著者

長谷川 昭 海野 徳仁 高木 章雄 鈴木 貞臣 本谷 義信 亀谷 悟 田中 和夫 澤田 義博

出版者

公益社団法人 日本地震学会

雑誌

地震 第2輯 (ISSN:00371114)

巻号頁・発行日

vol.36, no.2, pp.129-150, 1983-06-25 (Released:2010-03-11)

参考文献数

18

被引用文献数

13 13

---

Precise relocation of earthquakes occurring in Hokkaido and northern Honshu during the period from January, 1979 to October 1981 is made by using 35 stations of the microearthquake observation networks of Tohoku University, of Hokkaido University, of Hirosaki University and of Central Research Institute of Electric Power Industry. Obtained hypocenter distribution shows the double-planed structure of the deep seismic zone in the whole area of Hokkaido and northern Honshu including the junction between the northeastern Japan arc and the Kurile arc. At the junction the deep seismic zone is contorted but is still double-planed at least in the upper 150km depth range. Beneath the southern end of the Kurile arc (central and eastern Hokkaido) the upper seismic plane of the double seismic zone disappears at depths greater than about 120km, whereas the seismicity in the upper seismic plane is still active in this depth range beneath the northeastern Japan arc.Hypocenters on the deep seismic zone beneath Hokkaido, relocated in the present study, are systematically shifted to the SE or SSE direction in comparison with the locations by the Hokkaido University network. This systematic shift of hypocenters is found to be well explained by the existence of the subducted lithosphere with seismic wave velocities higher than the surrounding mantle.