Analysis of the earthquake observation data in and around the Horonobe area

We have compiled seismic data obtained by JNC seismographic station and Japan Meteorological Agency (JMA) Hi-net stations including Wakkanai-kita, Wakkanai-higashi, Wakkanai-nishi, Sarufutu-kita, Sarufutu-minami, Hamatonbetu, Horonobe, Toyotomi, Nakatonbetu, Teshio, Otoineppu and Nakagawa station from December 20th, 2002 to September 30th, 2004 in and around the Horonobe area. In that period, 1,618 earthquakes were recorded by JMA stations in the area. 103 events out of them were recorded at least two JNC seismographic stations and were able to detect the arrival time of P- and S-wave. In this study, the hypocenters were calculated by hypomh and cross-spectruma method on the basis of JMA and JNC data. Cross-spectruma method is higher precise than hypomh method. As a result of cross-spectruma analysis, we could identify the 7 groups of hypocenter areas in and around the Horonobe area. It is examined that the relationship between the hypocenter information and geological structures based on hypocenter areas, existing topographical and geological features. (author)