Abstract
We use ALOS-2 and Sentinel-1 data spanning 2015–2020 to obtain the post-seismic deformation of the 2015 Mw 7.8 Nepal earthquake. ALOS-2 observations reveal that the post-seismic deformation was mainly distributed in four areas. A large-scale uplift deformation occurred in the northern subsidence area of the co-seismic deformation field, with a maximum uplift of ~80 mm within 4.5 yr after the mainshock. While in the southern coseismic uplift area, the direction of the post-seismic deformation is generally opposite to the co-seismic deformation. Additionally, two notable deformation areas are located in the region around 29° N, and near the MFT, respectively. Sentinel-1 observations reveal post-seismic uplift deformation on the north side of the co-seismic deformation field with an average rate of ~20 mm/yr in line-of-stght. The kinematic afterslip constrained by InSAR data shows that the frictional slip is distributed in both updip and downdip areas. The maximum cumulative afterslip is 0.35 m in downdip areas, and 0.2 m in the updip areas, constrained by the ALOS measurements. The stress-driven afterslip model shows that the afterslip is distributed in the downdip area with a maximum slip of 0.3 m during the first year after the earthquake. Within the 4.5 yr after the mainshock, the estimated moment released by afterslip is ~1.5174 × 1020 Nm,about 21.2% of that released by the main earthquake.
Highlights
In order to further explore the temporal characteristics of afterslip and its released moment, based on the kinematic afterslip evolution model constrained by ALOS-2 postseismic deformation, we calculated the seismic moment released by the afterslip in three different time intervals, these are the 4.5 yr, 2.5 yr and 2.5–4.5 yr periods after the Nepal
The post-seismic deformation of the ALOS-2 data is mainly distributed in four areas
The direction of the post-seismic deformation is opposite to the co-seismic deformation near the co-seismic deformation field, and another two deformation areas are located in the region of 29◦ N and near the MFT
Summary
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. Many studies have been carried out on the post-seismic deformation and afterslip that followed the Nepal earthquake, based on GPS and InSAR data, some studies have shown that the afterslip filled the slip-gap between the Mw 7.8 and Mw 7.3 earthquakes [8,9,10]. Used the 5 years of available GPS data and found that in the intermediate-field post-seismic deformation was caused by equal parts of afterslip and viscoelastic relaxation [14]. In this study we use the 4.5 yr ALOS-2 data for after the mainshock, with better coherence, to observe the characteristics of the post-seismic deformation in this area. We processed the 4.5 yr Sentinel-1 data based on the PS-InSAR (Permanent Scatterer InSAR) technique to obtain the average deformation-rate field, and the short-term post-seismic deformation based on the DInSAR (Differential InSAR) and Stacking technologies, to observe the post-seismic deformation and analyze the presence of afterslip in the updip zone
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