Accession Number : AD0499590

Title :   The 1950 Seismic Refraction Studies of Bikini and Kwajalein Atolls and Sylvania Guyot,

Corporate Author : SCRIPPS INSTITUTION OF OCEANOGRAPHY LA JOLLA CA

Personal Author(s) : Raitt, Russell W.

Report Date : 15 JUL 1952

Pagination or Media Count : 45

Abstract : Seismic refraction studies made at Bikini Atoll, Sylvania Guyot, and Kwajalein Atoll during the Mid-Pacific Expedition of 1950 expanded the scope of the original 1946 studies to include a section across Sylvania Guyot and several deep water sections extending from Bikini Atoll. Also Bikini Lagoon was surveyed in much greater detail, with particular emphasis on more complete control with reversed profiles. In addition, one short section was obtained at Kwajalein Atoll. It was found that the seismic velocities beneath Bikini Lagoon vary laterally as well as with depth. They can be grouped into six more or less well defined layers averaging approximately 2.5, 3, 4, 5.5, 6.5, and 8 km/sec. The first four were observed only in the lagoon profiles and the latter two were found only in deep water. From sections taken on Sylvania Guyot and the flanks of Bikini Atoll near regions where samples of volcanic rock were obtained from the sea bottom, it was concluded that the third layer, of about 4 km/sec seismic velocity, represents volcanic rock. Its estimated depth under Bikini Lagoon varies from 600 m to 2100 m and averages about 1300 m. One short section at the south end of Kwajalein Lagoon, shows somewhat greater depths of the third layer than Bikini but the lagoon coverage was insufficient to demonstrate that Kwajalein differs significantly from bikini. Indications were found that the 6.5 km/sec layer is deeper under Bikini Atoll than under the surrounding deep sea. If real, this local depression is unlikely to be greater than 3 km.

Descriptors :   (*SEISMIC WAVES, REFRACTION), (*STRUCTURAL GEOLOGY, MARSHALL ISLANDS), PROPAGATION, VELOCITY, SEISMOLOGICAL STATIONS, PACIFIC OCEAN, DEEP WATER, SHALLOW WATER, ROCK, OCEAN BOTTOM TOPOGRAPHY, EXPLOSIVE CHARGES, TNT, WAVE PROPAGATION, BIKINI ATOLL, KWAJALEIN ATOLL.

Subject Categories : Geology, Geochemistry and Mineralogy
      Seismology

Distribution Statement : APPROVED FOR PUBLIC RELEASE