Implication for seismic hazards in Pakistan based on preliminary
geodetic measurements

M. Asif Khan 1, S. Faisal Khan  1, 5, Din Muhammad 2, Sarosh Lohdi 3, R. Bilham 4 and R. Bendick 5

1National Centre of Excellence in Geology, University of Peshawar, Peshawar, Pakistan
2Department of Geology, University of Baluchistan, Quetta, Pakistan
3Department of Civil Engineering, NED University, Karachi, Pakistan
4Department of Geological Sciences, University of Colorado, Boulder, USA
5Department of Geology, University of Montana, USA

Geodetic measurements in Pakistan using GPS technology started in 2001 soon after the Bhuj earthquake of 2001. This brief survey was confined to measurements on three points in the vicinity of Nagar Parker in the Thar Desert, SE of Sindh. In the same year, a survey campaign was carried out establishing about half a dozen points in northern Pakistan between Peshawar and Hunza along the Karakoram Highway. In 2002, a separate campaign resulted in the installation of about half a dozen points across the Potwar plateau between Islamabad and Chiniote. Following the 2005 Kashmir Earthquake, all these points were re-measured and a whole series of new survey points were established under a collaborative project between the universities of Peshawar, Baluchistan and NED from Pakistan, and Colorado, and Montana from USA. This campaign resulted in the establishment of a series of points across the Chaman fault, Baluchistan, and along the Coastal Highway, Makran, including some points in the southern Sindh province. There are now about six permanent GPS stations in Pakistan including one each in Peshawar, Karachi, and Quetta, and others in the field areas such as Mansehra and Potwar. In this presentation we give the salient results of these preliminary geodetic measurements and analyze their implications constraining the seismic hazards in Pakistan:

• The convergence rate across the Pakistan Himalayas amounts to 8.6±2 mm/yr in the direction normal to the NW striking Kashmir Himalayas. In comparison, the rate of contraction across the 150-km wide Central Himalayas is 18 mm/yr in the Indian subcontinent.
• A comparison between the geodetic data before and after the Kashmir Earthquake allows constraining the coseismic slip in the Indus-Kohistan Seismic Zone. Whereas between Bagh and Balakot the coseismic slip was 5.1±0.5 m, the coseismic slip NW of Balakot occurred on the wedge thrust belonging to the Indus-Kohistan seismic zone. The geometry of the wedge thrust allowed for surface displacements towards the NE even in areas which occurred in the hanging wall of the SW verging blind thrust belonging to the Indus-Kohistan seismic zone.
• Our data from Potwar, Sindh, Makran and Chaman, although in preliminary stages, suggest 8 mm/yr velocities for the Potwar Plateau and 3mm/yr for Karachi. At this stage only preliminary models are presented which may be used for going insight into the seismic hazards associated with these regions.