Study on Some Recent Earthquakes of Sikkim Himalayan Region and Construction of Suitable Seismic Model: A Mathematical Approach

摘要

Sikkim Himalayan region lies between Nepal-India border in the west and the Bhutan Himalaya in the east. The region is known to be characterized by strike-slip motion on certain deep-rooted faults. In the past, the region has experienced several devastating earthquakes, namely April 25, 2015 Nepal earthquake (M: 7.8); September 18, 2011 Mangan (Sikkim) earthquake (M: 6.9); February 14, 2006 Sikkim earthquake (M: 5.3), and the like. The present study mainly focuses on few major shocks and their source mechanism to explain properly the process of tectonics. A numerically stable computational scheme, using method of eigenfunction expansion has been used in the study to compute surface response or theoretical seismogram in a layered vertically stratified media overlying a half-space. Simple dislocation source model has been considered. The transverse (SH) and vertical (P-SV) components of displacement field have been computed exactly as summed modes by propagator matrix approach using Runga-Kutta method of order 4. The present result has been compared with the observed seismograms. The overflow error appearing in the numerical computation has been prevented by approximating layer matrices suitably or using generalized R/T (Reflection and Transmission) coefficients. The numerical result has been represented here graphically. The study has an advantage to get an idea of real earth structure or seismic source model by an inverse iterative technique.