At 6.4 on Richter Scale, Assam Recorded the Biggest Quake After 1960

An earthquake of magnitude 6.4 struck Sonitpur, Assam and adjoining areas, including Bhutan received a major jolt in the wee hours of April 28.

According to the Seismologist Department, a total of 6 aftershocks of magnitude ranging from M: 3.2 to M:4.7 were located within 2 hours 30 minutes from the time of occurrence of the Main shock of M:6.4, signifying the release of the stress in the vicinity of today's source zone in and around Sonitpur, Assam.Read more

Figure 1: Seismicity (M ≥ 4.0) in the Assam and surrounding the region during 1960 -March 2020 [earthquake data source: seismo.gov.in and Geological faults and lineaments source: Bhukosh, GSI] and the Mainshock of 28^th April 2021 is also shown

Meanwhile, Sonitpur, Assam the historical and instrumentally recorded earthquake data (NCS catalogue) reveals that the region is affected by moderate to large earthquakes and the most prominent events among those are the 29 th July 1960 Assam earthquake of M 6.0.

The epicentre is closer to the plate boundary and located at about 80 Km NE of Guwahati; 132 Km N of Shillong and 180 Km W of Jorhat. The preliminary analysis shows that the events are located near to Kopili Fault closer to Himalayan Frontal Thrust (HFT).

The area is seismically very active falling in the highest Seismic Hazard zone V associated with collisional tectonics where Indian plate subducts beneath the Eurasian Plate. Read more

Figure 2: Estimated earthquake Intensity Map of the Mainshock M:6.4 of 28^th April 2021