Characteristics of the Earthquake Swarms in the Andaman Sea Region, India, from 1960 – 2020

Abstract

The Andaman Sea region is the highly tectonically and seismically active region in India. This is the perfect site for studying earthquake swarms and how the swarms are reacting with the volcanic activities and tectonic processes. Using the International Seismological Centre (ISC) catalogue and USGS NEIC catalogue, we documented 17 earthquake swarms from 1960 to 2020. The hypocentre of the earthquake swarms was reported at 5 km. to 50 km and most of the incidents occurred below 20 km. depth. We examined the seismotectonic characteristics of these swarms. The moment tensor solutions of 6 swarms showing these events are controlled by pure normal faults with a significant strike-slip component, few are dominated by strike-slip faults but no thrust mechanisms are recorded. The b value distribution for the Andaman Sea region was calculated from the swarms’ data and the b value significantly varied between 1.4 –2.17. We conclude that the earthquake swarms in the Andaman and Nicobar Island region are probably the result of magma intrusion in the thin and hot oceanic crust. High b values, active volcanoes and cratered seamount support the volcanic background of these swarms.