[S-CG39] Science of slow earthquakes: Toward unified understandings of whole earthquake process

[SCG39-P07] Extension of aseismic slip propagation theory to slow earthquake migration

*Keisuke Ariyoshi¹, Roland Burgmann², Ampuero Jean-Paul³ (1.Japan Agency for Marine-Earth Science and Technology, 2.University of California, Berkeley, 3.Institut de Recherche pour le Développement, Université Côte d’Azur)

Keywords:rate- and state-dependent friction law, subduction zones, megathrust earthquakes

Recent observations have revealed various types of migrating slow earthquake phenomena. Very low-frequency earthquakes, one of the major types of slow earthquake, have migration speed in the range of about 1-10 km/day, which is much lower than shear wave speeds. Slow earthquakes also have anomalous moment-duration scaling, compared to regular earthquakes, and they are one possible mechanism of precursory slip before large earthquakes. To model and improve our understanding of the migration process of slow earthquakes and their longer duration relative to regular earthquakes, we assume a chain reaction model of numerous asperities along the strike direction, governed by rate- and state-dependent friction on a 3-D subduction plate boundary. From the simulation results, we find that the migration speed is quantitatively explained by an analytical derivation of frictional properties. By applying the analytical results to the simulation and observational results, we conclude that (i) the migration speed of slow slip transients can increase before megathrust earthquakes due to an increase of the background slip velocity, (ii) the longer duration of slow earthquakes given their seismic moment may be explained by the chain reaction model with time delay for stress transfer between nearby asperities mediated by aseismic slip propagation, and (iii) the characteristic slip distance for very low-frequency earthquakes can be roughly estimated in the range of 0.1 μm~2 mm.