HR: 1330h
AN: V22A-0571    [PDF]
TI: Spreading of Somma-Vesuvio Volcanic Complex: is the Hazard for Plinian Eruptions being reduced?
AU: Borgia, A
EM: andrea@borgia.net
AF: EDRA, via di Fioranello 31, Roma, 00134 Italy
AU: * Tizzani, P
AF: Dip. Scienze della Terra, Univ. Napoli, Largo S. Marcellino 10, Napoli, 80138 Italy
AU: Solaro, G
EM: gsolaro@unina.it
AF: Dip. Scienze della Terra, Univ. Napoli, Largo S. Marcellino 10, Napoli, 80138 Italy
AU: Luongo, G
AF: Dip. Scienze della Terra, Univ. Napoli, Largo S. Marcellino 10, Napoli, 80138 Italy
AU: Fusi, N
EM: nicoletta.fusi@unimib.it
AF: Dip. Scienze Geologiche, Univ. Milano-Bicocca, Piazza della Scienza 4, Milano, 20126 Italy
AB: Contrary to what is the common knowledge, a detailed structural study of active faulting and rifting of the summit area of Somma-Vesuvio volcanic complex, combined with INSAR, levelling data and seismic profiling at sea suggests that the present-day long-term dynamic behaviour of the complex and of its summit caldera is characterized by volcanic spreading. The structural evolution is controlled by a number of asymmetric, intersecting leaf-grabens. The boundary faults of these grabens intersect at different angles the Somma caldera walls generating a set of wedge-horsts. While normal faulting characterizes the Somma caldera walls, the lavas of the past 150 years, infilling the caldera, have been rifted all around the southern, eastern and northern base of Vesuvio's cone, which, in turn, is being displaced seaward. Associated to the subsidence and extension of the summit area, relative uplift occurs along the coast; in addition, deformation of recent sediments 6-18 km offshore also indicate compression and uplift, which appears to be unrelated to regional tectonics. A preliminary evaluation indicates that rifting of the lavas is in the order of 1-2 mm/a with a southwestward average direction of displacement. Based on these data, we suggest that a wide sector of Somma-Vesuvio is spreading on its plastic sedimentary substratum, which have been identified by drilling. Volcanic spreading appears to have controlled the magmatic evolution and the energy decrease of major historic explosive eruptions since 79 AD. If our interpretation is correct, major plinian eruptions should not occur in the near future. On the other hand, rifting around the caldera suggests that volcanic activity could soon be renewed.
DE: 8122 Dynamics, gravity and tectonics
DE: 8400 VOLCANOLOGY
DE: 8414 Eruption mechanisms
DE: 8419 Eruption monitoring (7280)
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2003 Fall Meeting