics of historical seismicity and to obtain insight into seismic potential, we performed a numerical simulation of slip behaviour along the fault using a 2-D elastic plate model. The friction on the model fault obeys a laboratory-derived rate- and state-dependent friction law, while the long-term slip rates along the fault are assumed to be consistent with geologically and geodetically estimated slip rates. To simulate segmented rupture behaviour we introduced non-uniformity into friction parameters along the fault. The simulation results indicate that seismic rupture is arrested in regions with frictional properties that are highly velocity-strengthening or large values of characteristic slip distance over which frictional stress evolves. In the regions where seismic rupture is arrested, post-seismic sliding occurs, causing time-dependent stress transfer along the fault. Post-seismic slip histories in highly velocity-strengthening regions are well approximated by logarithmic time functions, while those in regions with large characteristic slip distances increase more rapidly in the initial stages of post-seismic sliding. This difference in post-seismic sliding produces the difference in time-dependent stress transfer and, in consequence, the statistical characteristics of earthquake recurrence. Fault interactions near a fault branch point produce complexity in the simulated earthquake sequence. Simulated rupture commonly triggers additional rupture in a neighbouring segment with a time delay of several years. The simulated seismic activity shows good agreement with observational data with respect to the following statistical features: (1) successive seismically active periods are separated by periods of relative quiescence of 100–200 yr duration (2) and the duration of active period is a few tens of years. Strictly speaking, neither the time- nor slip-predictable models are able to describe the simulated local slip history for each fault segment. The ratio of the standard deviation to the average value of the recurrence intervals of simulated earthquakes ranges from 0.05 to 0.22, depending on the fault segment. The cumulative distribution function of the recurrence intervals of simulated earthquakes at each segment approximately obeys a Brownian passage time distribution or a lognormal distribution, which is commonly used in the statistical evaluation of earthquake occurrence. [ABSTRACT FROM AUTHOR]