One-dimensional layered Earth models of Canada for GIC applications, part 1: General description

Estimating the Geoelectric Field and Electric Power Transmission Line Voltage During a Geomagnetic Storm in Alberta, Canada Using Measured Magnetotelluric Impedance Data: The Influence of Three‐Dimensional Electrical Structures in the Lithosphere

“…The zone numbers for Alberta match the numbering of Trichtchenko et al (2019). The zone numbers for British Columbia (Zones 11, 12, 13, and 14 in Figure 1a) correspond to British Columbia Zones 3S, 4S, 5S, and 6 in Trichtchenko et al (2019). In this study, 9 of the zones in British Columbia were outside the region of interest and were not included.…”

“…For the 1-D approach, we follow the method of Trichtchenko et al (2019) which divided Alberta into 10 zones and British Columbia into 13 zones based on known geological domains (Figure 1a). The zone numbers for Alberta match the numbering of Trichtchenko et al (2019). The zone numbers for British Columbia (Zones 11, 12, 13, and 14 in Figure 1a) correspond to British Columbia Zones 3S, 4S, 5S, and 6 in Trichtchenko et al (2019).…”

“…USArray MT impedance tensors are available from the Data Management Ceter of the Incorporated Research Institutions for Seismology (IRIS) EMTF database (http:// ds.iris.edu/spud/emtf). One-dimensional zone information can be found in Trichtchenko et al (2019). Magnetic field data are freely available from NRCAN for Canadian IAGA observatories (https://www.geomag.nrcan.gc.ca/data-donnee/sd-en.php), the USGS Geomagnetism Program API data server (https:// www.usgs.gov/natural-hazards/geomagnetism), and the Canadian CARISMA network (https://www.carisma.ca/).…”

Frequency Considerations in GIC Applications

“…This can introduce errors in the electric field estimation with use of Equations 3 and 4, and in the comparative estimations of different magnetic storms in GIC-related studies, where dB/dt is often used as a proxy "index" of the geoelectric field as, for example, used in Viljanen et al (2001). model, Zone 3 (Z3) (Trichtchenko et al, 2019), were chosen for their proximity to the Ottawa Geomagnetic Observatory and their general representation of the common types of layered Earth models.…”

“…Calculation of the geoelectric field, as outlined in Equations 1-4, requires a definition of the surface impedance. Two examples of the one-dimensional layered Earth models for the Canadian province of Quebec, namely the Appalachian Geological Province model, Zone 2 (Z2) and the Grenville Geological Province model, Zone 3 (Z3) (Trichtchenko et al, 2019), were chosen for their proximity to the Ottawa Geomagnetic Observatory and their general representation of the common types of layered Earth models.…”