Publication Abstract

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Title 3D Numerical Modelling of Acoustic Emissions

Authors J.F. Hazzard and Young RP

Publication Reference 2002, Proceedings of the ISRM workshop on Geophysics in Rock Mechanics at the 5th North American Rock Mechanics Symposium, Toronto, Canada.

Abstract Earthquake systems are now often described using rate and state dependent fault models. This approach offers insights into the underlying physics of faulting since the friction parameters appearing in these laws relate to specific fault processes. Laboratory shearing experiments are used to determine the friction parameters of simulated faults for a range of conditions. Recently, significant efforts have been made to correlate friction parameters to direct observations of fault microstructures. ‘Snapshot’ microstructural observations from experiments terminated at increasing amounts of strain indicate that frictional stability and strain localization are intrinsically linked. However, a limitation of this method is that transient and dynamic grain scale processes must be inferred from intermittent static observations, hence true validation of these fault models is difficult. State of the art acoustic monitoring techniques offer the potential to gain new insights into dynamic grain scale processes operating in evolving fault zones. Acoustic emissions (AE) associated with grain-scale fracture can reveal the spatial and temporal distribution of damage as well as the dominant fracture mode (tensile or shear). Active source ultrasonic surveys can indicate the development of a structural fabric or anisotropy associated with strain localization. The application of acoustic techniques to high precision friction experiments is a novel and promising strategy. We anticipate this approach will yield valuable new insights into dynamic grain processes operating in evolving fault zones and allow the validation of certain aspects of geophysical rate and state fault models.

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Link http://www.liv.ac.uk/seismic/news/narms/narms.html



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