Diffuse, active interplate and intraplate fault arrays are associated with various geotechnical hazards, especially earthquakes and co-seismic mass wasting. When tectonic loading is shared amongst multiple fault arrays, earthquake recurrence interval calculations and reliable hazard forecasts are particularly challenging. This applies to diffusely deforming continental settings (e.g., Central Asia, Alaska) and some oceanic settings (e.g., the Azores, Ninetyeast Ridge). Actively deforming regions of Central Asia north of Tibet cover an area of four million km2, approximately equal to the size of Europe. Geodetic data suggest that active deformation in Central Asia is the result of a dynamic stress state driven by the distant Indo-Eurasia collision, Asia’s retreating Pacific margin, and stored potential energy in northern Tibet. Lessons learned that apply to all regions of actively deforming lithosphere include the following: 1) Paleozoic terrane mosaics are most susceptible to reactivation, especially along terrane margins that are adjacent to stronger, rigid Precambrian cratonic blocks; 2) thrust faults reactivate (and may invert) older faults, sedimentary strike belts and metamorphic foliation trends whereas, linked strike-slip faults typically cross-cut pre-existing structures; 3) the angle between the maximum horizontal stress and pre-existing basement strike trends is the dominant control on modern fault kinematics and earthquake focal mechanisms; 4) transpressional fault arrays, non-strain-partitioned oblique deformation belts, and restraining bend massifs are common orogenic architectures; they typically produce steeper mountain fronts susceptible to co-seismic landsliding; 5) understanding the diverse criteria that allow identification of tectonically active range-bounding faults is essential for reliable geotechnical assessments of seismic and landslide hazards.

Documenting the timing of kinematic reversals along individual strike-slip faults within regional transpressionaltranstensional systems is challenging, especially in areas of subdued topography and limited exposure of basinal successions. Within the northern Tibetan foreland, multiple NW- and W-striking faults (e.g., Nanjieshan, Heishan, Longshoushan) are developed within low-lying ranges, and exhibit Triassic dextral motion followed by a kinematic reversal to Quaternary sinistral slip. However, the timing of the fault inversion is uncertain and ranges from Cretaceous to Quaternary. Resolving this ambiguity is important for documenting the regional crustal evolution of Central Asia and the driving mechanisms for separate tectonic events expressed in the geological record. This study integrates K-Ar illite dating of Nanjieshan fault gouge with field structural analysis, micro-textural observations, and X-ray diffraction (XRD) measurements to constrain the fault inversion timing. Field evidence reveals sinistral strike-slip motion, marked by a left-stepping en-echelon pressure ridge and a 60-m-wide upward-widening fault core. XRD analysis shows increasing detrital illite polytypes with grain size, suggesting preferential 1 M/1Md illite neocrystallization in finer fractions due to fluid-driven fault process. K-Ar dating yields authigenic (122 Ma) and detrital (225 Ma) illite ages. The 122 Ma age robustly constrains Early Cretaceous sinistral reactivation, coeval with Neo-Tethyan subduction and the Lhasa-Qiangtang collision to the south and a dynamically evolving stress field tied to Pacific margin subduction rollback to the east. Regionally, the reactivated Nanjieshan Fault connects eastward to the Heishan-Jinta'Nanshan fault system, forming part of the Altyn Tagh Fault network that truncates NNE-SSW-trending Cretaceous extensional sags or basins (e.g., Jiuquan, Huahai, Chaoshui, Minle). Proposed spatial-kinematic linkages between inverted strike-slip faults and adjacent extensional basins throughout the region suggest the existence of a Cretaceous sinistral transtensional distributed (or mega-) shear fault system. This highlights diffuse transtension as a key mechanism for intraplate deformation.

