Tuesday, 28 August 2007
2.PS-67
Three-dimensional P wave tomography of Deception Island Volcano, South Shetland Islands
Daria Zandomeneghi1, Andrew H. Barclay2, Javier Almendros1, Jesus M. Ibanez1, Tami Ben-Zvi3, and William S. D. Wilcock4. (1) Instituto Andaluz de Geofisica, University of Granada, Campus de Cartuja, s/n, Granada, Spain, (2) Lamont-Doherty Earth Observatory, 61 Route 9W, Palisades, NY 10964, (3) Department of Earth and Space Sciences, University of Washington, Box 351310, Seattle, WA 98195, (4) School of Oceanography, University of Washington, Box 357940, Seattle, WA 98195
Deception Island is an active volcano located in Bransfield Strait between the Antarctic Peninsula and the South Shetland Islands. In January 2005 a seismic P wave tomography experiment took place in and around the island using 66 land and 14 ocean-bottom seismometers and more than 5000 airgun shots. A preliminary three-dimensional inversion of the travel times resolves strong velocity contrasts to 5 km depth. The most striking feature is the low seismic velocity beneath the caldera floor which represents an extensive region of magma beneath a sediment-filled basin. A low velocity zone to the east of the volcano corresponds to seafloor sediments, and high velocities to the northwest are attributed to crystalline basement of the South Shetland Islands platform. NE-SW and NW-SE trends in the tomographic image are compatible with the regional tectonic directions and we suggest that the volcanic evolution of Deception Island is conditioned by Bransfield Basin geodynamics.