1. A filter that maximizes the output in response to a signal of particular shape. The elements of a matched filter are the elements of the signal in reverse order; hence filtering with a matched filter is equivalent to crosscorrelating with the signal. Used where the waveform of the signal is known, as in deconvolving vibroseis data. Also called crosscorrelation filter and correlator. The matched filter has the same amplitude-frequency response and the negative phase-frequency response (reversed in sign) as the waveform to which it is matched. A matched filter is the most powerful filter for identifying the presence of a given waveform in the presence of additive noise. See Anstey (1964) and Treitel and Robinson (1969). 2. Matched filters are used to separate data from more than one vibroseis source operating simultaneously.