Rupture Segmentation and Process of the 2001 Mw 7.8 Central Kunlun, China, Earthquake

Field investigations allow us to constrain the coseismic surface rupture zone of ~400 km with a strike slip up to 16.3 m associated with the 2001 Mw 7.8 Central Kunlun earthquake that occurred along one of the western segments of the Kunlun fault, northern Tibet. The rupture zone may be divided into four segments based on the geological structures, tectonic landform features, spatial displacement distributions obtained from field observations, and analysis of teleseismic waveforms. The deformational characteristics of the surface ruptures and focal mechanism solutions reveal that the earthquake had a nearly pure strike-slip mechanism. The inversion results from seismic data show that the rupture started from the west near the epicentral area bilaterally and rapidly extended to the east in an unilateral manner for 380 km and that the largest slip region was limited in the subsegment 150-280 km east of the epicenter, consistent with field observations. The average stress drop is estimated to be 7 MPa in the area where the largest displacements occurred, a value typical of intraplate earthquakes. The geologic evidence and the inversion results from seismic data clearly show that temporal and spatial displacement distributions and the rupture process are restricted by the pre-existing geological structures of the Kunlun fault.