Significant seismic activity in Hazara-Kashmir Syntaxis prior to the Muzaffarabad earthquake of October 08, 2005

Muhammad Qaisar, Muhammad Daud Shah, Tariq Mahmood and Karam Khan

Micro Seismic Studies Program, Ishfaq Ahmed Research Laboratories,
Pakistan Atomic Energy Commission, Islamabad

The Muzaffarabad earthquake of October 08, 2005 was preceded by the occurrence of two moderate earthquakes of magnitude ML 5.6 and 5.4 on February 14, 2004 in Kaghan Valley of northern Pakistan. The events were located in Mansehra district near the town of Paras, about 30 km NNW from Muzaffarabad. These earthquakes were the result of thrusting near the northern extent of the Hazara-Kashmir Syntaxis and activity occurred mainly in the WWS of MBT. The seismic as well as geological data suggest that the tectonic movement is concentrated in upper crust down to a depth of about 10 km. The composite focal mechanism solution of the earthquakes, using combined polarity data of local network and global stations, indicates dominantly thrusting with orientation striking 335o NNW-SSE and dipping 55o in NE.

The observations made during the field work indicate that the intensity contours are converging around the town of Paras in Kunhar Valley in an elongated shape trending NW-SE. The isoseismal map shows that the lateral extent of the intensity contours did not extend significantly far from peak intensity (MM VIII) point near Paras. Most of the damage took place along the strike of seismogenic fault. Sharp relief and loose/thin fluvial filled narrow valleys further added to the damage caused by the earthquake.