watex.utils.plot_skew#

watex.utils.plot_skew(edi_obj, method='Bahr', mode=None, threshold_line=None, fig_size=(7, 5), savefig=None, view=None, style=None, **kws)[source]#

Plot phase sensitive skew visualization.

Phase Sensitivity Skew (\(\eta\)) is a dimensionality tool that represents a measure of the skew of the phases of the impedance tensor. The parameter is thus unaffected by the distortion effect, unlike the Swift-skew and ellipticity dimensionality tools [1].

Values of \(\eta\) > 0.3 are considered to represent 3D data. Phase-sensitive skews less than 0.1 indicate 1D, 2D or distorted 2D (3-D /2-D) cases. Values of \(\eta\) between 0.1 and 0.3 indicates modified 3D/2D structures [2] according to Bahr’ methods. However, values :math:eta >=0.2` using the Swift methods, the smaller the value \(\eta\) ( close to \(0.\)), the closer the structure to 2D structure and vice versa.However, it is generally considered that an electrical structure of \(\eta < 0.4\) can be treated as a 2D medium. Here as the threshold_line for eta() using the Swift method should be set as 0.4.

New in version 0.1.5.

Parameters

  • edi_obj (str, watex.edi.Edi) – Full path to edifiles or Edi object.

  • method (str, default='Bahr':) – Kind of correction. Can be swift for the remove distorsion proposed by Swift in 1967 [3]. The value close to 0. assume the 1D and 2D structures, and 3D otherwise. Conversly to bahr for the remove distorsion proposed by Bahr in 1991 [2]. The latter threshold is set to 0.3. Above this value the structures is 3D.

  • threshold_line (float, optional) –

    Visualize th threshold line. Can be [‘bahr’, ‘swift’, ‘both’]:

    • Note that when method is set to swift, the value close to close to \(0.\) assume the 1D and 2D structures, and 3D otherwise.

    • when method is set to Bahr, \(\mu > 0.3\) is 3D structures, between \([0.1 - 0.3]\) assumes modified 3D/2D structures whereas \(<0.1\) 1D, 2D or distorted 2D.

  • mode (str, optional) – X-axis coordinates for visualisation. plot either 'frequency' or 'periods'. The default is 'frequency'

  • view (str, default='skew') – phase sensistive visualization. Can be rotational invariant invariant. Note that setting to mu or invariant does not change any interpretation since the distortion of Z are all rotational invariant whether using the Bahr or swift methods.

  • fig_size (tuple, default= (10, 4)) – Matplotlib figure size.

  • savefig (str, optional) – Save figure name. The default resolution dot-per-inch is 300.

  • style (str, default='classic') – Matplotlib plottings style.

  • kws (dict,) – Matplotlib Axes scatterplot additional keywords arguments.

Returns

ax – Return axis

Return type

Matplotlib.pyplot.Axis

See also

watex.methods.em.Processing.skew

Skew equation formulations.

watex.view.TPlot.plotSkew

Give a consistent plot where user can customize the plot using the plot parameter of watex.property.BasePlot class.

References

1

Bahr, K. (1988) Interpretation of the magnetotelluric impedance tensor: regional induction 395 and local telluric distortion. J. Geophys. Res., 62, 119–127.

2(1,2)

Bahr, K. (1991) Geological noise in magnetotelluric data: a classification of distortion types. 397 Phys. Earth Planet. Inter., 66, 24–38.

3

Bahr, K., 1991. Geological noise in magnetotelluric data: a classification of distortion types. Physics of the Earth and Planetary Interiors 66 (1–2), 24–38.

Examples

>>> import watex as wx
>>> from watex.utils.plotutils import plot_skew
>>> edi_sk = wx.fetch_data ("edis", return_data =True , samples = 20 )
>>> plot_skew (edi_sk)
>>> plot_skew (edi_sk, threshold_line= True)