Seismic evidence for a narrow zone of partial melting underlying the East Pacific Rise at 21°N

Research Article| May 01, 1977 Seismic evidence for a narrow zone of partial melting underlying the East Pacific Rise at 21°N IAN REID; IAN REID 1Institute of Geophysics and Planetary Physics, University of California, San Diego, La Jolla, California 92093 Search for other works by this author on: GSW Google Scholar JOHN A. ORCUTT; JOHN A. ORCUTT 1Institute of Geophysics and Planetary Physics, University of California, San Diego, La Jolla, California 92093 Search for other works by this author on: GSW Google Scholar WILLIAM A. PROTHERO WILLIAM A. PROTHERO 1Institute of Geophysics and Planetary Physics, University of California, San Diego, La Jolla, California 92093 Search for other works by this author on: GSW Google Scholar Author and Article Information IAN REID 1Institute of Geophysics and Planetary Physics, University of California, San Diego, La Jolla, California 92093 JOHN A. ORCUTT 1Institute of Geophysics and Planetary Physics, University of California, San Diego, La Jolla, California 92093 WILLIAM A. PROTHERO 1Institute of Geophysics and Planetary Physics, University of California, San Diego, La Jolla, California 92093 Publisher: Geological Society of America First Online: 01 Jun 2017 Online ISSN: 1943-2674 Print ISSN: 0016-7606 Geological Society of America GSA Bulletin (1977) 88 (5): 678–682. https://doi.org/10.1130/0016-7606(1977)88<678:SEFANZ>2.0.CO;2 Article history First Online: 01 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn Email Permissions Search Site Citation IAN REID, JOHN A. ORCUTT, WILLIAM A. PROTHERO; Seismic evidence for a narrow zone of partial melting underlying the East Pacific Rise at 21°N. GSA Bulletin 1977;; 88 (5): 678–682. doi: https://doi.org/10.1130/0016-7606(1977)88<678:SEFANZ>2.0.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGSA Bulletin Search Advanced Search Abstract Analysis of a seismic-refraction profile on the crest of the East Pacific Rise at 21 °N reveals considerable lateral inhomogeneity in the velocity structure. A split profile, of a total length of 120 km, was shot to a tripartite array of ocean-bottom seismometer capsules on or close to the spreading axis. The recorded travel times and amplitudes indicate the presence of a low-velocity zone in the immediate vicinity of the spreading axis, at a depth of about 2.5 km below the sea floor. This low-velocity zone is not evident a few (∼10) kilometres from the axis.Additional structural evidence was obtained from a deployment of the capsules at the intersection of the East Pacific Rise crest with the Rivera Fracture Zone, at 20 °N. A group of small earthquakes was recorded by the seismometers, and, for ray paths traversing or close to the rise crest axis, the shear waves appear to be anomalously attenuated, particularly at shorter periods. While the evidence is not conclusive, it suggests the presence of a shear-attenuative region beneath the rise crest, presumably identical with the low-velocity zone and consistent with the interpretation of this zone as a region of partial melting. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.