Numerical and experimental models on the formation mechanism of collapse basins during the Green Tuff orogenesis of Japan
Numerical and experimental models on the formation mechanism of collapse basins during the Green Tuff orogenesis of Japan
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DOI：
10.1007/bf01961233
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发表时间：
1984-09
期刊：
影响因子：
--
通讯作者：
H. Komuro;Y. Fujita;K. Kodama
中科院分区：
文献类型：
--
作者：
H. Komuro;Y. Fujita;K. Kodama
根据野外观测资料，提出了绿色凝灰岩地槽火山作用的地质模式，包括：1）平均直径为30 km的穹隆状隆起; 2）穹隆中部塌陷，形成平均直径为10 km的盆地; 3）塌陷盆地内部的火山活动。在平面应变有限元分析中，假定地壳为弹塑性均质层，由于岩浆库的上升，地壳底部发生正弦垂直位移。这些分析表明，圆顶的直径与岩浆库的深度成正比，而不是与其大小成正比。岩浆库的深度估计为12 ~ 24 km。为了再现塌陷盆地，进行了使用粉末材料的比例模型实验。这些三维模型被缩小到自然尺寸的1：200，000的比例。试验结果表明，拱顶顶部产生了径向和同心裂纹，由同心裂纹包围的中心部分塌陷形成盆地。塌陷部分的边界形成了一个陡峭的悬崖，高度约为2毫米。这相当于400米的自然大小，与实地观察几乎相似。
The geological model about volcanism of the Green Tuff geosyncline deduced from the field observations consists of the following processes:1)Dome-shaped uplift with a mean diameter of 30 km.2)Collapse of the central part of the domes forming basins with a mean diameter of 10 km.3)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.