Abstract Database


Supervisor: Nobuo HURUKAWA
Country: Pakistan
The Water and Power Development Authority in Pakistan (WAPDA) has been operating a seismic network in the northern areas of the country since 2010, in order to monitor seismicity in the region. To improve the identification of micro earthquake hypocenter locations, an average VP/VS ratio of 1.73 by plotting a Wadati diagram was obtained. Eight velocity models were examined using this value of the VP/VS ratio for the same data set. The Tarbela velocity model was found to be the best among these models considering the hypocenter distribution, the value of the root mean squared residual (RMS) and the number of zero-depth events. The crustal thickness of the Tarbela velocity model was modified from 33.5km to 60km considering RMS values for events outside the network. 185 earthquakes of M ≥ 0.6 reported by WAPDA for the period of 2010-2013 were relocated using the Modified Joint Hypocenter Determination (MJHD) method. Four groups of earthquakes were established. The first was along the Punjal Thrust in the Hazara Kashmir Syntaxes and the second along the Indus Kohistan Seismic Zone (IKSZ), which is 45 km long and 34km wide trending in a NW-SE direction. The seismicity for this area is mostly confined to a depth range of 0-30 km, extending in places to 60 km. Three subgroups were established within the IKSZ running in a NE-SW direction, which is perpendicular to the main trend of seismicity. The third group was found to be around  the Besham dome. The fourth group was along the Main Mantle Thrust (MMT). Two deep earthquakes were also located at depths greater than 250km. Furthermore, earthquake composite focal mechanisms in eight regions were obtained by using the relocated earthquakes. From these eight groups, seven thrust mechanisms and one normal mechanism were determined. For deeper crustal earthquakes (50-100km), a strike slip mechanism with E-W compression was established.