Dynamic Rupture in Recent Models of Earthquake Faults

Yehuda Ben-Zion

Published September 2001, SCEC Contribution #556

We discuss several problems of dynamic rupture relevant to mechanics of earthquake faults, material sciences, and physics of spatially extended dissipative systems. The problems include dynamic rupture along an interface separating different elastic solids, dynamic rupture on a planar surface governed by strongly velocity-weakening friction, and elastodynamic calculations of long deformation history on a smooth fault in an elastic continuum. These separate problems share a number of methodological and conceptual issues that form recurring themes in the paper. An important methodological issue for computational schemes is dependency of numerical results on the used grid size. This arises inevitably in computer simulations when the assumed constitutive laws do not include a length scale (e.g., of shear or extensional displacement) over which material properties evolve. Such simulations do not have a stable underlying solution, to which they may converge with sufficient grid refinement. However, they may provide rough approximations—lacking at present a rigorous foundation—to the behavior of systems containing elements of discreteness (associated with abrupt fluctuations) at scales relevant to observations of interest. Related important conceptual issues are connections between, or when appropriate separation of, small scale phenomena (e.g., nucleation of rupture, processes at rupture front) and large scale features of the response (e.g., overall space–time dimensions of rupture, statistics of many events). Additional recurring conceptual topics are crack vs. pulse modes of dynamic rupture, the stress under which earthquake faults slip, and the origin of spatio-temporal complexities of earthquakes. These seemingly different issues probably have one or more common origins. Dynamic rupture on an interface between different solids, strongly velocity-weakening friction on a homogeneous fault, and strong fault zone heterogeneities can all produce narrow self-healing slip pulses with low dynamic stress (and low associated frictional heat) during the active part of slip. Strong fault heterogeneities probably play the dominant role in producing the observed earthquake complexities. Improved understanding of the discussed problems will require establishing connections between discrete and continuum descriptions of mechanical failure processes, generalization of current models to realistic three-dimensional dynamic models, and high-resolution laboratory and in-situ observations over broad scales of space and time. These challenging problems provide by their subject matter and involved great difficulties important targets for multi-disciplinary research by engineers, earth scientists, and physicists.

Citation
Ben-Zion, Y. (2001). Dynamic Rupture in Recent Models of Earthquake Faults. Journal of the Mechanics and Physics of Solids, 49(9), 2209-2244. doi: 10.1016/S0022-5096(01)00036-9.