Structural Trends and Focal Mechanism Studies in the Potwar Area with Special Emphasis on Hydrocarbon Exploration

Abstract

In the present paper an attempt has been made, for the first time, to identify the surface/subsurface structural pattern for the area of Potwar with the help of focal mechanism studies- a technique that is widely known for interpreting structural traps at depth. For this purpose all available earthquake data (during 1964- 2002) from international seismological networks and the local seismic observatories have been collected for the compilation of seismicity map of the area. Based upon this seismicity map, the area appears to be very active compared to the adjacent regions of Kohat Plateau and Salt Range with apparently very prominent patterns of seismicity along Jhelum Fault and Main Boundary Thrust (MBT). Focal mechanism solutions of thirteen events for which required parameters were available indicate left-lateral strike-slip faulting for eleven events while two events (4 and 10) represent thrust faulting. Earthquakes number 1, 6, 8 and 11 are located near Qazian anticline and all are representing basement events (as depth indicated by nearest local seismic observatory is > 6 km) except event number 11 whose depth is 5.0 km. The dominance of strike-slip faulting is in agreement with the previous workers. Majority of the interpreted focal mechanism solutions are located in the northeastern (i.e. near Jhelum Fault) and the northern portion (i.e. near MBT) of the area, which are major structures of the Potwar area. P-axes orientations (i.e. the axis of maximum compressions) are in NW-SE and NE-SW directions. Basement is found to be involved in the deformation.