Rheology of the zagros lithosphere from post-seismic deformation of the 2017 Mw7.3 Kermanshah, Iraq, earthquake

Abstract

We use 2018-2020 Sentinel-1 InSAR time series data to study post-seismic deformation processes following the 2017 Mw 7.3 Kermanshah, Iraq earthquake. We remove displacements caused by two large aftershock sequences from the displacement field. We find that for a six month period the response is dominated by afterslip along the up-dip extension of the coseismic rupture zone, producing up to 6 cm of radar line-of-sight displacements. The moment magnitude of afterslip is Mw 5.9 or 12% of the mainshock moment. After that period, the displacement field is best explained by viscoelastic relaxation and a lower crustal viscosity of ηlc =x1019Pas. The viscosity of the uppermost mantle is not constrained by the data, except that it is larger than 0.6x1019Pas. The relatively high lower crustal and uppermost mantle viscosities are consistent with a cold and dry lithosphere of the Zagros region.