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During a 1983 Seabeam cruise, we surveyed the Easter-Nazca spreading center which forms the eastern boundary of the Easter microplate. We have analyzed all available bathymetry and magnetic anomaly data to determine the present fine-scale tectonic configuration and recent tectonic evolution of this spreading center. The narrowing of the axial (Brunhes) anomaly is best explained by a young propagating rift growing northward at an average rate of 150 mm/yr assuming an average spreading rate of 120 mm/yr. There are indications of a short episode of faster propagation (350 mm/yr) prior to 0.4 Ma. These are the fastest rates of rift propagation yet documented. The tip of the propagating rift is at about 25°S, 112°25′W, ∼180 km south of the previously hypothesized position. The recent spreading direction is N85°W. A large well-defined “sheared zone” to the west of the western pseudofault bounding the crust formed by the propagating rift suggests that the Easter-Pacific spreading center (360 km to the west) is being replaced by the fast propagator.

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Journal of Geophysical Research: Solid Earth, v. 91, issue B3, p. 3425-3438

©1986. American Geophysical Union. All Rights Reserved.

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