P-SV conversions at a shallow boundary beneath Campi Flegrei caldera (Italy) - evidence for the magma chamber

Journal Article · Thu Oct 01 04:00:00 EDT 1992 · Journal of Geophysical Research; (United States)

OSTI ID:6999005

Ferrucci, F; Hirn, A; De Natale, G; Virieux, J; Mirabile, L ^[1]

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1. CNR, Gruppo Nazionale per la Vulcanologia, Catania (Italy) Inst. de Physique du Globe, Paris (France) Osservatorio Vesuviano, Naples (Italy) CNRS, Inst. de Geodynamique, Valbonne (France) Ist. Universitario Navale, Naples (Italy)

Seismograms from an active seismic experiment carried out at Campi Flegrei caldera (near Naples, Italy), show a large-amplitude SV-polarized shear wave, following by less than 1.5-s P waves reflected at wide angle from a deep crustal interface. Early arriving SV-polarized waves, with the same delay to direct P waves, are also observed in seismograms from a regional 280 km-deep, magnitude 5.1 earthquake. Such short delays of S to P waves are consistent with a P-SV conversion on transmission occurring at a shallow boundary beneath the receivers. The large amplitude of the converted-SV phase, along with that the P waves are near vertical, requires a boundary separating a very low rigidity layer from the upper caldera fill. The converted phases are interpreted as a seismic marker of a magma chamber. The top of this magma chamber is located slightly deeper than the deepest earthquakes observed during the 1982-1984 unrest of Campi Flegrei. 8 refs.

• OSTI ID: 6999005
• Journal Information: Journal of Geophysical Research; (United States), Journal Name: Journal of Geophysical Research; (United States) Vol. 97; ISSN JGREA2; ISSN 0148-0227
• Country of Publication: United States
• Language: English

Related Subjects

54 ENVIRONMENTAL SCIENCES
540210* -- Environment
Terrestrial-- Basic Studies-- (1990-)
58 GEOSCIENCES
580000 -- Geosciences
CALDERAS
DEVELOPED COUNTRIES
EARTHQUAKES
EUROPE
ITALY
MAGMA
MEASURING INSTRUMENTS
P WAVES
PARTIAL WAVES
S WAVES
SEISMIC ARRAYS
SEISMIC DETECTORS
SEISMIC EVENTS
SEISMIC WAVES
SEISMOGRAPHS
SEISMOLOGY
VOLCANOES