1. A computer accessible memory medium that stores program instructions for analyzing seismic data, wherein the program instructions are executable by one or more processors to: receive two-dimensional (2-D) seismic data obtained from a seismic survey of a formation, wherein the 2-D seismic data includes one or more 2-D seismic lines, wherein each of the 2-D seismic lines includes a plurality of seismic traces and a respective plurality of trace positions, wherein the trace positions specify where the seismic traces were obtained; for each hypothetical diffractor location in a set of hypothetical diffractor locations, perform a set of operations including: analyzing at least a subset of the seismic traces of the one or more 2-D seismic lines to determine whether those seismic traces contain diffraction arrivals that are consistent with the hypothetical diffractor location, wherein each of the hypothetical diffractor locations satisfies a condition that none of the trace positions of the one or more 2-D seismic lines lies within a 3-D neighborhood of diameter 200 meters centered on the hypothetical diffractor location wherein an image is generated from the stored information; in response to determining that the analyzed seismic traces contain diffraction arrivals that are consistent with the hypothetical diffractor location, storing information identifying the hypothetical diffractor location as a probable diffractor location.