Coordinate variable data and header information for model MCR.MT.Bedrosian2016.resistivity.r0.0-n4.nc
netcdf MCR.MT.Bedrosian2016.resistivity.r0.0-n4 {
dimensions:
longitude = 180 ;
latitude = 129 ;
depth = 50 ;
variables:
float longitude(longitude) ;
longitude:long_name = "Longitude; positive east" ;
longitude:units = "degrees_east" ;
longitude:standard_name = "longitude" ;
float latitude(latitude) ;
latitude:long_name = "Latitude; positive north" ;
latitude:units = "degrees_north" ;
latitude:standard_name = "latitude" ;
float depth(depth) ;
depth:long_name = "depth below earth surface" ;
depth:units = "km" ;
depth:positive = "down" ;
float log10sigma(depth, latitude, longitude) ;
log10sigma:long_name = "electrical conductivity" ;
log10sigma:display_name = "log(10) electrical conductivity, in S/m" ;
log10sigma:units = "S/m" ;
// global attributes:
:title = "Three-dimensional electrical conductivity model of the Midcontinent Rift based on magnetotelluric data." ;
:id = "MCR-MT-2016" ;
:data_revision = "r0.0" ;
:summary = "The 3D MCR resistivity model (Bedrosian, 2016) is derived from inversion \nof full magnetotelluric impedance and vertical magnetic-field transfer functions. \nThe inverse resistivity model was calculated on a 3D rectilinear grid centered \nat 42.8267°N,90.647°W. The core model area has a 10-km uniform horizontal cell spacing \nextending from 99.35°W to 82.05°W and from 36.75°N to 48.55°N (1300 km N/S by 1300 km E/W). \nThe horizontal grid was padded by 10 cells with logarithmically increasing width \nin each direction. This additional padding is provided for numerical reasons so that \ninaccuracies in boundary conditions have minimal effect on the inverse solution. \nThe vertical mesh is non-uniform, with logarithmically spaced cell thickness starting \nfrom 100 m at the surface to a total depth of 722 km. There is little model resolution \nbelow 300 km depth; additional padding at depth is provided for numerical reasons. \nThe total model domain (150 x 150 x 50 cells) contains over 1.1 million model cells. \nThe inversion proceeded from a 100 Ω·m uniform start model without topography (flat Earth).\n\nThe model presented here is interpolated onto a uniform 0.1° × 0.1° grid that approximates \nthe 10-km horizontal cell size of the rectilinear modeling grid. The non-uniform vertical \ngrid of the original model is preserved. The model has been cropped between 82°W and 100°W \nand from 36°N and 49°N. The diffusive nature of magnetotelluric fields in the Earth \nserves to degrade resolution with increasing depth, however a minimum horizontal resolution \nof 30 km can be estimated based upon the applied model covariance (which defines the degree \nof smoothing regularization) and the horizontal cell size.\n\nThe model is derived from magnetotelluric data at 305 sites. Data were inverted using \nthe ModEM inversion code (Egbert and Kelbert, 2012; Kelbert et al., 2014). Inverted data \nconsist of long-period data collected during the EarthScope program (Kerr, 2013). All \ndata are publicly available through the IRIS Data Management Center (Kelbert et al., 2011).