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The activity of High Frequency (HF) marsquakes, as recorded by InSight at Homestead Hollow, Elysium Planitia, increased after about Ls=33°, and ceased almost completely by Ls=187°, following an apparently seasonal variation with a peak rate near aphelion. We define seismic rate models based on the declination of the Sun, annual solar tides, and the annual CO2 cycle as measured by atmospheric pressure. Evaluation of Akaike weights and evidence ratios shows that the declination of the Sun is the most likely, and the CO2 cycle the least likely driver of this seismic activity, although the discrimination is weak, and the occurrence of a few events in August 2020 is in favor for a triggering by CO2 ice load. We also show that no periodicity related to Phobos’ orbit is present in the HF event sequence. Event rate forecasts are presented to allow further discrimination of candidate mechanisms from future observations.

The activity of High Frequency (HF) marsquakes, as recorded by InSight at Homestead Hollow, Elysium Planitia, increased after about Ls=33°, and ceased almost completely by Ls=187°, following an apparently seasonal variation with a peak rate near aphelion. We define seismic rate models based on the declination of the Sun, annual solar tides, and the annual CO2 cycle as measured by atmospheric pressure. Evaluation of Akaike weights and evidence ratios shows that the declination of the Sun is the most likely, and the CO2 cycle the least likely driver of this seismic activity, although the discrimination is weak, and the occurrence of a few events in August 2020 is in favor for a triggering by CO2 ice load. We also show that no periodicity related to Phobos’ orbit is present in the HF event sequence. Event rate forecasts are presented to allow further discrimination of candidate mechanisms from future observations., This version is now (04. Oct. 2021) superseded by the published paper Knapmeyer et al. (2021), Seasonal seismic activity on Mars, Earth and Planetary Science Letters, Volume 576, 117171, ISSN 0012-821X, https://doi.org/10.1016/j.epsl.2021.117171. Please refer to the published paper. The version available at Zenodo is only of historical interest. This is the version of the paper that was submitted to "Earth and Planetary Science Letters" on 15. February 2021. Graphical abstract, Main manuscript, and supplementary information are put together into a single PDF with a cover sheet indicating that this is a submitted paper. This manuscript supersedes abstract 1069 submitted to the 52th LPSC conference (2021), https://doi.org/10.5281/zenodo.4478346. Results described in the LPSC abstract are affected by a bracketing error in the implementation of eq. 1 of this paper, which effectively made some parts of the parameter space inaccessible.