SEISMIC-REFRACTION MEASUREMENTS IN THE ATLANTIC OCEAN BASINS, IN THE MEDITERRANEAN SEA, ON THE MID-ATLANTIC RIDGE, AND IN THE NORWEGIAN SEA

Abstract

Research Article| March 01, 1959 SEISMIC-REFRACTION MEASUREMENTS IN THE ATLANTIC OCEAN BASINS, IN THE MEDITERRANEAN SEA, ON THE MID-ATLANTIC RIDGE, AND IN THE NORWEGIAN SEA JOHN EWING; JOHN EWING LAMONT GEOLOGICAL OBSERVATORY (COLUMBIA UNIVERSITY), PALISADES, N. Y. Search for other works by this author on: GSW Google Scholar MAURICE EWING MAURICE EWING LAMONT GEOLOGICAL OBSERVATORY (COLUMBIA UNIVERSITY), PALISADES, N. Y. Search for other works by this author on: GSW Google Scholar GSA Bulletin (1959) 70 (3): 291–318. https://doi.org/10.1130/0016-7606(1959)70[291:SMITAO]2.0.CO;2 Article history received: 11 Mar 1958 first online: 02 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation JOHN EWING, MAURICE EWING; SEISMIC-REFRACTION MEASUREMENTS IN THE ATLANTIC OCEAN BASINS, IN THE MEDITERRANEAN SEA, ON THE MID-ATLANTIC RIDGE, AND IN THE NORWEGIAN SEA. GSA Bulletin 1959;; 70 (3): 291–318. doi: https://doi.org/10.1130/0016-7606(1959)70[291:SMITAO]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 Seismic-refraction measurements in the western basins of the North Atlantic Ocean show that an average crustal section consists of ½–l km of low-velocity sediments and 4–6 km of oceanic crustal rock in which the seismic velocity is about 6.5 km/sec. There is good evidence from sub-bottom reflections and shear waves that in many places there is a layer with a velocity between 4.5 and 5.5 km/sec and a thickness of 1–2 km between the low-velocity sediments and the 6.5 km/sec layer, although it is not usually detected by refracted arrivals. These layers are underlain by the mantle which has an average seismic velocity near 8 km/sec. Measurements in the eastern basins show a similar crustal section, but the velocity below the deep discontinuity appears to be lower (7.7–7.8 km/sec).Measurements in the Mediterranean Sea show only low-velocity sediments underlain by a refracting layer in which the average velocity is about 4.5 km/sec.On the Mid-Atlantic Ridge the sediments are underlain by two refracting layers with velocities averaging 5.6 and 7.4 km/sec respectively. The results indicate that the ridge has been built by the upwelling of great amounts of basalt magma along a tensional fracture zone. Presumably the extensional forces and the supply of basalt magma come from convection currents deep in the mantle. Measurements in the Norwegian and Greenland seas show results very similar to those on the Mid-Atlantic Ridge, and, from this and the extension of the belt of active seismicity, it appears that the ridge structure continues through the Norwegian and Greenland seas into the Arctic Ocean.The results of a few stations on the continental shelf of North America, Britain, and Norway are presented and compared with previously published results in these areas. 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.