HR: 1340h
AN: V43A-1116    [Abstracts]
TI: Magma Intrusion, Deformation: the Importance of Crustal Layering.
AU: * Amoruso, A
EM: antonella.amoruso@sa.infn.it
AF: Dipartimento di Fisica Universita' di Salerno, Via S. Allende, Baronissi, SA 84081, Italy
AU: Crescentini, L
EM: luca.crescentini@sa.infn.it
AF: Dipartimento di Fisica Universita' di Salerno, Via S. Allende, Baronissi, SA 84081, Italy
AU: Linde, A T
EM: alinde@dtm.ciw.edu
AF: Department of Terrestrial Magnetism Carnegie Institution of Washington, 5241 Broad Branch Road, NW, Washington, DC 20015-1305, United States
AU: Sacks, I S
EM: sacks@dtm.ciw.edu
AF: Department of Terrestrial Magnetism Carnegie Institution of Washington, 5241 Broad Branch Road, NW, Washington, DC 20015-1305, United States
AB: The Campi Flegrei caldera (CF) is a volcano-tectonic depression, between Naples and the volcanic islands of Ischia and Procida, and is a highly populated area (about 400000 people). Since the last eruption (Monte Nuovo, 1538 A.D.) the CF caldera suffered notable unrest episodes, including large ground deformations, seismic swarms and increases in the degassing activity. The caldera had been continuously subsiding (at about 1.5 cm per year) from 1538 till 1969. A substantial ground uplift, more than 1 m of deformation, occurred in the period 1969-1972 and, after a small subsidence of about 30 cm after 1972, a very strong uplift occurred in the period 1982-1984 (about 1.8 m), with subsequent partial recovery. Superposed on the still continuing subsidence are some short uplift phases (mini-uplifts during 1989, 1994, 2000, 2004-2006); ground level remains about 2.5 m above pre-1970 levels at the town of Pozzuoli. Early papers on the 1982-1984 CF unrest usually invoked magmatic intrusion to explain observed ground deformation and gravity changes. Later papers invoked fluid intrusions or hybrid sources (including both magmatic and hydrothermal components). Some authors suggested the key role of freely slipping ring faults on the deformation pattern. We show that crustal layering plays a key role in deformation (horizontal and vertical displacement) pattern as well as gravity changes. Using a layered model appropriate for the CF caldera (based on seismically derived estimates of the P wave speed for the crust) we are able to better fit all deformation (horizontal and vertical displacement) and gravity data for the 1982-1984 large uplift with a horizontal crack source intruded by silicate melts. The same source is shared by the most recent (2004-2006) mini-uplift. In the case of the 1982-1984 large uplift, we also investigate whether the presence of a deeper deflating supply reservoir (as suggested for Uzu volcano in Japan) is required by the data.
DE: 8440 Calderas
DE: 8488 Volcanic hazards and risks
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2007 Fall Meeting