In the past, the free-air gradient −308.6 × 10−8 s−2 was used as the vertical gravity gradient of the measuring point in gravity data processing, which resulted in inaccurate instrument height corrections. To investigate the influence of using the vertical gravity gradient, theoretical gradients of the Jinzhai baseline field in the Dabie Mountains were calculated using DEM data and WGM2012 gravity anomaly data. Adjustment results were compared with those using the free-air gradient. Using the theoretically calculated vertical gravity gradient correction improved the scale factor calibration precision by an average of 0.00007. The average precision of gravity adjustment results under different datum controls increased from 2.23 × 10−8 m/s2 to 1.45 × 10−8 m/s2. In a single-datum control adjustment, the maximum effect of the actual vertical gravity gradient on datum transfer is 8.7 × 10−8 m/s2, while the effect without it is as low as 9.0 × 10−8 m/s2 and as high as 27.5 × 10−8 m/s2. In a multi-datum system, using the actual vertical gravity gradient yields the best results. Even with the three-datum control adjustment, the average effect of the free-air gradient correction on the results reaches 3.9 × 10−8 m/s2. Therefore, incorporating measured or theoretically calculated vertical gravity gradients into gravity data processing is essential for significantly enhancing its accuracy and precision.

On March 28, 2025, an MW7.7 earthquake struck Myanmar, with the epicenter located in the central segment of the Qinghai–Xizang–Yunnan–Myanmar–Indonesia η-type structure. This region hosts a series of active faults, including the right-lateral Sagaing Fault and the Red River Fault in southwestern Yunnan. Based on the fault geometry model published by Zhang et al. and the Crust1.0 layered medium model, this study simulates the co-seismic and post-seismic Coulomb stress changes at depths of 5, 10, and 15 km on the main fault zones within the study area. The results indicate that the earthquake was dominated by Coulomb stress unloading, with localized loading observed at the northern and southern ends of the rupture. On the Sagaing Fault, Coulomb stress changes were dominated by unloading: average decreases ranged from −2.4 to −4.7 bar across all depths and timescales, indicating a low likelihood of large-scale rupture on that fault. However, in the northern segment of the rupture, localized stress loading exceeded the critical threshold of 0.1 bar, suggesting a possible enhancement of local seismic hazard. In southwestern Yunnan, co-seismic Coulomb stress loading at all depths ranged from −0.37 × 10−2 to 1.8 × 10−2 bar. Post-seismic stress changes were minor, with a maximum of 3.2 × 10−3 bar. These results imply that the MW7.7 event induced only subtle adjustments to the long-term tectonic stress field in southwestern Yunnan; nevertheless, the presence of stress-loading regions within seismic gaps warrants continued attention to potential hazard.

Based on the relative gravity data of southeastern Gansu from 2020 to 2024 and the global gravity field model WGM2012, this paper calculates the horizontal and dynamic deviatoric stress (HDS, DDS) in this region and analyzes its relationship with seismic activity, focusing on the relevant characteristics of the 2023 Jishishan MS6.2 earthquake in Gansu. The results show that the HDS in the study area is mainly concentrated in tectonically active areas such as the Qilian-Haiyuan fault zone and the Qinghai Nanshan-Linxia fault zone. Seismic case studies indicate that earthquakes are mostly concentrated in areas with HDS exceeding 7 MPa. The study of the Jishishan MS6.2 earthquake case shows that the HDS level in the epicenter area is relatively high. From 2021 to 2023, the DDS disturbance in the periphery of the 2023 Jishishan MS6.2 epicenter intensified, especially in the year before the earthquake, when an arc-shaped high-value DDS zone appeared along the fault strike, suggesting that DDS anomalies may serve as potential indicators in earthquake risk assessment. Furthermore, Significant concentrations of deviatoric stress can still be observed in two high-HDS background areas: the eastern segment of the Tianzhu seismic gap and the southern segment of the Riyueshan fault. Their seismic hazard should be continuously monitored in the future.

