Evaluating fracture patterns within a resurgent caldera: Campi Flegrei, Italy

Abstract

Understanding deformation of active calderas allows their dynamics to be defined and their hazard mitigated. The Campi Flegrei resurgent caldera (Italy) is one of the most active and hazardous volcanoes in the world, characterized by post-collapse resurgence, eruptions, ground deformation, and seismicity. An original structural analysis provides an overview of the main fracture zones. NW-SE and NE-SW fractures (normal or transtensive faults and extensional fractures) predominate along the rim and within the caldera, suggesting a regional control, both during and after the collapses. While the NE-SW fractures are ubiquitous in the deposits of the last ∼37 ka, NW-SE fractures predominate in the last 4.5 ka, during resurgence. The most recently (<4.5 ka) strained area lies in the caldera center (Solfatara area), where the faults, with an overall ∼ENE-WSW extension direction, appear to be associated with the bending due to resurgence. Solfatara lies immediately to the east of the most uplifted part of the caldera (Pozzuoli area), where domes form and culminate both on the long-term (resurgence, accompanied by volcanic activity) and short-term deformation (1982)(1983)(1984) bradyseism, accompanied by seismic and hydrothermal activity). Similar volcano-tectonic behavior characterizes the short-and long-term uplifts, and only the intensity of the tectonic and volcanic activity varies, being related to varying amounts of uplift. Seismicity and hydrothermal manifestations occur during the bradyseisms, with moderate uplift, while surface faulting and eruptions occur during resurgence, with higher uplift. The features observed at Campi Flegrei are found at other major calderas, suggesting consistent behavior of large magmatic systems.

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

“…1) Di Vito et al, 1999;Milia and Torrente, 2000;Milia and Giordano, 2002;Bruno, 2004). Acocella et al (2004) and Acocella (2010) have suggested that NE-SW transfer faults likely played an important role in controlling the evolution of volcanic activity at Campi Flegrei. On the basis of high-resolution multichannel seismic data acquired in the Pozzuoli Bay, Sacchi et al (2009) have described the basic elements of the shallow structure of the NYT caldera.…”

“…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.…”

Distributed-Temperature-Sensing Using Optical Methods: A First Application in the Offshore Area of Campi Flegrei Caldera (Southern Italy) for Volcano Monitoring

“…Sacchi et al, (2014) [24] also show that a dome structure, correlated to the resurgence of the caldera, is centered in the Bay of Pozzuoli about 1.7 km south of Pozzuoli Harbor. This sector is marked by the presence of minor, normal faults that subsided the apical dome possibly by diffuse pore fluid circulation along the higher permeability zones [24][25][26][27][28][29][30][31][32]. As regards the thermal state of the caldera, there is surface evidence of the presence of a high temperature geothermal system, which is mainly developed in the central part of the caldera at Solfatara crater [6][7][8][9][10][11].…”

Laser Scanning Application for Geostructural analysis of Tuffaceous Coastal Cliffs: the case of Punta Epitaffio, Pozzuoli Bay, Italy

“…The geomorphological study was integrated with the analysis of the ground deformation field of the study area derived by Synthetic Aperture Radar interferometry (InSAR) data from satellite ENVISAT for the period 2003-2010[MATTM, 2015. The InSAR data were processed according with the method of Persistent Scatterers Pair (PSP) [Costantini et al, 2008[Costantini et al, , 2009.…”

“…The morpho-structural analysis allowed for the definition of the average orientation values of the main observed structural sets, which are mostly steep and planar with variable spatial density: a) Set K1 -average direction N110°-150°, sub-vertical and sub-orthogonal to the cliff; b) Set K2 -average direction N60-80°, sub-vertical and sub-parallel to the cliff; c) Set K3 -average direction N170°-190°, sub-vertical and sub-orthogonal to the cliff. The structural origin of the discontinuity sets is genetically associated to both Neapolitan Yellow Tuff caldera volcano-tectonic deformation and NW-SE and NE-SW regional extensional structures (Acocella, 2010;Vitale and Isaia, 2014). In this unstable sector (Fig.…”