The only parameter in this group is the Smooth Operator Len (Hz). This spinbox controls the length of the smoothing operator used in the smooth mean algorithm that is applied to the seismic mean spectrum. It has a range of 1 - 1/5th nyquist and by default it is set to a value of 1/25th nyquist. View the chart named "Seismic Mean" whilst changing the value in the spinbox, to see the effect of this parameter. The aim here is to iron out high frequency amplitude variations as we are only interested in the global shape of the seismic spectrum. The image to the left shows the smooth mean spectrum (black) overlaying the mean spectrum (red). Here the Smoothing Operator Len is set at 5Hz.

The spinbox controls in this group are the primary parameters used for curve fitting. By default, curve-fitting is performed on the global spectrum and will be performed on the "Full Range". The curve fitting consists of three curves "Below Principal", Principal" and "Above Principal". The intersection between the "Below Principal" and the "Principal" curves is at the "Low Cut" point. The intersection of the "Principal" and "Above Principal" curves is at the "High Cut" point. The "Low Cut" spinbox is the Min Fit Frequency of the principal curve and the "High Cut" spinbox is the Max Fit Frequency of the principal curve. The other curves outside this range are generated in accordance with the controls on the "Frequency Domain" tab on the "Advanced Controls" dialog.

Low Cut: This spin box allows you to specify the minimum frequency that the curve fit algorithm will attempt to fit for the principal curve. By default, this is set to zero Hz. However, if including lower frequencies is not of any concern to you or you wish to additionally use a low frequency curve or linear horizontal low frequency section, then setting this to a higher value can often result in a better curve fit over the frequency range of interest.

High Cut: This spin box allows you to specify the maximum frequency that the curve fit algorithm will attempt to fit for the principal curve. By default, this is set to the nyquist frequency. However, if including higher frequencies is not of any concern to you or you wish to additionally use a high frequency curve or linear horizontal high frequency section, then setting this to a lower value can often result in a better curve fit over the frequency range of interest.

Curve fitting is updated immediately the "Low Cut" control, "High Cut" control or the "Frequency Domain" controls on the "Advanced Controls" dialog are changed. In this case we have defaulted the Low Cut to zero Hz and have set the high cut to 90Hz. The Above Principal curve fit is horizontal.

At any time you can curve fit to the full spectrum 0 Hz - nyquist by toggling on the "Full Range" checkbox within the "Fit Well Log Curves" group.

The "Design Operator" group provides controls which allow you to perturb how the Coloured Inversion operator spectrum is generated. Specifically it allows you to adjust the bandwidth of the designed operator. Normally the default is that the bandwidth is automatically calculated. The "Design Operator" chart displays three spectra. The first spectrum is the band limited curve fit (green curve), the second spectrum is the smooth seismic mean (red curve) and the third spectrum is the Coloured Inversion operator (blue curve).

Auto Calc.: The top checkbox controls whether the "Low Cut" and "High Cut" (i.e. design operator bandwidth) values are automatically calculated. If this checkbox is ticked then the design operator bandwidth is automatically calculated. If the automatic calculation doesn't produce the optimum Coloured Inversion operator then you can uncheck this box and set the "Low Cut" and "High Cut" spinboxes manually.

Low Cut: In manual mode (the above Auto Calc. checkbox unticked), this control will be sensitised and you can adjust the low cut to optimise the Coloured Inversion operator. Using the "Residual Operator (QC)" chart will help. The objective is that within the bandwidth the residual operator should be essentially flat and centred around 0 dB.

High Cut: In manual mode (the above Auto Calc. checkbox unticked), this control will be sensitised and you can adjust the high cut to optimise the Coloured Inversion operator. Using the "Residual Operator (QC)" chart will help. As with the Low Cut, the objective is that within the bandwidth the residual operator should be essentially flat and centred around 0 dB.

Auto Cal.: The middle checkbox controls allows you to control the slopes on the derived operator. By default, this checkbox is ticked which results in the -60dB down point being at 0 Hz on the low side with the -60 dB down point 30 Hz above the High Cut on the high side. Unticking this check allows you to specify the frequency of the -60dB down point on both the low and high side. You can only use this option if you are manually setting the design operator "Low Cut" and "High Cut".

Auto Cal.: The bottom checkbox controls whether the "Num. Zero X-ings" (i.e. time domain operator truncation) value is automatically calculated. If this checkbox is ticked then the truncation of the time domain Coloured Inversion operator will be automatically determined. This is controlled by a parameter which sets the percentage of energy captured. The percentage of energy captured template parameter is currently set at 99.9%. It is planned that future versions of SciQt will allow you to set template (default) parameters. It is sometimes desirable to alter the amount of truncation applied in order to reduce the length of long tails of very small sample values, or to include additional samples of significant value. This can be achieved by you unchecking this box and set the "Num. Zero X-ings" manually.

Num. Zero X-ings: In manual mode (the above Auto Calc. checkbox unticked), this control will allow you to adjust the length of the time domain operator in steps of zero crossings. It is desirable to have the operator truncate to a sample point close to a zero crossings point as it reduces anonymous side effects which might be introduced when the operator is applied.

QC Against Input Seismic: This checkbox control (ticked) allows you to QC against the original set of random seismic traces instead of the alternative set of random seismic traces. By default, the original set of traces is used in the design of the Coloured Inversion operator and the alternative set of traces is used to QC the Coloured Inversion operator.