The Bay of Naples (southern Italy): Constraints on the volcanic structures inferred from a dense seismic survey

Abstract

[1] The bays of Naples and Pozzuoli host volcanic areas that have been active within recent history. In addition, the vicinities areas around the Vesuvius volcano and the Campi Flegrei caldera are extremely densely inhabited. Over the past decade, this situation has prompted several active seismic experiments focused on the Vesuvius volcano. More recently, the Serapis active seismic survey covered the entire Bay of Naples, with particular attention to Pozzuoli Bay. The processed Serapis P wave travel time collection, extended with a previously acquired data set, has allowed the computation of the most comprehensive three-dimensional P wave velocity distribution for the Bay of Naples, which includes a small-scale high-resolution model of the Campi Flegrei caldera. The joint interpretation of the velocity distribution together with both the available gravity measurements and models and the geothermal drilling information has allowed us to locate and map lithological units at depths. We propose a model of the Campi Flegrei caldera in relation to the underlying Mesozoic limestone unit. In this model, no magma chamber exists in the upper 6 km beneath the Bay of Naples. The feeding system of the Campi Flegrei caldera is directly controlled by the tectonic structures affecting the limestone unit beneath the Bay of Naples. Two NE-SW normal faults run beneath the Vesuvius volcano and Campi Flegrei, which are related to the pre-Pleistocene Apenninic tectonics.

Seismic images and rock properties of the very shallow structure of Campi Flegrei caldera (southern Italy)

“…4), referred to the first kilometer depth of Pozzuoli Bay, obtained using the same inversion method and data described in Judenherc and Zollo (2004). In addition, we performed a manual refined re-picking of the first arrivals followed trace by trace on all of the record sections.…”

“…Although various aspects remain controversial, many studies have implicated one or both of these events as causal in the formation of the caldera (Rosi et al 1983;Rosi and Sbrana 1987;Lirer et al 1987; Barberi et al 1991;Orsi and Scarpati 1989;Scarpati et al 1993;Orsi et al 1991Orsi et al , 1992Orsi et al , 1996Wohletz et al 1995), a wide sunken structure that forms part of Pozzuoli Gulf and the land area of Campi Flegrei (Agip 1987;Orsi et al 1996;Zollo et al 2003;Judenherc and Zollo 2004). After the formation of the caldera, the post-TGN volcanic activity was characterized by minor eruptions that formed the monogenic structures that have a circular distribution along the edge of the caldera, and the products of which have covered the collapsed structure.…”

“…These investigations have resulted in the identification of new, deep, structural features Judenherc and Zollo 2004):…”

The Neapolitan Yellow Tuff caldera offshore the Campi Flegrei: Stratal architecture and kinematic reconstruction during the last 15ky

“…The caldera is represented by a quasi-circular area of~8 km in diameter, that developed in the central sector of the Campi Flegrei, including the inland area and part the Pozzuoli Bay ( Fig. 1) Rosi and Sbrana, 1987;Barberi et al, 1991;Scandone et al, 1991;Scarpati et al, 1993;Wohletz et al, 1995;Orsi et al, 1996;Florio et al, 1999;Judenherc and Zollo, 2004 Following the NYT eruption, the evolution of the Campi Flegrei was dominated by hydromagmatic activity with occasional plinian phases and minor effusive activity forming lava domes . Several tens of monogenic phreato-magmatic vents including tuff rings, tuff cones, cinder and spatter cones, have been active in the last 15 kyr mostly inside the NYT caldera collapse Di Vito et al, 1999;Insinga et al, 2006;Di Renzo et al, 2011;Fedele et al, 2011).…”

“…In the Pozzuoli Bay, the structural elements of the caldera collapse have been largely inferred, on the basis of seafloor morphology and associated deposits Fusi et al, 1991;Fevola et al, 1993;Orsi et al, 1996;Di Vito et al, 1999). More recently, Capuano and Achauer (2003), Judenherc and Zollo (2004) and Dello Iacono et al (2009) have documented the southern border of the NYT caldera down to a depth of 0.25-0.5 km beneath the seafloor, using low-resolution active seismic tomography images. Acocella et al (2004) and Acocella (2010) describe the occurrence of the caldera collapse and resurgence dome in the Campi Flegrei district on the basis of modelling (analogue) experiments.…”