Abstract
AbstractThe energy released during earthquake rupture is partly radiated as seismic waves and mostly dissipated by frictional heating on the fault interface and by off‐fault fracturing of surrounding host rock. Quantification of these individual components is crucial to understand the physics of rupture. We use a quasi‐static rock fracture experiment combined with a novel seismic tomography method to quantify the contribution of off‐fault fracturing to the energy budget of a rupture and find that this contribution is around 3% of the total energy budget and 10% of the fracture energy Gc. The off‐fault dissipated energy changes the physical properties of the rock at the early stages of rupture, illustrated by the 50% drop in elastic moduli of the rock near the fault, and thus is expected to greatly influence later stages of rupture and slip. These constraints are a unique benchmark for calibration of dynamic rupture models.
Highlights
Strain energy released during earthquakes is partly radiated as seismic waves that cause ground shaking and mostly dissipated by frictional heating on the fault interface and by fracturing of the rocks surrounding the fault
The energy released during earthquake rupture is partly radiated as seismic waves and mostly dissipated by frictional heating on the fault interface and by off-fault fracturing of surrounding host rock
The constraints on rupture energetics were obtained during quasi-static rupture propagation and are representative of the nucleation phase of an earthquake
Summary
Strain energy released during earthquakes is partly radiated as seismic waves that cause ground shaking and mostly dissipated by frictional heating on the fault interface and by fracturing of the rocks surrounding the fault. The latter energy sink, and a component of frictional heating, constitutes the fracture energy (Gc, sometimes referred to as rupture energy) that dictates the dynamics of rupture propagation (Rice, 1980). To establish the off-fault energy dissipation component Goff, one possibility is to use the change in off-fault elastic properties caused by off-fault deformation Such changes must be measured in situ during rupture, ideally under realistic crustal conditions (i.e., at elevated pressure and temperature). The size and geometry of the off-fault damage zone and the actual local wave speeds therein remain unconstrained because of the lack of spatial resolution of conventional laboratory ultrasonic measurements
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