The structural connectivity and kinematic relationship between the Altyn Tagh sinistral strike-slip fault (ATF) and Qilian Shan fold-and-thrust belt along the north Tibetan margin east of 96 degrees E is an important question for tectonicists interested in the evolving active deformation field of Central Asia and associated earthquake hazards of China's Hexi Corridor region. New results from a detailed 130-km-long N-S magnetotelluric (MT) survey from the Qilian Shan to Beishan elucidates the locations and down-dip orientations of major faults. Importantly, the results indicate that the Heishan-Jinta'Nanshan fault system roots steeply into the lower crust, is unconnected to the Qilian Shan thrust wedge, and has reactivated the margin of the North China Craton and an older, regional ductile shear belt. The structurally linked ATF-Heishan-Jinta'Nanshan system defines a fundamental kinematic boundary in central Asia between the NE directed Qilian Shan thrust belt to the south and the eastwardly extruding Beishan-Alxa Block to the north. In this study, we present results of a comprehensive electrical resistivity survey conducted in the western Hexi Corridor region of China. The survey reveals significant sub-surface faults and crustal boundaries, providing insights into the crustal structure between northernmost Tibet (Qilian Shan) and the Beishan. We document how the strike-slip crustal boundary known as the Altyn Tagh Fault (ATF)-Heishan-Jinta'Nanshan system is steep and spatially unconnected to the Qilian Shan east of 98 degrees E. It separates crustal blocks with contrasting motion histories; the southern block experiences compressional deformation, whereas the northern block accommodates extensional and transtensional deformation. Furthermore, the northeast trending ATF bends and converges into the more east-west-oriented Heishan-Jinta'Nanshan system. We propose that this is a result of the Heishan-Jinta'Nanshan system reactivating an older ductile shear belt and a mechanically weak boundary along the northwestern margin of the Precambrian North China Craton. Our study confirms the significance of inherited crustal structures in localizing continental interior reactivation and associated earthquake hazards. A new detailed 3D resistivity model from Northern Tibet to the Southern Beishan clarifies the crustal structure in the NW Hexi Corridor The Heishan fault system penetrates steeply to the lower crust and is unconnected to the Qilian Shan thrust wedge Crustal thickening and mountain uplift in Qilian Shan is kinematically separated from eastward Beishan-Alxa Block extrusion further north

Large continental strike-slip fault systems typically comprise a principal displacement zone and subordinate splay faults, exhibiting complex geometries, connectivity, and kinematics. Understanding the three-dimensional arrangement of major and minor faults is important for determining strain distribution, landform development, and potential earthquake behavior. This study examines the Quaternary deformation, fault kinematics, and late Holocene ruptures along the Nanjieshan Fault system (NJSF), a major branch of the Altyn Tagh Fault (ATF) system in the North Tibetan Foreland. The E-W-trending NJSF comprises a principal strike-slip fault flanked by two thrust faults, forming a regional, sinistral positive flower structure. Cosmogenic exposure dating, field data and remote sensing observations indicate that the strike-slip rate of the main NJSF is similar to 0.5 mm/a since similar to 45 ka, consistent with the low slip rates observed on other faults northwest of the ATF. Paleoseismological trenches reveal three surface-rupturing events on the NJSF in the last 2,500 years that may coincide temporally with the last two major earthquakes documented on the principal ATF, suggesting quasi-simultaneous rupture behavior. Coulomb stress change modeling indicates that a future ATF earthquake is unlikely to trigger failure along the NJSF. Conversely, rupture of the NJSF could induce stress loading on the ATF, potentially bringing it to failure. A synchronous rupture on the ATF and its major branch faults could be facilitated by mechanically weakened fault rocks and supra-hydrostatic fluid pressures within the deep southward-dipping branch faults of the North Tibetan foreland. We conclude that improved prediction of future slip behavior along major strike-slip fault systems requires detailed geochronological analysis of paleo-earthquake events along subordinate branching faults.

