No spreading across the southern Juan de Fuca ridge axial cleft during 1994-1996

C.D. Chadwell; J. A. Hildebrand; Fred N. Spiess; J. L. Morton; W. R. Normark; C.A. Reiss

doi:10.1029/1999gl900570

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No spreading across the southern Juan de Fuca ridge axial cleft during 1994-1996

C.D. Chadwell·J. A. Hildebrand·Fred N. Spiess·J. L. Morton·W. R. Normark·C.A. Reiss

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Abstract

Direct-path acoustic measurements between seafloor transponders observed no significant extension (−10±14 mm/yr) from August 1994 to September 1996 at the southern Juan de Fuca Ridge (44°40′ N and 130°20′ W). The acoustic path for the measurement is a 691-m baseline straddling the axial cleft, which bounds the Pacific and Juan de Fuca plates. Given an expected full-spreading rate of 56 mm/yr, these data suggest that extension across this plate boundary occurs episodically within the narrow (∼ 1 km) region of the axial valley floor, and that active deformation is occurring between the axial cleft and the plate interior. A cleft-parallel 714-m baseline located 300 m to the west of the cleft on the Pacific plate monitored system performance and, as expected, observed no motion (+5±7 mm/yr) between the 1994 and 1996 surveys.

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C.D. Chadwell, J. A. Hildebrand, Fred N. Spiess, J. L. Morton, W. R. Normark, C.A. Reiss. 1999-08-15. No spreading across the southern Juan de Fuca ridge axial cleft during 1994-1996. https://doi.org/10.1029/1999gl900570

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