Velocity structure and hypocentral location of earthquakes by simultaneous inversion method: Application to the area of Kalabagh, Pakistan | [Journal of Himalayan Earth Sciences • 2014]

Author(s):

1. M. Qaisar: Center for Earthquake Studies, NCP Quaid-i-Azam University Campus, Islamabad, Pakistan

2. M. B. Shahid: Micro Seismic Studies Progamme, Islamabad, Pakistan

3. Tariq Mahmood: Micro Seismic Studies Progamme, Islamabad, Pakistan

4. Karam Khan: Micro Seismic Studies Progamme, Islamabad, Pakistan

5. Suhail Ahmad: Micro Seismic Studies Progamme, Islamabad, Pakistan

Abstract:

A layered P-wave velocity model in the crust and just below the Moho is estimated for the Kalabagh area. The arrival-time data of p-waves from local earthquakes that occurred within the Kalabagh seismic network operated from March 1981 to September 1990 are used for inversion. A damped least-squares method is applied in the inversion process for determining the hypocenter and velocity parameters simultaneously. The estimated P-wave velocities are 5.33±0.04 and 5.56±0.05 km/s in the upper crust (above a depth of 11km), 6.27±0.03 and 6.57±0.08 km/s in the intermediate crust (from 11 to 25 km of depth) and 6.94±0.09 km/s in the lower crust i.e. up to the Moho discontinuity which is, in this case, at 35.5 km depth. The velocity just below the Moho is found to be 8.00±0.09 km/s. The 90% of relocated events show an epicentral accuracy of the order of 2km or better. Most of the relocated events are found at a depth range of 5 to 20 km, indicating that the active zone lies in this depth range.

Page(s): 141-149

DOI: DOI not available

Published: Journal: Journal of Himalayan Earth Sciences, Volume: 47, Issue: 1, Year: 2014

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