Regional earthquake magnitude conversion relations for peninsular India

Abstract

A homogenous earthquake catalogue is a crucial component for the purpose of evaluating a region's seismicity, seismotectonics, seismic hazard and risk. A variety of magnitude scales, including the local magnitude (ML), body wave magnitude (mb), surface wave magnitude (Ms), seismic moment magnitude (Mw), and others, are generally present in earthquake catalogues. Every study done so far for Peninsular India have used the homogenised Mw scale earthquake catalogue. However, recent studies have questioned the applicability of Mw scale for earthquakes of small and intermediate magnitudes. Hence, in this study, regional magnitude conversion relations in terms of Mwg for peninsular India (8-28 N, 68-87 E) are presented. The conversion relations are developed using data from national, regional, and international seismological agencies such as National Earthquake Information Centre (NEIC), International Seismological Centre (ISC), Global Centroid Moment Tensor (GCMT) and National Center for Seismology (NCS). General orthogonal regression (GOR) and standard least square regression (SLR) techniques have been used to generate regression relations between Mwg and mb, Mwg and Ms, and Mwg and ML for ISC, NEIC, NCS and GCMT events. According to the analysis, the equation developed by the GOR methodology outperforms the equation developed by the traditional method (SLR) in all cases. Correlation coefficient (Rxy) equals 0.91 and 0.92, for Mwg-mb, ISC, Mwg-mb, NEIC respectively, which indicates a relatively strong relationship. Also, Rxy are 0.97 and 0.98, for Mwg-Ms, ISC, Mwg-Ms, NEIC respectively, indicating a strong relationship. For Mwg-ML, Rxy equals 0.85, which indicates a moderate relationship. The generated regional magnitude conversion relations can be used for homogenization of the earthquake catalogue, which will also help this region's seismic hazard assessment in future