Geomagnetic storms can cause power grid instabilities and blackouts due to excessive geomagnetically induced currents (GICs) flowing in electric transmission systems. In this study, we assess regional vulnerability to GICs by modeling the geoelectric fields induced by significant historic geomagnetic disturbance events in the presence of 3D subsurface geology using data from the Australian Lithospheric Architecture Magnetotelluric Project (AusLAMP) magnetotelluric array, Australia‐Wide Array of Geomagnetic Stations (AWAGS) magnetometer array, and Geoscience Australia geomagnetic observatory network. We analyze the vertical component of the magnetic field with respect to the horizontal magnetic‐field polarization for two magnetic storms and gain insight into the inductive effects associated with field polarization orientations in the 3D case. We also analyze the telluric field intensity and polarization for a unit geomagnetic field polarized in northerly and easterly directions at AusLAMP sites and find that in the presence of 3D geology the induced field has a very polarization‐sensitive anomaly. We model the geoelectric fields in southeastern Australia for the 1989 “Québec storm.” The induced ground electric fields are typically in the range 1,000–2,000 mV/km with a few sites within 2,000–5,000 mV/km on highly resistive regions and in coastal areas, and below 300 mV/km on inland sedimentary basins. The current study focuses on magnetic‐field variations with periods between 120 and ~20,000 s due to bandwidth limits in our magnetotelluric tensor data and the Nyquist limit for the 60 s sampling of our geomagnetic‐field data. Hence, our modeled maximum values should be considered lower estimates of potential real values.

中文翻译：

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在3D地下地质中模拟由地磁干扰引起的地电场，以澳大利亚东南部地区为例

由于电力传输系统中流过的过多地磁感应电流（GIC），地磁风暴​​会导致电网不稳定和停电。在这项研究中，我们使用来自澳大利亚岩石圈建筑大地电磁项目（AusLAMP）大地电磁阵列，澳大利亚地磁全阵列的数据，对存在3D地下地质的重大历史性地磁扰动事件引起的地电场进行建模，从而评估GIC的区域脆弱性台站（AWAGS）磁力计阵列和澳大利亚Geoscience地磁观测站网络。我们针对两个磁暴分析了磁场相对于水平磁场极化的垂直分量，并深入了解了3D情况下与磁场极化方向相关的感应效应。我们还分析了在AusLAMP站点向北和向东方向极化的单位地磁场的碲场强度和极化，发现在3D地质学的情况下，感应磁场的极化敏感性非常高。我们为1989年“魁北克风暴”在澳大利亚东南部的地电场建模。感应的地面电场通常在1,000–2,000 mV / km的范围内，在高电阻区域和沿海地区的一些站点在2,000–5,000 mV / km的范围内，而内陆沉积盆地的站点在300 mV / km以下。当前的研究重点是由于我们的大地电磁张量数据的带宽限制和60 s的地磁场数据采样的奈奎斯特限制，导致磁场变化在120到20,000 s之间。因此，