An Earthquake Classification Scheme Adapted for Japan Determined by the Goodness of Fit for Ground‐Motion Prediction Equations

Abstract Establishing a set of ground‐motion prediction equations (GMPEs) for Japan requires earthquake source categories in the dataset. Earthquakes are typically divided into three groups: shallow crustal events that occur in the Earth’s crust, subduction interface events that occur at the interface between the crust or mantle and the subducting plate, and the subduction slab events that occur within the subducting plate. In the present study, we compared the hypocentral locations published in the catalogs of the International Seismological Centre/Engdahl–van der Hilst–Buland (ISC‐EHB; Engdahl et al. , 1998), the Japan Meteorological Agency (JMA), and the National Earthquake Information Center (NEIC) of the U.S. Geological Survey (USGS). The hypocentral location for the same earthquake varies significantly from one catalog to another. We used the subduction interface model from the USGS, Slab 1.0, to help guide the classification. We designed four classification schemes using locations from these three catalogs. We then fitted a set of random effects models to the strong‐motion dataset from these earthquakes to assess the merits of the classification schemes. Our results showed that using ISC‐EHB locations for events before 2005, and then using the preference order of catalogs as (1) JMA locations with high precision levels, (2) ISC‐EHB, and (3) NEIC (excluding the events with a fixed depth) for events since 2005, together with some conditions for subduction interface events, produced the best GMPEs in terms of the maximum log likelihood. We also found that having a separate group for the earthquakes above the subduction interface, but with a depth over 25 km, improved the goodness of fit of the GMPEs. Online Material: Figures of azimuthal‐dependent distance shift of epicenters between catalogs, and between‐event and within‐event residuals.