Translations:The seismic reflection method/4/en

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What is seismic acquisition? The essential features of seismic data acquisition are as follows: (1) At a fixed point on the surface of the earth, a source of energy — such as an array of dynamite charges or air guns or swept-frequency vibrators (as in vibroseis) — is activated. Such an activated source is called a shot. (2) Seismic waves from the shot propagate downward from the source point and go deep into the earth (Bois, 1968[1],). (3) Eventually, the waves are reflected from geologic interfaces and propagate upward from those interfaces. A primary reflection is a reflection that travels directly down to the interface and then directly back up to the surface. A multiple reflection is a reflection that has bounced back and forth among various interfaces as it proceeds on its trip. (4) The reflected waves, both primaries and multiples, are detected on the surface by receivers. The receiver points are located at various horizontal distances from the source point. (5) The digitized signal recorded at each receiver point for a given source point is called a trace. (6) After one shot is completed, the source point and the corresponding receiver points are moved so that another shot can take place. This acquisition method is repeated again and again until the entire prospect is covered. It is not economically feasible to make a nearly continuous survey. Instead, within the confines of a given exploration budget, a fixed number of source and receiver points must be used. The points are chosen to obtain the best possible representation of the prospect. Such a procedure represents a sampling in the space domain.

  1. Bois, P., 1968, Determination de l’impulsion sismique: Geophysical Prospecting, 16, 4–20.