Accession Number : AD0493442

Title :   Seismology. Number 4. Crustal Structure and Surface Wave Dispersion.

Descriptive Note : Technical rept.,

Corporate Author : LAMONT GEOLOGICAL OBSERVATORY PALISADES NY

Personal Author(s) : Ewing, Maurice ; Press, Frank

Report Date : JUL 1949

Pagination or Media Count : 13

Abstract : A recent seismic refraction profile in 2800 fm. (5.1 km.) at Latitude 34 degrees 00 minutes N. Longitude 66 degrees 30 minutes W. in the Atlantic Ocean proved that basement rocks having velocity of 7.58 km./sec. for compressional waves were covered by 1.37 km. of sediment. On the basis of this velocity we tentatively identified the layer as P sub n, indicating the absence of the granitic and intermediate layers. This velocity is higher than most of the values deduced for the uppermost sub-oceanic rocks from studies of the velocity and the dispersion of earthquake surface waves over oceanic paths. If this refraction measurement is representative of ocean wide conditions, it is evidently in conflict with the crustal layering inferred from previous studies on studies on surface waves. The present study indicates that the observed surface wave dispersion is to be expected if proper account is taken of the influence of the water and sediment over an ocean bottom consisting of a very thick basaltic layer, as indicated by the seismic refraction measurements.

Descriptors :   (*SEISMIC WAVES, OCEAN BOTTOM), PROPAGATION, VELOCITY, DEEP WATER, ATLANTIC OCEAN, SEDIMENTATION, ROCK, TIME, EARTHQUAKES, MARINE GEOPHYSICS, THICKNESS, MARINE GEOLOGY, MATHEMATICAL MODELS, RAYLEIGH WAVES.

Subject Categories : Seismology

Distribution Statement : APPROVED FOR PUBLIC RELEASE