The tectonic setting of Taiwan and its surrounding regions is characterized by the complex interaction between the northwest-oriented Ryukyu subduction zone and the east-oriented Manila subduction zone. Within this subduction framework, the elastic thickness of the lithosphere (Te) serves as a critical parameter for elucidating the mechanical behavior of the area. In this study, we employed the admittance-correlation method to estimate Te values across Taiwan and adjacent territories. The findings indicate that sedimentary loading results in an overestimation of the maximum Te by approximately 50 km; after adjustment, the Te values range from 0 to 60 km throughout the study area. On Taiwan, Te values predominantly lie between 20 and 30 km, decreasing to 10-20 km near the margins adjacent to the Ryukyu and Manila subduction fronts. The Philippine Sea Plate exhibits comparatively higher Te values, ranging from 40 to 65 km. The spatial distribution of Te broadly corresponds with major tectonic subdivisions. Statistical analyses reveal a weak negative correlation between Te and surface heat flow (r = -0.44) and a weak positive correlation with shear-wave velocity anomalies at a depth of 100 km (r = 0.22), suggesting that the thermal structure exerts only a moderate influence on lithospheric strength in this region. Nonetheless, within oceanic crustal domains, the relationship between Te and oceanic crustal age largely adheres to models of crustal cooling and lithospheric thickening, consistent with isotherm depths of approximately 200-400 degrees C. Additionally, dynamic topography associated with slab subduction may locally diminish Te by up to 25 km. Cross-sectional profiles through northern Taiwan and the Philippine Sea block reveal pronounced coupling between subduction geometry and Te distribution. The observed spatial patterns of Te reflect the mechanical imprint of prolonged tectonic evolution, with the orientation of Te gradients generally aligned with the direction of maximum principal compressive stress. Collectively, these results suggest that subduction geometry and tectonic processes are important factors influencing the spatial variability and evolutionary trajectory of lithospheric strength in Taiwan and its environs.

Three-dimensional gravity inversion technology involves inferring the underground density structure based on observed gravity anomaly data. In addition to gravity inversion based on physics-driven methods, deep learning, as a purely data-driven technique, is increasingly gaining attention in geophysical inversion problems. However, purely data-driven methods rely on the implicit relationships within the data during the inversion process, which results in a lack of clear physical significance. This study proposes a three-dimensional gravity inversion method that integrates physical equations with deep learning. Based on the U-Net architecture, the gravity forward equation is incorporated as a physical constraint term, and a composite loss function—comprising three-dimensional mean squared error, a depth-weighting function, and three-dimensional intersection-over-union loss—is constructed to enhance inversion accuracy. Numerical experiments indicate that this method outperforms traditional algorithms in terms of density recovery accuracy and boundary clarity. When applied to gravity anomaly data from the Tangshan earthquake region in China, this method successfully inverted the three-dimensional subsurface density structure, revealing a high-density anomaly beneath the seismic source area, which provides important evidence for understanding the regional earthquake generation mechanism.

High precision surface gravity observation is one of the key means to study the internal deformation and material transport of the Earth. In the past decade, with the rapid development of modern precision geodetic observation technologies and the accumulation of high-precision gravity observation data on the surface, the application and research of absolute gravity observation in China's earthquake prevention and disaster reduction undertakings and the field of earth science have been deepened and expanded. This article mainly summarizes the application and research progress of absolute gravity observation in geodesy and geophysics in China, including the development of absolute gravity observation technologies (absolute gravity observation network, absolute gravity data processing), as well as the research progress of absolute gravity in earthquake monitoring (earthquake monitoring and prediction, calibration, and comparative observations of seismic gravity instruments) and geodynamics (crustal structural deformation, surface material migration, establishment and evaluation of gravity field models). Finally, some suggestions are proposed for development trends and application research directions of absolute gravity observation in terms of spatial resolution, gravity measurement network design, and new gravity observation technologies. With the gradual maturation of various types of independently developed absolute gravimeters in China, it is believed that absolute gravity observation will bring broader opportunities and prospects in application and research.

