Three‐dimensional earthquake sequence simulations with evolving temperature and pore pressure due to shear heating: Effect of heterogeneous hydraulic diffusivity
نویسندگان
چکیده
[1] A new methodology for three‐dimensional (3‐D) simulations of earthquake sequences is presented that accounts not only for inertial effects during seismic events but also for shear‐induced temperature variations on the fault and the associated evolution of pore fluid pressure. In particular, the methodology allows to capture thermal pressurization (TP) due to frictional heating in a shear zone. One‐dimensional (1‐D) diffusion of heat and pore fluids in the fault‐normal direction is incorporated using a spectral method, which is unconditionally stable, accurate with affordable computational resources, and highly suitable to earthquake sequence calculations that use variable time steps. The approach is used to investigate the effect of heterogeneous hydraulic properties by considering a fault model with two regions of different hydraulic diffusivities and hence different potential for TP. We find that the region of more efficient TP produces larger slip in model‐spanning events. The slip deficit in the other region is filled with more frequent smaller events, creating spatiotemporal complexity of large events on the fault. Interestingly, the area of maximum slip in model‐spanning events is not associated with the maximum temperature increase because of stronger dynamic weakening in that area. The region of more efficient TP has lower interseismic shear stress, which discourages rupture nucleation there, contrary to what was concluded in prior studies. Seismic events nucleate in the region of less efficient TP where interseismic shear stress is higher. In our model, hypocenters of large events do not occur in areas of large slip or large stress drop.
منابع مشابه
Injection-induced seismicity: Poroelastic and earthquake nucleation effects
The standard model of injection-induced seismicity considers changes in Coulomb strength due solely to changes in pore pressure. We consider two additional effects: full poroelastic coupling of stress and pore pressure, and time-dependent earthquake nucleation. We model stress and pore pressure due to specified injection rate in a homogeneous, poroelastic medium. Stress and pore pressure are us...
متن کاملDoes Shear Heating of Pore Fluid Contribute to Earthquake Nucleation?
[1] Earthquake nucleation requires reduction of frictional strength = ( p) with slip or slip rate, where , n, and p are the friction coefficient, normal stress, and fluid pressure, respectively. For rate state at fixed ( p), instabilities can occur when d ss/dv < 0, where ss is the steady state friction and v is slip rate. Shear heating increases p and, if dilatancy and pore pressure diffusion ...
متن کاملDoes hydrologic circulation mask frictional heat on faults after large earthquakes?
[1] Knowledge of frictional resistance along faults is important for understanding the mechanics of earthquakes and faulting. The clearest in situ measure of fault friction potentially comes from temperature measurements in boreholes crossing fault zones within a few years of rupture. However, large temperature signals from frictional heating on faults have not been observed. Unambiguously inte...
متن کاملSheared granular layers: Competition between flash heating and particle comminution
Quantitatively predicting the dynamic response and energy partition of granular fault gouges under shear remains a major challenge in seismology. Earthquake laboratory experiments are limited by capacity of equipments and thus cannot provide similar conditions in real earthquake ruptures. This motivates the development of computational models of granular fault gouge that accurately predict thei...
متن کاملCoupled thermo-hydro-mechanical processes in fault zones during rapid slip
The physical processes which occur during an earthquake exhibit several coupled phenomena as large variations of stress, pore pressure and temperature take place in the slip zone. Thermo-poro-mechanical couplings due to shear heating can be associated to phase transition such as vaporization of the pore fluid, melting of fault gouge and to chemical effects such as dehydration of minerals or dec...
متن کامل