Ormsby filter

A common type of synthetic wavelet in reflection seismology.

$A(t)={\frac {\pi f_{1}^{2}}{f_{2}-f_{1}}}\mathrm {sinc} ^{2}(f_{1}t)-{\frac {\pi f_{2}^{2}}{f_{2}-f_{1}}}\mathrm {sinc} ^{2}(f_{2}t)-{\frac {\pi f_{3}^{2}}{f_{4}-f_{3}}}\mathrm {sinc} ^{2}(f_{3}t)+{\frac {\pi f_{4}^{2}}{f_{4}-f_{3}}}\mathrm {sinc} ^{2}(f_{4}t)$

where

• f₁ = low-cut frequency
• f₂ = low-pass frequency
• f₃ = high-pass frequency
• f₄ = high-cut frequency

An example might have frequencies of 5–10–40–45 Hz. This defines a trapezoidal shape in the frequency spectrum.

Ormsby-filtered wavelets have several sidelobes, unlike Ricker wavelets which only have two, one either side.

See also

• Ricker wavelet
• Butterworth filter
• Klauder filter

External links

• Ryan, 1994. A choice of wavelets. CSEG Recorder September 1994.
• Ormsby filter — Sheriff's Encyclopedic Dictionary

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