Total of 450 earthquakes recorded in Assam, NE and vicinity in 2023

Assam hit by region’s highest of 68 earthquakes

Staff Reporter

Guwahati: It is a documented fact that we do not feel the ‘jolt’ of every earthquake that strikes the place where we live. Some of the earthquakes are of small magnitude and do not shake us up, so to speak.

In the last year, 2023, numerous earthquakes struck Assam and the NE region, but only a few were of high magnitude. According to a report, a total of 450 earthquake events were reported from the NE region and its neighbourhood.

The North Eastern Regional Node for Disaster Risk Reduction, North Eastern Space Applications Centre (NESAC), prepared a report titled ‘Earthquake Catalogue for the North Eastern Region of India—2023’, which mentions the number of earthquakes that hit the region. The report is a compilation of all reported earthquake events for the year 2023 collected from the National Center for Seismology (NCS), the United States Geological Survey (USGS), as well as any local reporting.

It is also mentioned in the report that the highest number of 68 earthquakes struck Assam, amongst all states in the NE region.

According to the report prepared by NESAC, Department of Space, Govt. of India, at Umiam, Meghalaya, a total of 450 earthquake incidents have been documented for the entire NER and its vicinity (87–98 degrees East and 21–30 degrees North) during the year 2023. No major damage or casualties have been reported in the NER region due to the earthquake events in 2023. Out of 450 earthquake events reported from the NER region and its neighbourhood, 68 were reported from Assam, 49 were reported from Manipur, 45 were reported from Meghalaya, 35 were reported from Arunachal Pradesh, 10 from Nagaland, 7 from Mizoram, 3 from Sikkim, and 1 from Tripura, with 232 events reported from the NER neighbourhood. 149 events were below Moment Magnitude (Mw) 3, 210 events were between Mw 3-4, 78 events were between Mw 4-5, and 13 events were between Mw 5-6. Out of 13 events having a magnitude greater than Mw 5, three instances were in Assam, one instance in Meghalaya, and the rest of the events were in the NER adjoining areas.

Regarding Assam, the report says that the state is characterized by significant seismic activity due to its location near the convergence of the Indian and Eurasian plates. The seismo-tectonic setting of Assam is influenced by compressional tectonic stresses, particularly in the north-south direction. Major faults play a crucial role in the seismo-tectonics of Assam. One of the prominent faults is the Kopili Fault, which is associated with the Main Himalayan Thrust (MHT). The MHT is a major fault system that separates the Indian plate from the Eurasian plate. Other significant faults in the region are: Lohit Thrust, Haflong Fault, Naga Thrust, Disang Thrust, Kulsi Fault, Dhubri Fault, Ultapani Thrust, and Atherkhet Fault. These faults contribute to the seismic activity in Assam, and their interactions with the tectonic forces in the area lead to the occurrence of earthquakes.

In the year 2023, a total of 68 earthquakes were triggered in Assam, which is the highest in the North Eastern states. The majority of the earthquakes occurred in central Assam, around the Kopili and Atherkhet Faults. Out of 68 events, there were three instances where the magnitude was greater than Mw 5. Other events ranged between Mw 2.1 and Mw 4.4. The majority of the events (46) were at shallow depths ranging below 10 km.

Historically, the NE region has experienced two great earthquakes of magnitude greater than 8.0 and about 20 large earthquakes of magnitude between 8.0 and 7.0 since 1897. The 1897 Shillong earthquake is one of the largest recorded earthquakes in Indian history. It caused widespread damage, triggering landslides, damaging buildings, and leading to the loss of life. In recent years, the north-eastern region has experienced several significant earthquakes. The 1950 Assam-Tibet earthquake and the 2011 Sikkim earthquake, both with magnitudes exceeding 6.9, resulted in casualties and extensive infrastructure damage. Apart from these earthquakes, several strong events have also caused widespread damage in the NER of India. These events serve as reminders of the seismic vulnerability of the region.

The report by the North Eastern Space Applications Centre says the North Eastern Region (NER) of India, nestled between the mighty Himalayas and the Indian Plate, is prone to frequent seismic activity, making it one of the most seismically active areas in the country. Earthquakes in the northeast have left a lasting impact on the region, shaping its geography and influencing the lives of its residents. NER lies in seismic zone V as per IS 1893 (2002) in the country and is considered one of the most seismically active zones in the world. It has a very complex tectonic and geological setup. NER is situated at the convergence of multiple tectonic plates, including the Indian, Eurasian, and Burmese plates. The complex interaction between these plates gives rise to a network of active fault lines that traverse the region, leading to significant seismic activity. The most prominent fault line in this area is the Main Central Thrust (MCT), which runs along the southern edge of the Himalayas and is responsible for numerous earthquakes in the region.

The north-eastern states of India, such as Arunachal Pradesh, Assam, Manipur, Meghalaya, Mizoram, Nagaland, Sikkim, and Tripura, are particularly vulnerable to earthquakes. These states lie close to the eastern Himalayan belt, where the Indian plate is being subducted beneath the Eurasian plate. The collision and subduction of these plates generate immense strain, which is periodically released through seismic events.

 Also Read: Assam: Earthquake Of Magnitude 4.0 Jolts Hailakandi (sentinelassam.com)

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