Reverse circulation
25 July 2017Shallow hazards
25 July 2017Seismograph
A device that detects vibrations in the earth. It is used in studying the earth’s interior and in prospecting for probable oil-bearing structures. Vibrations are created by discharging explosives in shallow boreholes, by striking the surface with a heavy blow, or by vibrating a heavy plate in contact with the ground. The type and velocity of the vibrations as recorded by the seismograph indicate the general characteristics of the section of earth through which the vibrations pass.