2 0 0 0 OA 北ペルーで採集された巨大なレプトセファルス幼生
- 著者
- 多部田 修
- 出版者
- The Ichthyological Society of Japan
- 雑誌
- 魚類学雑誌 (ISSN:00215090)
- 巻号頁・発行日
- vol.17, no.2, pp.80-81, 1970-07-15 (Released:2010-06-28)
- 参考文献数
- 6
ペルーの沖合で採集された大型のレプトセファルス幼生にっいて, 予報的にその形態と採集の記録を報告した.この幼生は全長74.7cmで, 糸状の尾部をもち, 腹鰭と発達した背鰭がなく, Leptocephalus giganteus Castle, 1959によく似ているが, 色素配列が異なる.この種はSmith (1970) によればNotacanthiformのものと考えられている.また, 今回の標本にはL.giganteusには記載のない肉質小突起が体側下縁に認められる.採集地は8°22'S: 79°56'W (水深218m) で, トロールネットによって, かなり上層と思われるところから採集された.
2 0 0 0 OA 三宅島, 神津島, 新島周辺の過去の地震活動
- 著者
- 浜田 信生
- 出版者
- Tokyo Geographical Society
- 雑誌
- 地学雑誌 (ISSN:0022135X)
- 巻号頁・発行日
- vol.110, no.2, pp.132-144, 2001-04-25 (Released:2009-11-12)
- 参考文献数
- 20
- 被引用文献数
- 5 4
Based on macro seismic and instrumental observation data covering a period of over hundred years, the characteristics of seismic activity around Miyakejima, Kozushima, and Niijima, the northern Izu islands, were investigated. Seismic activity is distributed along the Zenisu ridge and the Nishi-Shitito ridge to the west and along Niijima, Miyakejima, Mikurajima and Hachijojima islands to the east. Most of the seismic activity in the region is of the swarm type and is often induced by a large earthquake or magmatic activity at Miyakejima and other volcanoes. Comparison of macro-seismic data of large earthquakes in the late 1800s and the early 1900s with a seismic intensity map of recent earthquakes suggested that the maximum size of an earthquake in the region is around a magnitude of 6.5 on the JMA magnitude scale. Linear arrangements of seismicity in the NE-SW direction, which is parallel with the Zenisu ridge, and in the NW-SE direction, which is almost normal to the former and parallel to the direction of the plate motion of the Philippine Sea plate, are often recognized. While the strike slip-type earthquake with a NE-SW tension axis is predominant in the region along Niijima, Miyakejima, Mikurajima, and Hachijojima islands, a strike slip with E-W tension axis is predominant in the region along the Zenisu ridge and the Nishi-Shitito ridge. A complex tectonic setting of the region, back arc spreading, collision of the Philippine Sea plate to the Eurasian plate around the Izu peninsula, deformation of the plate due to the subduction of slab from the Suruga and the Sagami trough, must shape the characteristics of seismic activity in the region such as the upper limit of earthquake scale, swarm-type activity, close relation with volcanic activity, and regional stress pattern.