Earthquake magnitude is critical for both seismic and tsunami hazard assessments, as well as early warning. However, because modern seismological observations are limited in duration, the magnitudes of many past events were not recorded or are poorly constrained over hundreds and/or thousands of years of the earthquake cycle. This gap limits our understanding of long-term seismicity and hampers effective hazard mitigation. Here, we propose a novel approach to estimate earthquake magnitude using fault zone scarp area. Theoretical considerations suggest that coseismic scarp area scales with moment magnitude (Mw) according to a and blind faults. For near-surface faults, this relationship is calibrated using a global dataset of 16 modern earthquakes and six paleoearthquakes, including events on highangle normal faults and low-angle thrusts, and provides a good fit to the global dataset. For blind fault structures, the relationship is validated by comparing pre- and postearthquake surface deformation associated with the 2011 Tohoku-oki earthquake along blind fault structure in the coastal zone of shallow seismic-reflection data collected offarea can be measured, both on land and off shore, enabling the extension of earthquake catalogs beyond the limits of modern records. By filling gaps in seismic records, this method improves seismic and tsunami hazard assessments, refines recurrence rates and worstcase scenarios, and supports more effective preparedness and mitigation.

The Neogene intracontinental deformation pattern in the northern Tibetan Plateau (NTP) remains a topic of active debate, particularly concerning the tectonic interplay between the large-scale strike-slip Altyn Tagh fault zone (ATF) and the Qilian Shan thrust system. To clarify the timing and mechanisms of this interaction, we conducted an integrated analysis of Neogene sediments from the Hongyazi intermontane basin, which is influenced by both the left-lateral strike-slip motion along the ATF and the northeast-directed crustal shortening associated with the Qilian Shan. A high-resolution magnetostratigraphic framework spanning 17.76-8.69 Ma was established, constrained by a calcite U-Pb age and biostratigraphic data. Lithology, gravel composition, and detrital zircon U-Pb age distributions collectively record a marked change at similar to 12.4 Ma, revealing a shift in sediment provenance linked to rapid uplift of the Danghenan Shan. Notably, paleomagnetic data indicate that vertical-axis rotations of the Hongyazi Basin and other basins adjacent to the western Qilian Shan thrust belts reversed from clockwise to counterclockwise at the same time, coinciding with a progressive slowing of the rotation of basins adjacent to the western ATF. The synchronicity between this rotational reversal and accelerated deformation in the Qilian Shan signals a major tectonic reorganization across the NTP, driven by the coupled effects of ATF shearing and crustal shortening within the Qilian Shan. Thereafter, the strain-accommodating role of the ATF progressively weakened, and the India-Eurasia convergence was increasingly absorbed by broadly distributed crustal shortening across the NTP. This shift marked a fundamental tectonic transition in the Neogene northward growth of the plateau, from boundary-parallel strike-slip faulting to internally distributed, continuous deformation.

Abstract Following the end‐Permian mass extinction, the Middle Triassic Anisian Stage was still characterized by environmental perturbations that hindered biological flourishing, yet it remains uncertain whether these persistent Tethyan disturbances were coupled with the closure of the Paleo‐Tethys Ocean. This study presents a high‐resolution integrated analysis of the Anisian Pha Kan Formation in the Lampang Basin, Southeast Asia, combining zircon U–Pb geochronology, chemostratigraphy, and magnetic susceptibility. We established a floating astronomical time scale (ATS) tuned to 405‐kyr long eccentricity cycles anchored by a high‐precision U–Pb age of 244.24 ± 0.78 Ma. The results reveal two distinct environmental regimes. The early Anisian period was characterized by intense regional volcanism coupled with sharp negative carbon and oxygen isotope excursions, indicating volcanic activity‐driven climate instability. Subsequently, the Pelsonian substage records the Pelsonian Negative Carbon Isotope Excursion (PENCIE). Our high‐resolution analysis reveals that this carbon cycle perturbation is precisely coupled with a significant sedimentary shift at ∼244 Ma, marked by enhanced sedimentary noise and a synchronous rise in magnetic susceptibility (MS) and frequency‐dependent MS. We interpret this synchronous transition as a tectonically driven forced regression and enhanced terrigenous input from pedogenically mature soils. The timing of this uplift event provides critical constraints on the assembly of Southeast Asia, supporting a Middle Triassic collision between the Sibumasu and Indochina terranes. Collectively, these findings suggest that sustained environmental perturbations driven by the coupling of arc volcanism and orogenic uplift hindered ecosystem recovery throughout the Middle Triassic, challenging the paradigm of Anisian environmental stability.

