Crustal elasticity contrast across the East Kunlun fault in northern Tibet inferred from InSAR measurements of the 2001 Mw 7.8 Kokoxili earthquake

We use coseismic deformation data of the 2001 Mw 7.8 Kokoxili earthquake obtained from InSAR measurements to study crustal elasticity contrast across the East Kunlun fault. Coseismic deformation field of the earthquake documented by InSAR studies indicated that the displacements on the south side were 20% similar to 30% higher than that on the north side of the fault. We develop an elastic finite element model and invert InSAR data from two deformation profiles to estimate two parameters: the Young' s modulus contrast across the fault and the fault rupture depth. The starting lithospheric structural model is adopted from a seismic reflection study on the north side of the East Kunlun fault. Our result shows optimal estimates of the earthquake rupture depth as 20 similar to 22 km and the crustal Young' s modulus contrast between the south and north side as 81% similar to 92%. Such a result, obtained from study of crustal deformation, suggests a softer crust south than north of the fault, which is consistent with previous tomographic and magnetotelluric studies of a low-velocity and high-conductivity layer existing in lower crust of the Kokoxili-Qiangtang block south of the Kunlun fault.