Geoelectric hazard maps for the continental United States

What is it about?

In support of a multiagency project for assessing induction hazards, we present maps ofextreme-value geoelectric amplitudes over about half of the continental United States. These mapsare constructed using a parameterization of induction: estimates of Earth surface impedance, obtainedat discrete geographic sites from magnetotelluric survey data, are convolved with latitude-dependentstatistical maps of extreme-value geomagnetic activity, obtained from decades of magnetic observatorydata. Geoelectric amplitudes are estimated for geomagnetic waveforms having 240 s sinusoidal periodand amplitudes over 10 min that exceed a once-per-century threshold. As a result of the combination ofgeographic differences in geomagnetic activity and Earth surface impedance, once-per-century geoelectricamplitudes span more than 2 orders of magnitude and are an intricate function of location. For north-southinduction, once-per-century geoelectric amplitudes across large parts of the United States have a medianvalue of 0.26 V/km; for east-west geomagnetic variation the median value is 0.23 V/km. At some locations,once-per-century geoelectric amplitudes exceed 3 V/km.

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Why is it important?

This work provides realistic estimates of geoelectric hazards that can interfere with the operation of electric-power grid systems.

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