The invention provides methods and apparatus for detecting seismic waves
propagating through a subterranean formation surrounding a borehole. In a
first embodiment, a sensor module uses the rotation of bogey wheels to
extend and retract a sensor package for selective contact and magnetic
coupling to casing lining the borehole. In a second embodiment, a sensor
module is magnetically coupled to the casing wall during its travel and
dragged therealong while maintaining contact therewith. In a third
embodiment, a sensor module is interfaced with the borehole environment
to detect seismic waves using coupling through liquid in the borehole.
Two or more of the above embodiments may be combined within a single
sensor array to provide a resulting seismic survey combining the optimum
of the outputs of each embodiment into a single data set.