Source Parameters and Slip Distribution of the 2019 Mw 5.8 Mirpur (Pakistan) Earthquake Inferred from the Corrected InSAR Observations

Abstract

AbstractOn 24 September 2019, an Mw 5.8 earthquake occurred on the Mangla-Samwal anticline near Mirpur city, Pakistan. Because the seismogenic fault is hidden and the near-field seismic data are scarce, the magnitude and slip distribution of this earthquake are not determined. Furthermore, due to small deformation and significant atmospheric noise in the coseismic interferograms, it is difficult to accurately determine source parameters and slip distribution using the original single ascending and descending Interferometric Synthetic Aperture Radar observations. In this article, we used Sentinel-1A satellite Synthetic Aperture Radar data to generate 60 ascending and 56 descending coseismic interferograms and performed atmospheric error correction including Kriging interpolation correction and displacement stacking to obtain more accurate coseismic displacement fields for the 2019 Mw 5.8 Mirpur earthquake. Considering the local geological structures, focal mechanism solutions, and the optimal fault parameters obtained from the coseismic displacement inversion, we determine that the strike and dip of the fault of the 2019 Mirpur earthquake are 296.3° and 4.0°, respectively. Based on this fault model, the fault plane was extended to 12.0 km long and 11.0 km wide and divided into subfaults of 1.0×1.0  km2. We inverted the coseismic displacement fields to obtain slip distribution on the fault plane. Slip is mainly distributed at a depth of 4.7 ∼ 5.0 km, with a maximum of 0.95 m at a depth of 4.88 km. The slip distribution shows that this earthquake was a thrust event with right-lateral strike-slip components, which is consistent with the focal mechanism solution from the U.S. Geological Survey. The estimated geodetic moment is about 7.14×1017  N·m, equivalent to Mw 5.8.