To analyze the triggering relationship of historical earthquakes to the 2023 Jishishan earthquake and estimate the seismic risk in the adjacent region after the earthquake,we calculate the evolution process of seismic stress generated by 11 earthquakes with Ms ≥ 6.0 and 1 earthquake with Ms5.7 near the source in the past 100 years.The results show that before the 2023 Jishishan earthquake,the entire Lajishan Northern Edge Fault zone was under the stress shadow generated by the 12 earthquakes.The stress reduction at the 2023 Jishishan earthquake epicenter was approximately 15.1 kPa,and the contribution of this stress shadow mainly comes from the 1920 Ms8.5 Haiyuan earthquake.The coseismic stress drop at the epicenter was around-292.1 kPa,and the maximum stress drop for the 2023 Jishishan earthquake was around-346.2 kPa.The Jishishan earthquake increased the stress of the two seismic gaps in the Lajishan Northern Edge Fault by 14.7 kPa and 59.7 kPa respectively,the stress on the Lajishan Southern Edge Fault zone increased by 10.9 kPa,and the stress on the east section of Xunhua Nanshan Fault increased by 11.1 kPa.These stress increments potentially elevate the seismic hazard along these fault zones.In the future earthquake prevention and disaster reduction,attention should be paid to the seismic risk of these fault zones.

Based on the Bouguer anomalies from terrestrial measurements and EIGEN-6C4(European Improved Gravity model of the Earth by New techniques version 6C4)gravity data,and constrained by the USTClitho2.0(Unified Seismic Tomography models for continental China lithosphere version 2.0)lithospheric structure model,a series of methods,including Bouguer correction considering lateral crustal density variations,multi-scale wavelet decomposition,isostatic correction,gravity inversion of the Moho,and inversion of effective elastic thickness of the lithosphere(Te)were employed to derive the Bouguer anomaly and its multi-scale decomposition results,deep isostatic anomaly,Moho depth,effective elastic thickness of the lithosphere,and load ratio for the central-southern segment of the Tan-Lu fault zone.By integrating seismic activity and geophysical data,this paper comprehensively analyzes the tectonic background of the gravity anomaly and its relationship with seismic activity in this region.The results reveal a distinct three-segment distribution of gravity anomalies along the Tan-Lu Fault Zone:the segment south of Jiashan,the Jiashan-Xinyi segment,and the Xinyi-Anqiu segment.This segmentation closely corresponds to the characteristics of seismic activity.The seismically active segments,south of Jiashan and Xinyi-Anqiu,are characterized by linear belts of shallow Bouguer anomalies,high-gradient belts of deep Bouguer anomalies,steep or uplifted Moho,crustal gravity disequilibrium,low effective elastic thickness of the lithosphere,and high load ratios.These features indicate a severely disrupted deep structure,low lithospheric mechanical strength,and ongoing isostatic adjustment,which facilitate stress release and frequent seismic activity.In contrast,the Jiashan-Xinyi segment,which exhibits weak seismic activity,shows scattered shallow Bouguer anomalies,with high Bouguer anomaly zones and slight positive isostatic anomaly zones crossing through the Tan-Lu fault zone.It also features a relatively smooth Moho,high effective elastic thickness of the lithosphere,and low load ratios,corresponding to the remnant deep structure of the Yangtze block subducting beneath the North China block.This segment has a less disrupted deep structure,higher lithospheric mechanical strength,and weaker isostatic adjustments,making the lithosphere less prone to rupture and resulting in lower seismic frequency.The M8.5 Tancheng earthquake occurred near the northern edge of the deep structure transecting the Tan-Lu fault zone,which is the area most prone to stress accumulation.Abrupt changes in deep structures and effective elastic thickness of the lithosphere likely caused uneven stress distribution and strong isostatic adjustment,triggering the earthquake.The Jiashan-Xinyi segment exhibits deep structural conditions conducive to long-term stress accumulation,warranting continued monitoring of its stress accumulation dynamics and potential strong earthquake risks.

