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The Seismic instantaneous attributes module computes trace-by-trace, sample-by-sample seismic attributes derived from the complex trace representation. Each trace is transformed into its analytic signal using a Hilbert transform, which yields the instantaneous envelope (amplitude), phase, and frequency at every time sample. These quantities are independent of each other and reveal structural, stratigraphic, and rock-property information that is not directly visible in the raw amplitude data.
The module applies to individual gathers or post-stack sections. Select the desired attribute type from the parameter list and the module replaces the input amplitude data with the chosen attribute volume. Different attribute types are suited to different interpretation objectives: envelope-based attributes highlight reflector brightness and lateral continuity, phase and frequency attributes reveal discontinuities and thin-bed tuning effects, and quality-factor (Q) attributes indicate attenuation zones.
The seismic data container connecting to the input dataset. Connect to the output of the preceding module in the processing workflow.
The input seismic gather on which the instantaneous attribute will be computed. The module processes each trace independently using a Hilbert transform and outputs a gather of the same dimensions containing the chosen attribute values.
The duration of the sliding time gate (in seconds) used by attributes that require local averaging, specifically the Dominate frequency and Thin bed indicator attributes. Within this window the instantaneous frequency is averaged (weighted by envelope) to produce a smoothed estimate of dominant frequency, or differenced from its local average to isolate thin-bed tuning effects. For other attribute types this parameter has no effect. A shorter window preserves fine time-resolution; a longer window reduces noise in the frequency estimate. Default: 0.012 s (12 ms).
Selects which attribute is computed and written to the output gather. One attribute is produced per run. Available options:
Envelope — the instantaneous amplitude, computed as the modulus of the analytic signal (square root of the sum of the squared real and Hilbert-transformed traces). Highlights reflection strength and is useful for identifying bright spots, gas accumulations, and lateral amplitude changes. Default.
Instantaneous phase — the arctangent of the ratio of the Hilbert-transformed trace to the real trace. Phase is amplitude-independent and therefore emphasises reflector continuity and discontinuities such as faults. Values range from -pi to +pi.
Instantaneous unwrap phase — the phase after removing 2-pi discontinuities, producing a monotonically increasing phase function. Useful for cycle counting and velocity analysis.
Instantaneous frequency — the time derivative of the instantaneous phase, scaled to give frequency in Hz. Represents the dominant frequency of the wavelet at each time sample. High values indicate sharp wavelet features; abrupt drops near the base of reservoirs can indicate gas. Output values are clamped to the Nyquist frequency.
Frequency derivative — the time derivative of the instantaneous frequency. Highlights rapid changes in frequency content and can indicate interfaces between zones of different attenuation character.
Instantaneous bandwidth — the absolute value of the time derivative of the envelope divided by 2-pi times the envelope, following Barnes (1992). Measures the spectral width of the wavelet at each sample. Narrow bandwidth indicates a nearly monochromatic wavelet; broad bandwidth indicates a sharp, impulsive event.
Cosine of instantaneous phase — the cosine of the instantaneous phase, producing a normalised amplitude-independent trace. Enhances reflector continuity and is particularly useful for structural mapping across amplitude variations.
Dominate frequency — the envelope-weighted average of the instantaneous frequency within a sliding time window of length set by the Time window parameter. Gives a more stable estimate of the local dominant frequency than the raw instantaneous frequency, reducing noise spikes.
Thin bed indicator — the difference between the instantaneous frequency and the locally-averaged dominant frequency within the Time window. Large positive values indicate that the local frequency is higher than its neighbourhood average, a signature associated with thin-bed tuning effects below the quarter-wavelength limit.
Envelope derivative — the first time derivative of the envelope. Positive values correspond to rising amplitude; negative values to falling amplitude. Useful for identifying the top and base of bright reflectors and amplitude anomalies.
Second derivative of envelope — the second time derivative of the envelope, highlighting points of inflection in the amplitude trend. Sensitive to curvature of the envelope and can reveal subtle amplitude modulation not apparent in the envelope itself.
Instantaneous Q — the quality factor derived from the ratio of instantaneous frequency to the rate of change of the envelope, following Barnes (1992). A low Q value indicates high attenuation; high Q indicates low attenuation. Use this attribute to map absorptive zones such as gas-saturated sediments or fractured intervals.