J. A. Hildebrand Fred N. Spiess J. L. Morton W. R. Normark C.A. Reiss C.D. Chadwell 1999 <div class=""><div class="article-section__content en main"><p>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.</p></div></div> application/pdf 10.1029/1999GL900570 en American Geophysical Union No spreading across the southern Juan de Fuca ridge axial cleft during 1994-1996 article