震源区介质Q值变化物理机制的模拟实验研究

MODEL EXPERIMENTAL STUDY ON THE PHYSICAL MECHANISM OF VARIATION OF MEDIUM Q VALUE IN SOURCE AREA

利用较大岩石样品 ,实验研究了加载时同时向样品内注水过程中穿过样品超声波波速和尾波 Qc值的变化特征。结果表明 ,在压力作用下 ,岩石破坏前通过岩石的尾波Qc值下降 ,如果有压力水进入 ,则岩石的尾波值 Qc会大幅下降。因此 ,我们可以认为 ,地壳岩石破坏发生地震前的尾波下降的物理机制是岩石在压力下产生扩容裂隙及流体进入裂隙双重作用的结果。

The variation characteristics of ultrasound wave velocities cross the sample and coda Q c values of samples when loading stress and injecting pressured water have been studied experimentally using considerable large rock samples.The results show that the Q c values decrease under stress loading before its failure,and decrease bigger when injecting pressured water. So it is considered that the physical mechanism of the decreasing of coda Q c value before crust rock failure and earthquake occurrence is the results both of producing the EDA(Extensive Dilatancy Anisotropy)cracks and the fluid entering under loading local stress.