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Estimation of the detailed structure of tsunami source based on survey results of submarine active aults

基于海底活动地质调查结果的海啸震源详细结构估算

基本信息

批准号：
15310124
负责人：
SHIMAZAKI Kunihiko
金额：
$ 7.42万
依托单位：
The 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：
2003
资助国家：
日本
起止时间：
2003 至 2004
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-15310124/
关键词：
Tsunami Beppu Bay Submarine active fault Keicho-Bungo earthquake

项目摘要

Submarine cored sediments from the Asamigawa Fault in the Oita port, Beppu Bay, and the seismic profile records show that the fault is one of the causative faults of the 1596 Keicho-Bungo earthquake. The single-channel high-resolution records illustrate not only seismic offsets of sediment layers, but also submarine avalanche caused by the 1596 event. The mass of avalanche-derived sediment is 2-3m high and roughly 100m wide. The observation appears to be consistent with the legend of sunken Uryujima island and historically documented landslides of Takasakiyama mountain.The seismic profiting records in the entire area of Beppu Bay show two apparent reflecting layers in most parts, namely the Akahoya ash layer (about 6700 yrs B.P.) and Yufu ash layer (about 2500 yrs B.P). The observed cumulative vertical offsets shown by the Akahoya ash are found to be proportional to that of the Yufu ash, indicating the similarity of fault offset distribution for each seismic event. On the basis of the … More similarity, fault offsets at the time of the 1596 Keicho-Bungo earthquake is estimated and tsunami source model is constructed, which shows very complicated pattern, contrasting to much simpler conventional source models used for tsunami hazard estimate. For a comparison, a simple tsunami source model is also constructed by assuming the central Beppu Bay fault is the sole causative fault of the 1596 earthquake. Numerical simulation shows that the southern coast suffers the highest tsunami for the both source model. However, radiation in the other directions is very different between the two models. It suggests that a simple conventional source model may predict some major feature of tsunami, but not in details. This indicates a limit of tsunami forecast ; tsunami measure dependent on fine feature of simulated tsunami may be fatal. Furthermore, the result of this study suggests some disagreement in estimated fault heterogeneities between seismic and tsunami observations may be due to a complicated feature of actual submarine faults. Less

别府湾大分港浅见川断层的海底取芯沉积物和地震剖面记录表明，该断层是1596年京町丰后地震的发震断层之一。单道高分辨率记录不仅反映了沉积层的地震偏移，而且反映了1596年地震引起的海底雪崩。雪崩产生的沉积物高2- 3米，宽约100米。这一观测结果似乎与Uryujima岛沉没的传说和历史记载的高崎山滑坡相一致。整个别府湾地区的地震记录显示，在大部分地区有两个明显的反射层，即Akahoya火山灰层（约6700年B. P.）玉符灰层（约2500年B.P）。Akahoya火山灰的累积垂直偏移量与鱼府火山灰的累积垂直偏移量成正比，表明各地震事件的断层偏移量分布具有相似性。的基础上 ...更多信息相似性，断层偏移在1596年Keicho-Bungo地震的时间估计和海啸源模型的构建，它显示出非常复杂的模式，对比简单得多的传统源模型用于海啸危险性估计。为了比较，还建立了一个简单的海啸震源模型，假设中央别府湾断层是1596年地震的唯一成因断层。数值模拟结果表明，在双源模式下，南部海岸遭受的海啸最大。然而，在其他方向上的辐射在两个模型之间是非常不同的。这表明，一个简单的传统源模型可以预测一些主要特征的海啸，但不是细节。这表明海啸预报的局限性;依赖于模拟海啸的精细特征的海啸措施可能是致命的。此外，这项研究的结果表明，一些不一致的估计故障之间的地震和海啸观测的不均匀性可能是由于一个复杂的功能，实际的海底断层。少