Unraveling seismic hazard by estimating prolonged crustal strain buildup in Kumaun-Garhwal, Northwest Himalaya using GPS measurements

Abstract

Himalayan mountain belt is one of the most rapidly deforming plate collision zones and is prone to produce megathrust earthquakes. In this study, a detailed measure of present-day deformation and strain-build up rate in the Kumaun-Garhwal region of Northwest Himalaya is carried out through eighteen GNSS stations extending from Gangetic Plains to Higher Himalaya during 2014–2019, to assess the seismic hazard potential of the region. The recorded GPS data at sites is analyzed along with nearby stable International GNSS stations for estimating daily basis precise positioning of the sites and further velocity solution is generated after applying the random noise estimated from GPS time series data. The acquired site velocity is used to calculate the principal strain rates and rotation rates using two independent approaches; least-square inversion approach based on scale factor and triangulation method. The derived strain rate reveals a mean rate of compression of ∼−0.07 ± 0.01 μ strain/yr towards northeast-southwest that gradually increases from the Outer Himalaya to Higher Himalaya for both approaches. We assume that this plate boundary compression deforms the Himalayan wedge across the Main Himalaya Thrust (MHT) and use Okada formulation for a rectangular dip-slip dislocation to calculate the plate convergence rate. Based on a regular grid search, we obtain a best fit convergence rate of 16.7 ± 2.0 mm/yr and locking depth of 17.4 ± 3.5 km. The strain budget analysis indicates that the Northwest Himalayan region has enough potential to produce at least one devastating earthquake of Mw ∼8 in the present scenarios.