The Qilian Shan-Hexi Corridor forms the northeastern frontal zone of Tibetan Plateau expansion, where multiple active tectonic processes generate a complex tectono-geomorphic pattern. Within the corridor, NE-striking frontal thrust-nappe systems, including the Gulang, Yumu Shan, and Jiayuguan-Wenshu Shan nappes, coexist with the southwest-vergent Dahuang Shan back-thrust nappes, whose frontal boundary is the Minle-Yongchang Fault (MYF). Despite its tectonic importance, the geometry, Late Quaternary activity, and geomorphic expression of the MYF remain insufficiently constrained. This study integrates channel steepness index (ksn) analysis based on a 30 m DEM, field investigations, dating of offset geomorphic surfaces, and geomorphic mapping using highresolution satellite imagery and UAV photogrammetry, including fault trace identification and river terrace delineation, to assess the segmental back-thrusting behavior of the MYF and its underlying mechanisms. Our analyses identify three segments: Yongchang (YC), Dahuang Shan (DH), and Yonggu (YG) from east to west. The YC segment shows no clear geomorphic evidence of Late Quaternary tectonic activity, whereas the central DH segment is the most active, exhibiting strong relief and newly documented evidence of sustained Late Quaternary reverse faulting. The YG segment is a Holocene-active blind thrust-fold belt, with a vertical slip rate of 0.21 +/- 0.05 mm/yr. The ksn variations correspond closely to geomorphic responses, emphasizing clear segmentation. Fault-scarp measurements yield a vertical slip rate of 0.85 +/- 0.08 mm/yr for the DH segment, significantly higher than those of the YG and YC segments. The MYF likely represents a back-thrust generated by compression of the Qilian Block against the Alxa Block. The three segments show a systematic westward propagation and younging of tectono-geomorphic development, providing new constraints on deformation accommodation within the Hexi Corridor.

The continuous extrusion and expansion of the Tibetan Plateau toward the northeast have led to intense crustal shortening and left-lateral shearing in the Qilian Shan region. The Qilian-Haiyuan fault zone, a major block-boundary fault in the region, is the subject of considerable debate regarding the intensity of extrusion and thrusting, as well as the onset time and maximum displacement of left-lateral strike-slip motion. This study focuses on the Laohushan fault within the central-eastern segment of the Qilian-Haiyuan fault zone. Through geological mapping, stratigraphic correlation, and cosmogenic nuclide burial dating, we established a chronological framework for the Cenozoic strata. The provenance characteristics, such as paleocurrent directions and heavy mineral assemblages, suggest that the Pliocene strata on both sides originated from the same paleodrainage system. The conclusions suggest that the maximum strikeslip displacement of the Miocene strata is 15.2 +/- 0.7 km. Based on the late Quaternary slip rate of 4.5 +/- 1.0 mm/yr, the onset time of strike-slip activity is estimated to be 3.4 Ma. The base of the growth fold suggests that the onset of early compressional thrusting occurred earlier than 7.8 Ma. The Qilian-Haiyuan fault zone underwent two main evolutionary stages. During the middle Miocene (13-8 Ma), thrusting activities exhibited a west-to-east propagation pattern. During the Pliocene (5-2.5 Ma), it transitioned to predominantly strike-slip activity. The northeastward compressive expansion of the Tibetan Plateau may also be accommodated by a cyclic mechanism involving the alternating conversion of thrust and strike-slip faults, while simultaneously generating new thrust faults propagating forward.

