HR: 0800h
AN: S21B-0556    [Abstracts]
TI: Effects of Non-linear Terms and Fault Width on Pore Fluid Pressurization
AU: * Vredevoogd, M A
EM: m_vredevoogd@yahoo.com
AF: University of California, Riverside, 900 University Avenue Earth Sciences Department, Riverside, CA 92521, United States
AU: Oglesby, D D
EM: david.oglesby@ucr.edu
AF: University of California, Riverside, 900 University Avenue Earth Sciences Department, Riverside, CA 92521, United States
AU: Park, S K
EM: magneto@ucrmt.ucr.edu
AF: University of California, Riverside, 900 University Avenue Earth Sciences Department, Riverside, CA 92521, United States
AB: Faults generate heat due to friction while slipping in earthquakes. If there are pore fluids along the fault, they will be heated and expand. The pore fluids will have little effect on faults in high permeability settings, as they quickly escape. In a low permeability setting, the expanding pore fluids are not able to escape quickly, and thermal expansion of the fluids will increase the fluid pressure, lowering the effective normal stress (and thus frictional stress) along the fault. To investigate this process, we solve the non-linear equations presented in Mase and Smith (1985). These equations involve several non-linear terms that make it necessary to solve the equations iteratively. We have previously shown some results of this methodology for various permeability structures and slip rates. Here we focus on the importance of individual terms in the equations by running models with individual terms neglected. Among our results, we find that conduction significantly affects the temperature and pressure, while advection has a negligible effect on the solution. The implications may be important for researchers constructing simplified models of the pore fluid pressurization process. We also look at the effect of fault width (the width of the area that is shearing and producing heat). In particular, we are interested in the effects of the fault width on the maximum temperature reached, as well as the total amount of frictional heat generated. While a wider fault will tend to have a lower peak temperature because of the distributed slip, it can also result in a larger overall heat generation, because the average temperature over the fault width can be higher than for a narrow fault with a higher, but narrower temperature peak. In contrast, while the narrow faults initially have the highest pressures, the wider faults eventually surpass them both in maximum pressure, and in the amount of overall pressurization.
DE: 4430 Complex systems
DE: 4445 Nonlinear differential equations
DE: 7209 Earthquake dynamics (1242)
DE: 7290 Computational seismology
SC: Seismology [S]
MN: 2007 Fall Meeting