. Early geophysical papers of the Society of Exploration Geophysicists . Fig. 3.âA cross-sectional profile of a single dipping stratum with the Mintrop shortest time path from the shot point to the receiving station R. and X2" are the coordinates of a point on the time-travel curve shot down dip. The true velocity V2 of the inclined layer is obtained from the following relations: B +A a = ââ¢ââ ââ (20) V2 â Vi/sin a. (21) The equations (i)-(2i) apply only where the velocities of the layers are all in an ascending order of magnitude from V\ to Vn, and these equations are essentially the on
. Early geophysical papers of the Society of Exploration Geophysicists . Fig. 3.âA cross-sectional profile of a single dipping stratum with the Mintrop shortest time path from the shot point to the receiving station R. and X2" are the coordinates of a point on the time-travel curve shot down dip. The true velocity V2 of the inclined layer is obtained from the following relations: B +A a = ââ¢ââ ââ (20) V2 â Vi/sin a. (21) The equations (i)-(2i) apply only where the velocities of the layers are all in an ascending order of magnitude from V\ to Vn, and these equations are essentially the ones given by D. C. Barton in a paper entitled "The Seismic Method of Mapping Geologic ;5 However, if the area under consideration yields strata of several subse- quent dips of different angles, the calculations become very compli- cated and it is quite laborious to determine the various dips, true velocities, and thicknesses of the beds from enlarging on the expres- sions (i)-(2i). To simplify this problem, the following semi-graphical method was developed. In most cases the thickness of the first bed can be calculated by the straightforward formula for parallel beds. The result, of course, gives the depth of the surface of the second bed only in the immediate vicinity of the shot point at each end of the profile. In general it may be assumed that the surface of this bed extends across the profile in a linear variation from the two shot points, and that this bed has the 5 D. C. Barton, Geophysical Prospecting for IQ2Q, p. 572. 785
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