Numerical model of long-term fault slip (earthquake cycle) simulation had been initially developed with a 90-degree dip angle to the free surface, neglecting dynamic stress transfer. At present we can implement either effect of lower dip angle or the dynamic stress transfer into the model, but mounting both effects is still difficult. Here we perform numerical experiments of the earthquake cycle model to compare the dip-angle effect with the dynamic effect. Qualitatively, both prolong earthquake recurrence interval by enlarging event magnitude. We find that the effect of the low dip angle can be greater than the dynamic stress transfer when the dip angle is as small as actual subduction plate interface. This tendency is stronger as seismic area is shallower.
We implement three elementary processes into a spring-slider model obeying the rate- and state-dependent friction law. All the processes in this model allow to change pore fluid pressure on the frictional interface. One is thermal fluid pressurization due to frictional heating. The second is fluid depressurization by gouge dilatancy. The third is fluid pressurization owing to pore sealing driven by chemical reactions. We perform numerical experiments varying the thickness of the gouge layer (w) and the hydraulically activated layer (why), to check the difference in slip instability. We find that stickslip events with the thermal pressurization occur in case with sufficiently small w. In other cases, smaller why (less permeable) leads to more stable slip, e.g., slow slip events. In addition, faster apparent loading for the block motion occurs when w is quite large and why is small.
Reliability of Ca-in-Orthopyroxene (Opx) thermometer proposed by Brey & Köhler (1990) is examined by using a compiled database of subliquidus equilibrium and above-liquidus melting experiments for multi-component peridotitic samples. The thermometer represents experimental temperature conditions, Texp, with average ΔT [ = TCa-in-Opx − Texp where TCa-in-Opx is temperature estimated by the thermometer] of −7°C and within standard deviation of 77°C. ΔT is independent on composition of Opx but shows negative relation with reciprocal absolute temperature, indicating that the geothermometer includes temperature-dependent systematic error. A revised model of Ca-in-Opx thermometer is established by adding a correction for the temperature-dependent systematic error. Reliability of the revised Ca-in-Opx thermometer is compared with that of two-pyroxene thermometer. The result strongly suggests that two-pyroxene thermometer is much reliable than Ca-in-Opx thermometer and the former should be used to estimate equilibrium temperatures of two pyroxene bearing peridotites.