Acoustic Emission Accompanying Preparation of Dynamic Slip on a Model Heterogeneous Fault of Meter Scale

Regularities in distribution of tectonic fault sections with different frictional properties control to a great extent the dynamics of fault sliding. The impossibility of directly studying the structure of fault zones at seismogenic depths makes it especially important to develop diagnostic methods that would provide information on the structural features of earthquake sources formation areas and, thereby, predict the sliding dynamics. This work presents results of laboratory experiments directed to studying regularities of elastic wave emission during shear deformation of a model fault with a spatially inhomogeneous structure of the sliding interface. The model fault was a loaded contact of diabase blocks 750 × 120 mm2 in size. Two round zones, each 100 mm in diameter, were made at the interface. Those zones had high strength showing the property of velocity weakening, the so-called asperities. The relative position of asperities changed in experiments. The process of dynamic slip formation, caused by asperity disruption, was accompanied by emission of a great number of acoustic pulses that were recorded in the frequency range of 20-80 kHz. During the experiments, the data on spatial distribution of pulses allow to detect two separate contact regions only when the distance between these regions exceeded 20 mm. Differences in the statistics of pulses emitted at different asperities were observed.

tectonic fault, asperity, acoustic emission, slow slip, spatio-temporal analysis, laboratory experiment