History of 1935 Quetta earthquake

Quetta and its neighboring 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 Mw  and previous estimates of 8.1 Mw  are now regarded as an overestimate. The epicenter 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 Mw  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.