Gravity induced seismicity modulation on planetary bodies and their natural satellites

Groundbased monitoring of seismicity and modulation capability in the field of planetary seismology remains equivocal due to the lack of natural observations. Using constraints from natural observation (including earthquakes, moonquakes and marsquakes) and theoretical model, we present the variation in gravitational acceleration "g" of different solar system objects, combined with natural external harmonic forcing are responsible for seismicity modulation on the planetary bodies and their natural satellites. From the global diversity in seismicity modulation, it has been observed that the plate-boundary regions on the Earth are susceptible to both shorter-period and long-period modulation. In contrast, stable plate interior regions appear to be more sensitive to long-period seismicity modulation, however, short-period modulation is lacking. For the moonquakes, as gravitational acceleration "g" is substantially lower than the Earth, hence all types of observed seismicity modulations for shallow moonquakes, thermal moonquakes and deep moonquakes are possible. Further, seasonal variation with an annual seismicity burst and seismic periodicity at polar wobble periods for high-frequency marsquakes indicate a natural signature, whereas diurnal and semi-diurnal periodicity along with Phobos' tidal period indicates possible artifact due to different detection probabilities and non-seismic noise on the Martian environment. The gravity induced resonance destabilization model in the context of rate-state-dependent friction appears better in agreement with the contrast/diversity in seismicity modulation linked to the Earth, Moon, and Mars.