[S-CG40] Science of slow-to-fast earthquakes

[SCG40-28] Slow slip events and pore pressure oscillations

*Alexis Alejandro Saez Uribe¹, Aitaro Kato² (1.Swiss Federal Institute of Technology in Lausanne (EPFL), Switzerland, 2.Earthquake Research Institute (ERI), the University of Tokyo, Japan)

Keywords:Slow slip events, Pore pressure transients, Scaling relations, Hydro-mechanical model

Multiple lines of evidence suggest that slow slip events (SSE) in subduction zones occur at depths where pore fluids are inferred to be overpressurized up to near lithostatic pressures. Moreover, recent observations further suggest that both the onset and arrest of SSE appeared to be spatially and temporally correlated with oscillations of pore pressure. In this study, we consider a physical model in which SSE are the result of unconditionally stable frictional slip that propagates due to an interfacial fluid source producing pore pressure changes along the plate boundary. It is shown that in this model, the dynamics of slow slip transients depend strongly on the temporal evolution of the pore pressure changes themselves. Due to limited observational constraints on pore pressure changes, we do not impose a particular fluid source but rather constrain it from observations of fault slip which are more abundant and detailed. We determine the characteristics of the fluid source that are consistent with these observations, specifically focusing on the spatiotemporal evolution of pore pressure and injection flow rate at the fluid source. A continuum spectrum of fluid sources is obtained under the assumption that common scaling relations for SSE hold. This includes, for instance, the variation of the moment-duration scaling relation ranging from a linear to a cubic power law. Other scaling relations such as the rupture speed versus the duration of the events are also considered. In particular, we discuss what fluid sources produce SSE that propagates either at a constant rupture speed or in a decelerating manner, including the diffusional case. Such fluid sources vary from episodes characterized by sudden, violent increases in pore pressure, to cases in which the variation of fluid pressure with time is rather smooth. In any case, these episodes must be followed by a depressurization stage, which notably induces a transition from crack-like to pulse-like propagation mode and the final arrest of slip.