Details of the Abstract
| Title of paper | Non-inductive electric fields in Florida and Kilauea, Hawaii magnetotelluric data: oceanographic signals degrading the transfer functions |
| List of authors | Crosbie, J., Bedrosian, P., Peterson, D., Kelbert, A. |
| Affiliation(s) | USGS Geology, Geophysics, and Geochemistry Science Center, Denver, CO - USA, USGS Geology, Geophysics, and Geochemistry Science Center, Denver, CO - USA, USGS Geology, Geophysics, and Geochemistry Science Center, Denver, CO - USA, USGS Geologic Hazards Science Center, Golden, CO - USA, |
| Summary |
Magnetotelluric transfer functions estimated from data collected in coastal Florida show mode degradation over a broad geographic area, specifically in the impedances Zxy and at long periods (> 3000 seconds). The vertical magnetic field transfer functions (tippers) and the other principal impedance components (Zyx) remain unaffected, implicating the north-south electric field as the causative factor. There are indications that the north-south electric field includes a considerable non-inductive component. Synchronous data recorded at sites far from the coast are unaffected. The degraded impedances are not due to the “vanishing mode” effect, arising from attenuated electric fields in conductive ground, as apparent resistivities are modest (5-100 ohm-m). We analyze the spectral density matrix for arrays of synchronous stations (Egbert 1997) incorporating both impacted and clean stations. An examination of the associated signal and incoherent noise power is ongoing and may help to elucidate the source of these non-inductive electric fields. Magnetotelluric data collected at Kīlauea, Hawaii between May 2022 and August 2023 also show non-inductive electric field signals. Long-period impedances (> 1 second) are severely degraded. Low-quality impedances tend to be near the coastline. In the spectra and time series, non-inductive electric field disturbances are observed on time scales ranging from 10s of seconds to ~1 day with amplitudes that are one to two orders of magnitude greater than the inductive magnetotelluric signal. We speculate that these long period non-inductive electric fields are the result of exclusion-diffusion potentials arising from ocean current forcing the saline-freshwater interface beneath the edge of the island. |
| Session Keyword | 1.0 Instrumentation, data acquisition and processing |
| File upload |
1.0_non-inductive_electric_fi_crosbie_01.pdf
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