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

The magnitude (MW) 6.9 (Ms 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.

Research highlights
► The 2010 MW 6.9 Yushu earthquake produced a 33-km-long surface rupture zone along 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.
► The co-seismic left-lateral strike-slip displacements are 0.3–3.2 m (typically 1–2 m).
► The left-lateral strike-slip motion indicates that the Ganzi-Yushu Fault Zone partitions deformation into eastward extrusion of and northeastward shortening of the central Tibetan Plateau.