The P-wave travel times to Japanese stations were investigated. Kurile Islands earthquakes gave arrivals earlier than those expected from the Jeffreys-Bullen table. Neither location errors nor reading errors are likely to be the cause of this phenomenon. The early arrivals may be due to a high velocity structure beneath the Island Arc from the Kuriles to Japan. It is found that the upper boundary of this high-velocity structure is dipping toward south west and not shallower than 60km. Its thickness is increasing in the same direction and the lower boundary is not deeper than 400km. This pronounced anomalous structure could not be found in any direction other than that of the Kurile Islands. The seismic waves which travel in this anomalous region are less attenuated than those travelling elsewhere, especially in higher frequency range.|Nihon no kansoku ten made no P-ha no soji o shirabeta. Chishima no jishin wa Jeffreys-Bullen hyo kara kitaisareru yorimo hayai totatsu-jikoku o ataeru. Shino kettei aruiwa yomitori no gosa ga kono gensyo no gen'in towa kangaerarezu, Chishima kara Nihon made no kojyo-retto no shita no kosokudo kozo ni yoru mono to omowareru. Kono kosokudo kozo no jyogen wa nan-seini shitamuki ni katamuiteori, 60km yori mo asaku wa naranai. Kono kozo no atsusa wa onajiku nansei-hoko ni zokashi, sono kagen wa 400 km yori mo fukaku wa nai. Kono ijyo-kozo wa Chishima-retto igai no dono hoko kara mo miidasarenai. Kono ijyo-chiiki o toru jishin no nami wa tokuni koshuha-ryoiki ni oite hokano basho kara kita nami to kurabete gensui ga sukunai.
雑誌名
東京大學地震研究所彙報 = Bulletin of the Earthquake Research Institute, University of Tokyo
巻
47
号
3
ページ
467 - 486
発行年
1969-06-30
ISSN
00408972
書誌レコードID
AN00162258
フォーマット
application/pdf
日本十進分類法
453
出版者
東京大学地震研究所
出版者別名
Earthquake Research Institute, University of Tokyo
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20. On the Anomaly of Travel Time of P waves Observed at Japanese Stations Part(1)
ji0473005.pdf
(1.26MB)
