The phenomenon of velocity anisotropy in stratified rocks has been observed in surface outcrops by McCollum (1932), Weatherby (1934), Ricker (1953), White and Sengbush (1953), and their associates. In 1944, 1948, and 1953 Shell Oil Company measured oblique times from shots spaced at large distances from a well to a seismometer in the well and found evidence of velocity anisotropy. Cholet and Richards (1954) also observed this phenomenon in well-velocity surveys at Berriane (North Sahara).An anisotropy factor A which is defined as the ratio of the velocity along the layers to the velocity perpendicular to the layers, has been computed from oblique-time and well-survey data. The factor A varies between 1.1 and 1.4 for the data collected in this report.At present, information on velocity anisotropy is limited and it is therefore suggested that oblique time measurements be made along with vertical velocity surveys whenever possible.

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