变形过程中岩石P波速度场的空间变化

在一次地震之前,在不同观测点测量岩石中弹性波速度,经常得到不同的结果.这一现象提示我们:岩石破坏前,其物理性质的变化在空间上的分布是不均匀的,破坏前兆的获得应该建立在对岩石性质的空间分布,即对物理场分析的基础上. 本实验观测了岩石样品在单轴压缩下,P波走时空间分布变化的全过程.实验表明:在岩石的破坏过程中,岩性的空间分布具有同步性变化的中长期前兆和差异性变化的短期前兆的特点.在岩石接近破坏时,岩性的变化表现出严重的不均匀性.岩石的整个破坏过程可以看成岩石的物性分布是由无序向有序的演化,即是一个熵减小的过程. 

SPATIAL VELOCITY VARIATIONS OF P WAVES DURING ROCK DEFORMATIONS

Before an earthquake,the velocities of elastic waves observed at different stations usually have different values. This phenomenon suggests that the spatial distribution of the variations of rock properties is inhomogeneous before the failure of rocks. The precursors to failure in rocks should come from the changes of the spatial distributions (physical fields) of the rocks.The process of spatial variations in the travel times of P-wave in the rock under uniaxial stress is studied. The experimental results show that the long-term precursor of failure of rocks is characterized by synchronism in variations of the P-wave velocities,and the short-term precursor by nonuniformity. The process of the rupture in rocks is the evolution process from disorder to order in the spatial distributions of the vairations of physical properties of rocks,or the process of the decrease in entropy.