Ralph A Landrum Jr: Western Atlas International, E Eugene Thigpen, December 22, 1987: US04715020 (69 worldwide citation)

The invention is a method of performing a plurality of vibratory seismic surveys simultaneously. A plurality of vibratory sources transmit signals into the earth. Each vibratory source successively transmits the same signal, except that an offset phase of the signal is selectively shifted for succes ...

Ralph A Landrum Jr, Juan B Vallhonrat, Paul M Perry: Noise-suppression method. Western Geophysical Co of America, William A Knox, August 10, 1982: US04344158 (16 worldwide citation)

A method is disclosed for improving the signal-to-noise ratio of low level seismic signals resulting from weak acoustic sources. The method has application to the summation of signals from swept-frequency sources. A reference model of the level of a valid seismic signal is built for each of a number ...

Kent J Goodloe, Ralph A Landrum Jr: Western Geophysical Company of America, William A Knox, May 7, 1985: US04516230 (12 worldwide citation)

In accordance with an embodiment of this invention, voltages are received from the pilot valve torque motor, the main servo valve and the actuator indicating the value of the torque motor current, spool position and actuator displacement. The received voltages are compared to a preselected threshold ...

Ralph A Landrum Jr: Western Geophysical Company of America, William A Knox, January 28, 1986: US04567583 (6 worldwide citation)

A seismic vibrator for shaking the ground is driven by an input sweep signal. A control signal, which is a function of the output force level of the vibrator, modulates the sweep signal to limit the output force level to a value that will prevent ground decoupling. At the beginning of a sweep, an ad ...