An analysis is made of Earth-surface geoelectric fields and voltages on electricity transmission power-grids induced by a late-phase E3 nuclear electromagnetic pulse (EMP). A hypothetical scenario is considered of an explosion of several hundred kilotons set several hundred kilometers above the eastern-midcontinental United States. Ground-level E3 geoelectric fields are estimated by convolving a standard parameterization of E3 geomagnetic field variation with magnetotelluric Earth-surface impedance tensors derived from wideband measurements acquired across the study region during a recent survey. These impedance tensors are a function of subsurface three-dimensional electrical conductivity structure. Results, presented as a movie-map, demonstrate that localized differences in surface impedance strongly distort the amplitude, polarization, and variational phase of induced E3 geoelectric fields. Locations with a high degree of E3 geoelectric polarization tend to have high geoelectric amplitude. Uniform half-space models and one-dimensional, depth-dependent models of Earth-surface impedance, such as those widely used in government and industry reports informing power-grid vulnerability assessment projects, do not provide accurate estimates of the E3 geoelectric hazard in complex geological settings. In particular, for the Eastern-Midcontinent, half-space models can lead to (order-one) overestimates/underestimates of EMP-induced geovoltages on parts of the power grid by as much as 1,000 volts (a range of 2,000 volts)—comparable to the amplitudes of the geovoltages themselves.

中文翻译：

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用核电磁脉冲深入地球：真实的表面阻抗影响 E3 地电灾害的测绘

分析了由晚期 E3 核电磁脉冲 (EMP) 引起的地表地电场和输电电网上的电压。假设情景是在美国东部和中部上空数百公里处发生数百千吨的爆炸。地面 E3 地电场是通过将 E3 地磁场变化的标准参数化与最近一次调查期间从整个研究区域获得的宽带测量得出的大地电磁地球表面阻抗张量卷积来估计的。这些阻抗张量是地下三维导电结构的函数。结果以电影地图的形式呈现，表明表面阻抗的局部差异严重扭曲了振幅、极化、和感应 E3 地电场的变相。E3 地电极化程度高的位置往往具有高地电振幅。地球表面阻抗的统一半空间模型和一维深度相关模型，例如广泛用于政府和行业报告中告知电网脆弱性评估项目的模型，不能提供复杂环境中 E3 地电灾害的准确估计地质环境。特别是，对于东部-中部大陆，半空间模型可能导致（一阶）高估/低估部分电网上 EMP 诱发的地电压高达 地表阻抗的深度相关模型，例如广泛用于政府和行业报告中告知电网脆弱性评估项目的模型，无法准确估计复杂地质环境中的 E3 地电灾害。特别是，对于东部-中部大陆，半空间模型可能导致（一阶）高估/低估部分电网上 EMP 诱发的地电压高达 地表阻抗的深度相关模型，例如广泛用于政府和行业报告中告知电网脆弱性评估项目的模型，无法准确估计复杂地质环境中的 E3 地电灾害。特别是，对于东部-中部大陆，半空间模型可能导致（一阶）高估/低估部分电网上 EMP 诱发的地电压高达1,000 伏（范围为 2,000 伏）——与地电压本身的幅度相当。