Alternative source for marine geophysical exploration

Paul Yeatman, Sara Stout-Grandy, Bruce Armstrong

Abstract


Fundamental physics issues associated with low frequency sources, particularly when they are operated near the water surface, and why it is so difficult to achieve even a small fraction of the power that an air gun produces with electroacoustic other marine vibroseis technologies, are discussed. The power level achieved at 5m depth is about the same as in the free field at 25Hz, but at lower frequency it is attenuated and at higher frequencies it is boosted by the surface reflection. Studies were conducted to find that low frequency projectors just either produce large displacements or have large radiating areas, or both. The operating frequency of a transducer greatly affects the transducer size and effectiveness. To reduce the operating frequency, transducer is made less stiff. In air backed transducers, such as flex-tensionals, the operating frequency is lowered by reducing the mechanical stiffness of the flexing member.

Keywords


Geophysical prospecting; Air guns; Alternative source; Free fields; Fundamental physics; Geophysical exploration; Higher frequencies; Large displacements; Low frequency; Lower frequencies; Mechanical stiffness; Operating frequency; Power levels; Surface reflections; Vibroseis; Water surface

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