Controlled by the squeezing collision between the Yangtze block and the North China block and the left movement of the Tanlu fault, the Xu-Su region developed into an arc-shaped nappe structure, and many destructive earthquakes occurred in its periphery. The geological structure of this area is complex, and there is the possibility of moderate and strong earthquakes. To further explore the crust density structure and identify the main faults and deep structural features in the Xu-Su region, based on the observed seismic data and gravity/GNSS co-site observation data, combined with the EGM2008 global gravity field model, we obtained the density of three-dimensional structure using cross gradient method joint inversion. Based on this, a geological model of the Xu-Su region was established. The results show that the crustal density anomaly amplitude within 0–25 km of the Xu-Su region ranges from −280 to 490 kg/m³, showing a zonal distribution in east-west direction and a segmented north-south direction. There are several density anomalies in the shallow (0–4 km) region at Tongshan, Huaibei, Xiayi, Woyang, etc. The density anomalies are significantly correlated with the distribution of regional faults. The density structure is divided into two large regions by Subei fault, which can be further divided along the east-west Kouziji-Nanzhao fault and Guzhen-Huaiyuan fault. The earthquakes are obviously related to the regional fault activity and the spatial distribution of abnormal bodies. The earthquake-prone areas (5–15 km) correspond to the abnormal density mutation zone, upper uplift zone, and transformation zone near Xiaoxian, Tongshan, and Xushuanglou faults. The comprehensive results show three weak seismic activity areas in the whole region, which are located near the Huaibei, Xiaoxian, and Wohe faults. The results provide theoretical support for seismic risk analysis in this area, and these three areas should be emphasized in future seismic hazard analysis.

The 1679 Sanhe-Pinggu M8 earthquake occurred in the transition zone between the Yanshan fold beltand the North China Plain, but its shallow and deep seismogenic tectonic dynamic environment is still uncle his study utilizes the high-resolution Bouguer gravity anomaly data and the latest global gravity field modelWGM2012 data. Firstly, the trend analysis method is utilized to obtain the trend anomaly signals related to theMoho. Subsequently, these trend anomaly signals are combined with the results of Wavelet Multi-scale signalseparation through weighted averaging to derive the regional gravity anomalies in the study area. The iterativeinversion algorithm is further applied to obtain spatial images of Moho fluctuations and density disturbancesdistributions within the Earth's crust. The results reveal that the 1679 M8 Sanhe-Pinggu earthquake occurred atthe transitional zone between area of high and low local gravity anomalies. Within this zone, the gravity anomalycontours exhibit a curvature from NNE to NE, creating an environment conducive to the concentration andaccumulation of tectonic stress and strain. It is similar to the 1976 Tangshan earthquake, both located on theeastern side of the Taiyuan-Yanqing Bouguer gravity anomaly gradient zone (the middle segment of the gravitygradient zone in eastern China) and the Moho abrupt change zone. The three-dimensional density structure of thecrust in the epicentral region (39.4 degrees N- 40.3 degrees N, 115.7 degrees E- 117.5 degrees E) reveals a characteristic pattern of highdensity in the central part and low density in the north and south. High and low density bodies are mostlysegmented or confined by faults, showing an alternating distribution that corresponds to the geological featuresof alternating uplifts and depressions. It is inferred that the high-density bodies may be formed due to theupwelling and intrusion of mantle magma, as well as melting activities, while the low-density bodies may becaused by the extension of the North China Plain and the isostasy of the Yanshan uplift. The uplifting activity ofthe high-density Daxing body in the northeastern part of the central region is crucial for the formation anddevelopment of the Xiadian Fault, as well as the preparation and occurrence of the Sanhe-Pinggu earthquake.Finally, a seismogenic model involving the combined effects of magma upwelling and faults is proposed for theSanhe-Pinggu earthquake. These findings provide valuable insights for studies on tectonic-magmatic activitiesduring the destruction and evolution of the North China Craton, assessments of seismic hazards in the CapitalCircle, and the identification of megathrust earthquake source

On September 5,2022,an earthquake of magnitude MS6.8 occurred in Luding County,Sichuan Province.This earthquake occurred at the key part of the southeast-clockwise extrusion of material on the eastern margin of the Qinghai Plateau,the Y-shaped confluence of the Xianshuihe,Longmenshan and Anninghe fault zones.In this study,the three-dimensional dynamic crustal density changes in the earthquake area are obtained by the typical gravity change data from 2019 to 2022 before the earthquake and gravity inversion by growing bodies.The results indicate that gravity changes presented an obvious four-quadrant and gradient belt distribution in the Luding area before the earthquake.The three-dimensional density horizontal slices show that small density changes occurred at the epicenter in the mid-to-upper crust between 2019.9-2020.9 and 2019.9-2021.9.At the same time,the surrounding areas exhibited a positive and negative quadrant distribution.These observations indicate that the source region was likely in a stable locked state,with locking-in shear forces oriented in the NW and NE di-rections.From 2021.9 to 2022.8,the epicentral region showed negative density changes,indicating that the source region was in the expansion stage,approaching a near-seismic state.The three-dimensional density vertical slices reveal a southeastward migration of positive and negative densities near the epicenter and on the western of the Xianshuihe Fault Zone,indicating that the material is flowing out to the southeast.The observed local negative density changes at the epicenter along the Longmenshan Fault Zone are likely associated with the NE-oriented extensional stress shown by the seismic source mech-anism.The above results can provide a basis for interpreting pre-earthquake gravity and density changes,thereby contributing to the advancement of earthquake precursor theory.

