Frictional and Hydraulic Properties of Plate Interfaces Constrained by a
Tidal Response Model Considering Dilatancy/Compaction
Abstract
Tidal triggering of tectonic tremors has been observed at plate
boundaries around the circum-Pacific region. It has been reported that
the response of tremors to tidal stress during episodic tremor and slow
slip (ETS) changes between the early and later stages of ETS. Several
physical models have been constructed, with which observations for the
tidal response during ETS have been partly reproduced. However, no model
has been proposed that reproduces all the observations. In this study, a
model adopted in previous studies is extended to include the effects of
dilatancy/compaction that occur in the fault creep region. The
analytical approximate solution derived in this study and numerical
computational results reveal how the tidal response depends on the
physical properties of the fault. Furthermore, the model reproduces all
the above observations simultaneously for a specific range of fault
parameters. Of particular importance is that the occurrence of
dilatancy/compaction is essential to reproduce the tidal response at the
early stage of the ETS. The value of the critical distance dc is
constrained to be approximately 1~10 cm. This agrees
with the values that have been widely used in seismic cycle numerical
simulations rather than those obtained in laboratory experiments. The
fluid pressure diffusivity is constrained to be at least 10^(-5)
m^2/s or less, and the effective normal stress is constrained to
10^(5~6) Pa. In conclusion, this study shows that
reproducing the tidal response of tectonic tremors during the ETS is
useful for estimating fault physical properties, including hydraulic
properties.