Seismicity of Japan from 1885 through 1925 : A New Catalog of Earthquakes of M=6 Felt in Japan and Smaller Earthquakes Which Caused Damage in Japan

Only one catalog has been available for moderate to large earthquakes occurring in the region of Japan in the years 1885 to 1925. However, this catalog, published by the Central Meteorological Observatory in 1952, has often been criticized as misleading, because no con- sideration is given to the depth of focus and magnitude values are unreasonably large for many earthquakes. A new catalog of earthquakes of M≧6 is prepared in this study to meet the demand in earthquake prediction and earthquake risk studies in Japan. Both instrumental and macroseismic data are used in the determination of focal parameters. Most of the data are taken from either published reports of the Central Meteorological Observatory, the Imperial Earthquake Investigation Committee, or written station reports collected and stored by the Japan Meteorological Agency and the University of Tokyo. The hypocenter location is mainly based on the S-P time intervals and the magnitude determination is mostly due to the maximum amplitude recorded by old-fashioned seismographs. For older events, the determination is more dependent on the seismic intensity distributions. The catalog (Table 7) lists 555 earthquakes of M≧5.9 and 53 destructive earthquakes of M ≧5.8. The procedure for the focal parameter determination is explained in detail using six sample earthquakes. Referring to the epicenter maps constructed from this catalog, characteristics of the seismicity of Japan in the period 1885-1925 are described. More detailed studies using this catalog will be given elsewhere. A special description of 79 selected earthquakes of particular interests is given in the last half of the paper