Earthquake interaction across multiple time scales can reveal complex stress evolution and rupture patterns. Here, we investigate the role of static stress change in the 2023 Mw 7.8 and 7.6 earthquake doublet along the East Anatolian Fault (EAF), using simulations of 19 historical earthquakes (M >= 6.1) and the 2023 earthquake doublet from 1822 to 2023. Focusing on six cascading sub-events during the 2023 Kahramanmara & scedil; earthquake doublet, we reveal how one sub-event's stress alteration can impact the emergence and rupture of subsequent sub-events. Our analysis unveils that the 2023 Mw 7.8 earthquake was delayed due to stress shadow effects from historical events, while the 2023 Mw 7.6 earthquake was accelerated as a result of stress increases from historical events and ultimately triggered by the 2023 Mw 7.8 earthquake. This study underscores the importance of grasping earthquake preparation, rupture initiation, propagation, and termination in the context of intricate fault systems worldwide. Based on these results, we draw attention to increased seismic hazards in the Elazig-Bingol seismic gap of the EAF and the northern section of the Dead Sea Fault (DSF), necessitating increased monitoring and preparedness efforts.

The gravity inversion results of three-dimensional density interface are often not unique,which brings some difficulties to further scientific research.The classical particle swarm optimization algorithm has a higher global extremum search ability,faster inversion speed in computing highdimensional nonlinear inversion problems,and the final solution is independent of the initial model compared with traditional inversion density interface algorithms such as L-M,Tikhonov regularization,Gauss-Newton method,etc.However,in classical particle swarm optimization,the initial model setting and parameter selection are not perfect.Therefore,this paper further enhances the algorithm based on the classical particle swarm optimization algorithm,referring to the previous optimization ideas.The test results of various models show that the optimized particle swarm optimization algorithm has a stable ability to search for the optimal global solution,and the depth error is smaller.In addition,if we adopt parallel computing,the inversion speed can be effectively improved.We obtained the Indosinian density interface depth model of the Changning area by inversion using multiple measured high-density gravity profile data based on the improved algorithm.The overall scope of the survey area is small and diamond-shaped,including the complete Changning-Shuanghe anticline and some surrounding synclines.The inversion results show that the Indosinian density interface generally presents the characteristics of uplift in the middle and depressions around it,and the depth range is 0.3～3.3km,which is basically consistent with the inversion results of the drilling data and previous gravity data,and the details are more prominent.It can better express its structural characteristics.The depression degree of the interface on the right side is significantly larger than that on the left side.The uplift part corresponds to the Changning-Shuanghe complex large anticline,and the depth varies from 0.3km to 1.9km.The core of the anticline is exposed to the surface by uplifting and erosion of the tectonic movement.The inversion result provides essential information for studying the seismotectonic environment and is also a vital reference for studying the multi-layer density interface model.Density interface fluctuation is the product and sign of a specific area under the action of multistage tectonic movement,which plays an essential role in studying basin basement,regional structure,and deep structural fluctuation.It provides critical information for the analysis of the origin of earthquakes.Therefore,we analyzed the structural characteristics of this area and its relationship with earthquakes combined with the undulating morphology of the Indosinian surface.Earthquakes in the Changning area are concentrated on the north and south sides of the large anticline.The seismic distribution pattern and focal parameters on both sides are obviously different.The main reason for this phenomenon is that there are significant differences in the causes of earthquakes.The Indosinian surface in the north wing of the anticline is steeper than that in the south wing.The location of the strip distributed shallow earthquakes in the north wing is highly related to the fluctuation of the Indosinian surface,and they mainly occur at the places where the Indosinian surface fluctuates violently.The local density changes drastically,and the earthquakes’occurrence is greatly affected by hidden faults.The clumped distributed shallow earthquakes in the south wing occur at locations where there is an apparent depression on the Indosinian surface,which may be caused by shale gas exploitation,and the earthquakes are more affected by local stress changes.Deep earthquakes may be closely related to the revival of basement faults.There may still be seismic risk in the northeast wing of the large anticline in the future.In general,the optimized particle swarm algorithm has achieved good results in both model testing and practical applications.In order to further improve the accuracy of the inversion results,we will focus on improving the applicability of the algorithm in various situations and the ways of adding multiple constraint information.More detailed geophysical research should be carried out in this area,which will help to better understand its crustal structure,earthquake mechanism,geological structure,and the development of earthquake prevention and disaster reduction.

