Seismo-Tectonic Studies on Split Subduction of the Steeply Dipping Plate

急倾板块分裂俯冲的地震构造研究

• 批准号: 09440161
• 负责人: KAKUTA Toshiki
• 金额: $ 1.34万
• 依托单位: Kagoshima University
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (B).
• 财政年份: 1997
• 资助国家: 日本
• 起止时间: 1997 至 2000
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-09440161/
• 关键词: split subduction; left-lateral strike slip; narrow seismic zone; block boundary of seismicity; Tokara submarine canyon; mantle wedge; Amami Oshima; OBS observation; 庵美大島周辺域の地震活動; 臨時地震観測; 3次元構造探査; 鹿児島地溝の地震; 阿多カルデラの群発地震; 奄美大島の地震活動; 定常的ハイレベルの活動

The 1997 Northwestern Kagoshima Earthquakes (M6.5, 6.3) suggest a left-lateral strike slip movement due to subduction of the Philippine Sea plate splitted into several blocks ; they occurred in a narrow seismic zone through the crust in South Kyushu with a strike of nearly E-W and a block boundary of seismicity is found on the east extension of the zone in a region of Hyuganada. It is probably another evidence that westward migration of swarm type earthquakes was observed along the zone from January through July, 1995. Then we investigated especially crustal structures along the seismic zone on land and west off Kyushu.Seismic activity in and around the Tokara submarine canyon, north off Amami Oshima, Ryukyu islands was investigated in detail by deploying not only OBS's but also temporary stations, because a left-lateral tectonic line is geologically supposed along the canyon and because dip angles of the subducting plate are iferred to differ largely on the both sides with each other. From the temporary observation in Amami Oshima, we found crustal earthquakes at depths of 11 to 19km and active earthquakes in a mantle wedge where any earthquakes have never been found in Kyushu except the east region off Tanegashima island. The subducting plate is also estimated at depths of 40-50 km with a low dip angle of about 25° under the island. From the observation of 10 OBS's and 9 land stations deployed aroud the Tokara submarine canyon, any clear difference was, however, not found in dip angle between both sides of the canyon, although some clusters of crustal and intraplate earthquakes were found along the canyon.

1997年，北岛西北部地震（M6.5，6.3）表明，由于菲律宾海板的俯冲俯冲成几个街区，左侧罢工滑动运动。它们发生在北九州南部的狭窄地震区域，几乎是E-W的罢工，在Hyuganada地区的东部延伸中发现了地震范围的块边界。这可能是另一个证据表明，从1995年1月到1995年7月，沿该区域观察到向西迁移地震。然后，我们调查了沿着地震区域沿着地震区和Kyoshu的地壳结构进行调查。构造线在地质上是沿峡谷期望的，并且因为俯冲板的倾角在很大程度上彼此不同。从Amami Oshima的临时观察中，我们发现了地壳地震在11至19公里的深处，并且在地幔楔形物中，在地幔楔形物中，在kyushu中从未在Tanegashi岛附近的东部地区发现任何地震。俯冲板还估计在40-50 km的深度，低倾角角度约为25°。从观察10个OBS和9个地下的陆地站部部署了Tokara潜艇峡谷，尽管沿峡谷发现了某些地壳和碎屑地震的簇，但在峡谷两侧的倾斜角度都没有发现任何明显的差异。

项目成果

MIYAMACHI Hiroki: "Fine structure of aftershock distribution of the 1997 Northwestern Kagoshima Earthquakes with a three-dimensional velocity model."Earth Planets Space. 51. 233-246 (1999)

宫町弘树：“1997 年鹿儿岛西北部地震的余震分布的精细结构与三维速度模型。”地球行星空间。

宮町宏樹: "1997年鹿児島県北西部地震の臨時余震観測" 北海道大学地球物理学研究報告. 61. 85-98 (1998)

Hiroki Miyamachi：“1997年鹿儿岛西北部地震的异常余震观测”北海道大学地球物理研究报告61。85-98（1998）。

MIYAMACHI Hiroki.: "Fine structure of aftershock distribution of the 1997 Northwestern Kagoshima Earthquakes with a three-dimensional velocity model"Earth Planets Space. 51-4. 233-246 (1999)

宫町弘树：“1997年鹿儿岛西北部地震余震分布的精细结构与三维速度模型”地球行星空间。

MIYAMACHI Hiroki.: "Temporary seismic observation of aftershocks for the 1997 Northwestern Earthquakes in Kagoshima Prefecture"Geophys.Bull.Hokkaido Univ.. 61. 85-97 (1998)

宫町宏树：“1997年鹿儿岛县西北地震余震的临时地震观测”Geophys.Bull.Hokkaido Univ.. 61. 85-97 (1998)

Hiroki Miyamachi: "Fine structure of aftershock distribution of the 1997 northwestern Kagoshima earthquakes with a three-dimensional velocity structure"Earth.Planets and Space. 51・4. 233-246 (1999)

Hiroki Miyamachi：“1997年鹿儿岛西北部地震的余震分布的三维速度结构”地球.行星和空间51・4（1999）。