A Python workflow for automated seismic horizon tracking and termination detection on a real 2D marine seismic line from the US Atlantic margin. The analysis implements sequence stratigraphy principles (Mitchum, Vail & Sangree, 1977) to classify reflector termination types directly from SEGY data.
1. Data Loading
Loaded a post-stack migrated 2D SEGY line (3,195 traces, 7.7 seconds TWT,
4ms sample rate) from the USGS National Archive of Marine Seismic Surveys
(NAMSS). Survey B-06-82-AT acquired in 1982 offshore US East Coast.
2. Seismic Visualization
Displayed full seismic section and zoomed into the shelf-slope transition
zone (traces 400–1800, 800–3500 ms) using industry-standard Red-White-Blue
colormap.
3. Automated Horizon Tracking
Implemented a waveform similarity tracker using cosine similarity between
adjacent CDP traces. Seeds a reflector at a user-defined trace/TWT point
and tracks forward and backward across the line. Parameters: search window
8 samples, reference half-length 6 samples, minimum similarity 0.4.
Tracked 4 horizons:
- H1 - Seafloor (1,400 traces)
- H2 - Unconformity (721 traces)
- H3 - Mid Sediment Package (535 traces)
- H4 - Deep Reflector (469 traces)
4. Termination Detection
Implemented automated termination classification following Mitchum, Vail &
Sangree (1977):
- Onlap - reflectors terminating upward against a surface
- Truncation - reflectors cut from above by erosion
- Downlap - prograding reflectors terminating against a base
- Toplap - near-flat termination below a surface
Detection uses local dip estimation via linear regression over endpoint windows of each horizon pair.
6 termination events detected across 3 horizon pairs:
| ID | Type | Trace | TWT | Horizons |
|---|---|---|---|---|
| T1 | Onlap | 400 | 1122 ms | H1/H2 |
| T2 | Truncation | 1120 | 1196 ms | H1/H2 |
| T3 | Onlap | 442 | 1479 ms | H2/H3 |
| T4 | Truncation | 976 | 1583 ms | H2/H3 |
| T5 | Onlap | 442 | 2194 ms | H3/H4 |
| T6 | Truncation | 868 | 2200 ms | H3/H4 |
The alternating onlap/truncation pattern across the stratigraphic column reflects repeated transgressive/regressive cycles on the US Atlantic passive margin.
USGS National Archive of Marine Seismic Surveys (NAMSS) - Public Domain
Survey: B-06-82-AT | 2D Multichannel Seismic | US Atlantic Margin | 1982
Contributor: Bureau of Ocean Energy Management
https://walrus.wr.usgs.gov/namss/
Mitchum, R.M., Vail, P.R., and Sangree, J.B. (1977). Seismic stratigraphy and global changes of sea level, Part 6: Stratigraphic interpretation of seismic reflection patterns in depositional sequences. AAPG Memoir 26.
Python segyio numpy scipy matplotlib
Tarun Joshi | Petroleum Engineering M.Eng., Texas A&M University
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