岩石摩擦滑动中声发射的多普勒效应

在双剪摩擦滑动实验中可观测到声发射的多普勒效应。对于单个声发射事件，顺断裂扩展方向上的探头可记录到较短周期的初动波半周期，而在断裂扩展反方向上的探头记录则反之，在扩展过程中，声发射前续波由初始破裂引起的前激波、声源破裂扩展的扩展相和停止相组成，显示出声源破裂有一由静到动的加速过程。而在时间序列上，声发射事件存在着３个阶段：较强声发射事件发生初期，前激波时间超前较长，停止相不明显，声发射源的破裂速度较慢；第二阶段停止相突出，扩展速度加快，前激波到时超前量减小；最后，在原初始半周期处叠加了较大振幅的高频波

THE DOPPLER EFFECTS OF AE WAVEFORM IN ROCK FRICTION

The waveform of AE（acoustic emission）events during rock friction has been studied．112large AE events through AE transducers attached along the faults have been recorded by a multi-channel digital recording system.The Doppler effects are evident by the waveforms of large AE events. For example，the firsthalf cycle of acoustic wave at AE transducers 1～3 is longer and at AE transducers 4～6 shorter.So it is shown that the displacement propagates in direction from AE transducer 1 to AE trans-ducer 3 with a dimension of 5．1 cm.The first phase（fore－excitation wave），source spreadingphase and stopping phase can be easily distinguished from the waveform of AE events．The ve-locity of fore－excitation wave and stopping phase is the same as P-wave. According to the break-ing phase recorded in different channels the breaking velocity of AE source increases from 0km／sto 2．62 km／s.It shows that the large AE events have an accelerating breaking process.The waveform of different events in a sequence of AE