- 著者
-
笹谷 努
Yoshii Toshikatsu
Ikami Akira
Tanada Toshikazu
Nishiki Tsukasa
Kato Susumu
- 出版者
- 東京大学地震研究所
- 雑誌
- 東京大学地震研究所彙報 (ISSN:00408972)
- 巻号頁・発行日
- vol.65, no.1, pp.p33-48, 1990-06
- 被引用文献数
-
5
In October 1982, a seismic refraction experiment was conducted by the Research Group for Explosion Seismology in the Miyota-Shikishima Profile in Nagano and Yamanashi Prefectures, central Japan. Five shots were fired on the 60 km-long profile. The upper crustal structure derived from travel-time data is simple and has a high velocity gradient; 4.0km/s at the surface to 6.0km/s at about 2.5km depth. Based on the amplitude-distance pattern of the refraction phases, we confirmed the existence of the velocity gradient. A few explosive sources generated clear S waves with amplitudes large enough to be read. We obtained an average POISSON'S ratio of around 0.246 in the uppermost crust from S to P travel time ratios. The other later arrivals were interpreted as reflected phases from a deep interface, the Conrad discontinuity. We modeled the interface shape by the ray-tracing technique. The interface inclines teward the north by about 20°.地震予知計画による4度目の爆破地震の実験が, 1982年10月,日本中部の長野県から山梨県にかけての御代田-敷島測線上で行われた. 60kmの測線上の5個所で爆破が行われ,約60点の臨時観測点で観測された.この実験の概要と,得られた記録や走時データなどの基礎的な資料については,すでに報告されている(爆破地震動研究グループ, 1986).ここでは,これらのデータの解析結果について報告する.