  | |
| Local date | 12 June 1897 (1897-06-12) |
|---|---|
| Magnitude | 8.2–8.3[1]Mw |
| Depth | 34 km |
| Epicenter | 26°00′N90°42′E / 26.0°N 90.7°E /26.0; 90.7[2] |
| Areas affected | India,Bhutan,Bangladesh |
| Max. intensity | MMI X (Extreme)[3] |
| Casualties | 1,542[4] |
TheAssam earthquake of 1897 occurred on 12 June, inAssam,British India at 11:06[2]UTC, and had an estimatedmoment magnitude of 8.2–8.3.[1] It resulted in approximately 1,542 human casualties and caused catastrophic damage to infrastructures. Damage from the earthquake extended intoCalcutta, where dozens of buildings were severely damaged, with some buildings partially collapsing. Tremors were felt across India, reaching as far asAhmedabad andPeshawar.Seiches were also observed inBurma.[4]
The earthquake occurred on the south–southwest-dipping reverse Oldham Fault that forms the northern edge of theShillong Plateau.[2][6][7] There was a minimum displacement on the main fault of 11 m, although some calculations have placed this figure at as high as 16 m; one of the greatest for any measured earthquake.[6] The calculatedarea of slip extended 180 km along the strike and from 9–45 km beneath the surface, indicating that the entire thickness of thecrust was involved.
Thought to have happened 32 km beneath the surface, the earthquake left masonry buildings in ruins over 400,000 km2 area and was felt over 650,000 km2 fromBurma toDelhi. Numerous buildings in the neighboring country ofBhutan were heavily damaged.[8] Dozens of aftershocks were felt in and around the region with the last event being felt on 9 October 1897 at 01:40UT in Calcutta.[4]
The earthquake resulted inShillong Plateau being thrust violently upwards by about 11 meters. The fault was about 110 km in length while the fault slip was about 18 m (accuracy more or less by 7 m). At the epicenter, vertical acceleration is thought to have been greater than 1g and the surface velocity estimated at 3 m/s.[6]
InShillong, the earthquake damaged every stone house and half the houses built of wood.[5]: 5 The shock leveled the ground and resulted in 13 deaths. Fissures were also reported in the area. In SohraCherrapunji, it resulted in a landslide, which led to 600 deaths.[9] InGoalpara, it resulted in waves from theBrahmaputra River, on whose bank the town is situated, destroying the market.[9] InNalbari, there were reported sightings of earth-waves and water waves. InGuwahati, the earthquake lasted for three minutes. The Brahmaputra rose by 7.6 ft. Damage was caused toUmananda Island temple and railway lines, where five people died.[9] InNagaon, every brick house was damaged, while traditional houses made of wood, with grass roofs, were bent. There were many small fissures/volcanos and the road was impassable for vehicles.[9]
In theSylhet region, shocks took place at 16:30 local time, according to villagers living at the foot of the hills north ofSunamganj. There were 545 casualties; 55 inSylhet town; 178 inNorth Sylhet; 287 inSunamganj; seven inHabiganj; eight inSouth Sylhet and 10 inKarimganj. Many building collapses, fissures and drownings furthered the number of deaths. A woman inSunamganj is said to have fallen through a fissure whilst on a river with her husband. The husband tried to hold onto her hair but lost hold of her. The woman's body was not recovered from thecrevasse. TheAssam Bengal Railway was severely damaged.[10][11][5]: 295–298
Richard Dixon Oldham, the Superintendent of theGeological Survey of India, analysed seismic records of the earthquake, mainly from stations in Italy, and reported the first clear evidence of different type ofseismic waves, travelling through the earth on different paths and at different speeds.[5]: 227–256
