Publication Date:
2018-12-10
Description:
The Ionian Sea in southern Italy is at the center of active interaction and convergence between the Eurasian and African-Adriatic plates in the Mediterranean. This area is seismically active with instrumentally/historically-recorded Mw 〉 7.0 earthquakes and it is affected by recently-discovered long strike-slip faults across the active Calabrian accretionary wedge. Many mud volcanoes occur on top of the wedge. A recently-discovered one (here named Bortoluzzi Mud Volcano, BMV) was surveyed during the Seismofaults 2017 cruise (May 2017). Bathymetric-backscatter surveys, seismic reflection profiles, geochemical and earthquake data as well as a gravity core are here used to geologically, geochemically, and geophysically characterize this structure. The BMV is a circular feature ≃22 m high and ≃1100 m in diameter with steep slopes (up to a dip of 22°). It sits atop the Calabrian accretionary wedge and a system of flower-like oblique-slip faults that are probably seismically active as demonstrated by earthquake hypocentral and focal data. Geochemistry of water samples from the seawater column on top of the BMV shows a significant contamination of the bottom waters from saline (evaporite-type) CH4-dominated crustal-derived fluids similar to the fluids collected from a mud volcano located in the Calabria main land over the same accretionary wedge. These results attest for the occurrence of an open crustal conduit through the BMV down to at least the Messinian evaporites at about −3000 m. This evidence is also substantiated by Helium isotope ratios and by different geochemical data from three sea water columns located elsewhere in the Ionian Sea. Conclusions are drawn on the origin of the BMV and on the potential of this type of structures for tracking the seismic cycle of active faults. Due to the widespread diffusion of mud volcanoes in seismically active settings, this study may contribute to indicate a potential and feasible future path for the use of these ubiquitous structures in favor of the mitigation of natural hazards.
Electronic ISSN:
1869-9537
Topics:
Geosciences
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