Seismic and global measurements of fault slip and energy release from laboratory experiments

An acoustic emission (AE) system with eight channels of recording was used to monitor failure of a sandstone in plane-strain compression. The recorded wave forms were analyzed for event location and source characterization. The complicated deconvolution process was eliminated by assuming that the first peak of the signal recorded by an AE sensor corresponds to the first peak of the normal displacement at the sensor. The seismic moment tensor of each event was evaluated, and the source mechanisms were determined. The sources of the post-peak events were characterized as being caused predominantly by shear. The slip displacement of each acoustic emission was estimated from the seismic moment tensor by assuming a constant strain drop of 10−4 over the slip area. Within a certain portion of the post-peak regime where 110 events were captured, the slip displacement was 0.0217 mm from the seismic estimate and 0.0335 mm from the global measurement. The seismic energy per unit area from acoustic emission was compared with the strain energy release rate computed from the same portion of the post-peak, stress-displacement curve. The seismic estimate of energy release rate was 5.73 J/m2 from the 110 events and the global estimate was 8.67 J/m2.