Saturday, 27 November 2021

Magnitude 6.2 Earthquake in the India-Myanmar border region.

The Indian National Centre for Seismology recorded a Magnitude 6.1 Earthquake at a depth of 27 km, in the India-Myanmar border region, about 140 km to the southeast of the city of Aizawl in Mizoram State, India, at about 5.15 am local time on Friday 26 November 2021 (slightly after 11.45 pm on Thursday 25 November, GMT). Earthquakes this large and at this shallow a depth are considered to be extremely dangerous, as much energy is being dissipated close to the surface, where it can potentially do the most harm, although on this occasion there are no reports of any damage or casualties. The Earthquake was felt across northern Myanmar, Bangladesh, northeast India, and Bhutan.

The approximate location of the 26 November 2021 India-Myanmar border region Earthquake. USGS.

Earthquake activity in northeast India is influenced by the uplift of the Tibetan Plateau, due to the impact of India into Eurasia to the south. The Indian Plate is moving northwards at a rate of 5 cm per year, causing it to impact into Eurasia, which is also moving northward, but only at a rate of 2 cm per year. The collision of the Indian and Eurasian plates has led to the formation of the Himalayan Mountains, the Tibetan Plateau, and the mountains of southwest China, Central Asia and the Hindu Kush.

Block diagram showing how the impact of the Indian Plate into Eurasia is causing uplift on the Tibetan Plateau. Jayne Doucette/Woods Hole Oceanographic Institution.

The India-Myanmar border region is an area particularly prone to Earthquakes; much of Myanmar lies on the Burma Plate, a small tectonic plate caught between  the Eurasian Plate to the northeast, the Indian Plate to the west and southwest and the Sunda Plate to the southeast. As these larger plates move together the Burma Plate is being squeezed and fractured, with a major fault line, the Kabaw Fault, having formed across much of the north of the country, along which the Burma Plate is slowly splitting. Most Earthquakes in the region are caused by movement on this fault.

The movement of the Burma and surrounding plates. Sheth et al. (2011).

Witness accounts of quakes can help geologists to understand these events and the rock structures that cause them. If you felt this quake you can report it to the Indian National Centre for Seismology here.

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