Internal Structure of Venere Mud Volcano in the Crotone Forearc Basin, Calabrian Arc, Italy, from Multibeam Bathymetry, Wide-Angle and Multichannel Seismic Data

Abstract

<p>Mud volcanoes (MVs) have been found in various geological settings on passive and active margins but are mostly known from collision zones on Earth. Mud volcanoes are well known to occur on land (e.g. in Azerbaijan), where at least 1000 MVs have been counted. The amount of submarine MVs is believed to be much larger and recent improvements in seafloor mapping led to the discovery of many MVs in all oceans. To contribute to the knowledge of submarine MVs, in particular the internal structure across Venere MV, we conducted a multi-geophysical imaging approach using high resolution multibeam bathymetry, (constraining seafloor expressions), multichannel, and wide-angle seismic data (constraining the internal structure and P-wave velocity distribution). Venere MV is located at the southern rim of the Crotone forearc basin of the Calabrian arc, offshore southern Italy, in a water depth of ~1500 m. The dimension of Venere MV from its bathymetric expression is ~10 km in the EW- and ~7 km in the NS-direction. Two circular cones of ~100 m elevation and ~1.5 km diameter are located in the center of Venere MV. The upper 200 m below the seafloor (bsf) consist of layers with seismic P-wave velocities gradually increasing from 1.53 to 1.7 km/s (sub-) parallel to the seafloor. A prominent reflection ~200 m bsf and a sudden increase of seismic P-wave velocities from 1.7 to 1.8 km/s mark a change with depth in the internal structure, where reflections dip, and seismic P-wave velocities laterally decrease towards the center of Venere MV. The MCS as well as seismic P-wave velocity structure indicate two separate feeder conduits of the two center cones of Venere MV. However, we do not map the roots of the MV, which are at depths beyond our data resolution. Reduced reflectivity occurs ~4 km across the center of the MV 200 m bsf and downwards. We mapped the chaotic reflections of the acoustic basement in depths varying from 500 m to 800 m bsf. Reduced reflectivity of the acoustic basement occurs beneath the center of the MV as well. Mapping of the fault system leads to the subseafloor dimension of Venere MV that exceeds its seafloor dimension by the factor of two.</p>