geophysics · seismic resolution
Dominant Wavelength
λ = V / f
click formula to derive ↑
Inputs
ft/s
Hz
Description
Computes the dominant wavelength of a seismic wavelet from its interval velocity and dominant frequency — the fundamental yardstick both vertical (tuning thickness) and horizontal (Fresnel zone) seismic resolution limits are expressed in terms of.
Variables
| Symbol | Unit | Description |
|---|---|---|
| λ | ft | Dominant Wavelength |
| V | ft/s | Representative interval velocity above/around the target — from sonic log, checkshot, or Dix interval velocity. Higher velocities produce longer wavelengths at the same frequency. |
| f | Hz | Dominant (peak spectral) frequency of the seismic wavelet at the target level — typically read from an amplitude spectrum, and generally decreasing with depth due to attenuation. |
Assumptions
- A single representative velocity and dominant frequency adequately describe the wavelet at the depth/target of interest
- Frequency was read from an actual amplitude spectrum (or a defensible regional estimate), not an arbitrary guess
Limitations
- Real seismic wavelets are broadband, not monochromatic — 'dominant frequency' is the spectral peak, not the only frequency present; see Vertical Resolution's Kallweit-Wood note for how the full bandwidth (not just the peak) affects practical resolution
- Both velocity and dominant frequency generally change with depth (velocity increases, frequency decreases due to attenuation) — this calc gives a single local value, not a depth-varying function
Use Cases
- → Quick resolution sanity check: Get a fast wavelength estimate before running the full tuning-thickness or Fresnel-zone calculations for a prospect.
- → Comparing targets at different depths: Compare wavelength (and therefore resolution potential) between a shallow, high-frequency target and a deep, low-frequency one.
- → Processing/acquisition target-setting: Back-solve for the frequency content needed to resolve a known reservoir thickness, informing acquisition or reprocessing frequency targets.
Related Calculations
Region Notes
Permian Basin
Wolfcamp-depth conventional 3D surveys typically carry dominant frequencies of 25-35 Hz at target depth with interval velocities 4,000-4,500 m/s, giving wavelengths on the order of 115-180 m.
Gulf of Mexico
Shallow Miocene-Pliocene targets can retain dominant frequencies of 40-60 Hz where unconsolidated, dropping toward 20-30 Hz for deeper, more consolidated targets under the same survey.
Global
Always state the depth/target the dominant frequency was read at — frequency attenuation with depth means a single wavelength value from one survey is not transferable to a different target depth.
References
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