The southeastern margin of the Tibetan Plateau lies within the oblique convergence zone of the India-Eurasia collision. Since the Cenozoic, this region has experienced intense crust-mantle interactions, active tectono-magmatic processes, and complex focal mechanisms, reflecting a crustal structure with pronounced vertical layering and lateral segmentation. To better understand the regional stress regime and fault activity, we compiled a comprehensive database of focal mechanism solutions for the southeastern Tibetan Plateau. We collected and integrated earthquake data from 1950 to 2023 across the Sichuan-Yunnan region and adjacent areas. After data cleaning and integration, a database of 9902 high-quality focal mechanism solutions was established. Using a damped stress inversion method, we derived regional stress field models on 1°×1° and 0.2°×0.2° grids. The results reveal that: (1) focal mechanism types exhibit significant spatial heterogeneity; strike-slip events dominate the region, thrust events concentrate along the Longmenshan fault zone, and normal faulting prevails along the western boundary of the Sichuan-Yunnan block. (2) The large-scale stress field shows a systematic clockwise rotation of the maximum compressive stress axis (σ1) from north to south, consistent with the far-field effect of the ongoing India-Eurasia collision. (3) The high-resolution results reveal multi-scale stress variations, with strong horizontal continuity of σ1 across the plateau, supporting a long-term stable compressional regime. In contrast, higher three-dimensional complexity occurs along the block boundaries and southern Yunnan, particularly across the Lijiang-Xiaojinhe fault, where a clear north-south stress gradient is observed. This study provides the first systematic stress field characterization based on a unified focal mechanism database for the southeastern Tibetan Plateau, offering refined constraints on crustal deformation and insights into the geodynamic processes governing continental earthquake generation.

On March 19,1962,the Xinfengjiang Reservoir in Heyuan City,Guangdong Province,induced an M6.1 earthquake as it approached its first full-capacity impoundment peak.This event stands as one of the largest reservoir-induced earthquakes recorded in China and one of the few globally exceeding magnitude 6.Since this mainshock,moderate and small earthquakes have persisted within the reservoir area,characterized by high fre-quency and widespread distribution.The seismogenic mechanism remains unclear due to the complex geological structure of the reservoir area,featuring intersecting faults and well-developed joints and fractures.While most exi-sting research focuses on earthquakes with M≥4.0,systematic studies on M3-4 events are still lacking.To reveal the primary seismogenic structures and the complex genesis mechanism of reservoir earthquakes in this region,this paper conducts a systematic study on source parameters of moderate and small earthquakes occurring between 2008 and 2023. We employed the double-difference earthquake relocation method to relocate events of M≥1.0.The Cut and Paste(CAP)method was applied to invert for focal mechanism solutions and source depths of events with M≥3.0.Additionally,we obtained the regional stress field with the damped regional-scale stress tensor inversion method.Furthermore,to overcome the ambiguity of the two nodal planes in focal mechanism solutions and identify the true causative fault,rupture directivity parameters for events of M≥3.0 were inverted using the source time-frequency signature method. The results indicate distinct spatial heterogeneity in the seismicity of the Xinfengjiang Reservoir area,with the overall seismogenic structures exhibiting a NW-SE trend.Current earthquake types near Xichang Town and Yukeng Village are predominantly strike-slip,while the dam area is dominated by normal faulting.The overall stress field in the reservoir area aligns with that of South China,characterized by a NW-SE oriented maximum prin-cipal compressive stress(σ1).However,local stress field variations exist,showing an approximately 10° clockwise rotation in the orientations of the maximum and minimum principal stresses from south to north.The R-values are approximately 0.26 and 0.22 near Xichang Town,0.32 near Yukeng Village,and 0.1 and 0.06 in the dam area,in-dicating a regional stress state biased towards extension,which is more pronounced near the dam. Combined with the analysis of rupture directivity parameters,it is revealed that the Xichang seismic zone con-tains two intersecting faults at approximately 10 km depth-a NW-trending dextral strike-slip fault and a NEE-trending sinistral strike-slip fault;the Yukeng Village area features a pre-existing NNW-trending sinistral strike-slip fault at 8-10 km depth;the Laohuilong Village area exhibits a NW-trending fracture at about 5 km depth;the north-ern dam area is characterized by a NW-trending strike-slip fault at～10 km depth intersecting with the Renzishi Fault;the southern dam area contains a WNW-trending strike-slip fault at 6-10 km depth;the southeastern dam area presents a NEE-trending sinistral strike-slip fault at～10 km depth intersecting with the Heyuan Fault.Compre-hensive research indicates that current seismic activities in the Xinfengjiang Reservoir area are jointly influenced by regional tectonic background and long-term reservoir impoundment,leading to reactivation or kinematic transform-ation of pre-existing faults,thereby triggering frequent small earthquake swarms.These findings provide important seismological evidence for understanding the mechanisms of reservoir-induced seismicity and assessing regional seismic hazards.

