Research of deformation processes associated with double plate subduction in the Kanto District

关东地区双板块俯冲变形过程研究

基本信息

批准号：
16540384
负责人：
SAGIYA Takeshi
金额：
$ 2.05万
依托单位：
Nagoya University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2004
资助国家：
日本
起止时间：
2004 至 2005
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-16540384/
关键词：
Kanto District Double plate subduction Locked zone Philippine Sea plate Pacific plate Postseismic deformation Kanto earthquake 地殻変動 GPS 二重沈み込みプレート境界有限要素法 2000年三宅・神津イベント

项目摘要

I estimated slip deficit distribution on the plate interface in the Kanto district using a plate configuration model based on large-scale seismic exploration results and microseismicity. The plate interface was estimated as shallower than previous models, and the resultant slip deficit is estimated on the shallower part of the plate boundary of the Philippine Sea plate. The deeper limit of the locked zone is estimated as 15-20km. The shallower locked zone indicates stronger seismic motion in case of large earthquakes, which is an important implication for seismic hazard assessment. Spatial distribution of the locked zone is consistent with the focal region of the 1923 Kanto earthquake. In addition, there is another locked zone southeast off the southern tip of the Boso Peninsula. Rupture of this locked zone may be a crucial factor to distinguish the two types of Kanto earthquake (the 1923-type and the 1703-type).The subducted Philippine Sea plate contacts the Pacific plate at its bottom. The slip deficit estimated on the Philippine Sea plate is slightly shifted counterclockwise from the relative motion between the NE Japan and the Philippine Sea plate. This difference is attributed to the effect of the Pacific plate subduction. After the 2000 Miyake-Kohzu seismovolcanic event, the crustal deformation pattern in the Kanto district changed. I investigated various possibilities, and concluded that this pattern change was caused by an "afterslip" on the interface between the Philippine Sea plate and the Pacific plate. Such an interplate sliding motion cannot be detected in a usual situation, but I speculate that a tremendous disturbance due to the Miyake-Kohzu event triggered such a rare event.

我使用基于大规模地震勘探结果和微震活动的板块配置模型估算了关东地区板块界面上的滑移赤字分布。板块界面被估计为比以前的模型浅，并且在菲律宾海板块的板块边界的较浅部分上估计了由此产生的滑移赤字。锁定区域的深度估计为15-20公里。锁定区越浅表明发生大地震时地震活动越强，这对于地震危险性评估具有重要意义。锁定区的空间分布与1923年关东地震的震源区一致。此外，房总半岛南端东南方还有另一个锁定区。这个锁定带的破裂可能是区分关东地震两种类型（1923年型和1703年型）的关键因素。俯冲的菲律宾海板块在其底部与太平洋板块接触。菲律宾海板块上估计的滑移赤字与日本东北部和菲律宾海板块之间的相对运动略有逆时针偏移。这种差异归因于太平洋板块俯冲的影响。 2000年三宅甲津地震火山事件后，关东地区地壳变形模式发生了变化。我调查了各种可能性，得出的结论是，这种模式变化是由菲律宾海板块和太平洋板块界面上的“后滑”引起的。这种板间滑动运动在通常情况下是无法检测到的，但我推测三宅-甲津事件造成的巨大扰动引发了如此罕见的事件。