Exciting news! We're transitioning to the Statewide California Earthquake Center. Our new website is under construction, but we'll continue using this website for SCEC business in the meantime. We're also archiving the Southern Center site to preserve its rich history. A new and improved platform is coming soon!

Criticality of Rupture Dynamics in 3-D

Raul Madariaga, & Lynnea Olsen

Published December 2000, SCEC Contribution #485

We study the propagation of seismic ruptures along a fault surface using a fourth-order finite difference program. When prestress is uniform, rupture propagation is simple but presents essential differences with the circular self-similar shear crack models of Kostrov. The best known is that rupture can only start from a finite initial patch (or asperity). The other is that the rupture front becomes elongated in the in-plane direction. Finally, if the initial stress is sufficiently high, the rupture front in the in-plane direction becomes super-shear and the rupture front develops a couple of “ears” in the in-plane direction. We show that we can understand these features in terms of single nondimensional parameter s that is roughly the ratio of available strain energy to energy release rate. For low values of s rupture does not occur because Griffith's criterion is not satisfied. A bifurcation occurs when s is larger than a certain critical value, sc. For even larger values of s rupture jumps to super-shear speeds. We then carefully study spontaneous rupture propagation along a long strike-slip fault and along a rectangular asperity. As for the simple uniform fault, we observe three regimes: no rupture for subcritical values of s, sub-shear speeds for a narrow range of supercritical values of s, and super-shear speeds for s > 1.3sc. Thus, there seems to be a certain universality in the behavior of seismic ruptures.

Madariaga, R., & Olsen, L. (2000). Criticality of Rupture Dynamics in 3-D. Pure and Applied Geophysics, 157(11-12), 1981-2001. doi: 10.1007/PL00001071.