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 late 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 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 ETS. The
value of the critical distance dc is constrained to be approximately 10
cm. This is in agreement 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 ETS is useful for estimating fault physical properties, including
hydraulic properties.