1. A method of correlating seismic events associated with different types of seismic transmission modes, comprising: calculating a shift estimate between a first set of seismic events or attributes associated with said seismic events attributable to one type of transmission mode and a second set of seismic events or attributes associated with said seismic events attributable to a different type of transmission mode using a smoothed version of at least one of said sets of seismic events or attributes associated with said seismic events, and updating said shift estimate using a less severely smoothed or unsmoothed version of said at least one set of seismic events or attributes associated with said seismic events.