The existence of aftershocks in an earthquake sequence can impact the analysis of the mainshock. In this study, we present a method for deleting an aftershock sequence based on the spatial relationship between earthquakes and faults. This method improves the performance of space window selection in the classical K-K method by eliminating aftershocks with an ideal fault buffer zone. The determination of fault buffer zones is based on a trial-and-error analysis of 69,714 earthquake records from the China Seismic Network Center (CENC) collected between 1980 and 2020. We selected 20 typical big earthquakes (ML7.0–8.0 or ~Ms6.6–8.0; for earthquakes above magnitude Ms7 or ML7.2, ML is approximately equal to Ms) as the mainshocks to establish the fault buffer zones. We also propose an empirical formula to determine the distance of the fault buffer zone by counting the aftershock deletion effect at different buffer distances. Compared with the classical K-K method, our method considers the correlation between the spatial distribution of aftershocks and faults, eliminates earthquake groups that are not related to the mainshock, greatly reduces the spatial range of aftershocks, improves the performance of deleting aftershocks of different magnitudes, and provides a new rule and reference for aftershock deletion.

The Tangshan M(S)7. 8 earthquake in 1976 was located at the transitional part between the Yanshan fold and the North China Plain. The research on the existing crustal structure in the earthquake area is still not fine enough, and there are some controversies in the understanding of its seismogenic tectonic conditions. Combining the high-resolution Bouguer gravity anomaly data in Tangshan earthquake area with the latest global gravity field model WGM2012, based on wavelet multi-scale signal separation technology and spatial domain iterative inversion algorithm, the Moho surface fluctuation and the inner crust density disturbance distribution images in the earthquake area are obtained. The results show that the Tangshan earthquake area is located on the east side of Taiyuan-Yanqing Buge gravity anomaly gradient belt (that is, the middle part of the famous gravity gradient belt in eastern China) and the Moho steep belt, its isoline curves from NNE to NE, and the Moho depth is between 32 similar to 37 km. The epicenter of Tangshan is located in the transition between Moho steep belt and uplift area. The internal density distribution of the crust in the earthquake area presents the characteristics of high in the south and low in the north, and the scattered high-density bodies in the shallow part gradually aggregate with increasing depth. The former reflects the difference of tectonic movement between the North China Plain and Yanshan fold, while the latter reflects that the shallow high-density bodies mainly originate from deep upper mantle magmatism. From the density structure profile of the vertical and parallel Tangshan fault, it can be found that the Tangshan fault runs through the Moho surface, and its deep (about >7 km) pre-existing fracture surface is gradually opened by the intrusion of upper mantle magma under the action of horizontal tension and uplift compression of Moho surface, and the magma expands more and more as it goes up. The relatively uniform shallow part (within a depth of about 7 km) may be due to the continuous deposition of new strata and diagenesis on the surface, which prevents magma from invading, thus forming a locking area where stress and strain are easy to accumulate at the top of high-density body. This may be an important reason why the Tangshan earthquake occurred on the top of the high-density body and showed the characteristics of flower-like rupture in the shallow. Combining with the existing achievements, the seismogenic model of the Tangshan earthquake by the combined action of magmatic upwelling and faults is put forward from the point of view of material migration movement, and at the same time, it provides new evidence for the seismic sounding speculation of the seismogenic structural conditions of the Tangshan earthquake.

