MTGeophysics.jl

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3D data maps ​

Before inverting 3D data it helps to look at them on a map. Two quantities are especially useful:

  • The phase tensor is drawn as an ellipse at each site. It is not affected by galvanic distortion, and its shape and orientation show the dimensionality and strike of the structure under the site.

  • The induction vector is drawn as an arrow computed from the tipper. By default the arrows point towards conductors.

Plot a phase tensor and induction vector map ​

julia
using MTGeophysics

PlotPTIVMap("data.dat")

The window steps through the periods. Ellipses have the same size at every site and are coloured by β skew, Φmin or Φ2. You can add shapefiles from the window and export the figure.

From the command line:

bash
julia --project=. examples/plot_PTIV_map.jl <data.dat> [EPSG:XXXX]

Export to GIS ​

To write every period as shapefiles, without opening a window (for example on a cluster):

julia
write_ptiv_gis("data.dat"; crs = "EPSG:4326", output_dir = "ptiv-gis")

Each period gives one shapefile of ellipses (*_PT_T<period>.shp) and one of arrows (*_IV_T<period>.shp). A README.txt in the folder records the conventions used.

Use the values in a script ​

julia
d  = load_data_modem("data.dat")
PT = phase_tensors_from_data(d)                       # periods × sites
IV = induction_vectors_from_data(d; convention = :parkinson)
PT[1, 1].beta                                         # skew angle, in degrees

Entries are nothing where a value cannot be computed, for example when a component is missing.