Electro-acoustic effect in rock fracturing

Electromagnetic (EM) and acoustic emissions (AE) and their relations during the process of fracturing of various rock samples have been studied. The s amples were fractured under either uniaxial compression or under double she aring. The data were recorded using a high-speed recording system with 16 f requency channels and three-component acoustic transducers. Our result show s that the emissions and properties of EM and AE were affected strongly by the sizes and mineral compositions of rock samples. The relationships betwe en EM and AE emissions were various; for example, some EM emissions were ac companied by AE, but some were not. Our result suggests that in addition to micro fracturing, there may exist some nonfracturing mechanism responsible for electromagnetic emissions.