The Tuolaishan fault, located in the mid-western segment of the Qilian-Haiyuan fault on the northeastern Tibetan Plateau, represents a key tectonic belt at the leading edge of plateau expansion. However, previous studies lack slip-rate constraints on this fault, hampering a comprehensive understanding of faulting behavior along the entire zone. Here, we integrate high-resolution UAV photogrammetry, field geological and geomorphological surveys, and multi-method chronological dating (OSL, ¹⁰Be, and ¹⁴C) to conduct detailed tectonic geomorphic analysis and displacement measurements on three typical sections (Daxigou, Zhalonggongma, and Binggou) of the Tuolaishan fault. Our results show that the Tuolaishan fault is a Holocene-active fault dominated by left-lateral strike-slip with a minor thrust component. The calculated late Quaternary horizontal slip rates decrease westward from ~4.47±0.28 mm/yr at Daxigou to ~3.97±0.31 mm/yr at Binggou, yielding an average of 4.0–4.5 mm/yr. This represents a reduction of 1.5 ~ 2 mm/yr compared to the adjacent Lenglongling fault segment. The Lenglongling fault bifurcates near Liuhuanggou into three branches with distinct kinematics: the Sunan-Qilian fault (strike-slip with thrust component), the North Tuoleshan fault (thrust-dominated), and the Tuolaishan fault (main strike-slip branch). Together, they accommodate the westward-propagating strain, with the Tuolaishan fault taking up the dominant strike-slip component while the other two branches absorb part of the slip and shortening strain, forming a semi-flower-structure system distinct from the asymmetric flower structure of the Lenglongling segment. Our high-precision quantitative data provide critical evidence for assessing regional seismic hazards and understanding the tectonic deformation processes along the northeastern of the Tibetan Plateau.

Drainage systems play an important role in shaping landforms, and studies of their evolutionary history reveal information about the impacts of tectonics and climate change on a landscape. In this paper, we study the Qinwangchuan (QWC) Basin, located in the northern part of the Longzhong Basin on the northeastern Tibetan Plateau. Based on chronology (cosmogenic nuclide burial dating and optically stimulated luminescence dating), provenance, and chi-map analysis, we investigate Quaternary fluvial sediments and terraces of the QWC Basin, the Jiangou River, and the adjacent Zhuanglang River, to understand regional fluvial evolution. Results show that large-scale fluvial activity in the QWC-Jiangou system began at similar to 1500 ka, and subsequently, regionally varied tectonic activity led to distinct landforms developing in different river reaches. Compression caused the development of depressions within the basin and the deposition of thick fluvial gravel-sand layers, while base level lowering induced by the downcutting of the Yellow River resulted in the formation of five successive terraces along the Jiangou River. Evidence suggests that the QWC-Jiangou system and Zhuanglang River evolved independently, and there was no large-scale abrupt capture of the Jinqiang River by the Zhuanglang River (as proposed in previous studies); however, chi-map analysis reveals that the Xijishui River and Longtan River gradually captured the upper reaches of the QWC Basin's drainage system. Both drainage reorganization and the stepwise aridification of central Asia resulted in the gradual shrinkage of rivers within the QWC Basin, and these had completely dried up by similar to 50 ka. Environmental degradation caused by the drying of the QWC Basin led to the short-distance transport of alluvial sand, resulting in localised sand dune accumulation south of the basin between 40 and 13 ka. This study highlights the need to integrate sedimentological, geomorphological, and tectonic evidence to reconstruct drainage evolution in the northeastern Tibetan Plateau, with full consideration of the joint impacts of tectonics and climate.

The Tibetan Plateau is one of the regions with the most active neotectonic movement and frequent seismic activity in the world. The Bayan Har Block, located in the Northern Tibetan Plateau, has been the main area for clusters of major earthquakes with M ⩾ 7 on the Chinese mainland in the past 28 years. The Kunzhong fault (KZF) is an important branch of the East Kunlun fault zone (EKF), which forms the northern boundary of the Bayan Har Block. The KZF is crucial for understanding regional tectonic evolution and seismic activity, but research on its Late Quaternary tectonic activity remains limited. On the basis of satellite image interpretation, field investigations, and high-resolution unmanned aerial vehicle photogrammetry, this study identifies an ∼40 km-long seismic surface rupture zone well preserved in the eastern segment of the KZF. The rupture zone is characterized by left-lateral dislocated small gullies, cracks and scarps, with a maximum co-seismic horizontal displacement of ∼2.9 ± 0.1 m. This earthquake’s magnitude is estimated to be M7.2 ± 0.2 according to the statistical relationships between parameters of strike-slip seismic surface rupture zone and magnitude. Based on the surface rupture characteristics, seismogenic faults, and historical seismic records, this earthquake may have been a clustered event occurring shortly before or after the 1937 Tuosuo Lake MS7.5 earthquake. Alternatively, it may also have been a joint earthquake involving the KZF and EKF that occurred simultaneously with the Tuosuo Lake earthquake. Combined with deep crustal magnetotelluric profiles, these findings suggest that the region between the KZF and EKF forms a diffuse transition boundary zone in the northern Bayan Har Block. In seismic risk assessments of active faults, greater attention should be given to clustered or joint rupture earthquakes occurring along both main block boundary faults and their branch faults.

