Rayleigh Pulse-Induced Fault Slip: Model and Application
Rayleigh (R-) pulse interaction with a partially contacting strike-slip fault is experimentally as well as numerically investigated. This study is intended to offer an improved understanding of earthquake rupture mechanisms. The fault is subjected to static pre-stresses. Using dynamic photoelasticity in conjunction with high speed cinematography, the evolution of the R-pulse interaction is recorded by means of isochromatic fringe patterns (contours of maximum in-plane shear stress). It is shown that fault instability (slip) can be triggered by a pulse which propagates along the fault interface at Rayleigh wave speed. Numerically, a finite difference wave propagation simulator SWIFD is used for a quantitative analysis of the problem. Dynamic rupture in laterally heterogeneous structures is discussed by considering the effect of acoustic impedance mismatch on the wave patterns. The results indicate that upon fault rupture, head waves, which carry a relatively large amount of concentrated energy, can be generated which propagate off the fault contact region. Such head waves can cause concentrated wave-induced damage in a particular region located inside an adjacent acoustically softer area. This type of damage concentration was observed in Kobe, Japan, on the occasion of the 1995 Hanshin earthquake.