Source Study of the Himalayan Earthquakes Using Physics-based Modelling Tools

Mahanti, Sankha Subhra (2021) Source Study of the Himalayan Earthquakes Using Physics-based Modelling Tools. Masters thesis, Indian Institute of Science Education and Research Kolkata.

Text (MS Dissertation of Sankha Subhra Mahanti (16MS180)) 16MS180_Thesis_file.pdf - Submitted Version Restricted to Repository staff only Download (26MB)

Abstract

The Indian plate is colliding with the Eurasian plate resulting in the tectonically active Himalaya region. Hence, this is an active seismic zone with frequent seismic activity. But due to the non-uniform rate of convergence of the Indian and Eurasian plate, the tectonic nature varies. So, the nature of earthquakes vary as well. Hence, we look at the earthquakes along the Himalayan arc in the last 30 years and compare the earthquake mechanisms at different regions. We use three different inversion methods using tools from Physics and Mathematics to model the earthquakes. The large megathrust earthquakes are modelled as multiple point sources using finite fault inversion method whereas moderate to strong earthquakes are modelled as a single point source using moment tensor inversion method. Moreover, we applied a new bootstrapping based probabilistic inversion method and compared the results. Then we compared our obtained slip vectors with GPS velocity direction. The match with the GPS motion data validates our inversion results. Finally, we look at the obtained mechanisms in cross-section probles across the Himalaya at different regions along with microseismicity distribution, local structure and topography. From this, we identify the regions where the earthquakes are rupturing the Main Himalayan Thrust and releasing the stress and regions where the earthquakes are decoupled from the MHT and occur inside the Indian plate.

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