SUMMARY Continental intraplate regions exhibit slow deformation yet host destructive earthquakes, posing fundamental questions about strain partitioning far from plate boundaries. Here we combine a refined Global Navigation Satellite System (GNSS) velocity field and elastic block modelling to investigate the Datong basin-range system in North China, a key intraplate deformation zone at the intersection of major fault systems and Quaternary volcanism. We find that left-lateral shear (~2 mm yr−1) and NW–SE extension (~1 mm yr−1) are accommodated across multiple faults and coherent block rotations, indicating broadly distributed deformation rather than localization on a single structure. Integration with mantle tomography reveals a low-velocity anomaly beneath Datong, suggesting that upwelling-driven thermal weakening augments far-field stresses from India–Asia collision and Pacific plate rollback. This deep–shallow coupling implies non-negligible seismic hazard and highlights the role of mantle dynamics in intraplate deformation.

[Objective]The Tianshan is an intracontinental orogenic belt reactivated in the Cenozoic by far-field effects of the India-Asia collision.Its Cenozoic tectonic evolution is thus key to understanding intracontinental deformation mechanisms.[Methods]Based on stratigraphic sedimentary characteristics and provenance tracing of a section on the northern margin of the Turpan Basin(south of the Bogda Shan),the Late Cretaceous to Cenozoic tectonic and geomorphic evolution of the East Tianshan and its adjacent region has been constrained.[Results]Field investigations reveal that the Paleocene and lower Oligocene strata in this area consist predominantly of red mudstones,indicating a lacustrine environment and stable tectonic conditions.The uppermost Cretaceous and Eocene strata contain relatively thin conglomerate deposits with small clast diameters,suggesting slight tectonic uplift of the Bogda Shan.In contrast,the upper Oligocene to Pliocene strata are composed of extremely thick,coarse conglomerates,reflecting long-term and intense tectonic activity.Detrital zircon U-Pb ages show that,from the Late Cretaceous to the Oligocene,the northern Turpan Basin continuously received detrital material from the West Tianshan,implying low topographic relief of the Bogda Shan during this period.Since the Miocene,however,the Bogda Shan has become the primary sediment source,indicating its rapid tectonic uplift.[Conclusions]In summary,the Bogda Shan remained tectonically stable with low relief during the Late Cretaceous to Oligocene.Since the late Oligocene,it has undergone intense deformation and rapid uplift,becoming the sole provenance area for the northern Turpan Basin.[Significance]This study refines the Cenozoic tectono-geomorphic evolution of the East Tianshan,thereby contributing to a better understanding of the intracontinental deformation processes resulting from the India-Asia collision.

The southeastern Tibetan Plateau, an intracontinental deformation archetype recording oblique Indian-Eurasian convergence, has long been used to test geodynamic models of plateau growth. Driven by India's northward indentation, it has undergone multiphase deformation with kinematic and structural transitions. To explore its evolutionary dynamics, we developed 3D visco-elasto-plastic thermomechanical models reconstructing three tectonic stages: (i) crustal shortening; (ii) block lateral extrusion; and (iii) kinematic reversal in the southeastern Tibetan Plateau. Simulations show that strain localization along large-scale shear zones is initially controlled by lithospheric heterogeneities enabling rigid block extrusion. Since the mid-late Miocene, vertically stratified crustal rheology has promoted decoupling, in which potential energy-driven ductile lower crustal flow affects upper crustal deformation and triggers kinematic reversal. This transition reconciles block extrusion and lower crustal flow, which operate sequentially rather than exclusively and are modulated by temporal variations in crustal rheology and boundary conditions, resolving the long-lasting debate of geodynamics during continental collision.

