Annual Meeting - SCEC.org

Report | SCEC Research Accomplishments
Numerous research groups are exploring various topics through dynamic rupture modeling. Segall and Dunham continued
their analysis of thermal pressurization, analyzing its effect through all phases of nucleation and into the early stage of
dynamic rupture using rate and state friction with the aging form of the state evolution law on an infinitely thin fault. Their
simulations begin using a quasi-static nucleation code and switch to an elastodynamic code just before seismic radiation
becomes significant (Schmitt et al. 2011). When they compare purely quasi-dynamic simulations to those incorporating
elastodynamics, they find that the slip distributions are the same, but rupture propagation is about 2.5 times faster in the
quasi-dynamic case. Incorporating elastodynamics slows crack growth to the P-wave speed. For an infinitely thin slip surface,
they find that thermal pressurization begins to dominate fault-weakening at 0.06 mm/s, and once a maximum velocity of 0.2
mm/s is reached, thermal pressurization is the only important weakening term (Figure 26). Inconsistent with observations,
incorporating thermal pressurization in the dynamic simulations results in a total loss of shear strength, an artifact that they
attribute to the spatially uniform stress and shear resistance. They have begun to explore models with two types of
Figure 25. Simulations of the normal stress changes and shear stress response in the experiments that are shown in Fig. 2 of SCEC
Report #10145. The left 4 panels are using the constitutive relations of Linker and Dieterich (1992), arranged in the same order as in
Fig. 2. Right 4 panels are using the constitutive relations of Prakash (1998).
60 | Southern California Earthquake Center