The CMP gather plotted in the initial depth domain illustrates seismic data with accurate reflector positioning and moveout behavior. This visualization aligns stacked events horizontally and supports precise velocity analysis and imaging workflows.
Geophysicists rely on this depth-domain CMP view to validate structural assumptions before migration. The following sections break down key aspects of how these gathers support depth-domain interpretation and modeling.
| Gather ID | Source Depth (m) | Receiver Depth (m) | Reflection Depth (m) | Stacking Velocity (m/s) |
|---|---|---|---|---|
| CMP-001 | 15 | 15 | 1200 | 2100 |
| CMP-042 | 15 | 15 | 1850 | 2250 |
| CMP-113 | 15 | 15 | 2400 | 2400 |
| CMP-207 | 15 | 15 | 3100 | 2550 |
| CMP-301 | 15 | 15 | 4000 | 2750 |
Depth Domain CMP Gather Configuration
Configuring CMP gathers in the initial depth domain requires consistent reference geometries. Source and receiver depths are fixed at 15 m to simplify near-surface statics and focusing behavior. Each gather maintains a horizontal reflector geometry to support reliable interval velocity estimation.
Reflector Positioning in Depth Domain
Mapping Seismic Events to True Depths
Reflector positioning in the initial depth domain is derived from time migration or equivalent tomographic velocity models. Events plotted at true depths reduce misinterpretation risk associated with interval velocity errors. The table above demonstrates how reflection depths increase systematically across the gather set.
Velocity Analysis and Moveout Correction
Applying NMO Using Stacking Velocities
Normal moveout correction relies on stacking velocities listed in the table. These velocities align events horizontally in the depth-domain CMP gather when the correct velocity is applied. Small deviations from the true velocity cause residual moveout, which can be quantified through diagnostic plots.
Imaging Consistency and Structural Interpretation
Supporting Robust Depth Imaging Workflows
Consistent reflector geometry in the depth domain CMP gather improves lateral continuity after migration. Interpreters use these gathers to validate structure maps and fault orientations. The gather headers preserve trace positioning, enabling direct comparison with well ties and depth conversions.
Key Takeaways for Depth Domain CMP Gathers
- Use consistent source and receiver depths to minimize near-surface artifacts.
- Validate reflector positions against well logs before velocity analysis.
- Apply stacking velocities that match the initial depth-domain geometry.
- Monitor moveout residuals to refine velocity models iteratively.
- Compare depth-domain gathers with time-domain gathers to assess conversion accuracy.
FAQ
Reader questions
How is the initial depth domain CMP gather constructed from observed data?
It is built by applying source and receiver coordinates, event times, and a velocity model to map traces into common midpoint positioning in depth.
What role does stacking velocity play in moveout correction for these gathers?
Stacking velocity corrects normal moveout so that reflections align horizontally, enabling coherent stacking and improved imaging in depth.
Why are source and receiver depths fixed at 15 m in this illustration?
Fixed near-surface depths simplify statics and highlight reflector positioning without the added complexity of varying surface elevations.
How does reflector depth uncertainty affect velocity analysis in the depth domain?
Uncertainty in reflector depth can bias interval velocity estimates, which is why the table pairs reflection depths with corresponding stacking velocities.