Seismicity and seismic hazard parameters in and around Pakistan

Abstract

Pakistan holds a key position within the Indian–Eurasian collision zone and is a highly earthquake-prone country of South Asia. Besides the devastating earthquakes of Quetta 1935, Makran 1945 and Pattan 1974, the earthquakes that happened in Bhuj 2001, Kashmir 2005 and Hindu Kush 2015 are three typical examples of the new millennium. In this study, the earthquake probability and the return period for magnitude recurrence hazard have been analysed using a magnitude homogenous earthquake catalogue. In Gumbel’s theory of extreme values, the Gumbel III distribution has a vital role to play as far as seismic hazard analysis of any regional seismicity is concerned. The Gumbel III distribution is used here to estimate the upper bound magnitude (ω value) and other earthquake hazard parameters in and around Pakistan. This method is applied to the whole of Pakistan (23° N–39° N; 59° E–80° E) and shallow (0–70 km) and intermediate (70–300 km) depth earthquakes in the Hindu Kush region across the Afghanistan–Pakistan border over the period 1930–2007. From the entire Pakistan dataset, the ω value is estimated as 8.12 (± 0.59). Furthermore, intermediate earthquakes in Hindu Kush have a ω value of 8.15 (± 0.56) compared with 7.08 (± 0.92) for the shallow earthquakes in the Hindu Kush. From probabilistic analysis of a spatial matrix of cells, results of earthquake expected magnitude parameters are then calculated, mapped, contoured and discussed in the context of recognized seismotectonic zones (Hindu Kush, Karakorum–Himalaya, Chaman fault system and Makran–Kutch) which characterize the seismicity of Pakistan and the surrounding region (Afghanistan, Tajikistan and India).