1950 Assam–Tibet earthquake
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| Date | 15 August 1950 |
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| Origin time | 14:09:34 |
| Magnitude | 8.6 Mw |
| Depth | 15 km (9.3 mi) |
| Epicenter | 28°22′N 96°27′E / 28.36°N 96.45°E |
| Type | Strike-slip |
| Areas affected | Tibet, India |
| Max. intensity | XI (Extreme) |
| Casualties | 1,500–3,300 |
The 1950 Assam–Tibet earthquake, also known as the Assam earthquake, occurred on 15 August and had a moment magnitude of 8.6. The epicentre was located near Rima, Tibet. The earthquake was destructive in both Assam and Tibet, and between 1,500 and 3,300 people were killed.
It was the sixth largest earthquake of the 20th century. It is also the largest known earthquake to have not been caused by an oceanic subduction. Instead, this quake was caused by two continental plates colliding.
In an attempt to further uncover the seismic history of Northeast India, field studies were conducted by scientists with the National Geophysical Research Institute and Institute of Physics, Bhubaneswar. The study discovered signs of soil liquefaction including sills and sand volcanoes inside of at least twelve trenches in alluvial fans and on the Burhi Dihing River Valley that were formed by past seismic activity. Radiocarbon dating identified the deposits at roughly 500 years old, which would correspond with a recorded earthquake in 1548.
Strictly this was not an Indian earthquake; the epicenter was near Rima, in Tibet. Rima is situated within modern-day Zayü County. This shock was more damaging in Assam, in terms of property loss, than the earthquake of 1897. To the effects of shaking were added those of flood; the rivers rose high after the earthquake, bringing down sand, mud, trees, and all kinds of debris. Pilots flying over the meizoseismal area reported great changes in topography; this was largely due to enormous slides, some of which were photographed. The only available on-the-spot account is that of Frank Kingdon-Ward, a botanical explorer who was at Rima. However, he had little opportunity for observations; he confirms violent shaking at Rima, extensive slides, and the rise of the streams, but his attention was perforce directed to the difficulties of getting out and back to India. A new account of the earthquake is now available in "Once I Was Young" a book by Helen Myers Morse (Terre-Haute, Indiana, 2003, page 167-171), She was living near Putao (North Myanmar) at the time and wrote letters home. She - and 3 other American missionaries in different villages - speaks of the main shake, and the numerous aftershocks, as well as of the noise coming out of the earth.
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