Coseismic deformation of the 2001 Ms 8.1 Kunlun earthquake inferred from GPS

Abstract:

In 2015 we carried out a GPS survey of triangulation network sites centered in the Kusai Lake area, the segment with the maximum slips caused by the 2001 Kunlun Ms 8.1 earthquake. We reprocessed the GPS data both from campaign sites surveyed before and from the newly surveyed near-field triangulation sites, and provided an updated set of observed GPS displacements associated with this event.

Due to the large amount of interseismic and postseismic displacement accumulated in the 13 years elapsed between the event and the post-earthquake survey, we first modeled the displacements due to the pre-earthquake velocity and the effects of afterslip and viscoelastic relaxation separately, and removed them from the observed displacements to output a reasonable coseismic displacement field with the near-field observations. Constrained by the GPS coseismic displacements, we used a variable slip model to further invert for the coseismic slip distribution of this event.

The GPS-derived result shows good agreement with previous studies from field measurements, high-resolution satellite images and InSAR. The largest slip occurred on the Kusai Lake segment, with the maximum slip of 8.0 m at 93.6° E. Furthermore, due to the existence of near-field observations in the Kusai Lake segment, we estimated a more detailed slip pattern of two subsegments, one with smaller slip of 4~6 m extending to a deeper depth of ~20 km and the other with larger slips 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.