The Altyn Tagh fault (ATF) is a major intracontinental strike‐slip fault system that defines the northern margin of the Tibetan Plateau. The fault system loses its obvious surface expression north of the Qilian Shan fold‐and‐thrust belt, but may link eastward with multiple faults in the northern Hexi Corridor and southern Alxa block. To better understand the potential connectivity and displacement transfer between the ATF and the northern Hexi Corridor fault array, we carried out a multidisciplinary field and remote sensing‐based investigation of the actively deforming Heishan and Jinta'Nanshan region north of Jiayuguan City. We document Quaternary sinistral strike‐slip motion on the Heishan fault (HF) system and active sinistral transpression within a 70‐km‐long, E‐W deforming belt east of the Heishan, which is characterized by multiple left‐stepping, en‐échelon Quaternary folds and linking faults. Cosmogenic 10 Be dating of displaced terrace surfaces yields a vertical slip rate of ∼0.2 mm/a for the northern Heishan thrust and a sinistral strike‐slip rate of 0.6 ± 0.2 mm/a for the HF. Within the uplifted core of the Heishan massif, the HF contains ductilely deformed Paleozoic basement lithologies with dextral‐sense shear fabrics that indicate that the modern HF has reactivated and inverted an older shear zone. A previously published magnetotelluric profile across the HF system suggests that it roots into a steep, deeply penetrating fault that is unlinked to the Qilian Shan thrust wedge. Instead, we suggest that the active sinistral deformation belt of the Heishan‐Jinta'Nanshan represents the eastward‐evolving, upper crustal expression of the modern ATF system.

The NNW‐trending Jiayuguan Fault (JYGF) is an actively developing thrust fault that delimits the SW margin of Jiayuguan, a major industrial city in the northwestern Hexi Corridor, China. In this study, we document the geometry, kinematics, and slip rates of the JYGF based on analysis of satellite imagery, low‐altitude photogrammetry, field observations, paleo‐seismic trenching, and Quaternary dating. The JYGF hanging‐wall contains a NE‐vergent asymmetric anticline of Cretaceous redbeds unconformably overlain by faulted, tilted and folded alluvial fan and fluvial terrace surfaces. Subsidiary fault scarps are associated with anticlinal flexure and contractional strain. The vertical uplift and crustal shortening rates are both ∼0.1 mm/a since ∼420 ka and geomorphic markers and dated landforms indicate southeastward fault propagation and hanging‐wall uplift from the Heishan toward the modern Beida River channel. The NW end of the fault appears to connect with the Altyn‐Tagh‐Heishan‐Jinta'Nanshan sinistral strike‐slip fault array suggesting that the JYGF is one of several parallel, splay faults that transfer strike‐slip motion to active folding and thrusting in the region. We relocate the 1992 Ms 5.4 earthquake epicenter using the NonLinLoc method and suggest that the JYGF may link southeastward with Quaternary‐active faults and folds in the Wenshushan. A seismic rupture along the total fault length of 25–40 km for the JYGF‐Wenshushan deforming belt corresponds to a potential earthquake magnitude in the 6.6–7.0 range. Compartmentalized faulting and folding in the NW–most Hexi Corridor defines a triangular block of active deformation where NE‐directed contractional deformation of the Qilian Shan foreland interacts with E‐W left‐lateral displacement along the Altyn‐Tagh‐Heishan‐Jinta'Nanshan sinistral strike‐slip system.

