Implications of long lasting post-seismic deformation following the 2005 Mw 7.6 Kashmir earthquake inferred from GNSS & InSAR data

• Quantification of long-term post-seismic deformation using GNSS and InSAR data. • Spatial and temporal variation of post-seismic slip along the ramp and the MHT. • Analysis of temporal and spatial correlation between aftershocks and afterslips. • Importance of post-seismic deformation of the seismic hazard assessment. Deformation in the western Himalayas is characterized by out-of-sequence fault activity and significant deformation along the Balakot-Bagh thrust, north of the Main Frontal Thrust, as shown by the 2005 Mw 7.6 earthquake. Using GNSS, Envisat, and Sentinel-1 InSAR data over varying time periods in the past two decades, we study the post-seismic deformation that occurred after this main shock. Displacement time series reveal a heterogeneous spatial and temporal distribution of post-seismic deformation. Inverting the surface displacements enables us to estimate the slip distribution and identify afterslip along the crustal ramp affected by the main shock, as well as two slip zones along the Main Himalayan Thrust, one to the northwest and one to the southeast of the rupture zone. This asymmetry coincides with the distribution of aftershocks, especially the strong concentration of deformation and aftershocks at the northwestern end of the rupture area. The clear relationship between the temporal decrease of aftershocks and the geodetic time series indicates that the main mechanisms of post-seismic deformation are afterslip and slow slip events. The northwest-southeast segmentation of slip seems to be linked to tectonic features influencing the slip distribution. We estimated that the total amount of co-seismic and post-seismic moment released is approximately 4.70 × 10²⁰ N·m, equivalent to an Mw 7.7 earthquake. However, it amounts to a very small fraction, only 30 % of the strain accumulated since the last surface rupture of that fault, which is estimate to ∼2000 years ago from paleoseismology (Kondo et al., 2008).