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expanding spread

expanding spread In seismic refraction shooting, a method in which a spread of geophones is used at increased offset for repeated shots at the same location. This is equivalent to using many spreads of geophones for a single shot. In seismic-reflection surveys it is used to provide information about root-mean-square velocities and depths to reflectors using the T2−X2 method. See also ELECTRICAL SOUNDING.

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