The Qilian-Haiyuan fault is a boundary fault with strike slipping in the Qilian Shan (Shan means mountain or mountain range in Chinese) on the northeastern Tibetan Plateau. Several strong earthquakes (M >= 7) have occurred in this fault zone, and the risk of future major earthquakes is highly concerning. We identified a seismic surface rupture zone of unknown age at the Halahu fault, which is located at the western end of the Qilian- Haiyuan fault. The Halahu fault plays a crucial role in structural transformation at the westernmost point of the Qilian-Haiyuan fault zone, and historical seismic records are vital for assessing the future seismic risk associated with the fault. We found via field investigation that the existing length of the rupture zone is more than 24 km, which is characterized mainly by cracks, the offset of the trench, and the offset of terrace edges. Twenty-eight left-lateral coseismic offsets were determined using field measurements and UAV image analysis, with a minimum offset of 0.6+0.1 m and a maximum offset of 2.5+0.2 m. Historical earthquake records confirm that the surface rupture zone was caused by the M61/2 earthquake that occurred east of Hala Lake on July 14, 1930 east of Hala Lake; however, the magnitude of that earthquake should be revised to be approximately M63/4 on the basis of field survey data. Research has shown that major earthquakes have shifted from the Bayan Har active block to the Qinghai-Tibet block boundary fault zone. This study identified and dated earthquake surface rupture zones, offering essential guidance for future research and assessments of fault earthquake risk. Our results indicate that the Halahu, Tuolaishan, and Jinqianghe-Laohushan faults have high potential for strong future earthquakes.

[Objective]The early Cenozoic collision between the Indian and Eurasian plates triggered multi-stage uplift of the Tibetan Plateau,resulting in its remarkable landscapes and abundant mineral resources,while profoundly influencing climate,environment,and hazard evolution across Asia and beyond.The Tibetan Plateau and its surroundings have undergone intense tectonic activity and recurrent natural disasters,particularly earthquakes,which have significantly shaped its tectonic and geomorphic evolution.Seismic records indicate that more than half of the major earthquakes on the Chinese mainland and the surrounding regions occur within the plateau and its margins,controlled by the diverse types,scales,and distributions of active faults.[Methods]This study synthesizes decades of research on active faults and earthquake hazards across the Tibetan Plateau.It builds on the results of the Active Faults and Earthquake Hazards theme of the Second Tibetan Plateau Scientific Expedition and Research Program(STEP),which provided detailed documentation of major active fault zones.This study integrated current deformation fields,seismicity,and stress regimes to examine the seismotectonic settings associated with strong earthquakes across different regions of the plateau.Based on this analysis,the future seismic hazard potential of the plateau was further evaluated.[Conclusion]The image of active faults on the Tibetan Plateau indicates that different regions comprise fault systems with diverse scales,kinematics,and activity patterns.The tectonic settings associated with strong earthquakes have evolved through prolonged,multi-stage deformation,progressively establishing the present seismotectonic framework governing the nucleation and occurrence of large earthquakes.Current patterns of crustal deformation reveal northeastward deceleration with limited eastward extrusion of crustal blocks.Stress regimes,in contrast,are characterized by shear-extension in the interior and compression along the margins.Seismic hazard trends inferred from active tectonics and crustal deformation suggest a distinct segmented zonal pattern of strong earthquake activity,with plateau margins and fault-dense interiors representing the primary loci of future large earthquakes.Additionally,tectonic and geomorphic boundary zones demonstrate an increased likelihood for strong seismic events.

