Seismology

Himalaya is the result of convergent movement of Indian plate moving to the northward and under thrusting to the south moving Eurasian plate. The collision of these two plates has formed the widespread Tertiary transgressions and development of major thrusts and nappes, directed towards the converging plate (Indian subcontinent). The study area during this training work, the Kumaon Himalaya is located near the central part of the Himalayan orogen and has been a critical area for studying the typical characteristics of the Himalayan tectonics, in contrast to the areas in close proximity to NE and NW- syntaxes where complications arise due to complex tectonics. In order to understand seismotectonics and sub-surface structure, the data of local earthquakes is used which is recorded by 13 broadband seismological stations established in the region, arranged in a linear array arrangement. These seismological stations cover all the major geo-tectonic units of the region e.g. the HFT, MBT, MCT, Munsiari Thrust (MT) etc. A maximum of 25 local events were selected from raw data and analysed under SEISAN software for estimation of the Hypocentral Parameters (Focal Depth, Origin Time, Epicentre and Magnitude). These events were then produced on a map, according to their estimated magnitudes. A further analysis is carried out for the analysis of Shear Wave Splitting Parameters on the selected local S-waves for studying the Crustal Anisotropy beneath the Kumaon Himalayan region. The waveform Cross-Correlation method is applied to compute the shear wave splitting parameters (i.e. Fast Polarization Direction and Delay time). The computed Fast polarisation Directions (FPD) shows NE-SW orientation, possibly due to the microcracks present in the subsurface.