[J02-2] Recent large earthquakes II

[J02-2-05] Coseismic deformation associated with the 2001 Ms 8.1 Kunlun earthquake from GPS and its tectonic implications

^○Kaihua Ding¹, Qi Wang¹, Jeffrey Freymueller², Ping He¹, Shuiping Li¹, Yunguo Chen¹, Yangmao Wen³, Caijun Xu³, Shaomin Yang⁴, Xuejun Qiao⁴ (1.University of Geosciences, Wuhan, China, 2.University of Alaska, Fairbanks, USA, 3.Wuhan University, Wuhan, China, 4.Institute of Seismology, China Earthquake Administration, Wuhan, China)

We conducted several GPS surveys of triangulation network in the vicinity of surface rupture caused by the 2001 Kunlun Ms 8.1 earthquake, to deduce its coseismic deformation. Since we first carried out the near-filed survey in 2015, we have collected GPS data at 33 triangulation network sites, which are spreading along the surface rupture and centered in the Kusai Lake, Kokoxili, China. Due to the availability of these near-filed observations, we provided an updated set of GPS coseismic displacements, after removing the interseismic and postseismic deformation. The GPS-derived coseismic displacement filed shows that the maximum coseismic displacement is 2.412m at a site with the closest distance of ~2km to the surface rupture.
Constrained by the GPS coseismic displacements, we used a variable slip model to further invert for the coseismic slip distribution associated with this event. The GPS-derived result is in consistent with previous studies from field measurements, high-resolution satellite images and InSAR. The largest slip occurred on the Kusai Lake segment with two obvious asperities on the whole. As a result of the existence of near-field observations, we estimated a more detailed slip pattern of these two asperities, one with smaller slip of 4~6m extending to a deeper depth of ~20 km and the other with larger slip of 5~8 m to ~10 km depth. At the eastern end of the 426-km-long rupture, the GPS data show evidence for small (<2 m) but non-zero slip, in a section of the fault where the earlier InSAR data did not show any slip. Based on our preliminary results, we can get that slip is penetrating coseismically much deeper than the typically assumed depth of the seismogenic layer. In order to verify this, we are conducting more experiments.