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Wednesday, 4 October 2023

Magnitude 5.7 Earthquake in Bajhang District, Nepal.

The United States Geological Survey recorded a Magnitude 5.7 Earthquake at a depth of 20.1 km, in Bajhang District, Nepal slightly after 2.20 pm local time, (slightly after 9.20 am GMT) on Tuesday 3 October 2023. The event was felt as far away as New Delhi in India, and is reported to have injured at least seventeen people, with one more missing and presumed dead after being engulphed by a rockfall. A number of homes are reported to have collapsed in the town of Chainpur, and a major highway is reported to have been blocked by a landslide triggered by the event. The initial event has been followed by at least two significant aftershocks. 

The approximate location of the 3 October 2023 Bajhang District Earthquake. USGS.

Earthquake activity in Nepal is caused 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.

Much of northern India and neighbouring areas of Central Asia and the Himalayas, are prone to Earthquakes, caused by the impact of the Indian Plate into Eurasia from the south. When two tectonic plates collide in this way and one or both are oceanic then one will be subducted beneath the other (if one of the plates is continental then the other will be subducted), but if both plates are continental then subduction will not fully occur, but instead the plates will crumple, leading to folding and uplift (and quite a lot of Earthquakes). 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.

The movement of India into Eurasia over the last 71 million years. USGS.

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