HR: 17:15h
AN: NS34A-06    [Abstracts]
TI: Aeromagnetic Constraints on the Subsurface Structure of Stromboli Volcano, Aeolian Islands, Italy
AU: * Okuma, S
EM: s.okuma@aist.go.jp
AF: Geological Survey of Japan, AIST, Tsukuba Central 7, Higashi 1-1-1, Tsukuba, 305-8567, Japan
AU: Stotter, C
EM: christian.stotter@gmail.com
AF: OMV Exploration & Production GmbH, Gerasdorfer Straße 151, Vienna, A-1210, Austria
AU: Supper, R
EM: robert.supper@geologie.ac.at
AF: Geological Survey of Austria, Neulinggasse 38, Vienna, A-1030, Austria
AU: Nakatsuka, T
EM: tad.nktk@ni.aist.go.jp
AF: Geological Survey of Japan, AIST, Tsukuba Central 7, Higashi 1-1-1, Tsukuba, 305-8567, Japan
AU: Furukawa, R
EM: furukawa-r@aist.go.jp
AF: Geological Survey of Japan, AIST, Tsukuba Central 7, Higashi 1-1-1, Tsukuba, 305-8567, Japan
AB: Aeromagnetic surveys were conducted over Stromboli volcano and its surrounding areas in the Aeolian Islands, southern Italy in 2002 and 2004 to better understand the subsurface structure of the area. Observed data of those surveys were merged and aeromagnetic anomalies for Stromboli Island and its vicinity were reduced on a smoothed surface by the method, assuming equivalent anomalies below the observed surface (Nakatsuka and Okuma, 2006). Magnetic terrain corrections (Grauch, 1987) were applied to the anomalies of the study area, assuming a magnetic structure comprised of an ensemble of prism models extending from the ground surface to a depth of 3,000m below sea level: the average magnetization intensity was calculated to be 2.2 A/m by a comparison between the observed and synthetic anomalies and then the synthetic anomalies were removed from the observed. Next, apparent magnetization intensity mapping (Nakatsuka, 1995) was applied to the terrain-corrected anomalies. The apparent magnetization intensity map indicates magnetic heterogeneities among volcanic rocks which constitute the edifice of the volcano. The most obvious characteristics of the magnetization intensities is a magnetization low which occupies the center of the island where the summit craters reside closely, suggesting a demagnetization caused by the heat of conduits and/or a shallow magma chamber in addition to the thick accumulation of less magnetic pyroclastic rocks. By comparison with geologic maps, it can be seen that magnetization highs are distributed on exposures of basaltic-andesite to andesite lavas (Paleostromboli I), shoshonitic shied volcanoes (Neostromboli), at the south, north and west coasts of the volcano, respectively. Those magnetization highs further extend to offshore, implying the continuation of those volcanic rocks from land. An apparent magnetization low lies on an abrasion platform offshore of the northeastern volcano, suggesting that the platform is underlain by the hydrothermally altered center of the dissected edifice of an old volcano.
UR: http://staff.aist.go.jp/s.okuma/
DE: 1517 Magnetic anomalies: modeling and interpretation
DE: 5109 Magnetic and electrical properties (0925)
DE: 8428 Explosive volcanism
DE: 8488 Volcanic hazards and risks
SC: Near-Surface Geophysics [NS]
MN: 2007 Fall Meeting