Empirical estimation of natural geoelectric hazards

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Geoelectric field time series can be estimated by convolving estimates of Earth‐surface impedance, such as those obtained from magnetotelluric survey measurements, with historical records of geomagnetic variation obtained at magnetic observatories. This straightforward procedure permits the mapping of geoelectric field variation during magnetic storms. Statistical analysis of the time series allows extrapolation to extreme‐value amplitudes, such as might be realized during an intense magnetic storm in the future. The development of these products is illustrated for the Mid‐Atlantic United States, using impedances obtained from EarthScope survey data and geomagnetic variation records obtained at the Fredericksburg observatory operated by the U.S. Geological Survey. For this region, 100‐year geoelectric exceedance amplitudes have a range of almost three orders of magnitude (from 0.04 V/km at a site in southern Pennsylvania to 24.29 V/km at a site in central Virginia), and they have significant geographic granularity, which is due to site‐to‐site differences in surface impedance (and subsurface electrical conductivity structure). Maps of 100‐year exceedance amplitudes resemble those of geoelectric amplitudes for the March 1989 magnetic storm, and, in that sense, the March 1989 storm resembles what might be loosely called a “100‐year” event.

Additional publication details

Publication type Book chapter
Publication Subtype Book Chapter
Title Empirical estimation of natural geoelectric hazards
Chapter 6
DOI 10.1002/9781119434412.ch6
Year Published 2019
Language English
Publisher American Geophysical Union
Contributing office(s) Geologic Hazards Science Center
Description 11 p.
Larger Work Type Book
Larger Work Subtype Monograph
Larger Work Title Geomagnetically induced currents from the sun to the power grid
First page 95
Last page 105
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