Several continental-scale strike-slip faults in the southeastern Tibetan Plateau developed during the Cenozoic eastward growth of the plateau. However, geodynamic mechanisms driving plateau growth and their relationship to intracontinental deformation remain poorly resolved, primarily because the brittle deformation histories of major fault systems-such as the >1000-km-long Xianshuihe-Xiaojiang (XSH-XJ) fault system-are inadequately constrained and difficult to reconstruct. To address this gap, we performed thermochronological analyses of samples from the highest mountains (i.e., Jiaozi Shan and Dahaicao Shan) flanking the XJ segment of the fault system, including apatite (U-Th)/He, apatite fission track, and zircon (U-Th)/He dating, complemented by thermal history modeling. Results reveal differential exhumation and cooling across the XJ fault between ca. 26 Ma and 22 Ma, with greater cooling in the Jiaozi Shan (30-50 degrees C) than the Dahaicao Shan (<5 degrees C), implying an exhumation offset of 1-2 km. Since ca. 13 Ma, rapid cooling (50-70 degrees C) has occurred synchronously on both sides of the XJ fault, corresponding to similar to 2 km of accelerated exhumation. Together with structural analyses, it is interpreted that the two phases of exhumation and cooling were kinematically linked to a transition of deformation from late Oligocene east-vergent thrusting to late Miocene left-slip faulting. Integrating structural and geophysical data along the XSH-XJ fault system, we propose that the Oligocene shortening caused crustal thickening and in situ anatexis. These processes produced thermally and mechanically weakened lower crust, facilitating the late Miocene initiation of left-lateral slip. Our work highlights a dynamic linkage between the two phases of deformation, providing new insights into how kinematic inversions of major faults operate in the southeastern Tibetan Plateau.

The persistence of mountainous topography in tectonically quiescent settings remains one of the outstanding questions in geomorphology. Along the northern passive continental margin of the South China Sea (SCS), although topography is expected to be entirely eroded under a theoretical relief-decay threshold of ca 1 cm/kyr, mountainous terrain has persisted since the Oligocene without significant tectonic uplift. This long-term persistence of topography is attributed either to the preservation of relict features under subdued erosion rates or to a dynamic equilibrium between rock uplift and spatially variable erosion. Distinguishing between these two scenarios remains difficult due to a lack of multi-domains erosion rate constraints across the mountainous interior. In this study, we address this issue by utilizing four in-situ cosmogenic 10Be depth profiles to quantify erosion rates across representative geomorphic domains along the northern coast of the SCS, specifically flat-top surfaces, bare-rock and regolith-mantled hillslopes, and pediment platforms. We evaluate three numerical inversion models, including steady-state erosion, continuous exposure, and abrupt mass loss, using chisquare statistics, solution stability, and field observations. The optimal solutions show that erosion rates exceed the relief-decay threshold on regolith-mantled hillslopes (ca. 8.12 cm/kyr) and pediment platforms (ca. 3.38 cm/ kyr), match the threshold on flat-top surfaces (ca. 1.1 cm/kyr) and fall below it on bare-rock hillslopes (ca. 0.73 cm/kyr). These results demonstrate that erosion rates across the geomorphic domains exhibit pronounced spatial variability, with the majority of these geomorphic domains actively eroding at rates above the theoretical reliefdecay threshold. The above-threshold erosion, combined with the order-of-magnitude convergence among catchment-wide erosion rates, thermochronology-based erosion rates, and theoretical isostatic rock uplift rates, demonstrates that a dynamic equilibrium between rock uplift and spatially variable erosion is more likely to drive the long-term persistence of mountainous topography along the northern passive continental margin of the SCS.