The North Tuole Shan Fault (NTF) is a significant thrust fault system in the Qilian Mountains. Understanding its activity patterns and differential deformation characteristics is essential for deciphering regional tectonic uplift, crustal deformation mechanisms, and geomorphic evolution. However, the segmentation characteristics of this fault and their controlling factors remain poorly understood, hindering a comprehensive understanding of major fault evolution in the region. In this study, we extracted ksn values from 107 river channels along the northern slope of Tuole Shan in the central Qilian Mountains and compared them with previous findings on NTF activity. The results reveal a general consistency between fault activity variations and ksn distribution, indicating that ksn values serve as a reliable indicator for fault activity variations and their controlling factors. Further analysis suggests that ksn variations between the East and West Jingtie segments are predominantly governed by fault activity differences, with secondary influences from bedrock erosion resistance. Higher ksn values in the Qilian Segment are likely related to the transition of the Riyue Shan Fault (RYF) from dextral strike-slip motion to oblique thrusting at the fault tip. This transition intensifies tectonic loading, resulting in a simultaneous increase in ksn values and vertical slip rates. Existing studies on the strike-slip rate of the RYF, along with new analytical results, suggest that the angular variation involved in this kinematic transition is likely <= 30 degrees. This suggests that, in addition to faulting and lithology, lateral extrusion associated with strike-slip faulting may also play a significant role in controlling adjacent fault activity and shaping the tectonic landscape. These findings offer novel insights into the mechanisms regulating fault activity variations.

The Gonghe Basin, situated in the northeastern Tibetan Plateau, preserves multiple terrace levels formed by the Yellow River, which are critical for understanding the regional tectonic-climatic histories and integration processes of the Upper Yellow River. However, the chronology of these terraces- particularly the extensive First, Second, and Third Tala surfaces, which represent different stages of the basin's geomorphological and fluvial evolution-remains a subject of debate due to conflicting dating results spanning the Early Pleistocene to the Late Epipleistocene. This study addresses this geomorphic and chronological question by focusing on the Second Tala Surface, utilizing terrestrial in situ cosmogenic nuclide (TCN) and optically stimulated luminescence (OSL) dating methods to ascertain its formation age and the fluvial processes involved. Two 10Be profiles (samples STL01 and STL02) were strategically targeted at the leading and trailing edges of the Second Tala Surface. In addition, OSL samples were collected to account for the influence of loess cover on nuclide production. Our results reveal depositional cessation ages of 131.26 +/- 5.82 ka and 370.87 +/- 22.54 ka for STL01 and STL02, respectively. These chronological results suggest that the Yellow River had experienced significant lateral erosion and floodplain expansion prior to the formation of the Second Tala Surface. Regarding the younger age as the abandonment age of the Second Tala Surface, our results suggest that glacial-interglacial transitions and regional tectonic activities played a crucial role in the abandonment of the regional geomorphic surface. This research further provides new insights into the geomorphic evolution of the Upper Yellow River and highlights the dynamic interplay among tectonic deformation, climatic fluctuations, and fluvial reorganization in shaping the regional landscape.

River piracy, a dynamic process reshaping drainage networks, plays a pivotal role in landscape evolution, yet its timing and driving mechanisms in active orogens remain poorly constrained. This study focuses on the piracy between the Hongshuiba River and the Zhulongguan River in the northern Qilian Shan (Shan means "mountain" in Chinese), northeastern Tibetan Plateau, to resolve its chronology and geomorphic implications. Utilizing isochron 26Al/10Be burial dating of fluvial sediments from the abandoned water divide, we determine the piracy occurred at 0.79 +/- 0.24 Ma, marking the first radiometric age for such an event in this region. chi analyses reveal pre-piracy disequilibrium in the Zhulongguan River profile, attributed to an earlier piracy by the Beida River, which preconditioned the landscape for subsequent Hongshuiba-Zhulongguan piracy. Integrated results demonstrate that the Hongshuiba-Zhulongguan piracy was driven by tectonic uplift that amplified topographic gradients and the mid-Pleistocene climate transition, which enhanced erosional efficiency. These findings highlight the coupling between northward extension of the Qilian Shan and orbital-scale hydroclimatic variability in triggering threshold-driven drainage reorganization, offering insights into transient landscape responses in active orogens.

