A study on the enhancing earthquake frequency in northern Pakistan: is the climate change responsible?

In northern Pakistan, the collision between Indian and Eurasian plates has resulted in the formation of many faults. The concentration of ruptures, in this regime, makes it sensitive to the localized changes in the stress. The current climate changes have caused an increase in the rainfall and variation in the mass of glaciers, present in the northern Pakistan. The rainfall and glacial runoff have potential to erode and transport sediments and thus can change the balance of load across faults. On the other hand, glacial mass loss or gain also has potential of isostatic rebound or compression of crust, respectively. All these factors have been observed in the northern Pakistan. The seismic data of the duration 1965–2004 have been obtained from Pakistan Meteorological Department, and the sedimentation data have been acquired from Tarbela Dam Project. The study indicates a gradual increase in the earthquake frequency for the magnitudes 4.1–5.0 Mb. The epicentral distributions show that these events gradually cluster in the central Karakorum and Hindu Kush areas. The depth analysis suggests that the earthquakes with the foci 0–60 km are gathering in the central Karakorum and shocks with depth 0–120 are clustering in the Hindu Kush areas. The FMS study exhibits the dominance of normal faulting in the central Karakorum after 1999, and these characteristics do not correspond with behavior of previous mapped Raikot Fault, lying in the vicinity. The known significant variables during the study period are the different geological processes associated with climate change, which have potential to alter the load across faults and can possibly result in enhancing earthquake frequency by changing and releasing stresses at some local scale.