Pulse-like and crack-like ruptures in experiments mimicking crustal earthquakes
Theoretical studies have shown that the issue of rupture modes has important implications for fault constitutive laws, stress conditions on faults, energy partition and heat generation during earthquakes, scaling laws, and spatiotemporal complexity of fault slip. Early theoretical models treated earthquakes as crack-like ruptures, but seismic inversions indicate that earthquake ruptures may propagate in a self-healing pulse-like mode. A number of explanations for the existence of slip pulses have been proposed and continue to be vigorously debated. This study presents experimental observations of spontaneous pulse-like ruptures in a homogeneous linear-elastic setting that mimics crustal earthquakes; reveals how different rupture modes are selected based on the level of fault prestress; demonstrates that both rupture modes can transition to supershear speeds; and advocates, based on comparison with theoretical studies, the importance of velocity-weakening friction for earthquake dynamics.
© 2007 by the National Academy of Sciences. Edited by Adam M. Dziewonski, Harvard University, Cambridge, MA, and approved July 9, 2007 (received for review May 8, 2007). Published online on November 19, 2007, 10.1073/pnas.0704268104. This work was supported by National Science Foundation Grants EAR 0548277 (to N.L.) and EAR 0207873 (to A.J.R.), U.S. Department of Energy and Grant DE-FG52-06NA 26209 (to A.J.R.), and Office of Naval Research Multidisciplinary University Research Initiative Grant N000140610730 (to A.J.R.; Dr. Y.D.S. Rajapakse, Program Manager).
Published - LUXpnas07.pdf