RT Journal Article
SR Electronic
T1 The equation of motion for supershear frictional rupture fronts
JF Science Advances
JO Sci Adv
FD American Association for the Advancement of Science
SP eaat5622
DO 10.1126/sciadv.aat5622
VO 4
IS 7
A1 Kammer, David S.
A1 Svetlizky, Ilya
A1 Cohen, Gil
A1 Fineberg, Jay
YR 2018
UL http://advances.sciencemag.org/content/4/7/eaat5622.abstract
AB The rupture fronts that mediate the onset of frictional sliding may propagate at speeds below the Rayleigh wave speed or may surpass the shear wave speed and approach the longitudinal wave speed. While the conditions for the transition from sub-Rayleigh to supershear propagation have been studied extensively, little is known about what dictates supershear rupture speeds and how the interplay between the stresses that drive propagation and interface properties that resist motion affects them. By combining laboratory experiments and numerical simulations that reflect natural earthquakes, we find that supershear rupture propagation speeds can be predicted and described by a fracture mechanics–based equation of motion. This equation of motion quantitatively predicts rupture speeds, with the velocity selection dictated by the interface properties and stress. Our results reveal a critical rupture length, analogous to Griffith’s length for sub-Rayleigh cracks, below which supershear propagation is impossible. Above this critical length, supershear ruptures can exist, once excited, even for extremely low preexisting stress levels. These results significantly improve our fundamental understanding of what governs the speed of supershear earthquakes, with direct and important implications for interpreting their unique supershear seismic radiation patterns.