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Sun resonant forcing of Mars, Moon, and Earth seismicity
  • Mensur Omerbashich
Mensur Omerbashich
Journal of Geophysics

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Global seismicity on all three solar system’s bodies with in situ measurements — Earth, Moon, and Mars — is due mainly to Rieger resonance (RR) of the solar wind’s macroscopic flapping, driven by the well-known PRg=~154-days Rieger period and detected commonly in most heliophysical data types and the interplanetary magnetic field (IMF). Thus, spectra of InSight B/C-quality marsquakes rates revealed PRg as the only 99%-significant spectral peak in the 1–6 months (385.8–64.3-nHz) band of highest planetary energies. While a very high (>>12) fidelity Φ=2.8·10^6 characterizes PRg at Mars, modular 1/2PRg and 1/3PRg Rieger-type periodicities are co-driving Martian seismicity, at 89%–67% significance, and Φ>>12. A longer (v.9) release of InSight raw data revealed the entire RR, excluding a tectonically active Mars. Previous marsquakes studies showed a preference for higher frequencies, localization, temporal (dusktime) clustering, and annual variation — features that, taken together, are typical of a forced resonator. For check, I analyze rates of Oct 2015–Feb 2019, Mw5.6+ earthquakes, and all the Apollo moonquakes. To decouple magnetosphere and IMF effects, I analyze Earth and Moon seismicity during traversals of the Earth magnetotail vs. IMF separately. As shown with 99–67% confidence and Φ>>12, an unspecified majority of Mw5.6+ earthquakes and moonquakes also recur at RR periodicities, while about half of the spectral peaks split — but also into clusters that average to RR components, where magnetotail reconnecting clears the signal. The repeating of the Mars result for Earth and Moon means the solar wind co-drives geophysics, selenophysics, and areophysics. Without getting into causal mechanisms in detail, previous claims on solar wind/plasma dynamics being seismogenic are confirmed. This result calls for a reinterpretation of the seismicity phenomenon and reliance on global magnitude scales. Predictability of the solar wind threat is beneficial for physics-based seismic prediction and forecasting, and for the safety of space missions and solar system installations.