The active deformation field between northern Tibet and central Mongolia is dominated by diffuse sinistral transpressional reactivation of the southern Altaids Phanerozoic terrane collage. The angular relationship between NE-directed SHmax and pre-existing basement trends is the dominant control on Quaternary fault kinematics. Along Tibet’s northern margin, the Altyn Tagh system is widening northwards by transpressional duplexing. The Nanjieshan and Sanweishan comprise sinistral oblique-slip thrust ridges within a regional asymmetric flower structure centered on the Altyn Tagh Fault. In the southern Beishan, interconnected lensoidal domains of transpressional and transtensional faulting are subtly indicated by Quaternary fault scarps, low-relief rejuvenated landscapes and alluvial sedimentation. The SE Beishan and western Hexi Corridor region contain numerous Late Quaternary fault systems including the Heishan-Jinta'Nanshan sinistral strike-slip corridor and the Helishan-Longshoushan fault array that connects eastwards with the transtensional grabens of the Yabrai and Langshan in the eastern Alxa Block. Further north, the Paleozoic terrane collage of the Gobi Corridor was repeatedly reactivated during the Permo-Triassic, Jurassic, Cretaceous and Neogene. Late Cenozoic reactivation was likely facilitated by thermal weakening of the crust due to Jurassic-Miocene volcanism, and diffuse Cretaceous rifting and crustal thinning. Although terrane boundaries and other faults are reactivated in many areas, thrust and oblique-slip reactivation of WNW striking shallowly dipping sedimentary bedding and metamorphic fabrics is equally important. Conversely, modern E-W trending strike-slip faults in the Gobi Altai typically crosscut older basement trends. In the Altai and Gobi Altai, the Late Cenozoic fault array has created a transpressional basin and range physiographic province. Coalescence of separate ranges into topographically continuous mountain belts in the Altai, Gobi Altai and easternmost Tien Shan is an important mechanism of transpressional mountain building not predicted by classical plate tectonic models. Throughout the vast deforming region north of Tibet, tectonic loading is shared amongst a diffuse fault network challenging assumptions about earthquake recurrence intervals and seismic hazard forecasting.

The Alxa Block in western China is a significant tectonic unit in the middle part of the southern Central Asian Orogenic Belt that was affected by multiple Paleozoic and Meso-Cenozoic deformation events. In this study, the results from detailed mapping and structural analysis coupled with new U-Pb zircon ages indicate that the Langshan region of the northeastern Alxa Block has experienced ten deformation events since the Late Devonian. Four separate structural domains are identified based on distinctive litho tectonic relationships, and these domains contain intrusive and structural crosscutting relationships that allow the complex deformational history to be determined. Each deformation phase can be related to regional tectonic events associated with the consolidation of Central Asia's crust and subsequent intraplate reactivation. The first three events (D1-D3) are tied to convergence between the Alxa Block, the North China and the Yangtze Cratons prior to and during closure of the Paleo-Asian Ocean in the Mid Late Permian. Subsequently, sinistral displacement (D4) occurred between the Alxa Block and the North China Craton during the Triassic. Since the late Mesozoic, reactivation of the northeastern Alxa Block occurred repeatedly as an intraplate response to subduction of the Paleo-Pacific Plate, closure of the Mongol-Okhotsk Ocean (D5), retreating subduction of the Paleo-Pacific Ocean (D6), collision between the Qiangtang and Lhasa blocks and convergence between the East Asian margin and Western Philippine Block (D7), and later collision between India and Eurasia (D8-10). The Alxa Block provides a superb case study of how a continental interior region structurally records the multi-phase transition from plate margin tectonism to intraplate reactivation. The events documented in this study invite correlation with other Paleozoic-Recent tectonic events recorded elsewhere in the southern CAOB and adjacent cratonic blocks in Central Asia. (c) 2021 International Association for Gondwana Research. Published by Elsevier B.V. All rights reserved.

