[SSS04-P59] Characteristics of frictional properties’ relationship with slow earthquake migration speed
Keywords:afterslip, rate- and state-dependent friction law, stress perturbation
On the Sanriku-Haruka-Oki earthquakes, Matsuzawa et al. [2004 EPS] pointed out that propagation speed of the postseismic slip seems to be on the order of 10 km/day for the shallower part of the subduction plate boundary while it appears to be 10 km/month for the deeper part. These results indicate that the propagation speed of postseismic slip depends on frictional properties and effective normal stress in addition to slip velocity.
To better understand the frictional properties controlling the propagation speed of postseismic slip, some numerical simulations of interplate earthquakes based on a rate- and state-dependent friction law (RSF) [Dieterich, 1979 JGR; Ruina, 1983 JGR] have been recently performed. These previous studies suggest the propagation speed of postseismic slip becomes lower in case of higher frictional stability, longer characteristic slip distance [Kato and Hirasawa, 1999 PAGEOPH], and higher effective normal stress [Ariyoshi et al., 2007 EPSL]. Since we do not quantitatively understand why such cases make the postseismic slip propagation slower, it is necessary to find an analytical relation between the frictional properties and the propagation speed of postseismic slip.
In this study, we develop an expression for the propagation speed of postseismic slip as a function of frictional properties including effective normal stress, and discuss its validity quantitatively by comparing the expression with trial numerical simulation results in addition to previous studies. Since our expression is also applicable to various types of slow earthquake phenomena, the observed slow earthquake migrations can help to constrain the frictional condition in subduction zones.