The modern drainage network of eastern Tibet is widely believed to have developed through a series of river capture and flow reversal events; however, the timing and mechanisms driving this reorganization remain contentious. Among these events, the river capture that formed the First Bend of the Yangtze River (YFB) stands out as both iconic and particularly debated. Here we present sedimentary provenance data from the Late Miocene-Quaternary Dali Basin, located south of the YFB, which indicate that a southward-flowing Jinsha River (i.e., the present-day upper Yangtze River) sourced sediment to the Dali basin at similar to 7.4-6.4 Ma in a drainage configuration different from that of today. Because this interval postdates the initial establishment of a near-modern Jinsha River system prior to the Miocene, our results imply at least two discrete fluvial reorganizations occurred at the YFB-one preceding similar to 7.4 Ma and another following similar to 6.4 Ma. By integrating these findings with landscape evolution modeling, we infer that the initiation of rapid uplift of the Yulong-Haba Mountains and the Diancang Shan may have been responsible for these drainage reorganizations. These results underscore that Cenozoic drainage systems on the eastern Tibetan Plateau have evolved dynamically on a short timescale of similar to 10(5)-10(6)-year, rather than remaining in a long-term stationary configuration on similar to 10(7)-year timescales.

[Objective]Tectonic vergence records the geometric asymmetry and kinematic directionality of shortening during orogenic thickening and provides a key link between surface deformation and lithospheric-scale geodynamics.Although vergence is widely used in structural geology,its expression at the scale of entire orogenic belts remains insufficiently clarified,especially in intracontinental settings where stable plate-boundary subduction is absent.This study aims to compare vergence patterns from plate-margin orogens to intracontinental mountain belts and to identify the mechanisms controlling their formation,maintenance,weakening,and transformation.[Methods]We synthesize five representative orogenic systems:the Central Andes,Taiwan,the Alps,the Qilian Shan,and the Tian Shan.Surface structural styles,fold-thrust belt geometry,orogen-foreland basin coupling,geomorphic evolution,modern crustal deformation,seismicity,and lithospheric architecture—constrained by Moho/LAB geometry and geophysical imaging—are integrated to evaluate vergence at multiple scales.[Results]Plate-margin convergent systems commonly develop stable one-sided tectonic vergence.In the Central Andes,long-lived subduction of the Nazca slab provides persistent asymmetric forcing,causing shortening to be localized above the subduction interface and transmitted eastward toward the retroarc and foreland.The Altiplano Plateau,with crustal thickness locally reaching 60-75 km,records progressive Cenozoic crustal thickening,uplift,and eastward propagation of deformation.Taiwan,as a young arc-continent collision system,locally records early-stage bidirectional deformation around the Central Range and arc-side backthrusting near the Longitudinal Valley-Coastal Range system.However,foreland basin evolution,westward migration of the frontal fold-thrust belt,and modern shortening concentrated along the western Taiwan thrust system indicate that its long-term,orogen-scale,dominant vergence remains west-directed.The Alps demonstrate that tectonic vergence is time-dependent.During early subduction and continental collision,deformation was localized along a single subduction interface,producing a north-vergent simple-shear-dominated architecture.After collision,slab break-off,eclogitization of the orogenic root,and thermomechanical reorganization weakened the earlier interface-controlled deformation and promoted strain redistribution across both flanks of the orogen,leading to paired north-and south-vergent thrust systems and a more symmetric collisional structure.In intracontinental orogens,stable one-sided vergence is not guaranteed.The Qilian Shan and Tian Shan lack compelling evidence for a continuous,long-lived,single-sided lithospheric subduction interface.Their deformation is mainly expressed by distributed crustal thickening,high-angle reverse faulting on opposing flanks,and near-symmetric shortening.Recent studies from the Qilian Shan further show that lithospheric-scale tectonic wedges may develop along basin-mountain transition zones,where relatively rigid basin lithosphere wedges into the weakened lower crust of a thickened orogen.Such wedge structures are best interpreted as local expressions within a pure-shear,vertically coherent deformation framework rather than as large-scale simple-shear intracontinental subduction.[Conclusions]Lithospheric-scale tectonic vergence is controlled by the coupling among boundary conditions,negative-buoyancy forcing,and lithospheric strength-buoyancy structure.Persistent single-sided slabs or effective negative-buoyancy sources favor stable simple-shear vergence,whereas slab break-off,loss of one-sided forcing,and mechanically strong opposing blocks favor distributed pure-shear thickening and weak or near-symmetric vergence.[Significance]This study provides a unified framework for interpreting tectonic vergence from plate margins to continental interiors.It highlights vergence as a geometrically testable indicator for linking surface deformation,basin-orogen coupling,and lithospheric-scale geodynamic processes.

