High Resolution Measurements of the Shallow Structure of Oceanic Crust.
Final rept. 1 Oct 88-30 Jun 94,
WOODS HOLE OCEANOGRAPHIC INSTITUTION MA
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This program has supported a wide range of marine seismological research one cruise to the Juan de Fuca Ridge in 1989, a program of technical development culminating in the construction of a new version of the unique deep towed seismic source NOBEL, the development of new models of the detailed stratigraphy of the oceanic crust and the development with a large portion of the US seismological community of plans for a program of detailed study of the patterns of systematic evolution of the shallowmost velocity structure of the oceanic crust. The basis for this program was the recognition in the middle 1980s that the original findings of Houtz and Ewing 1976 - that the velocity of the uppermost igneous crust systematically increases as it moves away from the mid-ocean ridge at which it was formed - had profound effects on the nature of low-frequency acoustic bottom interaction. There was a need for new measurements to better define the trends first reported by Houtz and Ewing, and a need for improved understanding of the evolutionary processes that control the changes in porosity structure in the uppermost crust, that in turn determine its seismo-acoustic properties. It was towards these goals that this program was directed.