1. Source-point gap, where there is a larger interval between geophone groups on either side of the source point than between other groups. The result is that very short offsets (which are often noisy) are not recorded. 2. Interrecord gap, an interval of space on a digital magnetic tape during which no information is recorded. Serves to indicate the beginning of a new record or a new block of data. 3. Prediction lag (q.v.).