The construction of the high-resolution Moho depth model is significant for studying the characteristics of the complex tectonic movement (seafloor spreading, plate subduction phenomena) in Papua New Guinea. We calculate the region’s Moho relief and lithosphere thinning factor using the XGM 2019e gravity field model and nonlinear fast gravity inversion method under the GEMMA Moho depth model’s constraint considering the influence of lithosphere thermal gravity anomaly. The calculation result shows that the Moho depth is between 6—34 km, forming two large depressions in Woodlark Basin (WB) and Solomon Sea Plate (SSP) with deep scattered islands. In addition, the findings suggest that Significant differences exist in the shape and tectonic movement intensity of the North and South oceanic crust at the WB. Nevertheless, the lithosphere extends evenly in Manus Basin (MB). WB collided with the Solomon Islands at a higher angle than the SSP subducted under Bismarck Sea Plate (BSP); strong earthquakes may frequently occur on both sides and in deeper positions at West New Britain Trench in the future.

Recent years have witnessed the interesting trend that modern mobile apps perform more and more likely as user-to-user platforms, where app users can be freely and conveniently connected. Upon these platforms, rich and diverse data is often delivered across users, which brings users great conveniences and plentiful services, but also introduces privacy security concerns. While prior work has primarily studied illegitimate personal data collection problems in mobile apps, few paid little attention to the security of this emerging user-to-user platform feature, thus providing a rather limited understanding of the privacy risks in this aspect. In this paper, we focus on the security of the user-to-user platform feature and shed light on its caused insufficiently-studied but critical privacy risk, which is brought forward by cross-user personal data over-delivery (denoted as XPO). For the first time, this paper reveals the landscape of such XPO risk in wild, along with prevalence and severity assessment. To achieve this, we design a novel automated risk detection framework, named XPOChecker, that leverages the advantages of machine learning and program analysis to extensively and precisely identify potential privacy risks during user-to-user connections, and regulate whether the delivered data is legitimate or not. By applying XPOChecker on 13,820 real-world popular Android apps, we find that XPO is prevalent in practice, with 1,902 apps (13.76%) being affected. In addition to the mere exposure of diverse private user data which causes serious and broad privacy infringement, we demonstrate that the XPO exploits can invalidate privacy preservation mechanisms, leak business secrets, and even restore the sensitive membership of victims which potentially poses personal safety threats. Furthermore, we also confirm the existence of XPO risks in iOS apps for the first time. Last, to help understand and prevent XPO, we have responsibly launched two notification campaigns to inform the developers of the affected apps, with the conclusion of five underlying lessons from developers' feedback. We hope our work can make up for the deficiency of the understandings of XPO, help developers avoid XPO, and motivate further researches.

JavaScript cross-platform frameworks are becoming increasingly popular. They help developers easily and conveniently build cross-platform applications while just needing only one JavaScript codebase. Recent security reports showed several high-profile cross-platform applications (e.g., Slack, Microsoft Teams, and Github Atom) suffered injection issues, which were often introduced by Cross-site Scripting (XSS) or embedded untrusted remote content like ads. These injections open security holes for remote web attackers, and cause serious security risks, such as allowing injected malicious code to run arbitrary local executables in victim devices (referred to as XRCE attacks). However, until now, XRCE vectors and behaviors and the root cause of XRCE were rarely studied and understood. Although the cross-platform framework developers and community responded quickly by offering multiple security features and suggestions, these mitigations were empirically proposed with unknown effectiveness. In this paper, we conduct the first systematic study of the XRCE vulnerability class in the cross-platform ecosystem. We first build a generic model for different cross-platform applications to reduce their semantic and behavioral gaps. We use this model to (1) study XRCE by comprehensively defining its attack scenarios, surfaces, and behaviors, (2) investigate and study the state-of-the-art defenses, and verify their weakness against XRCE attacks. Our study on 640 real-world cross-platform applications shows, despite the availability of existing defenses, XRCE widely affects the cross-platform ecosystem. 75% of applications may be impacted by XRCE, including Microsoft Teams. (3) Finally, we propose XGuard, a novel defense technology to automatically mitigate all XRCE variants derived from our concluded XRCE behaviors.