An Updated Catalog of Earthquakes for Southern Pakistan and Surrounding Offshore Region

This study presents a procedure for compilation of earthquake catalog for southern Pakistan (spreading over Sindh and Balochistan provinces) and frontal offshore area of Arabian Sea. The active tectonic plate margins of Indian, Eurasian and Arabian Plates and their associated fault lineaments are dominant seismic sources in study area. These seismotectonic sources are extending beyond the terrestrial boundaries of southern Pakistan and diversified in their seismic potential, accumulation of stresses and earthquake generating mechanism. We have compiled earthquake datasets for pre-instrumental period (325 B.C. to 1900) and instrumental observations during January 1901 to August 2020. The seismological datasets are gathered from open source agencies including ISC, GCMT, USGS, PMD and published catalogs. Since earthquake magnitude has a crucial role in seismological studies, the catalog has been thoroughly processed for magnitude homogenization to Mw scale. We have developed magnitude conversion correlations for Mb and Ms to Mw by orthogonal and least square regression analyses. The comparison of these correlations with previously developed regression equations by other authors in similar environments helped us to determine the validity of derived correlations for the study area. The best correlated relations are used for converging multimagnitude types in compiled catalog to Mw scale. Further the catalog is processed for removal of foreshocks- and aftershocks by Reasenberg declustering algorithm. The declustered catalog is used for integrated analysis of various parameters such as completeness analysis in time and magnitude, histograms of depth and magnitude, estimation of GR parameters. It is observed that declustered catalog has completeness period (1960–2020) which is significant for appropriate seismicity analysis.