The southeastern Tibetan Plateau hosts several of the world's largest rivers, such as the Yangtze, Mekong, and Salween, which are proposed to have formed by early Cenozoic breakup of a Mississippi-like paleo-Red River. The model predicts that the modern Red River, which flows along the Ailaoshan-Red River Shear Zone (ASRRSZ) and eventually into the Song Hong-Yinggehai Basin (SHYGB), extended northward to involve the upper Yangtze, Mekong, and Salween Rivers in the past. To test model, this study reconstructs the Cenozoic exhumation history of the SHYGB's proximal sources using thermochronological datasets, and compares it with the sedimentation records. Results reveal that since the late Eocene, the Red River supplied similar to 84 % of the sediment in the SHYGB, with the remainder from Hainan Island to the east and central Vietnam to the west. The volumetric comparability contradicts the paleo-Red River model. We show that deep exhumation along the ASRRSZ dominated sediment 'source-to-sink' transport pattern of the Red River drainage basin.

The emergence of high topography in eastern Tibet is a critical expression of the eastward expansion of the Tibetan Plateau. However, both the timing and underlying mechanisms of this surface uplift remain incompletely understood and subject to ongoing debate. Sedimentary basin fills, as direct products of surface erosion, offer valuable archives for reconstructing paleo-landscapes and tracking topographic evolution. In this study, we present new detrital zircon UPb and apatite fission-track data from non-marine Cenozoic strata of the Shiqu Basin—an isolated intermontane basin situated within the interior of eastern Tibet—to constrain depositional age and sediment provenance. Our data indicate that basin deposition occurred primarily during the Eocene to Early Oligocene, with sediments sourced predominantly from the southeastern Songpan-Ganzi terrane. Integration with regional bedrock thermochronology and stratigraphic records from coeval basins in the southeastern Tibetan Plateau suggest that the development of significant topography in eastern Tibet had already initiated by the Eocene. By the Late Eocene to Early Oligocene, this region had likely evolved into a high-elevation, eastward-tilting landscape similar to that observed today. We infer that this phase of plateau growth was primarily driven by large-scale crustal shortening, potentially coupled with localized crustal flow.

Tsunamis are among the most devastating natural hazards, posing severe threats to human life and property in coastal regions across the globe. Volcanic tsunamis, although relatively infrequent, possess significant destructive potential and exhibit considerable uncertainty. Their triggering mechanisms are diverse and complex, encompassing volcanic earthquakes, flank instability, underwater explosions, pyroclastic flows and atmospheric pressure waves. In recent years, high-impact events such as the 2018 Anak Krakatau tsunami in Indonesia and the 2022 Hunga Tonga-Hunga Ha’apai eruption have drawn global attention and stimulated rapid advances in volcanic tsunami research. However, compared with earthquake or landslide generated tsunamis, the causative processes of volcanic tsunamis remain insufficiently understood, and current hazard assessment methods lag behind. This knowledge gap is particularly significant in volcanically active regions such as the South China Sea (SCS) and its surrounding regions, where potential risks remain poorly evaluated. In this study, we systematically review historical volcanic tsunamis worldwide, analyze their spatial-temporal distribution patterns and relationships with tectonic settings, and highlight the spatial distribution and triggering mechanisms of potential tsunami sources in the SCS. We further summarize recent progress in deterministic and probabilistic hazard assessment approaches and evaluate the current applications and limitations of numerical simulation techniques. Finally, we outline key research priorities for the SCS and its surrounding regions, encompassing real-time volcanic monitoring, numerical modeling, interdisciplinary integration, and tsunami early-warning system development, aiming to provide a scientific foundation for regional disaster-risk mitigation.

Quantifying fault frictional properties is fundamental to understanding slip behavior and seismic hazard. We analyze 2 years of Sentinel-1 SAR data following the 2023 Turkey earthquake doublet using Independent Component Analysis-enhanced Small Baseline Subset-InSAR, to resolve postseismic deformation and invert for afterslip on the East Anatolian and & Ccedil;ardak faults. Within a rate-and-state framework, we estimate the friction parameter in postseismically stable regions (R- 2 > 0.9), showing that afterslip dominantly occurs in high velocity-strengthening regions, whereas coseismic rupture and aftershocks cluster near low zones or adjacent unstable patches. Depth-dependent slip partitioning indicates a brittle-ductile transition modulated by frictional heterogeneity, and eastward migration of deep afterslip and segmentation of slip behavior highlight postseismic deformation complexity. Elevated values on the P & uuml;t & uuml;rge segment indicate rupture propagation was limited by velocity-strengthening regions. These results suggest that frictional heterogeneity likely governs slip partitioning and provide quantitative constraints for seismic hazard assessment in continental fault systems.