An interesting subset of Earth's mountain ranges are those that are forming or have formed in continental interior regions, far from any active plate boundary. Intracontinental, intraplate mountain ranges may evolve in any kinematic mode, as evidenced today in Central Asia where diverse Miocene-Recent mountain ranges such as the Altai, Tien Shan, Gobi Altai, Beishan and Ordos Block ranges are actively developing over a wide region north of Tibet. These separate orogens represent an intraplate response to the continental interior force balance that is derived from the distant Indo-Eurasia collision, Asia's actively retreating Pacific margin, and stored gravitational potential energy in Central Asia's lithosphere. Mechanically weak, Phanerozoic terrane collages and Precambrian craton boundaries are susceptible to crustal reactivation with the kinematics of faulting largely driven by the angular relationship between SHmax (maximum horizontal stress) and the pre-existing structural "grain" in the region. The arid climate and low erosion rates in Central Asia, compared to more humid regions, allow the tectonic signal of Late Cenozoic crustal reactivation to be clearly expressed in the landscape. In addition to fault-driven orogenic processes, long-wavelength epeirogenic movements leading to differential erosion and isostatic adjustments may also generate mountainous relief in aseismic, intracontinental regions. Ancient intracontinental, intraplate mountain ranges may go un-noticed by tectonicists and geomorphologists, because their landscape expression may be geologically short-lived, with limited-to-no magmatic, metamorphic, and thermochronological signature.

We combine field observations, drone photogrammetry, and petrographic and XRD analysis to document the internal lithological and structural variability of an exceptionally well-exposed strike-slip fault pressure ridge, in the northern Tibetan foreland. The ridge exposes alternating dm-m thick discolored zones of fault gouge, breccia, and cataclasite likely reflecting the original Riedel shear array and progressive widening of the fault zone as comminution, fluid pressures, mineral alteration, and strain hardening and weakening processes evolved and migrated vertically and laterally within the core. The principal fabric defines an internal foliation fan, and sinistral, oblique-thrust faults bound the ridge supporting a transpressive squeeze-up origin. Outcrop-and micro-scale grain size reduction, gouge formation, and calcite precipitation suggest that thermal pressurization, me-chanical lubrication, fault-valve fluid cycling, and periodic gouge zone lock-up may have been important factors controlling fault slip behavior and seismic energy release. Local variations in the distribution and thicknesses of brittle fault rocks, strain intensity, alteration mineralogy and fault core fabrics are a sobering reminder that a single 2-dimensional exposure across any regional fault system will fail to capture the complex petrological, mineralogical, mechanical and rheological heterogeneity that is typical of an evolving intraplate strike-slip fault system, especially where it reactivates an older fault/shear zone.

The Northeastern Gobi Altai region of Mongolia contains a wide range of impressive geological features of unique and superlative value that comprise an important geoheritage meriting long-term protection. World-class examples of earthquake rupture zones, restraining bend massifs, dinosaur fossil localities, volcanic landforms, large landslides, and other interesting geological and geomorphological features are concentrated in a single region that includes the southern flanks of the Hangay Dome, the Mongolian Valley of Lakes, and the NE Gobi Altai mountains. In addition, the region includes important endemic flora and fauna in diverse and in some cases, threatened ecosystems. The NE Gobi Altai is also an important geo-cultural region; traditional nomadic pastoralists have lived in the area for millennia closely connected to the region’s geology, landscapes, and natural resources. The region’s geoheritage and geo-culture face modern development threats including resource exploration/production, overgrazing, unregulated tourism, and lack of environmental management. It is recommended that the region be evaluated for Geopark status under the UNESCO umbrella to preserve its natural assets. If successful, the NE Gobi Altai region would be Mongolia’s first Geopark and could stimulate interest in a long-term conservation strategy for other Mongolian regions with important geoheritage. In this report, the scientific, educational and aesthetic value of the NE Gobi Altai is summarized and illustrated to raise international awareness of its valuable geoheritage.

Central Asia is Earth's premier region for studying processes of intraplate, intracontinental mountain building, and the distant effects of a major continental collision. The region is notable for having diverse mountain range types in various stages of structural and topographic evolution. Mesozoic-Cenozoic fault kinematics and the distribution of crustal reactivation are directly related to the orientation of inherited basement structures and the evolving intraplate stress field. The neotectonic deformation field of Central Asia provides important lessons for understanding the structural evolution of all continental interior regions, throughout Earth history.

