Low shear-velocity zone in the Neapolitan-area crust between the Campi Flegrei and Vesuvio volcanic areas

Abstract

Terra Nova, 22, 208–217, 2010 Abstract Some Vesuvio earthquakes recorded at OV‐INGV stations in the Campi Flegrei volcanic area have been processed by FTAN (frequency–time analysis) method. The group velocities of Rayleigh‐wave fundamental mode have been extracted in the period range 0.7–3 s. Regional group and phase velocity data have been considered as well at the inversion stage. Average shear wave velocity models for the uppermost 73 km of the lithosphere below the Neapolitan area, midway between Campi Flegrei and Vesuvio volcanic areas, have been obtained by the hedgehog nonlinear inversion method. The resulting structural models are characterized by the presence of the carbonate horizon at about 3 km depth. A main feature is represented by low VS velocities around 9 km depth. This low‐velocity layer, already found below both Campi Flegrei and Vesuvio, can be reasonably interpreted as a magmatic reservoir of Campania active volcanoes.

Active and Passive Experiments for S-Wave Velocity Measurements in Urban Areas

“…11). The obtained V S models are in agreement with V S velocities obtained by Nunziata (2010) along the VesuvioCampi Flegrei path, crossing Napoli and its gulf. The agreement with the data relative to Mofete (Campi Flegrei) drillings, that is V S computed from V P sonic log measurements (AGIP, 1987) by assuming a reasonable V P /V S ratio of 1.8, and ultrasonic measurements on saturated specimens (Zamora et al, 1994) is quite impressive and the following interpretative structural model can be formulated.…”

“…9), suggest that the presence of highly fractured sedimentary rocks cannot be escluded. The compact sedimentary horizon, with a V S of 3.6-3.7 km/s, has been found below the Neapolitan area at about 3 km of depth (Nunziata, 2010). (Fig.…”

VS Crustal Models and Spectral Amplification Effects in the L’Aquila Basin (Italy)

“…[12,13,14]). The FTAN method allows to isolate the different phases in a seismogram, in particular the fundamental mode of surface waves.…”

“…[12,13,14]) from recordings of earthquakes with M L ≥ 2.9 (Table 1) between April 5 and November 10, 2009, in the selected coordinate window of 42.4 ± 0.2 N and 13.4 ± 0.2 E. In addition, V S of the superficial 30 m of Aterno alluvial soils are defined by an active seismic experiment in the Coppito area, and compared with nearby crosshole measurements. The V S profiles vs. depth are then attributed to lithotypes along a geological cross section from the epicenter to a seismic station at L'Aquila.…”

Evaluation of Linear and Nonlinear Site Effects for the MW 6.3, 2009 L’Aquila Earthquake

“…2) (Costanzo et al, 2011) from the nonlinear inversion with Hedgehog method (Panza et al, 2007 and references therein) of the group velocity dispersion curves of the fundamental mode extracted with the FTAN method (e.g. Levshin et al, 1989;Nunziata, 2010). The models are characterized by an average velocity of 190 m/s.…”