. The Earth beneath the sea : History. Ocean bottom; Marine geophysics. 78 EWING AND NAFE [chap. 5 If a reflecting interface is shallower than the depth of penetration of the critical Ta,y, the Rn-Ri ciu've approaches and joins the Rs-Ri curve from below as demonstrated by the arrivals of profile B in Fig. 2. For this profile Rio = 7 sec and the best fit to the data is with the curve for K = sec~i. Fig. 4 shows the results from another profile for which i?io = 6 sec and K = sec~^ There are two reflecting interfaces, both shallower than the depth I or. Fig. 3. R^— Ri versus D for case wh
. The Earth beneath the sea : History. Ocean bottom; Marine geophysics. 78 EWING AND NAFE [chap. 5 If a reflecting interface is shallower than the depth of penetration of the critical Ta,y, the Rn-Ri ciu've approaches and joins the Rs-Ri curve from below as demonstrated by the arrivals of profile B in Fig. 2. For this profile Rio = 7 sec and the best fit to the data is with the curve for K = sec~i. Fig. 4 shows the results from another profile for which i?io = 6 sec and K = sec~^ There are two reflecting interfaces, both shallower than the depth I or. Fig. 3. R^— Ri versus D for case where 2-3 interface is deeper than depths penetrated by purely refracted ray. of penetration of the critical ray, as evidenced by the fact that both reflection curves pass below the cusp of the refraction curve for iC = sec~i. From the fact that both curves indicate approximately the same value of K, it would appear that the upper reflector is a thin layer, above and below which the velo- city and velocity gradient are not greatly different. This can be stated only qualitatively because the precision of picking the arrivals in the region where the curves come together is not high. •-/^ I ct R n Hr. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Hill, M. N. (Maurice Neville), 1919-. New York : Interscience Pub.
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