1. GeologyA velocity filter removes interfering signals by exploiting the difference between the travelling velocities of desired seismic waveform and undesired interfering signals. == Introduction == In geophysical applications sensors are used to measure and record the seismic signals. Many filtering techniques are available in which one output waveform is produced with a higher signal-to-noise ratio than the individual sensor recordings. Velocity filters are designed to remove interfering signals by exploiting the difference between the travelling velocities of desired seismic waveform and undesired interfering signals. In contrast to the one dimensional output produced by multi-channel filtering, velocity filters produce a two-dimensional output. Consider an array of N sensors that receive one desired and M undesired broadband interferences. Let the measurement of nth sensor be modeled by the expression: where n = 1, 2, ..., N; m = 0, 1, ..., M; sm(t) are signals travelling across the array... from wikipedia.org