No abstract

Statistical methods have been used to summarize the results of seismic refraction measurements. Statistics have been computed for depth to Moho, crustal thickness and upper mantle P,, velocity for various geographical and geological provinces. The average crustal thickness is about 35 f 2 km for the continents and 8 f0.2 km for the oceans; no significant variations were found in various continents and in various oceans. The average crustal thickness is thinnest for the ocean ridges (6.2 f0.3 km) and it increases progressively toward continents, being 7.6 f 0.3 km for ocean basins, 9.4 f 0-6 km for ocean trenches, and 14.4fl.3 km for continental margins. The average upper mantle P. velocity is essentially the same everywhere. Linear regression analysis shows that there is a good correlation between the depth to Moho and elevation/depth ( I = 0.65), and between crustal thickness and elevation/ depth ( I = 0-76). No significant correlation was found between upper mantle P,, velocity and elevation/depth, between depth to Moho and upper mantle P,, velocity, and between crustal thickness and upper mantle P,, velocity.