SCEC Award Number 07167 View PDF
Proposal Category Individual Proposal (Integration and Theory)
Proposal Title A Statistical Mechanics Description of Rupture Mechanics
Investigator(s)
Name Organization
Thomas Heaton California Institute of Technology
Other Participants Brad Aagaard (USGS), Deborah Smith (UCR), Ahmed Elbanna (Caltech)
SCEC Priorities B2, B3, B4 SCEC Groups SDOT, FARM, CDM
Report Due Date N/A Date Report Submitted N/A
Project Abstract
 We investigate systems that dynamically rupture with strong rate weakening friction. These systems often fail in a series of complex slip pulses that are spatially heterogeneous. We seek to understand the “material strength” of such complex systems. We are particularly interested in the failure of large systems like faults in the Earth’s crust. For this purpose, we use a simple 1d mass spring system with an idealized velocity dependent friction and measure the strength by two different ways; 1) by identifying the average prestress that caused failure, and 2) by calculating the dissipated energy per unit deformation volume. We find that, in the presence of strong velocity weakening friction, both measures show that the strength decreases as the system size increases. We also suggest that the rate at which strength decreases with size may correlate with the b-value of the Gutenberg-Richter frequency magnitude relationship for earthquakes.
Intellectual Merit Although strong rate weakening friction has been suspected for decades, it has not been feasible to explore its implications for earthquake dynamics; the problem is far too large and multi-scale to simulate with even the largest computers. We explore a simpler 1-d system and show that extremely heterogeneous prestress is expected in these systems. The concept of material strength must be redefined forn these systems.
Broader Impacts This work is a new paradigm in the understanding of material strength for the Earth's crust. It imples that at the very large scale of 10's of km, the Crust is weak (but in a very surprising way).
Exemplary Figure Figure 2