Seismic data from sonobuoy stations in the northern and equatorial Pacific

Abstract

Sonobuoy stations from the North Pacific have yielded 470 velocities, determined about equally from interval velocity (reflection) data and critical refraction data. The refraction velocities are corrected for dip and are tabulated with layer thicknesses. The interval velocities (also corrected for dip) from the sedimentary layers of the northern Pacific are plotted against one-way travel times and reveal characteristic velocity curves from various areas of the Pacific. Interval velocities from the opaque layer in the northwest Pacific reveal that its velocity is about 3.0 km/sec, or nearly double that of sediments at comparable depths elsewhere in the Pacific. Preliminary studies from the Bering Sea indicate that the human errors (interpretation of sonobuoy reflection curves) have little effect on plots of velocity versus one-way travel time. Sonobuoy refraction data from areas of the Pacific where the basement appears to be smooth (layer B), reveal that the smooth material is sometimes as much as several hundred meters thick and has a velocity that is less than that of typical basement. Although a wide range of velocities can exist in this material, there are many areas where it is likely to be less than 4.0 km/sec.