2D despiking#

Despike SEG-Y file(s) using a 2D moving window function.

Description#

Remove (single trace) noise bursts from seismic data using an user-defined moving 2D window (time x ntraces) approach:

Define moving 2D window (time x ntraces) with overlap in time domain (in percent)
Compute background amplitude per time sample over ntraces using user-specified function
- mean: average amplitude
- rms: root mean squared amplitude
- median: median amplitude
Compare reference trace amplitudes with computed background amplitudes using user-specified threshold and
- amplitude > threshold * background amplitude → spike detection
- amplitude <= threshold * background amplitude → no spike
Replace detected spike samples using user-specified method:
- scaled: Scale signal down to background amplitude (based on mode). Tapering applied.
- mode: Replace with background amplitude values
- threshold: Replace with threshold * background amplitude values.
- zeros: Replace with zero values.
- median: Replace with median values (calculated from neighboring traces).

Figure 1: Schematics of 2D despike algorithm.

Usage#

This script is designed to be used from the terminal (i.e. command line).

Command line interface#

The script can handle three different inputs:

single SEG-Y file (e.g., filename.sgy)
datalist of files to process (e.g., datalist.txt)
directory with input files (e.g., /input_dir)

There are two options to run the script. We recommend using the CLI entry point like:

>>> 08_despike {filename.sgy | datalist.txt | </directory>} [optional parameters]

Alternatively, the script can be executed using the (more verbose) command:

>>> python -m pseudo_3D_interpolation.despiking_2D_segy {filename.sgy | datalist.txt | </directory>} [optional parameters]

Optionally, the following parameters can be specified:

--help, -h: Show help.
--output_dir {DIR}: Output directory (either --inplace or --output_dir are required!).
--inplace: Replace input data without creating copy (either --inplace or --output_dir are required!).
--suffix {sgy}: File suffix (default: sgy). Only used if directory is specified.
--filename_suffix {SUFFIX}: Filename suffix (e.g. pad, static) to filter input files. Only used if directory is specified.
--txt_suffix {despk}: Suffix to append to output filename (default: despk).
--use_delay: Use delay recording time to split input data before despiking (e.g. for TOPAS, Parasound).
--byte_delay {109}: Byte position of input delay times in SEG-Y file(s) (default: 109).
--mode {MODE}: Mode used to compute background amplitude and detect spikes in data.
- mean, rms, or median
--window_time {TIME}: Moving window length in time domain (TWT [ms]).
--window_traces {TRACES}: Moving window length in offset domain (traces [#]).
--window_overlap {PERCENT}: Time overlap of moving windows (%) (default: 10).
--threshold_factor {FACTOR}: Used for spike detection (threshold_factor * background amplitude).
--out_amplitude {METHOD}: Replace spike amplitudes using selected method
- scaled, mode, threshold, zeros, median
--verbose {LEVEL}: Level of output verbosity (default: 0).

Python script#

Import function

import despike_2D

Create dummy data

import numpy as np

dt = 0.05  # ms
length = 250  # ms
ntraces = 100
shape = (int(length / dt), ntraces)

# create dummy data
data = np.ones(shape, dtype='float32')
# insert noise burst
noise_time = slice(int(100/dt), int(120/dt))
noise_trace = 50
data[noise_time, noise_trace] = 5
# add some noise
data += np.random.standard_normal(shape)

Despike dummy data

window = 30  # length (ms) of window, should be larger than noise (~20 ms)
data_despk = despike_2D(
    data, window, dt, overlap=10, ntraces=5, mode='mean', threshold=2, out='scaled', verbosity=0
    )

Compare original vs despiked data

print('original data:', data[noise_time, noise_trace], sep='\n')
    print('despiked data:', data_despk[noise_time, noise_trace], sep='\n')

Last update: Monday, 03 July 2023 at 09:46:51