|
<< Click to Display Table of Contents >> Navigation: Mutes > Kinematic mute by velocity |
Note: This module is deprecated. It is retained for compatibility with legacy processing flows and may be removed in future releases.
Kinematic Mute by Velocity applies a velocity-dependent mute to pre-stack seismic gathers. Unlike a conventional offset mute, which uses a fixed time-offset curve, this module defines the mute boundary as a function of both time and the local NMO velocity at each time sample. This makes the mute adaptive to the velocity field, which is particularly useful for attenuating noise and multiples whose moveout deviates from the primary reflection moveout defined by the input velocity function.
The processing sequence is as follows. First, forward NMO correction is applied to the input gather using the supplied velocity function and stretch factor. Next, for each time sample, all traces whose offset exceeds the velocity-scaled mute boundary are zeroed. Finally, inverse NMO correction is applied to restore the gather to its original time domain. The result is a gather in which far-offset traces containing significant NMO stretch or noise have been selectively muted, while the near-offset reflection signal is preserved.
The mute boundary at each time sample is calculated as: offset_max = 0.5 × v² × t / v0 × MuteValue, where v is the interval velocity at that time, t is the two-way travel time, v0 is the replacement velocity, and MuteValue is the user-defined mute scalar from the MuteParams table. Use this module when you need a mute that tracks the velocity structure of the subsurface rather than a fixed geometry.
The standard input data connection for the processing sequence. Connect the output of the preceding module in your processing flow to this item. This item carries the seismic gather data and associated trace headers into the module.
The pre-stack seismic gather on which the kinematic mute will be applied. This should be a CMP or CDP gather sorted by offset. The gather must contain valid offset header values, as the mute boundary is evaluated per-trace using the absolute offset of each trace. Each trace is individually compared against the velocity-scaled mute threshold at every time sample.
Controls the maximum allowable NMO stretch during the forward and inverse NMO correction steps, expressed as a fractional value (not a percentage). The stretch factor limits how far offset reflections are corrected before the mute is applied. A value of 1 (default) corresponds to 100% stretch — all samples are corrected regardless of stretch magnitude. Lower values apply a more conservative NMO correction and limit the maximum offset that is corrected. Increasing this value may allow more far-offset energy to be processed, but can introduce NMO stretch artifacts at shallow times.
Default value: 1 (100% stretch allowed). Typical values range from 0.2 to 1.0.
The reference velocity (in m/s) used as the denominator in the mute boundary formula. This value acts as a baseline or near-surface velocity against which the NMO velocity at each time sample is normalized. It is the v0 term in the mute offset equation: offset_max = 0.5 × v² × t / v0 × MuteValue. Set this to an appropriate near-surface or water velocity for your survey. For marine surveys, use the water velocity (typically 1480–1500 m/s). For land surveys, use the near-surface replacement velocity from your refraction statics analysis. Choosing a value that is too high will produce overly aggressive muting; a value that is too low will result in a permissive mute that passes unwanted noise.
Default value: 1600 m/s. Units: m/s.
A table of control points that define the velocity function and mute scalar as a function of time. Each row in the table is a triplet (Time, Velocity, Mute). The module linearly interpolates the Velocity and Mute values between the defined time control points to produce a smooth, sample-by-sample mute boundary. At least one control point must be provided; the module will report an error if the table is empty.
Each control point row contains three fields:
Time — Two-way travel time of the control point (in seconds). Define at least one shallow and one deep control point to cover the full time range of your data. The velocity and mute values are held constant beyond the first and last defined control points.
Velocity — The NMO velocity at this time control point (in m/s). This is the velocity used to perform the NMO correction and to scale the mute offset threshold. Use the same velocity function as your NMO correction for the best kinematic consistency. A higher velocity at a given time will produce a wider mute boundary (allowing larger offsets), while a lower velocity will narrow the mute window.
Mute — A dimensionless scalar that scales the maximum allowable offset at this time. Larger values permit larger offsets (a wider mute gate), and smaller values produce a tighter, more aggressive mute. A value of 1.0 applies no additional scaling beyond the velocity-time geometry. Adjust this value to fine-tune how aggressively the mute is applied at each time level — for example, increasing it at greater depths allows deep far-offset reflections to pass, while reducing it at shallow times suppresses NMO-stretched near-surface arrivals.