(rē b∂r) To time-shift adjacent traces and sum, thus emphasizing energy that comes from a particular direction relative to energy from other directions. By varying the amount of time shift, various directions can be searched to find a maximum for a particular arrival, thus ascertaining the raypath direction associated with it. Interfering events from different directions can be sorted in this way. The display as a function of arrival time for various directions is called a sonograph or sonogram. See Rieber (1936). Named for Frank Rieber (1891–1948), American geophysicist.