Geodetic strain rate, slip deficit and seismicity analysis in Central Seismic Gap of the Himalayan arc

Geodetic strain rate, slip deficit and seismicity analysis in Central Seismic Gap of the Himalayan arc

 

Measurements of principal strain tensors and degree of locking (or interseismic coupling) is carried out using geodetic data in the Kumaun-Garhwal region. Our precise velocity field measurements in the Kumaun Garhwal Himalaya yields 17.5±0.7 mm/yr of plate convergence rate and ~90-110 km of locking width of the frontal Main Himalaya Thrust (MHT). We derive geodetic strain rate, locking heterogeneity and crustal stress variation from these measurements to understand the geodynamics of crustal behaviour in this region for accessing the potential seismic hazardous regimes. The degree of locking (interseismic coupling) on the MHT that results in a highly coupled (>0.6) frontal part of MHT with varying width of locking (70-90 km) across the main structural trend in the Kumaun- Garhwal Himalaya. We observe high strain rate (102 nano strain/yr) in the Higher Himalaya that gradually decreases towards south up to Himalayan front as well as towards north in the Tethys Himalaya. Spatial variation in the principal strain rate in the northwest Himalaya is also observed. The zone comprising of Himachal and Garhwal region is found to have relatively high average geodetic strain rate (110 nano strain/yr) as compared to average strain rate (67 nano strain/yr) in the eastern zone comprising of Kumaun and western Nepal region.

Figure: Interseismic plate coupling in the Kumaun Garhwal Himalaya.

 

Citation: SAROJ K. MONDAL, RAJEEV K. YADAV, AMIT K BANSAL, JOSHI K. CATHERINE, VINEET K. GAHALAUT, Himalayan Geology, Vol. 43 (1B), 2022, pp. 140-150