Regional Earthquake Magnitude Conversion Relations for the Himalayan Seismic Belt

We present regional earthquake magnitude conversion relations among different magnitude scales (M-w, M-s, m(b), M-L, and M-D) for the Himalayan seismic belt developed from data of local, regional, and international seismological agencies (International Seismological Centre [ISC], National Earthquake Information Centre [NEIC], Global Centroid Moment Tensor Solution [CMT], International Data Centre [IDC], China Earthquake Administration [BJI], and National Centre for Seismology [NDI]). The intra(within the same magnitude scale) and inter- (with different magnitude scales) magnitude regression relations have been established using the general orthogonal regression and orthogonal distance regression techniques. Results show that the intramagnitude relations for M-w, M-s, and m(b) reported by the Global CMT, ISC, and NEIC exhibit 1:1 relationships, whereas M-L reported by the IDC, BJI, and NDI deviates from this relationship. The IDC underestimates M-s and m(b) compared with the ISC, NEIC, and Global CMT; this may be due to different measurement procedures adopted by the IDC agency. The inter-magnitude relations are established between M-w(,Global) (CMT) and M-s, m(b), and M-L reported by the ISC, NEIC, IDC, and NDI, and compared with the previously developed regional and global regression relations. The duration (M-D) and local (M-L) magnitudes reported by NDI exhibit a 1:1 relationship. The derived magnitude regression relations are expected to support the homogenization of the earthquake catalogs and to improve seismic hazard assessment in this region.