1935 Quetta earthquake

An earthquake occurred on 31 May 1935 between 2:30 am and 3:40 am at Quetta, Balochistan, British India (now part of Pakistan), close to the border with southern Afghanistan. The earthquake had a magnitude of 7.7 M_w  and anywhere between 30,000 and 60,000 people died from the impact. It was recorded as the deadliest earthquake to strike South Asia until 2005. The quake was centred 4 km south-west of Ali Jaan, Balochistan, British India.

Quetta and its neighbouring towns lie in the most active seismic region of Pakistan atop the Chaman and Chiltan faults. Movement on the Chaman Fault resulted in an earthquake early in the morning on 31 May 1935 estimated anywhere between the hours of 2:33 am and 3:40 am which lasted for three minutes with continuous aftershocks. Although there were no instruments good enough to precisely measure the magnitude of the earthquake, modern estimates cite the magnitude as being a minimum of 7.7 M_w  and previous estimates of 8.1 M_w  are now regarded as an overestimate. The epicentre of the quake was established to be 4-kilometres south-west of the town of Ali Jaan in Balochistan, some 153-kilometres away from Quetta in British India. The earthquake caused destruction in almost all the towns close to Quetta, including the city itself, and tremors were felt as far as Agra, now in India. The largest aftershock was later measured at 5.8 M_w  occurring on 2 June 1935. The aftershock, however, did not cause any damage in Quetta, but the towns of Mastung, Maguchar and Kalat were seriously affected.