Accurately delineating the fine geometric structures of active faults and assessing their present-day activity are of paramount importance for studying regional fault tectonics and evaluating seismic risk. The West Qinling Fault (WQLF) is situated in a critical zone where material from the Tibetan Plateau is extruded towards the northeast, and the fine geometric structures, kinematic characteristics, and present-day activity of its eastern segment (Tianshui-Baoji segment) can provide important insights into the mechanisms of structural transition at the termination of strike-slip faults and the mode of material expansion in the plateau. In this study, the spatial distribution of the Tianshui-Baoji segment and the characteristics of present-day activity are systematically investigated through detailed interpretations of high-resolution satellite images, digital elevation models (DEMs), unmanned aerial vehicle (UAV) images, geological and geomorphological field surveys, and isotopic dating techniques. The results indicate that the Tianshui-Baoji segment, which begins as a single fault, gradually splays into multiple branching faults towards the east. Both the main fault and these branches have remained active since the Late Pleistocene and even during the Holocene, thus warranting attention to the seismic risk potential in the eastern segment of the WQLF, particularly at its termination. Moreover, the splay of the Tianshui-Baoji segment has led to the gradual divergence of the fault activity of the component to the east, reducing the maximum magnitude of seismic events at the fault terminus and resulting in significant differences in the seismic recurrence intervals between the eastern segment and the central segments of the WQLF (Zhangxian segment, Gangu-Wushan segment).

The evolution of the river systems in the Qilian Mountains is complex, shaped by a combination of factors, including tectonics, climate and lithology. While extensive research has been conducted on the regional tectonic evolution and surface processes, the evolution of internal drainage divides and trends in river system reorganization remain poorly understood. Under the influence of tectonic and climatic disturbances, drainage divides, as basin boundaries, continuously migrate, a process that can span tens of millions of years. Thus, the analysis of drainage divide stability provides new insights and constraints on understanding basin evolution mechanisms. This study evaluates the drainage divide stability of the Heihe River within the Qilian Mountains using the χ‐plot and the Gilbert method. The results indicate that drainage divide stability varies across different parts of the basin, with a general pattern of synchronous expansion and contraction of the transverse and longitudinal rivers. The study reveals that the evolution of the Heihe River Basin is primarily controlled by regional tectonic evolution in the orogenic belt, with comparatively minor influences from climate, lithology and local fault activity. The evolutionary patterns observed in the Heihe River Basin offer valuable insights into the competitive dynamics between transverse and longitudinal rivers within orogenic belts and provide a new perspective on drainage reorganization in tectonically active regions.

The 143 A.D. west Gangu earthquake is documented to have occurred in the West Qinling area, which is located on the northeastern margin of the Tibetan Plateau. Initial limited historical records suggest the earthquake took place along the West Qinling fault (WQLF) in the western region of Gangu County. However, the absence of corresponding geological and geomorphological evidence has posed a considerable challenge in accurately quantifying parameters such as the precise location, magnitude, and seismogenic fault segment in earlier investigations. In this study, a comprehensive examination of multiple residual surface rupture zones within the macroseismic zone of this earthquake enabled the determination of the seismogenic structure, magnitude, and rupture zone scale through diverse methodologies, which include field geological investigations, chronology testing, Unmanned Aerial Vehicle (UAV) aerial surveying, and interpretation of landslides along the fault zone. The results reveal that the seismogenic structure of this seismic event is associated with the Zhangxian fault segment of the WQLF, also marked by a dense distribution of large landslides from Zhangxian to Yuanyangzhen. The epicenter was identified at the eastern end of the Zhangxian fault segment of the WQLF. Furthermore, the magnitude of the 143 A.D. west Gangu earthquake is estimated to be approximately Ms 7–7.3, with the residual surface rupture zone intermittently extending over about 22 km and a maximum horizontal dislocation along the rupture zone of 2.8 ± 0.5 m. This detailed investigation contributes foundational insights for further evaluating the seismic risk across various segments of the WQLF.

