Preliminary results from ultra-high-resolution 3D seismic imaging of fault networks in the Campi Flegrei Resurgence (Naples, Italy)

Abstract

Volcanism, hydrothermal activity, and caldera floor uplift (resurgence) at the Neapolitan Yellow Tuff (NYT) caldera (Campi Flegrei – Gulf of Pozzuoli) have spurred considerable research aimed at defining its structural framework and evolutionary history (e.g. Sacchi et al., 2014; Corradino et al., 2021; Natale et al., 2022) using 2D seismic reflection data. However, the complex fault network geometry developed at a decimetric scale, specifically in the apical zone of the resurgence, remains poorly constrained. Also, the relationship between fault networks and fluid circuation, which can lead to stress distribution variations and potentially earthquakes, is unknown. This is primarily due to the limitations of 2D seismic data, lacking resolution and spatial coverage to capture small-scale fault geometries and often affected by seismic artefacts, such as out-of-plane reflections, which can blur and distort subsurface structures. This study uses ultra-high-resolution 3D (UHR3D) seismic reflection data to investigate the fault network geometry (strikes, dips, and spatial extent) developed within the NYT resurgence apical graben. Data were collected utilizing innovative technologies during an oceanographic cruise organized in the frame of a joint project involving the University of Palermo, Catania and Napoli Federico II, CNR of Napoli and INGV Roma, and two companies, the Geo Marine Survey System (The Netherlands) and GeoSurvey (Portugal). The data processing employed advanced techniques developed to optimize UHR3D shallow marine seismic surveys. Seismic interpretation and attribute analyses reveals a complex fault network of more than 60 predominantly normal faults, striking NE-SW, and extending from the seafloor to at least approximately 120–170 meters depth. Amplitude anomalies, bright spots and localized velocity variations indicate the presence of active fluid pathways and how they are connected to the fault network. This research refines knowledge on understanding the process responsible for the formation of complex fault-network geometry and their potential as fluid conduits within the resurgence apical graben. The new f indings underscore the critical importance of accurately identifying resurgence structures for improving forecasts of caldera behavior during periods of unrest.