权益分类	功能权益	普通用户	{{item.name}}会员
{{category.name}}	{{benefitItem.name}}

Study on Crustal Dynamics and Earthquake Mechanism Bassed on Experiments on Deformation and Fracture of Rocks under High Confining pressure and Temperature

基于高围压高温岩石变形断裂实验的地壳动力学与地震机制研究

基本信息

批准号：
09440159
负责人：
SHIMADA Mitsuhiko
金额：
$ 7.04万
依托单位：
KYOTO UNIVERSITY
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
1997
资助国家：
日本
起止时间：
1997 至 1999
项目状态：
已结题

项目摘要

In experimental works on the deformation and fracture of rocks, we have concluded that the fracture mechanism changes at the confining pressure where the compressive strength equals the frictional strength, from the ordinary brittle fracture (designated as the low-pressure type) to the high-pressure type. We have also suggested the possibility that the high-pressure type occurs in the crust, considering the size effect on rock strength.The change of micromechanisms between them was discussed from the point view of structural geology. The relationship between the performance of them in the crust and faulting styles was discussed.The strength of granite at a confining pressure of 1500 MPa in the high-pressure type regime was observed to temperature of 600℃. The strength values at 200〜280℃ were found to be very low with a minimum at around 250℃. This behavior was explained as the switching the dominating factors from the activation of crack groups to the inhibition of them and the dominance of crystal plasticity with increasing temperature. The lithospheric strength inferred from these experimental results suggests the presence of a low-strength zone in depth of 8〜12km. This could provide an alternative explanation for the seismogenic zone in the crust : earthquakes could occur or nucleate easily where the strength is low.Development of cracks was observed using granite samples recovered from several stress levels of fault formation process during triaxial compression controlled with circumferential-strain rate. The fault was developed again by re-compression of the recovered sample on which surface strain gauges were distributed near the fault nucleus, and the change of strain field near the fault was measured in the fault developing process. New idea on the faulting process was proposed.

在岩石变形破裂的实验研究中，我们发现，当围压强度等于摩擦强度时，岩石的破裂机制发生了变化，由一般的脆性破裂（称为低压型）变为高压型。考虑到岩石强度的尺寸效应，提出了地壳中存在高压型的可能性，并从构造地质学角度讨论了它们之间的微观机制变化。讨论了它们在地壳中的表现与断裂类型的关系，并对高压型花岗岩在围压1500 MPa至600℃的强度进行了观测。在200 ~ 280℃时的强度值很低，在250℃左右达到最低值。这是由于随着温度的升高，裂纹群的激活作用逐渐减弱，晶体塑性逐渐增强。根据这些实验结果推断的岩石圈强度表明，在8 × 12 km深处存在一个低强度带。这可能为地壳中的孕震区提供了另一种解释：地震可能在强度较低的地方发生或成核。在周向应变率控制的三轴压缩过程中，从断层形成过程的几个应力水平恢复的花岗岩样品观察到裂纹的发展。通过在断层核附近布设表面应变片，对恢复后的样品进行再压缩，使断层再次发育，并测量了断层发育过程中断层附近应变场的变化。对断裂作用过程提出了新的认识。