5 magnitude earthquakes in the Andaman and Nicobar Islands
Andaman and Nicobar earthquakes: 25 seismic events recorded in two days — Analysis
In the last two days, 25 seismic events with magnitudes ranging from 3.8 to 5 have been reported in the region.
Following a dozen seismic events reported in the Andaman and Nicobar Region on Monday and Tuesday. The National Center for Seismology (NCS) reported that the events were mostly concentrate at the mid-crustal level and along the back-arc.
In the last two days, 25 seismic events with magnitudes ranging from 3.8 to 5 were report in the region. With the epicentres of these earthquakes located between the West Andaman Fault and the Andaman Spreading Ridge, according to the NCS analysis.
“The continuous occurrences of earthquakes with magnitudes ranging from M:3.8 to M:5.0 suggest the release of accumulated seismic strain due to the perturbation of the stress level in the areas of the subducting Indian plate and its surroundings,” according to the analysis.
Several (seismic) swarms and aftershocks have occurred in the Andaman Sea region over the last five decades. With varying depth and magnitude. “The current earthquake activity is not unusual, and such activity has occurred in the past,” according to the analysis.
Three major phases of swarm activity were report in 1983-1984, 1993. And 2005, as well as major aftershock activity in 2009-2010.
The 1983-1984 event included approximately 50 seismic events (3.5-5.5 M). From December 1983 to March 1984, the swarms congregated on the NE-SW oriented Andaman Spreading Ridge along the eastern area of the Alcock Rise. The 1993 swarm consisted of only about 35 seismic events (3.5-5 M). All of which were concentrate in the southwest segment of the central Andaman Spreading Ridge.
From January 26 to February 2, 2005, the most intense aggregate earthquake swarm known as the Nicobar cluster occurred in the Andaman Sea. The back-arc region of the Sumatra-Andaman subduction zone, between the Car-Nicobar and Great Nicobar Islands.
“There were also some major aftershocks activities at Andaman Trench and Andaman spreading Ridge. During the period from June-November 2005, August 2009 to June 2010. Added the continuous release of seismic strain in the region from time to time,” the report said.
Andaman and Nicobar Islands have a complex topography that includes a volcanic arc system. A back-arc spreading ridge, several sea-mounts, and faults. According to the seismic zonation map of India published in 2016 by the Bureau of Indian Standards. The region is in Zone-V, the highest level of seismic hazard potential.