On December 18,2023,an earthquake of MS6.2 occurred in Jishishan County,Gansu Province(102.79°E,35.70°N)with a focal depth of about 10 km.The earthquake was dominated by compressional thrusting with a small component of dextral strike-slip motion.According to the results of on-site emergency investigation,the epicenter of this earthquake was located on the East Jishishan fault(EJSSF),which is part of the southeastern segment of the North Lajishan fault zone(NLJSF).Near the epicenter,the EJSSF is composed of four secondary faults,including Jishixia fault(JSXF),Daduncun fault(DDCF),Zhaomuchuan fault(ZMCF),and Dahejia fault(DHJF),forming a relatively complex geometric pattern.Multiple tectonic fractures with two dominant directions and echelon fracture zones were formed along these secondary faults,and a small amount of centimeter-scale coseismic thrusting(dislocation value 2～4 cm)and right-lateral dislocation(dislocation value 3 cm)phenomena were formed along the DDCF,ZMCF and DHJF.Based on the results of previous small earthquake localization,it is concluded that the three secondary faults include the DDCF,ZMCF and DHJF of the EJSSF constitute the seismogenic structure of this earthquake.In fact,this is an earthquake event caused by the activity of secondary faults during the process of EJSSF expanding towards the interior of the Linxia Basin.Geological and geomorphic evidence indicates that the main fault(JSXF)has been active during the Holocene,the stress of the region may not be completely released by this earthquake,and the risk of larger earthquakes occurring in the future should be given sufficient attention.This earthquake also triggered a series of geological hazards and building damages such as different types of collapses,landslides,rolling rocks on slopes,liquefaction-mudflows and house damages,causing hundreds of casualties and severe economic losses.Through the investigation and analysis of the earthquake damage characteristics in different parts of the typical loess tableland in Dadun Village of the meizoseismal area,it was found that the earthquake caused severe collapse and damage to the old houses and walls built early on the upper part of the loess tableland,while causing multiple slope instability phenomena such as collapses,landslides,and surface tensile fissures of varying scales on the slope part of the middle of the tableland.The surface cracks and earthquake damage to houses in the lower part of the tableland were relatively minor.Considering that the site amplification effect of the upper part and slope of the loess tableland is one of the important reasons for the severe disasters caused by this earthquake,subsequent consideration should be given to the necessity of targeted earthquake-resistant fortifications for village houses and engineering construction on the loess tableland.

Abstract High‐resolution present‐day earth surface deformation maps from satellites provide important data constraints, which help us better understand tectonic processes and analyze seismic hazards. Here, we use Sentinel‐1 Radar images (2014–2020) and accurate positioning measurements (2009–2019) to get a high‐resolution three‐dimensional earth surface velocity map for the northeastern Tibetan Plateau, and we invert the slip rate and coupling ratio of major regional faults. We find ∼4 mm/yr uplift along an arc from the Qilianshan to Lajishan, relative to the neighboring low‐elevation area to the east, which indicates ongoing rapid orogeny. We find transient deformation along the Laohushan and 1920 M8.5 Haiyuan rupture segments of the Haiyuan fault, whereas the western Haiyuan, southern Liupanshan, central Lajishan and central‐western West Qinling faults are essentially locked above 15–20 km, suggesting a potentially high seismic hazard.

