Volcanic and Seismic Swarm Events on the Reykjanes Ridge and Their Similarities to Events on Iceland: Results of a Rapid Response Mission |
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| Authors: | Kathleen Crane Lynn Johnson Bruce Appelgate Clyde Nishimura Roger Buck Chris Jones Peter Vogt Rubin Kos’yan |
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| Institution: | (1) Institute of Geology and Mineral Resources of the Ocean, 1 Angliysky Prospect, 190121 St. Petersburg, Russia;(2) Polar Marine Geological Prospecting Expedition,  Sevmorgeologiya Association, 24 Pobedy St., 189510 Lomonosov, Russia;(3) Lamont-Doherty Earth Observatory, Palisades, NY, 10964, U.S.A;(4) Monterey Bay Aquarium Research Institute, P.O. Box 628, Moss Landing, CA, 93950, U.S.A;(5) Hawaii Institute of Geophysics, University of Hawaii, Honolulu, HI, 96822, U.S.A;(6) P.O. Shirshov Institute of Oceanology, Gelendzik, Russia |
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| Abstract: | On 21 May 1989, a major earthquake swarm on the Reykjanes Ridge at59°44 N, 29°32 W at a water depth of about 1000 m andabout 500 km southwest of Iceland was detected on both the WorldwideStandard Seismic Network (WWSSN) and Icelandic seismic networks. As part ofa multi-institutional response to this swarm, the Naval ResearchLaboratory arranged for a P3 Orion Aircraft to deploy sonobuoys and AXBTs inthe immediate vicinity of the swarm activity. The detection of the swarmmotivated a survey of the region in 1990, using the towed SeaMARC IIside-looking sonar system. In 1990–1991 the Russian ShirshovInstitute of Oceanology offered the use of its MIR deep-divingsubmersibles to investigate the rise axis for recent volcanism. During 1992,a scientific team comprised of five US and ten Russian scientists mobilizedthe twin, deep diving Russian submersibles to study the spreading axis ofthe Reykjanes Ridge. The resulting data analyses allows us to conclude thatthe 1989 seismic swarm event occurred adjacent to and east of the largeaxial high in the center of our survey area. The length, width and depthrange of the earthquakes were very similar to major seismic swarm eventsconfined to fissure systems in the Krafla region of Iceland. It is likelythat the earthquake swarm was located on a fresh, well-defined systemof fissures and faults extending south of the northernmost axial highstudied. The earthquake swarm was probably associated with an emanation oflava creating a region of high backscatter, located just to the east of thecentral axial high. In addition, the region of high-backscatterremains unsampled because it lay underneath the nadir of the processedSeaMARC tracks used to plan the submersible survey. However many sampleswere taken and structural studies of the evolving Reykjanes Ridge werecarried out. |
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| Keywords: | Mid-Ocean Ridge seismicity lava flow tectonics North Atlantic |
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