Simulating intense shock pulses due to asperities during fault-slip

• Unloading of fault surface asperities causes intense shock pulses.
• Near-field peak particle velocity increases threefold when the unloading occurs.
• Collision of fault surface asperities has a lesser influence on seismic waves.

Seismic waves arising from fault-slip that occurs in underground mines could inflict severe damage to mine openings. Experimental results have revealed that intense shock pulses could generate due to the unloading of fault surface asperities that move apart during the fault-slip. This study focuses on examining the effect of fault surface asperities on the seismic waves arising from fault-slip. By means of a mine-wide model, dynamic analyses are carried out in order to simulate collision and unloading of fault surface asperities. Saeb and Amadei's model and Barton's shear strength model are newly implemented into constitutive models of FLAC3D code for the analyses. Parametrical study is conducted with the dynamic analyses in order to examine the most influential factor on the generation of intense seismic waves. The results reveal that stress release due to the unloading of the asperities has a significant influence on the intensity of seismic waves, while the collision of asperities, stiffness of the fault, and asperity geometry have a much lesser influence. When the stress release is large, the peak particle velocity excited by seismic waves is found to increase threefold, compared to that for fault-slip occurring along a planar surface. It indicates that significant deterioration of rockmasses could be induced due to the high particle velocities. This study has numerically confirmed the hypothesis that intense shock pulses could occur due to the unloading of fault surface asperities.