3D Naples Campi Flegrei shallow
In 2008, a seismic cruise was carried out on R/V Urania as a cooperation of MTU and IAMC (Naples). Besides many regional seismic lines, a dense seismic grid was also acquired in the Gulf of Pozzuoli.
The 3D high-resolution multichannel seismic dataset was acquired in a (partly) submerged caldera setting, the Campi Flegrei caldera (CFc). The objectives were to examine the spatial and temporal evolution of the CFc since the last caldera-forming event, the Neapolitan Yellow Tuff (NYT, 15 ka) eruption, the caldera's shallow (<200 m) subsurface structure and post-NYT-collapse (<15 ka) deformational processes, the manifestation of magmatic and hydrothermal processes in the subsurface, as well as the volume, dispersal and explosivity of coastal post-collapse eruptions, thereby significantly advancing the current knowledge of the CFc.
The results onfirm the existence of a nested-caldera system comprising two caldera depressions bordered by an inner and a deeper (>200 m) outer caldera ring-fault zone. The seismic data revealed that the NYT collapse occurred exclusively along the inner caldera ring-fault and that the related NYT caldera depression is filled with on average ~61 m of sediment deposited between 15 and 8.6 ka. The geometry of the inner ring-fault, consisting of four fault segments, seems to be strongly influenced by regional NW-SE and NE SW-trending faults.
Furthermore, we the ring-faults apparently acted as pathway for the recent (<3.7 ka) ascent of fluids (gases and liquids) and the emplacement of intrusions. The outer ring-fault zone, which likely formed in the course of the Campanian Ignimbrite (CI, 39 ka) eruption, has had the main control on the release and ascent of fluids. Overall, the caldera ring-faults represent key locations for the interconnection between the magmatic-hydrothermal systems and the surface and, thus, potentially represent future eruption sites as well as important fluid pathways during the recent unrest episodes.
In addition, the volume, dispersal, and explosivity of the post-collapse Nisida Bank (10.3–9.5 ka), Nisida Island (~3.98 ka), and Capo Miseno (3.7 ka) eruptions, was assessed, yielding DRE values of 0.15 km3, 0.1 km3, and 0.08 km3, respectively, and an explosive magnitude of at least moderate-large scale (VEI 3).
Accordingly, eruption volumes may be underestimated by 3 to 4 times if the submerged portion of a (partly) submerged caldera is not considered, implying severe consequences for the hazard and risk evaluation. The spatial response of the post-collapse (<15 ka) depositional environment to volcanic activity, deformational processes and sea-level variations is presented in a comprehensive 3D evolutionary model.
Publication
Steinmann, Lena, Spiess V., Sacchi M. (2018) Post-collapse evolution of a coastal caldera system: Insights from a 3D multichannel seismic survey from the Campi Flegrei caldera (Italy). Journal of Volcanology and Geothermal Research 349, 83-98, https://doi.org/10.1016/j.jvolgeores.2017.09.023. (PDF)
