Resampling the seismic data

Theory

Resample module changes the sampling rate of seismic or velocity data by interpolating the input gathers onto a new time, depth, or frequency grid. It is used to make datasets compatible for further processing, improve numerical stability, or match required sampling for specific algorithms.

During the seismic data acquisition we record the data at sample interval say 2ms and we want to resample the data to 4ms for various reasons. By re-sampling we can reduce the number of samples that way we can minimize our data size without compromising the primary properties of seismic wavelet i.e., amplitude, frequency and phase. Re-sampling is beneficial up to certain sampling interval, above that it will degrade the seismic data by introducing aliasing. Resampling can be done in Frequency domain or using “sinc” function(sampling function).

Input data

Input DataItem

Input gather

the input gather can be a pre-stack or post-stack gather. Connect/reference to Output gather.

Parameters

Input gather type { Seismic, Velocity }

select the input gather type from the drop down menu. By default, Seismic.

Seismic - resamples the input seismic gather amplitudes

Velocity - resamples the input velocity model or functions.

Interpolator type { Linear, 8 points, Sinc }

select the interpolation method used for resampling. By default, Linear.

Linear - Fast, simple interpolation

8 points -  Higher-order interpolation using neighboring samples

Sinc - High-fidelity band-limited interpolation

Interpolator type - Sinc

uses sinc interpolation for accurate amplitude and phase preservation, especially suited for seismic data.

Aperture in samples

defines the number of neighboring samples used by the interpolator. Larger aperture leads to higher accuracy but slower performance. Whereas, Smaller aperture gives faster results but less accurate.

New sample rate - specifies the target sampling interval for the output data. By default, 4 ms.

From time - defines the starting time/depth/frequency for resampling. By default, -1 ms.

To time - defines the ending time/depth/frequency for resampling. By default, -1 ms.

Extend values - controls how values outside the original data range are handled. By default, FALSE (Unchecked) which means out-of-range samples may be set to zero or ignored. When enabled, boundary values are extended.

Gather domain { TIME, DEPTH, FREQUENCY } - Specifies the domain in which resampling is performed. By default, TIME. It automatically detects the input gather and accordingly changes the gather domain display.

Settings

Auto-connection

By default, TRUE(Checked).It will automatically connects to the next module. To avoid auto-connect, the user should uncheck this option.

Bad data values option { Fix, Notify, Continue }

Bad value fix - This is applicable whenever there is a bad value or NaN (Not a Number) in the data. By default, Notify. While testing, it is good to opt as Notify option. Once we understand the root cause of it, the user can either choose the option Fix or Continue. In this way, the job won't stop/fail during the production.

Notify

It will notify the issue if there are any bad values or NaN. This will halt the workflow execution.

Fix

It will fix the bad values and continue executing the workflow.

Continue

This option will continue the execution of the workflow however if there are any bad values or NaN, it won't fix it.

Number of threads

One less than total no of nodes/threads to execute a job in multi-thread mode. Limit number of threads on main machine.

Skip

By default, FALSE(Unchecked). This option helps to bypass the module from the workflow.

Output data

Output DataItem

Output gather

outputs resampled gather as an output gather.

Information

There is no information available for this module.

Examples

In this example workflow, we are resampling a pre-stack gather. The original sample interval of the input gather is 4ms and we are going to resample the input gather from 4 ms to 2 ms.

Actions

There are no action items available for this module.

Video lesson

YouTube video lesson, click here to open [VIDEO IN PROCESS...]

Related articles

Yilmaz. O., 1987, Seismic data processing: Society of Exploration Geophysicist

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