Objective On August 26, 2021, an Ms5.5 earthquake occurred in Aksai, Gansu Province. The epicenter is located along the southern piedmont of the Danghe Nan Shan. This event garnered significant attention because of its deformation characteristics and seismogenic mechanisms. Existing studies have mainly focused on emergency response and seismic activity analyses; however, there is a lack of research on tectonic deformation and seismic mechanisms. This study aimed to fill this gap by analyzing the deformation characteristics of the earthquake zone and revealing its seismogenic mechanism. Methods This study employed seismological methods combined with interferometric synthetic aperture radar (InSAR) technology to investigate the tectonic deformation and seismic mechanism of the 2021 Aksai Ms5.5 earthquake. Combining focal mechanism solutions, precise earthquake locations, and InSAR results, the seismogenic fault and its geometric and kinematic parameters were determined and validated through geological field surveys. Results This study applied joint inversion with both local and teleseismic waveforms (the generalized cut-and-paste joint, gCAPjoint) to source parameters. The fault solutions strike 315°, dip 41°, rake 81°, depth 6.9 km. We relocated the Aksai earthquake and its aftershocks using the hypoinverse and double-difference method (HypoDD), and accurate locations of 88 earthquakes were obtained. The 2021 Ms5.5 earthquake sequence in Aksai is distributed near the southern Danghe Nan Shan Fault, with a fault dip toward the NE. The co-seismic deformation field indicated by InSAR matched the macro-epicenter with the precise location results, confirming the reliability of the precise location. Both the ascending and descending orbit surface deformation fields showed uplift near the epicenter with similar magnitudes and signs in the line-of-sight direction, indicating that the earthquake rupture was mainly thrusting. Fault scarps near the epicenter along the southern piedmont of the Danghe Nan Shan were recognized in the field and satellite images. Combined data from focal mechanism solutions, precise earthquake locations, and InSAR coseismic deformation fields, along with field geological survey results, indicate that the seismogenic fault of this event was the southern Danghe Nan Shan Fault, with a strike of 315°, dip of 41°, and rake of 81°. Conclusion This study indicated that the seismogenic fault of this event was the southern Danghe Nan Shan Fault, which is a thrust fault. The fault solutions strike 315°, dip 41°, rake 81°, depth 6.9 km. Because of the northward extrusion thrust of the Qinghai-Xizang Block, the seismic activity in the northern part of the Qaidam Block has significantly increased. The future seismic risk of the eastern section of the Altyn Tagh Fault and western Qilian Shan should be emphasized. [ Significance ] This study provides new insights and methods for researching active tectonics. It holds significant scientific importance and innovation in understanding seismogenic mechanisms and structural transformation, as it helps to understand the mode and magnitude of slip transfer between the strike-slipping of the Altyn Tagh Fault and the shortening of the Qilian Shan and also contributes to a better evaluation of the seismic risk in this region.

Fault -offset landforms have long been recognized as holding important information about paleoseismic slip. Constructing an along -strike fault slip distribution could help reveal a fault's long-term rupture patterns and facilitate a more precise assessment of its future behavior. In this study, we documented the paleoseismic history of the Huangxianggou Fault, an oblique sinistral-thrust segment of the West Qingling Fault in the northeastern region of the Tibetan Plateau, using LiDAR-derived high -resolution DEM (0.1 m/pixel) and measurement of offset landforms. A total of 46 well-preserved and well -shaped landforms were chosen for horizontal and vertical displacement measurements, and the dense measurement data allow us to generate the cumulative offset probability distribution curves of horizontal and vertical displacements. Statistical analysis revealed at least seven surface -rupturing events, each with similar coseismic horizontal displacements of -7.0 m and vertical displacements of -0.7 m, in agreement with previous paleoseismic trench results. Using empirical relationships between moment magnitude and horizontal displacement, a plausible moment magnitude range of Mw7.3-7.7 was determined for these paleoearthquakes. Furthermore, by evaluating rupture parameters and fault slip rate, we determined a recurrence interval of 2.7-3.4 kyr for significant surface -rupturing events on this fault. The elapsed time since the last earthquake closely approaches this interval, suggesting a potential seismic risk for the Huangxianggou Fault. Our results emphasizes the importance of high -resolution topographic data in paleoseismic investigations, enabling the identification of numerous offset landforms and precise displacement measurements across faults. Paleoearthquake counts derived from horizontal and vertical displacement analyses were found to be consistent, highlighting the significance of vertical displacements in quantifying paleoearthquakes for strike -slip faults with a thrust component.

