Abstract

Robust relations correlating 10 different magnitudes of intermediate‐depth and deep‐focus earthquakes to moment magnitude are proposed, in order to be efficiently incorporated into the compilation process of homogeneous (with respect to magnitude) earthquake catalogs. By using global data available from International Seismological Centre (ISC), National Earthquake Information Center (NEIC), Comprehensive Nuclear‐Test‐Ban Treaty Organization’s International Data Centre (IDC), Institute of Physics of the Earth in Moscow, Russia, and China Earthquake Networks Center in Beijing, the performance of several widely used magnitude scales, such as body wave (mb, mB) and surface wave (Ms), is examined with respect to the moment magnitude scale (Mw). Similarly, appropriate Mw‐calibrated relations are also provided for regional magnitude scales such as the MJMA magnitude calculated by the Japan Meteorological Agency.

The analysis also involves the integration of focal depth as an additional variable to some of the above magnitude‐conversion relations. This depth effect proved to be important for ISC/NEIC’s body‐wave (mbIN) and surface‐wave (MsIN) magnitudes, leading to significant corrections for the estimated magnitudes. More specifically, a major change in the magnitude residual variation around the depth of 230 km was identified for the case of mbIN. Furthermore, the obtained results provide important observations on the behavior of certain magnitude scales. A typical case is the mb scale reported by IDC, which shows a systematic and large bias, with respect to the published Mw data values.

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