\nBoth full impedance (Z) and vertical magnetic field (T) transfer functions (tippers) were \ninverted for the combined data set at 11 periods from 8 to 17,000 s. Data were inverted \nwith statistically-determined errors but subject to error floors defined as 5% of the \nmagnitude of each tensor element and 0.01 in T. A sequential inversion approach \n(Bedrosian et al., 2018) was applied to balance the fit between impedance and tipper data \nand to build structure progressively within the model while simultaneously reducing error floors. \nA 100 Ω·m prior model was applied in all inversion steps and serves to damp unnecessary structure \nin those parts of the model domain with little data sensitivity. A final normalized \nroot-mean-square (nRMS) data misfit of 1.94 was obtained, representing a 70% reduction \nin misfit relative to the starting halfspace model. This model is incorporated \nas a component within the CONUS synthesis model CONUS-MT-2019 (Kelbert et al., 2019) \nand subsequent updates (CONUS-MT-2023; Murphy et al., 2023)." ;
:keywords = "regional, electromagnetic, magnetotelluric, resistivity, electrical conductivity, western United States" ;
:Conventions = "CF-1.0" ;
:Metadata_Conventions = "Unidata Dataset Discovery v1.0" ;
:author_name = "Paul A Bedrosian" ;
:author_url = "https://www.usgs.gov/staff-profiles/paul-a-bedrosian" ;
:author_email = "pbedrosian@usgs.gov" ;
:repository_name = "EMC" ;
:repository_institution = "IRIS EMC" ;
:repository_pid = "doi:10.17611/dp/emc.2023.mcrmt.2016.1" ;
:acknowledgment = "Model was provided by the author, Paul A Bedrosian\nU.S. Geological Survey, Geology, Geophysics and Geochemistry Science Center, Denver, CO" ;
:references = "Bedrosian, P. A. (2016) Making it and breaking it in the Midwest: Continental assembly and rifting from modeling of EarthScope magnetotelluric data. Precambrian Research, 278, 337-361. https://doi.org/10.1016/j.precamres.2016.03.009\nBedrosian, P. A., Peacock, J. R., Bowles-Martinez, E., Schultz, A., and Hill, G. J. (2018). Crustal inheritance and a top-down control on arc magmatism at Mount St Helens. Nature Geoscience, 11, 865–870. https://doi.org/10.1038/s41561-018-0217-2\nEgbert, G. D., and Kelbert, A. (2012). Computational recipes for electromagnetic inverse problems. Geophysical Journal International, 189, 251–267. https://doi.org/10.1111/j.1365-246X.2011.05347.x\nKelbert, A., Bedrosian, P.A. and Murphy, B.S. (2019). The first 3D conductivity model of the contiguous United States: reflections on geologic structure and application to induction hazards. Geomagnetically Induced Currents from the Sun to the Power Grid, pp.127-151, https://doi.org/https://doi.org/10.1002/9781119434412.ch8\nKelbert, A., Meqbel, N., Egbert, G. D., and Tandon, K. (2014). ModEM: A modular system for inversion of electromagnetic geophysical data. Computers and Geosciences, 66, 40–53. https://doi.org/10.1016/j.cageo.2014.01.010\nKelbert, A., Egbert, G. D., and Schultz, A. (2011). Data services products: EMTF, the magnetotelluric transfer functions. Retrieved from http://ds.iris.edu/ds/products/emtf\nKerr, R. A. (2013). Geophysical exploration linking deep Earth and backyard geology. Science, 340, 1283–1285. https://doi.org/10.1126/science.340.6138.1283\nMurphy, B.S., Bedrosian, P. and Kelbert, A., 2023. “Geoelectric constraints on the Precambrian assembly and architecture of southern Laurentia”, in Laurentia: Turning Points in the Evolution of a Continent, S.J. Whitmeyer, M.L. Williams, D.A. Kellett and B. Tikoff, Geological Society of America, https://doi.org/10.1130/2022.1220(13)" ;
:history = "2023-11-03" ;
:comment = "Created via three-step inversion of full impedance and vertical magnetic field transfer functions. Inversion methodology described in Bedrosian et al., (2018)." ;
:geospatial_lat_min = 36.15 ;
:geospatial_lat_max = 48.95 ;
:geospatial_lat_units = "degrees_north" ;
:geospatial_lat_resolution = "0.10" ;
:geospatial_lon_min = -99.95 ;