The Eastern Tianshan region, influenced by the far-field effect of northward compression and expansion of the Qinghai-Xizang block, features highly developed Late Quaternary active faults that exhibit significant neotectonic activity. Historically, the Barkol-Yiwu Basin, located to the north of the Eastern Tianshan, experienced two major earthquakes in 1842 and 1914, each with a magnitude of M71/2. In contrast, the Hami Basin on the southern margin of the Eastern Tianshan has no historical records of any major earthquakes, and its seismic potential, mechanisms, and future earthquake hazards remain unclear. Based on satellite image interpretation and field surveys, this study identified a relatively recent and well-preserved seismic surface rupture zone with good continuity in the Liushugou area of the western segment of the Northern Margin Fault of the Hami Basin (HMNF), which is the seismogenic structure responsible for the rupture. The surface rupture zone originates at Kekejin in the east, extends intermittently westward through Daipuseke Bulake and Liushugou, and terminates at Wuzun Bulake, with a total length of approximately 21 km. The rupture zone traverses the youngest geomorphic surface units, such as river beds or floodplains and first-order terraces (platforms), and is characterized by a series of single or multiple reverse fault scarps. The morphology of fault scarps is clear, presenting a light soil color with heights ranging from 0.15 m to 2.13 m and an average displacement of 0.56 m, suggesting that this surface rupture zone likely represents the most recent seismic event. Comparison with historical earthquake records in the Eastern Tianshan region suggests that the rupture zone may have been formed simultaneously with the Xiongkuer rupture zone by the 1842 M71/2 earthquake along the boundary faults on both sides of the Barkol Mountains, exhibiting a flower-like structural pattern. Alternatively, it might represent a separate, unrecorded seismic event occurring shortly after the 1842 earthquake. The estimated magnitude of the associated earthquake is about 6.6~6.9. Given that surface-rupturing earthquakes have already occurred in the western segment, the study indicates that the Erdaogou–Nanshankou section of the HMNF has surpassed the average recurrence interval for major earthquakes, indicating a potential future earthquake hazard.

The Qilian Mountains are situated on the northeastern margin of the Tibetan Plateau and serve as the leading edge of the plateau's northeastward expansion. The Menyuan Basin, characterized by typical basin landforms, provides valuable insights into the region's neotectonic activity and geomorphic evolution. As a representative mountain basin located in the central part of the Qilian Mountains, the Menyuan Basin's development pattern and geomorphic features are closely linked to tectonic activity. This study aims to investigate the variations in tectonic activity and their underlying causes along the north margin fault and different zones of the Menyuan Basin. To achieve this, 30 m resolution digital elevation model (DEM) data and ArcGIS spatial analysis technology were employed to extract the hypsometric integral (HI) and hypsometric integral curve (HC) of 15 rivers that traverse the northern edge of the basin. Subsequently, kriging interpolation was utilized to obtain the spatial distribution characteristics of HI within the basin. The findings reveal that HI values generally exhibit higher values on the western side and lower values on the eastern side of the Menyuan Basin, with the turning point (Laohugou) of the northern fault at the Menyuan Basin serving as the boundary. By combining the distribution of HI with field investigation results of active structures, it is observed that the eastern fault has extended into the basin's interior, giving rise to a series of active reverse fault–fold zones. This phenomenon may be attributed to changes in fault trends and the presence of northeastward faults. Additionally, a high HI anomaly is detected near Qingshizui Town in the basin's interior. Based on previous electromagnetic detection results, it is inferred that a buried fault exists within the basin. Furthermore, the study demonstrates that most rivers exhibit peak fluctuations in the stream length–gradient index (SL) at a specific position upstream of the main fault, indicating a strong correlation between the location of SL fluctuations and the position of the fault intersecting the river. In other words, tectonic activity can exert a significant influence on SL. Abnormal fluctuations near lithological transitions may suggest that local changes in lithology also impact the stream length-gradient index. The comprehensive analysis underscores the substantial differences in geomorphic development between the eastern and western sections of the northern edge of the Menyuan Basin, primarily controlled and influenced by the active structures in this region. Moreover, the aforementioned geomorphic parameters serve as sensitive indicators for evaluating tectonic activity.