期刊
PROGRESS IN EARTH AND PLANETARY SCIENCE
卷 5, 期 -, 页码 -出版社
SPRINGEROPEN
DOI: 10.1186/s40645-018-0230-5
关键词
Analog model; Digital image correlation; Japan Trench; Sandbox; Thrust formation
资金
- Sasakawa Scientific Research Grant from the Japan Science Society
- JSPS KAKENHI [18H03732, JP15H05717, 17K05687]
- Grants-in-Aid for Scientific Research [18H03732, 17K05687] Funding Source: KAKEN
The 2011 Tohoku-oki earthquake unexpectedly ruptured to the shallowest portion of the plate boundary fault and triggered a large tsunami. The shallow portion had generally been regarded as a seismically stable zone until this event, but its significance has now been dramatically revealed for future disaster mitigation. This research approaches the shallow portion, especially the formation process of its structure and plate boundary faults. Scientific drilling conducted near the Japan Trench after the earthquake reported a thin plate boundary fault (similar to 7 m) and thick deformation zone (similar to 100 m). This thin fault would be expected given the relatively small displacement near the trench (similar to 3.2 km), but the deformation zone thickness is anomalously wide given this small magnitude of slip. To understand the dynamic deformation processes that lead to the development of a thick deformation zone surrounding a thin fault core, we conducted forward modeling of an analog experiment with the technique to visualize fault activity. Sandbox experiments are effective for the approximation of the geological phenomenon and structure. The seismic profile of the largest slip region in the 2011 earthquake shows that a half-graben structure has been subducted underneath the frontal wedge, thus we focused on this structural architecture. As a result, we found a new fault formation pattern, i.e., the frontal thrust (the most frontal part of d,collement) periodically partitioned into pieces, which connect again to form a large-continuous fault. The fault also oscillates up and down during this process, which we call dancing, and a thick shear zone is formed in a relatively short time where this occurs, even though the fault only has a small displacement. By analogy, the thick deformation zone observed at the Japan Trench could be formed by such fault dancing. The energy of the fault activity is commonly estimated from the fault displacement derived from the thickness of the shear zones. Applying the thickness-displacement law without considering the effect of the dancing may cause overestimation. The architecture of the shear zone formed is similar to that of a m,lange, and the origin of tectonic m,langes may be explained by this mechanism.
作者
我是这篇论文的作者
点击您的名字以认领此论文并将其添加到您的个人资料中。
推荐
暂无数据