The Indochina block is one of the major blocks separating the northern and southern branches of the east Paleo-Tethys Ocean. Paleomagnetic studies on the late Paleozoic drift history of the Indochina block are crucial for quantitatively constraining the evolution of the east Paleo-Tethys Ocean. In this study, we conducted paleomagnetic analyses on the Wusu basalts in the Simao Basin (southwestern Yunnan Province, China), located in the northern part of the Indochina block. Paleomagnetic analysis of the Wusu basalts reveals a clockwise rotation in remanent magnetization directions. We interpret this observed rotational pattern as the tectonic result of bookshelf faulting within a dextral intra-arc shear zone, which was active during the oblique subduction of the east Paleo-Tethys Ocean. Paleomagnetic analysis passed an inclination-only fold test, indicating a paleolatitude of 14.2 degrees S +/- 3.2 degrees for the sampling area (23.3 degrees N, 101.6 degrees E) during the Early Permian (287 +/- 5 Ma). This new paleolatitude, combined with existing data, confirms a three-phase drift history for the Indochina and North Qiangtang blocks. They initially drifted northward slowly from the Late Carboniferous to the Early Permian, then remained relatively stable during the Early to Middle Permian, and underwent accelerated northward drift after the Middle Permian. Based on paleomagnetic analyses and regional magmatic records, we propose that the opposing subduction of the southern and northern branches of the east Paleo-Tethys Ocean during the Early to Middle Permian may have contributed to this period of relative stability.

The Qilian Shan is one of the most active and youngest intraplate orogenic belts in the Tibetan Plateau, its formation and uplift mechanisms can provide critical constraints for understanding the recent evolution of the plateau. However, the detailed uplift of the Qilian Shan remains debated. In this study, we deployed a 640 km long profile with short-period seismometers spacing of 1 km across the eastern Qilian Shan, and delineated the high-resolution crustal interfaces and velocity structures with receiver functions and joint inversion methods. The results reveal that the Moho along the entire profile continuously varies without any obvious offset. Combined with the high-angle fault contact between the basin and mountain constrained by surface geology and microseismic localization, we propose that the uplift of the eastern Qilian Shan is mainly characterized by pure shear deformation, rather than the simple shear deformation that might be induced by the subduction of the Asian lithosphere. Crustal thickening in the eastern Qilian Shan shows different segmentation characteristics: the lower crust is dominantly thickened in the North and South Qilian, while the upper crust is thickened in the Central Qilian. A weak layer at the base of the upper crust mediates the differential crustal thickening. The total shortening in the upper crust is approximately equivalent to that in the lower crust across the eastern Qilian Shan. Therefore, from the perspective of the entire orogenic belt, the crustal deformation is incomplete mechanical decoupling and remains a continuous deformation model.

Although passive continental margins have long been regarded as low seismicity and with limited tsunamigenic potential, historical records reveal that active faults within these tectonic settings can, in fact, generate tsunamis. Firstly, this study evaluates the tsunamigenic potential of the Qiongdongnan segment of the Continental Slope Fault Zone (QDN-CSFZ), a newly identified intraplate fault in the northern South China Sea (SCS). We constructed 280 earthquake scenarios (Mw 6.6–8.0) with different source mechanisms and incorporated a stochastic source model to capture heterogeneous rupture patterns. Our simulations reveal that tsunami wave propagation is governed by regional bathymetry, causing waves to travel mainly perpendicular to the fault strike and rapidly across deep basins toward the Xisha Islands. Earthquakes above Mw 7.4 on the QDN-CSFZ generate regionally significant tsunamis. Under the extreme Mw 8.0 scenario, maximum tsunami wave amplitudes could be >7 m at the Qiongdongnan, >6 m at the Xisha Islands, and >5 m at the Vietnam Coast. The QDN-CSFZ constitutes a “multi-mechanism, short-lead-time” near-field tsunami threat, which is fundamentally distinct from the “high-potential, long-lead-time” far-field threat associated with the Manila Subduction Zone. This study underscores the need for a paradigm shift in tsunami assessment and for developing tailored near-field warning systems in the northern SCS.