Apparent Density Calculation Filter

Use the Apparent Density Calculation option to apply a Fast Fourier Transform (FFT) apparent density filter to a channel.

The filter option is available with the following extensions and menus:

Depth to the top of model	Depth to the top of the model. Default: 1 Script Parameter: FFTDENS.DEPTH
Thickness of earth model	Thickness of the earth model in ground units. Default: 1 Script Parameter: FFTDENS.THICK
Low-pass cutoff (in ground units)	Low-pass Butterworth filter cutoff wavelength. Default: 1 Script Parameter: FFTDENS.LP
Background density (g/cm³)	Background density in g/cm³. Default: 0 Script Parameter: FFTDENS.DENS

To ensure correct density units, the input data fiducial base must be in meters.

The low-pass filter can be used to remove noise in the data that would otherwise be amplified by downward continuation.

A low-pass cutoff of 1 to 1.5 times the depth is normally appropriate.

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Parameters:

ω = wavenumber

t = Thickness (in ground units) of the earth model

G = Gravitational constant

d = Background density (g/cm³)