Abstract
Two active-source, high-resolution seismic profiles were acquired in the Solfatara tuff cone in May and November 2014, with dense, wide-aperture arrays. Common Receiver Surface processing was crucial in improving signal-to-noise ratio and reflector continuity. These surveys provide, for the first time, high-resolution seismic images of the Solfatara crater, depicting a ~400 m deep asymmetrical crater filled by volcanoclastic sediments and rocks and carved within an overall non-reflective pre-eruptive basement showing features consistent with the emplacement of shallow intrusive bodies. Seismic reflection data were interpreted using the trace complex attributes and clearly display several steep and segmented collapse faults, generally having normal kinematics and dipping toward the crater centre. Fault/fracture planes are imaged as sudden amplitude drops that generate narrow low-similarity and high-dip attributes. Uprising fluids degassed by a magmatic source are the most probable cause of the small-scale amplitude reduction. Seismic data also support the interpretation of the shallow structure of the Solfatara crater as a maar. Our results provides a solid framework to constrain the near-surface geological interpretation of such a complex area, which improves our understanding of the temporal changes of the structure in relation with other geophysical and geochemical measurements.
Highlights
Campi Flegrei is a large, 13-km-wide, nested caldera located within the metropolitan area of the city of Naples, Italy and formed by two main eruptive events with volcanic explosive indexes greater than five (Campanian Ignimbrite; ~39 ka and Neapolitan Yellow Tuff; ~15 ka)
Common Reflection Surface (CRS) processing was crucial in improving the signal-to-noise ratio and the reflector continuity of the two profiles acquired within the Solfatara crater
The improved signal-to noise ratio and continuity achieved by CRS processing allowed us to fully exploit the high-resolution information embedded in the two 2D seismic surveys and to gain clear and detailed images of the volcanoclastic filling of the crater
Summary
Campi Flegrei (hereinafter named as CF, Fig. 1) is a large, 13-km-wide, nested caldera located within the metropolitan area of the city of Naples, Italy and formed by two main eruptive events with volcanic explosive indexes greater than five (Campanian Ignimbrite; ~39 ka and Neapolitan Yellow Tuff; ~15 ka). Using the active-source data from the 3D RICEN array (Fig. 1B,C) de Landro et al.[14], obtained high-resolution tomographic P-wave velocity images of the first 30 m of the central part of the crater These images show a large spatial heterogeneity, caused by poorly consolidated sediments affected by a different degree of water and/or CO2 saturation. To image the structure of the crater at larger depths (down to ~1 km), during the RICEN experiment we conducted two high-resolution seismic profiles along two orthogonal NNE (i.e. solf_1) and WNW (i.e. solf_2) directions (Fig. 1B,C) Their purpose is to locate fractures and faults, whose position and geometry are fundamental in understanding the mechanisms of massive degassing and hydrothermal fluid circulation occurring near the surface. In contrast to CDP stacking, the great advantage of CRS stack is that it does not directly depend on the velocity model
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