Abstract

We determined focal mechanism solutions for 14,544 earthquakes that occurred in and around the Japanese Islands from July 1985 to December 1998 using first‐motion polarities reported by the Japan University Seismic Network and compiled by the Japan University Seismic Network Earthquake Catalog of First‐Motion Focal Mechanisms (JUNEC FM2). This catalog covers small‐magnitude earthquakes (M≥2.0) prior to the recent development of seismic observation networks and automated waveform data processing systems. This catalog will prove helpful in understanding the spatial and temporal heterogeneities of stress fields by combining recent focal mechanism solutions and also will be useful for statistical analyses.

Online Material: Figures of velocity structure, focal mechanisms, magnitude–frequency distributions, and temporal changes in station locations.

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