Numerical and experimental models on the formation mechanism of collapse basins during the Green Tuff orogenesis of Japan |
| |
| Authors: | H Komuro Y Fujita K Kodama |
| |
| Institution: | 1. Department of Geology, Faculty of Science, Shimane University, Matsue, Japan
2. Research Institute for Hazards in Snowy Area, Niigata University, Niigata, Japan
3. Geological Survey of Japan, Tsukuba, Japan
|
| |
| Abstract: | The geological model about volcanism of the Green Tuff geosyncline deduced from the field observations consists of the following processes: - Dome-shaped uplift with a mean diameter of 30 km.
- Collapse of the central part of the domes forming basins with a mean diameter of 10 km.
- Volcanic activity inside the collapse basins. It is considered that these consecutive processes resulted from the magmatic uplift from a deep part of the crust.
In finite element analyses performed as plane strain problems, earth's crust is assumed to be an elasto-plastic homogeneous layer and to undergo sinusoidal vertical displacement at the base of the layer due to an ascending magma reservoir. These analyses reveal that the diameter of the dome is proportional to the depth of the magma reservoir rather than to its size. The magma reservoir is estimated at 12 ～ 24 km in depth. Scale model experiments using powdered material were performed in order to reproduce a collapse basin. These three-dimensional models are reduced to a scale of 1:200,000 th of the natural size. The results of experiments show that radial and concentric cracks are produced on top of the dome and a central part encircled by concentric cracks collapses to form a basin. The boundary of the collapsed portion forms a steep cliff with a height of about 2 mm. This is equivalent to 400 m in natural size and is nearly similar to field observations. |
| |
| Keywords: | |
| 本文献已被 SpringerLink 等数据库收录！ |
|
