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

在岩石变形和断裂实验工作中，我们得出结论，在压缩强度等于摩擦强度的围压下，岩石的断裂机制发生变化，由普通的脆性断裂(称为低压型)转变为高压型。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，并从构造地质学的角度讨论了它们之间的微观机制变化。并对它们在地壳中的表现与断裂方式的关系进行了讨论。在600℃的高压区，观察到了围压为1500 Mpa的花岗岩的强度。在2 0 0~2 80℃范围内，强度值很低，在2 5 0℃左右达到最小。这是由于随着温度的升高，主控因素由裂纹群的激活转变为裂纹群的抑制和晶体塑性的主导。从这些实验结果推断的岩石圈强度表明，在8~12公里深处存在一个低强度带。这可能为地壳中的地震孕育区提供另一种解释：地震在强度较低的地方容易发生或成核。利用在周向应变率控制的三轴压缩过程中从断层形成过程的多个应力水平回收的花岗岩样品，观察到裂缝的发展。通过对断层核附近分布有表面应变片的回收样品的二次压缩，测量了断层发育过程中断层附近应变场的变化。对断裂作用提出了新的认识。

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.