The Shallow Seismic Structure of the East Pacific Rise

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The nature of the shallow oceanic crust produced at seafloor spreading centers is poorly constrained by available geophysical data. Recent studies suggest that the shallowest layers of the crust are characterized by extremely low seismic velocities, but that the velocity increases rapidly with depth. Understanding the processes that control these variations are important in determining the porosity of the crust, alteration of crustal rock, and the local and regional significance of crustal drilling data. The present award will support Dr. Fryer's participation in a near bottom refraction study of a segment of the East Pacific Rise in the eastern equatorial Pacific. The project will allow a detailed study of the shallow crust by using both a receiver and acoustic source deployed at the seafloor. This technique will provide a higher resolution study than is available from normal surface ship observations. Dr. Purdy of Woods Hole has responsibility for obtaining the field data. Dr. Fryer will be involved in analysis of the data from the experiment which will be compared to drilling results planned along this same section of ridge. The principal investigators on this project have distinguished records in both experimental and theoretical analysis of crustal data.