Coseismic Deformation of the 2010 Mw 6.9 Yushu Earthquake Derived from GPS Data

Abstract

On 13 April 2010 UTC 23:49:17 (Local time 7:49:17 on 14 April 2010), a large earthquake ( M w 6.9) struck Yushu county, Qinghai, China, killing 2,700 people, and causing widespread damage in the high mountainous regions of the central Tibetan Plateau. This event occurred on the pre‐existing left‐lateral strike‐slip Ganzi–Yushu fault, which is the western part of the Yushu‐Ganzi‐Xianshuihe fault zone. The Ganzi‐Yushu fault extends for ∼200 km along a northwest–southeast strike (Wang et al. , 2008). The event of 13 April 2010 is the largest one in this region since the last destructive earthquake about 272 years ago (Zhou et al. , 1996; 1997). Previous studies from geodetic surveys inferred an average slip of 14.4 mm/yr along the Ganzi‐Yushu‐Xianshuihe fault (Gan et al. , 2007). The principal horizontal strain rates over the Yushu area are characterized by a combination of north‐northeast–south‐southwest compression and west‐northwest–east‐southeast extension (Calais et al. , 2006), which are significant at the 95% confidence level. Field investigation revealed an ∼51‐km left‐lateral strike‐slip surface rupture (Chen et al. , 2010; J. Zhang et al. , 2010) with a coseismic displacement of 0.3–3.2 m (Lin et al. , 2011). Satellite image analyses show various lengths of surface breakage ranging between 39 and 80 km (Li et al. , 2011; Tobita et al. , 2011; Zha et al. , 2011). However, estimates from initial seismological inversion show the rupture belt is composed of at least 3 segments, with a total length of 50–70 km. Field observation demonstrates that coseismic surface rupture zone produced by the main shock is 31–33 km in length. Teleseismic waveform analysis suggested that the earthquake could be resolved into two subevents of up to 2.0‐m slip on a 119°‐striking fault dipping southwest (Y. Zhang …