1. A seismic data processing method, comprising: obtaining reaction mass acceleration data of a source of seismic energy; obtaining baseplate acceleration data of the source; obtaining seismic data of one or more seismic sensors responsive to the seismic energy of the source; deriving variables for a ground model by analyzing a frequency response relating the reaction mass acceleration data and the baseplate acceleration data as input and output relative to one another; filtering a source signal indicative of operation of the source by using the ground model with the derived variables; and making the filtered source signal available for processing with the seismic data of the one or more seismic sensors.