On the Mid-Pacific and Capricorn expeditions seismic-refraction observations were made at 42 stations scattered widely within an area of the Central Equatorial Pacific Ocean extending from latitudes 22° S. to 28° N. and longitudes 162° E. to 112° W. At 29 of these stations velocities of about 8 km/sec, or more were reached at the depth of greatest penetration of the refracted waves. The mean of these velocities was 8.24 km/sec.

The crustal thickness, defined as the depth below the sea floor at which the 8 km/sec, velocity is reached, ranges from 4.8 km to 13.0 km. The distribution of thicknesses is bimodal with seven anomalous stations giving values between 10 and 13 km. The group of 22 stations believed to be typical of the deep Pacific Basin has an average thickness of 6.31 km with a standard deviation of 1.01km.

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