:geospatial_lon_max = -82.05 ;
:geospatial_lon_units = "degrees_east" ;
:geospatial_lon_resolution = "0.10" ;
:geospatial_vertical_min = " 0" ;
:geospatial_vertical_max = 674.7 ;
:geospatial_vertical_units = "km" ;
:geospatial_vertical_positive = "down" ;
:model_primary_coords = "latlon" ;
:model_corner_description = "used to compute exact grid geometry from cell centers" ;
:model_corner_location = "upper_southwest" ;
:model_corner_latitude = 35.9999961853027 ;
:model_corner_longitude = -100. ;
:model_corner_depth = 0. ;
:model_rotation_units = "degrees" ;
:model_rotation_angle = 0. ;
:author_institution = "US Geological Survey" ;
:model = "MCR-MT_2016" ;
:reference = "Bedrosian (2016)" ;
:reference_pid = "doi:10.1016/j.precamres.2016.03.009" ;
data:
longitude = -99.95, -99.85, -99.75, -99.65, -99.55, -99.45, -99.35, -99.25,
-99.15, -99.05, -98.95, -98.85, -98.75, -98.65, -98.55, -98.45, -98.35,
-98.25, -98.15, -98.05, -97.95, -97.85, -97.75, -97.65, -97.55, -97.45,
-97.35, -97.25, -97.15, -97.05, -96.95, -96.85, -96.75, -96.65, -96.55,
-96.45, -96.35, -96.25, -96.15, -96.05, -95.95, -95.85, -95.75, -95.65,
-95.55, -95.45, -95.35, -95.25, -95.15, -95.05, -94.95, -94.85, -94.75,
-94.65, -94.55, -94.45, -94.35, -94.25, -94.15, -94.05, -93.95, -93.85,
-93.75, -93.65, -93.55, -93.45, -93.35, -93.25, -93.15, -93.05, -92.95,
-92.85, -92.75, -92.65, -92.55, -92.45, -92.35, -92.25, -92.15, -92.05,
-91.95, -91.85, -91.75, -91.65, -91.55, -91.45, -91.35, -91.25, -91.15,
-91.05, -90.95, -90.85, -90.75, -90.65, -90.55, -90.45, -90.35, -90.25,
-90.15, -90.05, -89.95, -89.85, -89.75, -89.65, -89.55, -89.45, -89.35,
-89.25, -89.15, -89.05, -88.95, -88.85, -88.75, -88.65, -88.55, -88.45,
-88.35, -88.25, -88.15, -88.05, -87.95, -87.85, -87.75, -87.65, -87.55,
-87.45, -87.35, -87.25, -87.15, -87.05, -86.95, -86.85, -86.75, -86.65,
-86.55, -86.45, -86.35, -86.25, -86.15, -86.05, -85.95, -85.85, -85.75,
-85.65, -85.55, -85.45, -85.35, -85.25, -85.15, -85.05, -84.95, -84.85,
-84.75, -84.65, -84.55, -84.45, -84.35, -84.25, -84.15, -84.05, -83.95,
-83.85, -83.75, -83.65, -83.55, -83.45, -83.35, -83.25, -83.15, -83.05,
-82.95, -82.85, -82.75, -82.65, -82.55, -82.45, -82.35, -82.25, -82.15,
-82.05 ;
latitude = 36.15, 36.25, 36.35, 36.45, 36.55, 36.65, 36.75, 36.85, 36.95,
37.05, 37.15, 37.25, 37.35, 37.45, 37.55, 37.65, 37.75, 37.85, 37.95,
38.05, 38.15, 38.25, 38.35, 38.45, 38.55, 38.65, 38.75, 38.85, 38.95,
39.05, 39.15, 39.25, 39.35, 39.45, 39.55, 39.65, 39.75, 39.85, 39.95,
40.05, 40.15, 40.25, 40.35, 40.45, 40.55, 40.65, 40.75, 40.85, 40.95,
41.05, 41.15, 41.25, 41.35, 41.45, 41.55, 41.65, 41.75, 41.85, 41.95,
42.05, 42.15, 42.25, 42.35, 42.45, 42.55, 42.65, 42.75, 42.85, 42.95,
43.05, 43.15, 43.25, 43.35, 43.45, 43.55, 43.65, 43.75, 43.85, 43.95,
44.05, 44.15, 44.25, 44.35, 44.45, 44.55, 44.65, 44.75, 44.85, 44.95,
45.05, 45.15, 45.25, 45.35, 45.45, 45.55, 45.65, 45.75, 45.85, 45.95,
46.05, 46.15, 46.25, 46.35, 46.45, 46.55, 46.65, 46.75, 46.85, 46.95,
47.05, 47.15, 47.25, 47.35, 47.45, 47.55, 47.65, 47.75, 47.85, 47.95,
48.05, 48.15, 48.25, 48.35, 48.45, 48.55, 48.65, 48.75, 48.85, 48.95 ;
depth = 0.05, 0.1575, 0.281, 0.423, 0.5865, 0.7745, 0.9905, 1.239, 1.525,
1.854, 2.2325, 2.6675, 3.1675, 3.7425, 4.404, 5.165, 6.04, 7.046, 8.203,
9.5335, 11.0635, 12.823, 14.846, 17.1725, 19.8485, 22.926, 26.465,
30.535, 35.2155, 40.598, 46.7875, 53.905, 62.0905, 71.504, 82.329,
94.778, 109.0945, 125.558, 144.491, 166.264, 191.303, 220.098, 253.2125,
291.2945, 335.089, 385.4525, 443.37, 509.975, 586.571, 674.6565 ;
}