Coseismic and early postseismic deformation for the 2015 Mw 6.4 Pishan earthquake from InSAR and GPS observations

The Pishan, Xinjiang earthquake occurred on 3 July 2015 along the western Kunlun Shan, northwestern edge of the Tibetan Plateau. As the largest event has recorded instrumentally since 1976 beneath the range front, it provided a window for us to know the present interaction between Tarim Basin and the Tibetan Plateau. Combine several Global Positioning System (GPS) campaign surveys and Interferometric Synthetic Aperture Radar data, a maximum coseismic displacement exceeding 10 cm and postseismic displacement nearly 3 cm were observed in the epicentral region. Our focal mechanism indicates this blind thrusting shallow event produces a coseismic slip concentrated on occurred on a subsurface plane of 22 km × 8 km in size with a dip of about 27° to the north and a strike of 114°, representing partial break of one ramp fault buried in Paleozoic strata at 8-16 km depths beneath the foothill of the western Kunlun Shan. The GPS and InSAR data show the pattern of postseismic displacement is the same as coseismic displacement, and postseismic velocities decay with a time scale of 72±1 days, 15±0.5 days and 179±2 days, assuming exponential, logarithmic and rate-strengthening friction law decay, respectively. Time series InSAR indicates postseismic deformation is nearly finished over a time period of 6 months after the earthquake, which rules out that afterslip is a plausible mechanism as the postseismic process.