Estimates of motion and strain rates across active faults in the frontal part of eastern Himalayas in North Bengal from GPS measurements

摘要

Within the 2500 km stretch of the Himalayas, a narrow window between longitudes 88.185 degrees E and 88.936 degrees E in the frontal Himalayas in North Bengal, crisscrossed by several active fault traces, presents an interesting region for crustal deformation study. We have estimated velocities of 8 GPS stations located in this area and the accumulating strain rate by two different methods. A total shortening of 11.1 +/- 1.5 mm yr-1 is occurring across a set of four E-W running faults: Gorubathan, Matiali, Chalsa and Baradighi. The strain rate becomes higher in the NE part of the network, reaching -(0.25 +/- 0.12) mu strain yr-1 with azimuth 21 degrees. A statistically significant extension of 10.9 +/- 1.6 mm yr-1 is estimated across the Gish transverse fault with a maximum strain rate of 0.36 +/- 0.08 mu strain yr-1 with azimuth 103 degrees. The accumulating strain will be probably released through future earthquakes.