Band-Pass Filter

Description Apply high-pass, low-pass or band-pass frequency filters to an input volume.
Module(s) Explorationist (for stacks), Image Gather Processing (for stacks and gathers)
Requirements Volume, Window model (optional)
Related Spectra Analysis, Spectral Decomposition
Works with 2D, Stacks, Gathers

The Band-pass Filter performs high-, low-, or band-pass filtering on a volume based on a frequency range. The process uses a zero-phase Butterworth filter that passes a range of frequencies and rejects frequencies outside the range.

Filters are defined using pass and stop frequencies, corresponding to the 95% and 5% amplitude points on the filter (see images below).

A time/depth-varying windowing model can be specified to apply different filters to different time windows.

Performance warning: Band-pass filtering is a computationally-intensive process that requires processing entire traces. The resulting output volume may be slow to use. Consider:

Create a band-pass filter

Create band-pass filter process
  1. In the Control Panel, open the Process tab.
  2. At the tab header, click the blue "+" icon and select New Process.
  3. Double-click or search for Band-pass Filter.
  4. Type a name for the process and click OK.

Define band-pass filter settings

  1. In the Details Panel, select the input volume. In this example, a gather volume is selected.
  2. Select the Use a minimum phase filter checkbox to apply a minimum phase filter.
  3. You can also choose to Output noise model instead of filtered traces check box.
  4. Select the Filter type :
    • High pass
    • Band pass
    • Low pass

Filtering Settings

  1. Select a Windowing Model
    • Select <<Whole Trace>> to apply one set of filter parameters to the whole trace.
    • Select a Windowing Model to apply different parameters to each window. See Creating a Windowing Model for more details on window models.
    • If a Windowing Model is used, pass and stop frequencies must be provided for each window.
  2. As a result of this process, a new volume is available in the Volume tab.

Filter type: Band pass

The band pass filter passes frequencies in a range between specified low and high values.

Define band-pass filter settings
  • Specify filters via Pass and Stop
    • If unchecked, define the filter with a 3dB down frequency and the slope in dB per octave
    • If checked, define the filter ramp between two values, a stop (5%) and a pass (95%) frequency
  • Specify the low cut-off and high cut-off frequency values as needed.

Filter type: High Pass

The high pass filter passes frequencies above a specified value.

  • Specify filters via Pass and Stop
    • If unchecked, define the filter with a 3dB down frequency and the slope in dB per octave
    • If checked, define the filter ramp between two values, a stop (5%) and a pass (95%) frequency
  • Specify the cut-off frequency values as needed.

Filter type: Low Pass

The low pass filter passes frequencies below a specified value.

  • Specify filters via Pass and Stop
    • If unchecked, define the filter with a 3dB down frequency and the slope in dB per octave
    • If checked, define the filter ramp between two values, a stop (5%) and a pass (95%) frequency
  • Specify the cut-off frequency values as needed.

The following example show a gather volume before and after the low-pass filter is applied.