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Monitering of submarine crustal activity by ocean acoustic waves and ocean-seismic waves

利用海洋声波和海洋地震波监测海底地壳活动

基本信息

批准号：
10440125
负责人：
FUKAO Yoshio
金额：
$ 8.32万
依托单位：
University of Tokyo
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B).
财政年份：
1998
资助国家：
日本
起止时间：
1998 至 2000
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-10440125/
关键词：
submarine volano OBS ocean acoustic waves seismic waves 海底 T-phase

项目摘要

(1) Study of anomalous submarine earthquakes by ocean acoustic wavesAn anomalous submarine earthquake with the CLVD mechanism happened near Torishima Island. We found that this earthquake generated a series of ocean acoustic wave trains. The analysis of the OBS records of these waves lead us to conclude that the crustal deformation associated with the CLVD earthquake squeezed magma fluid in the source region upward, that the ascent of the magma fluid generated volcanic earthquakes whose foci migrated upward progressively, and that these earthquakes generated a series of ocean acoustic wave trains.(2) Detection of submarine seismic activity by ocean-coupled shear wavesWe detected a series of events that generated "T phase-like" waves and found that they were the shallowest submarine seismic activity in a very localized area off Boso, Japan. Our theoretical study indicates that the observed "T-like" waves are the sediment-trapped shear waves coupled with ocean acoustic waves multiplly reflected at the sea surface. We named these waves "ocean-coupled sedimentary shear waves" which should be useful to detect any submarine shallowest activity.(3) Study of submarine volcanic activity by ocean acoustic wavesThe seismograms of OBS cable arrays often record ocean acoustic waves due to submarine volcanic activities. We located the origins of these waves near the northern end of the Mariana volcanic arc. The analysis of these waves indicate that the volcanic activity often starts gradually and stops abruptly and that ocean acoustic waves become more rich in lower-frequency content as the activity becomes more intense. We also detected a semi-diurnal migration of the T-phase origins, which is perhaps an apparent one due to the tidal effect of the velocity structure of the ocean.

(1)利用海洋声波研究海底地震异常在鸟岛附近发生了一次CLVD机制的海底地震异常。我们发现这次地震产生了一系列海洋声波序列。对这些波的OBS记录的分析表明，与CLVD地震有关的地壳形变将源区岩浆流体向上挤压，岩浆流体的上升产生了震源逐步向上迁移的火山地震，这些地震产生了一系列海洋声波列。(2)通过海洋耦合剪切波探测海底地震活动我们探测到一系列产生“类T相”波的事件，并发现它们是日本房总附近一个非常局部地区最浅的海底地震活动。理论研究表明，观测到的“类T”波是沉积物捕获的剪切波与海洋声波在海面多次反射的耦合。我们将这些波命名为“海洋耦合沉积剪切波”，这对探测任何海底最浅的活动都是有用的。(3)海底火山活动的海洋声波研究OBS电缆阵列的地震记录经常记录到海底火山活动引起的海洋声波。我们将这些波的起源定位在马里亚纳火山弧的北方端附近。对这些波的分析表明，火山活动往往是逐渐开始和突然停止的，随着活动的加强，海洋声波的低频内容也越来越丰富。我们还发现了一个半日迁移的T相起源，这可能是一个明显的一个由于潮汐效应的速度结构的海洋。