Co-seismic strike-slip surface rupture and displacement produced by the 2010 M W 6.9 Yushu earthquake, China, and implications for Tibetan tectonics

Abstract

The magnitude (M W) 6.9 (M s 7.1) Yushu earthquake occurred on 14 April 2010 in the Yushu area, central Tibetan Plateau, causing widespread damage in high mountain regions. Field investigations reveal that the earthquake produced a 33-km-long surface rupture zone, with dominantly left-lateral strike-slip along the Yushu Fault of the pre-existing strike-slip Ganzi-Yushu Fault Zone. The co-seismic surface ruptures are characterized by discontinuous shear faults, right-stepping en echelon tensional cracks, and left-stepping mole track structures that indicate a left-lateral strike-slip shear sense for the seismic fault. Field measurements indicate co-seismic left-lateral strike-slip displacements of approximately 0.3–3.2 m (typically 1–2 m), accompanied by a minor vertical component of <0.6 m. The present results show that (i) the Yushu earthquake occurred upon the pre-existing active Ganzi-Yushu Fault Zone, which controlled the spatial distribution of co-seismic surface ruptures and displacements; (ii) the left-lateral strike-slip motion indicates that the Ganzi-Yushu Fault Zone partitions deformation into eastward extrusion of and northeastward shortening the central Tibetan Plateau to accommodate the continuing penetration of the Indian plate into the Eurasian plate.