Dynamic rupture experiments elucidate tensile crack development during propagating earthquake ruptures
We used optical experiments and high-speed photography to interpret the origins of tensile fractures that form during dynamic shear rupture in laboratory experiments. Sub-Rayleigh (slower than the Rayleigh wave speed, c_R) shear ruptures in Homalite-100 produce damage zones consisting of an array of tensile cracks. These cracks nucleate and grow within cohesive zones behind the tips of shear ruptures that propagate dynamically along interfaces with frictional and cohesive strength, simulating a "strong" fault. The tensile cracks are produced only along one side of the interface where transient, fault-parallel, tensile stress perturbations are associated with the growing shear rupture tip. Results of this study represent an important potential bridge between geological observations of structures preserved along exhumed faults and theoretical models of earthquake propagation, potentially leading to diagnostic criteria for interpreting velocity, directivity, and static prestress states associated with past earthquakes on exhumed faults.
© 2009 Geological Society of America. Manuscript received 23 January 2009; revised manuscript received 15 April 2009; manuscript accepted 26 April 2009. Griffi th and Pollard were supported by the U.S. Geological Survey (USGS), Department of Interior, under USGS award number 08HQGR0010. Griffith also received support under National Science Foundation (NSF) grant OISE-0754258. Rosakis and Ko were supported by U.S. Department of Energy grant DE-FG52-06NA 26209, NSF grant EAR-0711545, and Office of Naval Research Multidisciplinary Research Initiative (ONR MURI) grant N0014-06-1-0730.