1. The various geophones or hydrophones that collectively feed a single channel. The number of phones may vary from one to several hundred. A large group is sometimes called a patch. See array (seismic). 2. A source group consists of the several sources or source locations that are combined together to form one seismic trace. They may be activated together or combined subsequently. 3. A lithostratigraphic subdivision; see stratigraphic classification.