Numerical simulation of afterslips and slow slip events that occurred in the same area in Hyuga-nada of southwest Japan

Abstract

SUMMARY We propose a model of numerical simulation for the coexistence of afterslip for ∼M7 earthquake and slow slip events in the Hyuga‐nada region of Japan that incorporates 3‐D geometry of the Philippine Sea Plate. Coseismic slip events, recurrence of slow slip events and afterslip are qualitatively reproduced using the composite law, which is a type of rate‐ and state‐dependent friction law with higher cut‐off velocity. In addition, characteristic slip distances in the area are larger than those in other seismic source areas. In our simulation, afterslip, which occurred at the velocity‐weakening regime, triggered an aseismic transient event. After the termination of this event, spontaneous slow slip events repeatedly occurred in the same area. After a similar event sequence was repeated, another afterslip occurrence triggered a larger coseismic slip in a wide area including that of the slow slip events. Following this coseismic slip, the aseismic slip area was locked until the next afterslip propagation, which triggered an aseismic transient event. These results suggest that detailed observation of spatial and temporal distribution within the area of aseismic slip may indicate the potential of recurring slow slip events and future large earthquakes.

Geodetic inversion for spatial distribution of slip under smoothness, discontinuity, and sparsity constraints

“…We refer to the afterslip as true slip (s t ). Nakata et al (2014) numerically reproduced the spatial and temporal distribution of a simulated afterslip on a plate interface following a Mw 6.8 earthquake using synthetic displacements as observed data, and a Network Inversion Filter based on Kalman filtering methods (Segall and Matthews 1997). The estimated afterslip distribution demonstrated a continuous and smooth, but weakly heterogeneous distribution that roughly corresponded to the coseismic slip area.…”

“…The distribution of the frictional property on the plate interface was reflected in the afterslip distribution during the simulation. Thus, the area of the simulated afterslip enclosed the seismic source of the Mw 6.8 earthquake, and exhibited a ring-shaped afterslip distribution with a sharp boundary (Nakata et al 2012). The afterslip depth-profile crossing the center of the seismic source area showed two peaks, and the local minimum corresponded to the large coseismic slip area (Fig.…”

“…We assessed the accuracy of our proposed method using example data obtained in previous studies (Nakata et al 2012; (Table A1, see Additional file 1 for what was done in each study). The data were obtained by simulating an earthquake generation cycle based on the rate-and state-dependent friction law with a realistic three-dimensional plate geometry (Nakata et al 2012).…”

“…The data were obtained by simulating an earthquake generation cycle based on the rate-and state-dependent friction law with a realistic three-dimensional plate geometry (Nakata et al 2012). We conducted numerical simulations of large interplate earthquakes and afterslips beneath the Hyuganada offshore region, southwest Japan.…”

“…Thus, the ring-shaped distribution is not just a characteristic of numerical simulations, and is considered a typical spatial distribution of afterslip and an example of discontinuous heterogeneity on the plate interface. Hence, here we use the ring-shaped afterslip distribution of Nakata et al (2012) as observation data. We refer to the afterslip as true slip (s t ).…”