Hierarchical temporal modulation of Martian seismicity with an intrinsic ~8-sol cycle and orbital-scale forcing

We report the detection of a previously unrecognized intrinsic periodic component in Martian seismicity based on the InSight seismic catalog. Using the seismicity index S, we identify a robust ~8-sol periodicity that emerges directly from seismic activity, indicating the presence of an intrinsic dynamical timescale of the Martian seismic system. In addition, longer-period components at ~687, ~343.5, and ~229 days are detected, corresponding to the Martian orbital period and its harmonics. These components are independently reproduced using geometrical configurations involving Phobos and Deimos. The combined results demonstrate that Martian seismicity is governed by deterministic multi-scale modulation, where intrinsic short-period dynamics are embedded within orbital-scale forcing. This finding provides new physical insight into planetary seismic processes and suggests that seismic activity on terrestrial bodies may exhibit structured temporal organization rather than purely stochastic behavior.