1. A method for generating an average gamma factor for recorded PS data and recorded PP data, comprising: (a) receiving seismic data containing information about subterranean formations in the earth, wherein the seismic data comprise PS data and PP data and were recorded using one or more seismic receivers during a seismic survey; (b) mapping one or more arrival times of the PS data onto one or more expected arrival times of the PP data using an estimated average gamma factor; (c) matching the frequency of the PP data with the frequency of the PS data; (d) identifying one or more corresponding pairs of events in the PS data and the PP data using forward modeling; (e) applying geophysical reasoning on the corresponding pairs of events; and (f) generating the average gamma factor, wherein the average gamma factor is a ratio of an average P wave velocity to an average S wave velocity, and wherein the average gamma factor represents the structure of the subterranean formations.