Methods of investigating an underground formation and producing hydrocarbons, and computer program product

A method of investigating an underground formation underneath the earth's surface, comprising obtaining a first data set representing change in a predetermined seismic parameter over a period of time for a plurality of points in the underground formation, which first data set is derived from a time-lapse seismic survey of the earth formation spanning the period of time; obtaining a second data set representing geodetic deformation over substantially the same period of time at a plurality of locations on the earth's surface, which second data set is derived from a geodetic survey spanning the period of time; jointly processing the first and second data sets to obtain a map of a parameter related to volume change in the underground formation; wherein a geomechanical model of the underground formation is postulated; also a method of producing hydrocarbons and a computer program.