Contemporary seismic moment budget along the Nepal Himalaya derived from high-resolution InSAR and GPS velocity field

Abstract

Throughout history, several large-magnitude earthquakes have caused damage to the Himalayan region and humanity. To understand the present-day strain rate distribution and associated seismic moment budget, a high-resolution velocity field is an essential component. The present study estimates the contemporary seismic moment budget along three spatial sections over the Nepal Himalaya using the state-of-the-art high-resolution velocity field. For this, (1) we integrate 5 years of InSAR data with 77 available GPS observations over the Nepal Himalaya; (2) we then calculate strain rate distribution (dilatational and maximum shear strain rates) from this integrated velocity field, and (3) at last, we compare the geodetic moment accumulation rate estimated from strain rate tensors with the seismic moment release rate based on an earthquake database of 500 years. The results reveal that: (1) the geodetic strain rate is not homogeneous over the Nepal Himalaya, rather along the main central thrust, a relatively higher strain rate is observed; (2) the geodetic moment rate from west to east across three sections ranges from \(23.39\times 10^{18}\) to \(16.59\times 10^{18}\) Nm/yr, with the minimum of \(8.05\times 10^{18}\) Nm/yr in central Nepal, whereas the seismic moment rate varies between \(5.02\times 10^{18}\) and \(11.41\times 10^{18}\) Nm/yr, with the minimum of \(3.69\times 10^{18}\) Nm/yr in central Nepal; (3) the difference between geodetic and seismic moment rates from west to east provides a moment deficit rate of \(18.37\times 10^{18}\) to \(5.18\times 10^{18}\) Nm/yr, with the minimum of \(4.36\times 10^{18}\) Nm/yr in central Nepal, and more importantly, (4) the inferred moment deficit rate suggests that the western and eastern Nepal have an earthquake potential of magnitude \(M_w\) 8.5 and \(M_w\) 8.1, respectively, whereas the central Nepal has energy budget equivalent to an \(M_w\) 7.9 event. In summary, the present study provides spatial distribution of earthquake potential in Nepal Himalaya using the most updated high-resolution InSAR and GPS velocity field, and the findings inevitably contribute to the time-dependent earthquake hazard analysis of the study region.