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Detection and mapping of Earth body resonances with cGPS
  • Mensur Omerbashich
Mensur Omerbashich
Journal of Geophysics

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I recently showed that Mw5.6+ earthquakes occur due to (as the lithosphere rides on) vast waves of the Moon-driven and gravitationally aided 1–72h long-periodic Earth body resonance (EBR). Here I report a methodologically independent proof: observation of actual EBR waves in solid matter using continuous GPS (cGPS). Superharmonic resonance periods from the EBR’s 55’–15 days (0.303 mHz–0.771605 μHz) band are thus recoverable in spectra of ITRF2014 positional components solved kinematically from 30-s cGPS samplings. The signal is so pure, strong, and stable that even daylong components are always and only periodic with Earth resonance periods constantly 99%-significant and of very high fidelity (ϕ>>12); very low fidelity (ϕ<<12) characterizes overtones and undertones. The examined cGPS stations have diurnal EBR fingerprints: unique sets of ~13-18 EBR periods, most clearly formed during ~M6+ quiescence, enabling depiction of EBR orientation for real-time EBR mapping. Furthermore, weeklong component time series reveal complete EBR and unavoidable undertone series (with very high fidelity, too) as the signature of an EBR’s companion sympathetic resonance. Also, I demonstrate the concept of EBR mapping using the Mexico City–Los Angeles–San Francisco cGPS profile alongside a tectonic plate boundary, successfully depicting the preparation phase of the 2020 Puerto Rico Mw6.4–Mw6.6 sequence. I finish by showing that the EBR has triggered the 2019 Ridgecrest Mw6.4–Mw7.1, sequence too. EBR maps can now be produced — for seismic prediction and to unobscure (decouple EBR from) geophysical observables such as stress/strain. Applications of EBR include geophysical prospecting and detection at all scales and at any time.
14 May 2022Published in Journal of Geophysics. ark:/88439/x073994