Large Scarps and Massive Slide on the Briatico–Bivona Shelf, Calabria, Italy: Potential Link with the Destructive September 1905 Earthquake

A multibeam sonar (MBS) survey of the northern Capo Vaticano shelf between the towns of Briatico and Bivona, Calabria, Italy, has revealed a markedly broken margin offset by three large scarps: the upper scarp (S1) at approximate depths of 16–22 m, the middle scarp (S2) at ~36–58 m, and the deeper scarp (S3) at ~88–101 m. The configuration of S1 shows high relief to 33 m and a slope to 598, which suggests a fault or tectonic–gravitative origin. Substantial volumes of sediment, mostly sand, are being rapidly transferred from the inner shelf toward and across the upper shelf break, and one could expect a smoothing and burial of the upper scarp, but 10 MBS profiles show the sharp, angular shape of that feature. Some of the mass gravitative deposits just below some headwall scarps that extend to the shelf-slope that break NE of Briatico also reveal very recent origins. Additionally, a massive slide block north of Bivona, ~350–400m in length, appears to have detached from the inner shelf and shifted onto the middle shelf. It is proposed that several of these seafloor features may, in some manner, be associated with the powerful and destructive September 1905 earthquake that affected a large sector of Calabria. Five potential epicenters on the SWmargin of Calabria have previously been proposed for that event, and this MBS study area is in proximity to one of those. It is recommended that two localities in the survey area, one NE of Briatico and the other north of Bivona, be selected as test zones for further geological and geophysical analyses.