THE WORK OF FAULT GENERATION IN THE LABORATORY

Fault systems may evolve to minimize the total work on the system. The work budget of sandbox experiments includes frictional heating, internal work, external work, work against gravity and seismic work. More enigmatic than these is the work required to propagate faults. While this term may be smaller than other terms in the work budget, observations of long-lived faults suggest that W_prop is not negligible. Measurements of external work from sandbox experiments show a drop in work associated with both the growth of new faults and the reactivation of older ones. The new faults develop when the total work savings of having the fault exceeds the cost of the new fault. The drop in work with new fault formation can thus be used to estimate the cost of fault growth in the sandbox. The cost of fault growth can be used in numerical models of sandbox experiments to predict fault development.