Research on the Quaternary Tectonics in the surrounding area of the Epicenter of 2000 Tottoriken-seibu Earthquake

2000年鸟取县西武地震震中周边地区第四纪构造研究

基本信息

批准号：
13640461
负责人：
YAMAUCHI Seiki
金额：
$ 1.15万
依托单位：
Shimane University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2001
资助国家：
日本
起止时间：
2001 至 2002
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-13640461/
关键词：
2000 Tottoriken-seibu earthquke epicenter after shock zone fracture system alkali basalt active fault middle Pleistocene reactivation 中期更新世アルカリ玄武岩岩体余地域

项目摘要

A surrounding area of the epicenter of the 2000 Tottoriken-seibu Earthquake is widely occupied by granitic rocks, which is unconformably covered by the late Pliocene to the early Pleistocene basalt lavas in places. Analysis of fracture systems in granitic rocks are carried out by using large joints, joint zones and shear zones, and a sequence of activity of each system is estimated on the basis of cross-cutting relationships. The results show that 13 fracture systems (A〜L) develop in this area and 3 systems (A〜C) reactivated at the last stage.Deep fractures which are recognized by linear arrangements of eruption centers of basalt lavas and faults cutting the lavas belong to A to D systems, which are estimated to have acted already in the early Pleistocene. An active fault which newly was found in the Koshikibara Basalt about 10km northeast of the epicenter belongs to B system and is parallel with and shows the same style of displacement with an earthquake source fault of the earthquake. Between both faults a deep fracture indicated by a linear arrangement of eruption centers of basalt is developed parallel with them. These similalities imply that three fractures may be formed under the same stress fields, probably in the early Pleistocene.Recently seismicity in this area have been active and their after shock zones coincide with B system. An after shck zone of the 2000 Tottoriken-seibu Earthquake appeared parallel with B system at the earliest stage, immediately it changed its direction to be parallel with C system. It may be concluded that the change was resulted from continuous reactivation of B and C systems at an epicenter of the earthquake, and instantly triggered to reactivate a nearby larger fracture of C system.

2000 Tottoriken-Seibu地震的震中的周围区域被花岗岩岩石广泛占据，该岩石被晚期的上新近晚期到早期更新世玄武岩熔岩所覆盖。通过使用大关节，关节区和剪切区进行花岗岩岩石中断裂系统的分析，并根据跨切割关系估算每个系统的一系列活性。结果表明，在该区域开发了13个断裂系统（A-L），而在最后阶段重新激活了3个系统（A-C）。深层断裂是通过玄武岩熔岩的线性排列认识到的，而切割熔岩的爆发中心则属于D系统，这些系统估计已经在早期的Pleistiscenecene中作用。在震中东北约10公里处的Koshikibara玄武岩中，新近发现的有源断层属于B系统，并且与地震的地震源断层相似，并与同样的位移风格显示。在两个断层之间，由玄武岩的喷发中心线性排列表示的深层断裂与它们平行。这些相似之处表明，可能在同一应力场下形成三个断裂，可能是在早期更新世上。该区域的地震性已经活跃，其后休克带与B系统一致。在最早的阶段，2000年Tottoriken-Seibu地震的后SHCK区与B系统平行，它立即改变了其方向，与C系统平行。可以得出的结论是，这种变化是由于地震中心的B和C系统的连续重新激活而产生的，并立即触发了C重新激活C系统的几乎较大的裂缝。