Teleseismic tomography of the Campanian volcanic area and surrounding Apenninic belt

The three-dimensional P-velocity structure of the crust and upper mantle be neath the Vesuvius volcano and the surrounding Apenninic belt is derived by teleseismic tomography to describe the deep volcanic structure and its rel ationship with the Adriatic lithosphere subducting beneath the belt. The data consist of 1615 P and PKP travel times derived from 135 teleseismi c events. We merged the data recorded by the stations of the Italian Seismi c Network located on the southern Apennines with stations deployed in a tem porary broad-band experiment around Vesuvius volcano (BROADVES). The travel time residuals, computed with respect to the IASP91 ID reference model, are inverted using the ACH code. The 3D velocity structure shows a lower crust characterised by strong lateral heterogeneities with velocity perturbation s ranging from -5 to +5%. In the lower crust along the Tyrrhenian margin, l ow-velocity anomalies are found beneath the volcanic complexes, suggesting the presence of deep crustal magmatic reservoirs. An almost continuous high -velocity body is reconstructed in the upper mantle beneath the Apenninic b elt from 65 down to 285 km depth. This high-velocity anomaly is interpreted as the signature of the Adriatic lithosphere subducting westward toward th e back-arc Tyrrhenian basin. The low-velocity anomaly in the crust beneath Vesuvius, located above the high-velocity zone dipping in the mantle, may i ndicate that magma is generated by the subducting slab and rises to lower c rustal depths where it is stored. (C) 2001 Elsevier Science B.V. All rights reserved.