The Assam earthquake of 1897 occurred on June 12 in Assam, India, and had an estimated moment magnitude of 8.3. Considering the size of the earthquake, the mortality rate was not that high, with about 1,542 casualties, but property damage was very heavy. Damage from the earthquake extended into Kolkata where dozens of buildings were badly damaged or partially collapsed. Shaking from the event was felt across India, as far as Ahmedabad and Peshawar. Seiches were also observed in Burma.
The earthquake occurred on the SSW-dipping reverse Oldham fault that forms the northern edge of the Shillong Plateau within the Indian Plate. There was a minimum displacement on the main fault of 11 m (36 ft), although up to 16 m (52 ft) has been calculated, one of the greatest for any measured earthquake. The calculated area of slip extended 180 km (110 mi) along strike and from 9–45 km (5.6–28.0 mi) below the surface, indicating that the entire thickness of the crust was involved.
Thought to have happened 20 miles (32 km) underground, it left 390,000 square kilometres (150,000 sq mi) of masonry buildings in ruins and was felt over 650,000 square kilometres (250,000 sq mi), from Burma to Delhi. Numerous buildings in the neighboring country of Bhutan were heavily damaged. Dozens of aftershocks were felt in and around the region with the last event being felt on October 9, 1897 at 01:40 UT in Kolkata.