Pore pressure in aquifers confined below a cryosphere will increase as
Mars cools and the cryosphere thickens. The increase in pore pressure
decreases the effective stress and hence will promote seismicity. We
calculate the rate of pore pressure change from cooling of the Martian
interior and the modulation of pore pressure from solar and Phobos tides
and barometric loading. Using the time-varying pressure and tidal
stresses, we compute Coulomb stress changes and the expected seismicity
rate from a rate-and-state friction model. Seismicity rate will vary by
several 10s of percent to two orders of magnitude if the mean pore
pressure is within 0.2 MPa and 0.01 MPa of lithostatic, respectively.
Seismic events promoted by high pore pressure may be tremor-like.
Documenting (or not) tidally-modulated shallow seismicity would provide
evidence for (or against) water-filled confined aquifers, that pore
pressure is high, and that the state of stress is close to failure —
with implications for processes that can deliver of water to the Martian