Rayleigh Pulse - Dynamic Triggering of Interface Slip

	Rayleigh Pulse - Dynamic Triggering of Interface Slip Koji Uenishi Institute of Mechanics, Vienna University of Technology, Vienna, Austria

Abstract

We present an experimental and numerical investigation of the interaction of a Rayleigh (R-) pulse with a partially contacting plane of weakness (interface) between similar and dissimilar materials. This study is intended to offer an improved understanding of the rupture mechanisms of earthquakes and rockbursts in mines. The interface is subjected to static normal and shear pre-stresses. Using two-dimensional dynamic photoelasticity in conjunction with high speed cinematography, the dynamic interaction process is recorded by means of isochromatic fringe patterns (contours of maximum in-plane shear stress). It is shown that interface slip (instability) can be triggered by a pulse that propagates along the interface at the relevant Rayleigh wave speed, and that the direction of the static shear pre-loading has an influence on the initiation of interface slip. Numerically, a finite difference wave propagation simulator SWIFD (Solids/Wave/Impact/Fracture/Damage) is used to discuss quantitatively the problem under different combinations of contacting materials. Dynamic rupture in laterally heterogeneous structures is analyzed by considering the effect of the acoustic impedance mismatch of the two contacting materials. The results indicate that upon interface rupture, Mach (head) waves, which carry a relatively large amount of concentrated energy, can be generated and propagated from the interface contact region (asperity) into the acoustically softer material. Such Mach waves can cause concentrated wave-induced damage into a particular region located inside the acoustically softer area. It is possible that the "damage belt" found in Kobe, Japan, on the occasion of the 1995 Hyogo-ken Nanbu Earthquake, was generated by these Mach waves.

Keywords

Acoustic impedance ratio, Contact mechanics, Dynamic faulting, Dynamic photoelasticity, Earthquake rupture mechanism, Finite difference method, Interface instability, Interface slip, Mohr-Coulomb condition, Rayleigh wave interaction, Rockburst.

Related Publications

Uenishi, K., H.P. Rossmanith, and A.E. Scheidegger (1999). Rayleigh Pulse - Dynamic Triggering of Fault Slip. Bull. Seism. Soc. Am., 89(5), 1296-1312.
Uenishi, K., and H.P. Rossmanith (2003). Optical Methods in Fault Dynamics. Opt. Laser. Eng., 40(4), 325-339.

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