Field investigations show that the surface wave magnitude (Ms) 8.1 Central Kunlun earthquake (Tibetan plateau) of 14 November 2001 produced a nearly 400-kilometer-long surface rupture zone, with as much as 16.3 meters of left-lateral strike-slip along the active Kunlun fault in northern Tibet. The rupture length and maximum displacement are the largest among the co-seismic surface rupture zones reported on so far. The strike-slip motion and the large rupture length generated by the earthquake indicate that the Kunlun fault partitions its deformation into an eastward extrusion of Tibet to accommodate the continuing penetration of the Indian plate into the Eurasian plate.

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[1] The 2008 M w 7.9 Wenchuan earthquake is a result of ongoing India-Tibet collision and reflects the growth of the Longmen Shan fold-and-thrust belt. In this paper, we construct a 3-D structural model of the geometry of the coseismic faults and related structures of the Wenchuan earthquake by integrating geological investigations, relocated aftershocks, and seismic reflection profiles. In the 3-D structural model, the differences between the southern and northern segments of the rupture are highlighted. The structural transition zone between the two segments contains a major geometric segment boundary, reflecting differences in the structural configuration of the thrust ramp and the tectonic evolution of the fault system, which appears to have localized significant damage from Anxian to Beichuan. Within the northern segment, we identify a transverse structure across which the Beichuan fault plunges under the Tangwangzhai syncline. This boundary corresponds to a marked change in the nature of the surface rupture and is illuminated by a microearthquake sequence perpendicular to the Longmen Shan thrust belt. In the southern segment, our investigations confirm that uplift due to active faulting and folding is largely responsible for the areas of steepest topography. On the basis of this association, the southwestern segment of the Longmen Shan, south of the Wenchuan earthquake, is likely active and presents a significant earthquake hazard, despite the lack of historical earthquakes in this region. This study illustrates the importance of building 3-D models to study active faulting and folding, as well as to assess earthquake hazard.

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