SPATIO-TEMPORAL EVALUATION OF LONG-TERM EARTHQUAKE EVENTS AND ITS CONTRIBUTION IN GENESIS OF TSUNAMI IN THE INDIAN OCEAN

Abstract. A very high magnitude earthquake (9.1 MW) triggered a devastating Tsunami in the Indian Ocean on 26th December 2004. The epicentre was located at 3.3° N, 95.8° E with a focal depth of ~30 km. The impacts of Tsunami were felt as far away in Somalia, Tanzania and Kenya along the east coast of Africa. Considering the role of earthquake, in the present study the spatio-temporal analysis of long term (1901 to 2019) earthquake events was performed, which recorded by USGS to understand the genesis of Tsunami (2004) in the Indian Ocean. The study exhibited that the maximum frequency of earthquake was observed between the ranges of 4 MW to 6 MW on the Richter scale during 2001–2010. There was only one earthquake event > 8 MW on the Richter scale (26th December 2004 having depth 30 km) in the Indian Ocean recorded during 1901–2019. The study exhibited that the maximum earthquake was observed between 30–40 km below the surface, and primarily of moderate to low magnitudes. The proximity analysis along the major fault line indicates that the maximum earthquakes were in the buffer of 200 km from fault line in Bay of Bengal. The decadal variation of earthquake exhibits that the maximum number of earthquake events (8427 events) were triggered during the year 2001–2010, whereas during the year 2004, the total 902 earthquake events > 4 MW was recorded. The study indicates that the earthquakes > 7 MW (on Richter scale) and depth below 30 km (shallow earthquake) are primarily responsible to major Tsunami events in the Indian Ocean. The very high magnitude (> 9 MW on the Richter scale) and shallow depth (~30 km) are the major cause of 2004 Tsunami and its high level of damage. There were very low frequency (10–15 events) of earthquake occurred having magnitude > 7 and depth < 30 km.