In this study, new structural field data and geological observations are coupled with remote sensing analysis and compilation of previous published work to establish a new kinematic framework for the neotectonic reactivation of the Alxa block, China. The Alxa block occupies a key position in Central Asia north and east of the contractional and sinistrally transpressive deforming zones of the Qilianshan-Hexi Corridor-easternmost Altyn Tagh Fault and Beishan deforming belts, south of the sinistrally transpressive southernmost Gobi Altai, and west of - or overlapping with Ordos block extensional and transtensional graben systems. In addition, the Alxa block is internally transected by important fault systems (Bayan Nuru, Bayanwula, Chahanbulage) that record previously unrecognized Late Cenozoic activity. Active mountain building processes in the Alxa block show remarkable variation from large extensional horst blocks (Helanshan, SW Langshan, SW Yabrai) to localized uplifts along sinistral wrench-belts (Bigesitai) to dominantly contractional (Longshoushan) and sinistral transpressional ranges (Helishan). The triangular wedge-shape of the Alxa block likely pre-disposed it to eastward extrusion in response to NE-directed India-Eurasia collision-derived compressional stresses from the south, and E-W tensional forces driven by Pacific margin rollback to the east. A combination of inherited regional lithospheric structure and the modern east-directed geodetically derived crustal velocity field led to: 1) crustal thinning and subsidence of the Ejina basin to the west in the wake of the eastward extruding Alxa block, and 2) distributed sinistral transtension and crustal extension within the Alxa block interior, and in the Hetao and Yinchuan grabens to the east.

We report remote sensing evidence and reconnaissance field observations for an actively evolving transpressional duplex 150 km north of Tibet, in the southern Beishan region of western China. We analyze Landsat-8, Google Earth and SRTM-30 data to reveal active fault traces, kinematics, offset contacts and landforms, and the overall duplex geometry in an area of limited recorded seismicity compared to surrounding regions. Eight NE-striking faults transfer sinistral displacement between E-W bounding faults and accommodate N-S shortening by sinistral-reverse displacements that have tilted the internal duplex blocks. The potential moment magnitude of a surface-rupturing event on one fault, that displays a twenty km-long, 1-3 m-high surface scarp, is estimated to be 6.6. Our study adds to the growing body of evidence that suggests the Beishan is a region of subtly expressed, but widespread, continental interior, strike-slip reactivation at low strain rates - challenging the long-held view that the Beishan has anomalous crustal stability within the huge Indo-Eurasia deformation field.

The Asian continent is a composite continent which consists of several Precambrian cratonic blocks and intervening Phanerozoic orogenic belts. The geological records in China and Mongolia are essential in understanding the complex amalgamation history of the Asian continent. The Precambrian blocks in China and Mongolia mainly include the North China Block, Tarim Block, South China Block and Tuva-Mongol Block. Major orogens in China and Mongolia include the Altaids in the north and the Tethysides in the south, which is related to the consumption and final closure of the Paleo-Asian Ocean and Tethyan Ocean, respectively. This contribution presents a brief introduction of the tectonic evolution history of the major cratonic blocks and orogenic belts in China and Mongolia in the context of assembly and dispersal of the Columbia, Rodinia and Pangea supercontinents.

We present results from a multidisciplinary investigation of the Jiujing fault (JJF) system and adjacent Jiujing Basin in the southern Beishan block, western China. Structural and geomorphological fieldwork involving fault and landform investigations, remote sensing analysis of satellite and drone imagery, analysis of drill-core data, paleoseismological trench studies, and Quaternary dating of alluvial sediments suggest the JJF is a late Pleistocene to Holocene oblique sinistral-slip normal fault. Satellite image analysis indicates that the JJF is a connecting structure between two regional E-W-trending Quaternary left-lateral fault systems. The Jiujing Basin is the largest and best developed of three parallel NE-striking transtensional basins within an evolving sinistral transtensional duplex. Sinistral transtension is compatible with the orientation of inherited basement strike belts, NE-directed SH(max)and the modern P-NE-directed geodetic velocity field. Cosmogenic Al-26/Be-10 burial dating of the deepest sediments in the Jiujing Basin indicates that the basin began to form at similar to 5.5 Ma. Our study reveals a previously unreported actively deforming domain of transtensional deformation 100 km north of Tibet in a sector of the Beishan previously considered tectonically quiescent. Recognition of latest Miocene-Recent crustal reactivation in the Jiujing region has important implications for earthquake hazards in the Beishan and western Hexi Corridor/North Tibetan foreland sectors of the Silk Road Economic Belt. Additionally, we compare the timing of latest Miocene-Recent crustal reactivation in the southern Beishan with the documented onset of reactivation in other deforming regions north of Tibet.

