The Altyn Tagh fault accommodates sinistral motion between the Tibetan Plateau and the Tarim block within the India-Eurasia collision zone. We used well-preserved evidence for surface-rupturing earthquakes to reconstruct the earthquake history for the central Altyn Tagh fault. We identified three geometric fault segments bounded by left steps and a bend. Geomorphic offsets indicate that the most recent event had maximum surface displacement of ϳ5.5 m in the west (38.5؇N, 90.0؇E), ϳ7 m in the central part of our study area, and ϳ4 m in the east (38.8؇N, 91.5؇E). The 14 C dates and trench logs of disrupted sediments indicate that these offsets occurred either in a single earthquake with a surfacerupture length Ͼ240 km dated as 680 ؎ 108 yr B.P. or as two events. If there were two events, the westernmost recent event occurred 518 ؎ 268 yr ago, whereas the eastern event occurred 650 ؎ 80 yr ago and had a surface rupture length Ͼ155 km. We find two events in the past 0.8-2.2 k.y. in the west and two or three events in the east, yielding recurrence intervals of 0.7 ؎ 0.4 k.y. and 1.1 ؎ 0.3 k.y., respectively. These recurrence rates for major earthquakes are lower than expected if the long-term fault slip rate is Ͼ20 mm/yr. Explanations for the discrepancy include an overdue major earthquake, or accelerated deformation elsewhere in the India-Eurasia orogen.
The central Jiangnan Orogen, genetically formed by the Proterozoic Yangtze‐Cathaysia collision, presents as a composite structural feature in the Phanerozoic with multiple ductile and brittle fabrics whose geometries, kinematics, and ages are crucial to decipher the tectonic evolution of south China. New structural observations coupled with thermochronological and geochronological studies of these fabrics document four main stages of deformation. The earliest stage in early Paleozoic time (460–420 Ma) corresponds to combined E‐trending dextral and northwest directed thrust shearing that was variably partitioned in anastomosing high‐strain zones under greenschist‐facies conditions (~400–500°C), related to the continued Yangtze‐Cathaysia convergence externally driven by the suturing of south China with Australia. This event was heterogeneously overprinted by the second stage characterized by ~E‐oriented folding in middle Triassic time, geodynamically resulting from the continental collision of south China with Indochina and North China. The third stage was locally developed by northwest and southeast vergent thrusts that truncated ~E‐oriented folds in the Late Jurassic, due to northwestward subduction of the Paleo‐Pacific plate. The latest stage involved normal faulting and tectonic unroofing in Cretaceous time, which resulted in basin opening and reset footwall 40Ar/39Ar ages in proximity to the Hengshan detachment fault, associated with roll‐back of the subducting Paleo‐Pacific plate.
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