. The Earth beneath the sea : History . Fig. 1. Ray diagram and time-distance graph foi- reflections in a tliree-layer model, Ci<C2<C'3. O = detector X = shot Oi = Of waves and of the first-order reflected waves from two shots to a detector. The shots and detector are in Layer 1, which has a seismic velocity Ci and thickness ^1. Underneath are two layers with velocities C2 and C3. The upper part of the figure shows the travel time vs. distance graph for the arrivals. The direct waves determine the straight line, D. The reflected waves determine the hyper- boUc curves, Ri and Rn.^ The inv

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. The Earth beneath the sea : History . Fig. 1. Ray diagram and time-distance graph foi- reflections in a tliree-layer model, Ci<C2<C'3. O = detector X = shot Oi = Of waves and of the first-order reflected waves from two shots to a detector. The shots and detector are in Layer 1, which has a seismic velocity Ci and thickness ^1. Underneath are two layers with velocities C2 and C3. The upper part of the figure shows the travel time vs. distance graph for the arrivals. The direct waves determine the straight line, D. The reflected waves determine the hyper- boUc curves, Ri and Rn.^ The inverse slope of D, ADfAT, gives the seismic velocity in Layer 1. The Ri curve is asymptotic to D. Its intercept on the ordinate, 2Ai/C*i, gives the travel time for a reflected wave from the top of 1 In this and succeeding discussions, Rj, Rh, Rm- . .designate reflected waves from the 1st, 2nd, 3rd. .interfaces below the surface. Arabic subscripts R2, Ra- â .designate second, third. . order reflections from the sea floor.

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Keywords: ., bookcentury1900, bookcollectionbiodivers, booksubjectoceanbottom