In this study, we document the kinematics and Late Quaternary slip rates of actively developing faults and folds on the northern side of the Altyn Tagh Fault (ATF) that accommodate uplift and lateral expansion of the northern Tibetan Plateau. Field observations and detailed measurements using Unmanned-Aerial-Vehicle Structure-from-Motion high-resolution imagery of offset fan surfaces, gullies, and channel risers coupled with optically stimulated luminescence and 10Be ages constrain the timing and slip rates of the Sanweishan Fault (SWSF) and Nanjieshan Fault (NJSF) systems. The NE striking SWSF is characterized by sinistral strike slip with a top-to-the-NW thrusting component. Offset geomorphic markers and dating results yield Pleistocene strike slip and vertical uplift rates of 0.06-1.25 mm/a and 0.05-0.08 mm/a, respectively. The E-W trending NJSF is dominated by north and south directed thrusting and km-scale folding with variable components of sinistral strike slip. The calculated total N-S shortening rate across the NJSF is similar to 0.3 mm/a. Low rates of deformation for the SWSF and NJSF account for less than 10% of the total intraplate strain accommodated along the northeasternmost ATF system. Over a 1,000-km length, the northward expansion of the Tibetan Plateau occurs by progressive northeastward growth of a transpressional duplex rooted SE into the ATF. An assumed crustal strength discontinuity along the northeast trending southern margin of the Tarim Craton focuses oblique convergence along the ATF. Oblique-slip thrusting and sinistral strike slip along the ATF and to the north accommodate the oblique convergence, consistent with the ENE directed geodetically derived crustal velocity field driven by India's continued indentation 1,500 km to the south.

The 2008 Mw 7.9 Wenchuan, China, earthquake produced many damaging landslides in the Longmenshan region along the eastern margin of the Tibetan Plateau, China. Among the thousands of reported landslides, some are geologically notable because of their close spatial relationship to local fault rupture complexities. The Leigu landslide is particularly interesting because it formed at a restraining bend along the Beichuan-Yingxiu fault system in a structural position that favored hill-slope collapse because of a variety of preexisting structural and geomorphological conditions. The 2008 landslide reactivated an older landslide that is indicated by a preserved paleo-scarp upslope from the main 2008 event scarp. Our field and analytical results coupled with a review of existing geological information on the region indicate that the landslide site is located between two regional folds with opposing plunge directions and that the restraining bend is the displacement transfer zone between two parallel, but offset segments of the Beichuan-Yingxui Fault system. In addition, NE-oriented steep joints were reactivated as slip surfaces in the upper slopes of the landslide area within an anticline hinge zone that focuses vertical uplift. Steep valley walls due to incision of the antecedent Laochangkou River and abundant rainfall during the earthquake period, combined with intense seismic acceleration were contributing factors to the landslide event. During the earthquake, approximately equal components of strike-slip and SE-directed thrusting occurred on surface ruptures within the bend, offsetting older landslide deposits and man-made structures. Field results indicate that sliding was facilitated by loose unconsolidated materials from the previous landslide that were remobilized above a soft, low-friction basal slip surface. The Leigu landslide provides an important case study for evaluating potential landslide hazards close to active fault systems where complex 3-D structural geometries and high-relief, steep terrain combine to generate significant ground instability during large magnitude earthquakes.