Deep Seismic Imaging of the Offshore Sector of the Campi Flegrei Caldera to Complement an Amphibic ICDP/IODP Drilling Initiative

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The Campi Flegrei Volcanic District belongs to the worlds most active volcanic systems. The most pronounced volcanic feature in that area is the half-submerged, quasi-circular Campi Flegrei caldera. It is still under debate whether the caldera formation was related to only one ignimbritic eruption namely, the Neapolitan Yellow Tuff (NYT) eruption at 15 ka, or if it is a nested-caldera system related to the NYT and the Campanian Ignimbrite eruption at 39 ka. The last volcanic eruption occurred in 1538 AD at the Monte Nuovo after 3500 years of quiescence. In the last decades, the Campi Flegrei caldera has been characterized by short-term episodes of unrest involving considerable ground deformation (uplift and subsidence of several meters), seismicity and increased temperature at fumaroles. Furthermore, long-term deformation can be observed in the central part of the caldera with uplift rates of several tens of meters within a few thousand years. Both long-term and short term uplift could be interpreted as eruption precursor, thereby posing high-concern for a future eruption, which would expose more than 1.5 million people living in the surroundings of the volcanic district to extreme volcanic risks. In order to improve the understanding of such unrest mechanisms and to correctly assess eruption hazards, the Campi Flegrei Volcanic District became subject to a joint approach for scientific drilling in the ICDP and IODP programmes. During a partially DFG funded, German-Italian expedition in 2008, high-resolution multi-channel seismic data were acquired to support the onshore and offshore drilling campaigns. The seismic data provide an insight into the evolution of the Campi Flegrei caldera since the NYT eruption and have been interpreted within the framework of an ongoing project in the DFG ICDP Priority Programme. Despite outstanding data quality of the uppermost 300 m below the seafloor, the signal penetration is not sufficient to achieve the required depths (~2 km) of the ICDP/IODP drilling campaigns. In the context of the present proposal another expedition is planned for 2015, during which a low-frequency seismic system shall be deployed in order to achieve signal penetration down to the target depth of the proposed ICDP/IODP drill sites. This to-be acquired seismic dataset may serve as a basis for the correlation of the recently completed onland ICDP drilling and proposed IODP drill sites in the Gulf of Pozzuoli and Naples Bay in order to develop a large scale picture of the study area. Eventually, the data shall be used to prepare an updated marine drilling campaign. Furthermore, the to-be acquired deep-penetrating seismic data would form an optimal complement to the already existing high-resolution seismic data. A joint interpretation of both datasets would provide not yet existing insights into the development of the Campi Flegrei caldera, including the time span before the Neapolitan Yellow Tuff eruption.