Inter-seismic deformation field of the Ganzi-Yushu fault before the 2010 Mw 6.9 Yushu earthquake

The 14 April 2010 Mw 6.9 Yushu earthquake ruptured the northwestern segment of the Ganzi-Yushu fault in Qinghai Province, China. Using GPS data obtained from 1999 to 2007 in the vicinity of the Ganzi-Yushu fault, we estimate the slip rates of the Fenghuoshan and Ganzi-Yushu faults, and the northwestern segment of the Xianshuihe fault as 6.1±1.9, 6.6±1.5, and 9.7±0.7mm/a for left lateral components, and 2.8±1.9, 1.7±1.6, and −2.0±0.9mm/a for shortening components, respectively. The Maduo-Gande fault slips left laterally at a rate of about 1–2mm/a, and ~3mm/a sinistral shear motion is left unexplained, possibly caused by deformation across one or more unknown faults in the region. These results agree with geological estimates of the fault slip rates, and show a progressive increase of shear motion from northwest to southeast across segments of the Xianshuihe–Ganzi-Yushu fault zone, implying variation in transferring and absorbing deformation in different regions in and around the Tibetan plateau.