Landslide Frequency and Failure Mechanisms at NE Gela Basin (Strait of Sicily)

Abstract

Despite intense research by both academia and industry, the parameters controlling slope stability at continental margins are often speculated upon. Lack of core recovery and age control on failed sediments prevent the assessment of failure timing/frequency and the role of prefailure architecture as shaped by paleoenvironmental changes. This study uses an integrated chronological framework from two boreholes and complementary ultrahigh‐resolution acoustic profiling in order to assess (1) the frequency of submarine landsliding at the continental margin of NE Gela Basin and (2) the associated mechanisms of failure. Accurate age control was achieved through absolute radiocarbon dating and indirect dating relying on isotope stratigraphic and micropaleontological reconstructions. A total of nine major slope failure events have been recognized that occurred within the last 87 kyr (~10 kyr return frequency), though there is evidence for additional syndepositional, small‐scaled transport processes of lower volume. Preferential failure involves translational movement of mudflows along subhorizontal surfaces that are induced by sedimentological changes relating to prefailure stratal architecture. Along with sequence‐stratigraphic boundaries reflecting paleoenvironmental fluctuations, recovered core material suggests that intercalated volcaniclastic layers are key to the basal confinement and lateral movement of these events in the study area. Another major predisposing factor is given by rapid loading of fine‐grained homogenous strata and successive generation of excess pore pressure, as expressed by several fluid escape structures. Recurrent failure, however, requires repeated generation of favorable conditions, and seismic activity, though low if compared to many other Mediterranean settings, is shown to represent a legitimate trigger mechanism.

Tsunamis From Submarine Collapses Along the Eastern Slope of the Gela Basin (Strait of Sicily)

“…Moving to the east of the GS, several other landslides have been recognized by Trincardi and Argnani (1990) and in more recent investigations (Minisini and Trincardi, 2009;Kuhlmann et al, 2017). The most interesting cases are the so-called Twin Slides located about 30 km far from the GS (see Figure 1B).…”

“…The estimated volume is slightly less than 0.5 km 3 for both slides. The Northern and Southern Twin Slides (NTS and STS) have been interpreted as the final stage of a very complex sliding sequence, tentatively reconstructed in Kuhlmann et al (2017), that started with a larger "Father Slide" (black line in Figure 1B) 87 ka ago and that repeats periodically about every 10 kyr.…”

“…In this paper, we consider the Gela Basin eastern slope (GBES from now on) that is found in the northern part of the Strait of Sicily and extends from the shelf-edge at relatively shallow water (∼200 m) rapidly deepening to about 900 m depth. Studies based on morpho-bathymetric data show that the GBES has been extensively affected by submarine mass wasting during the Late Quaternary, involving volumes of sediments in the order of magnitude of 1 km 3 (e.g., Minisini et al, 2007;Kuhlmann et al, 2017). Among the recorded landslide events, we select two as representative of potential scenarios along the GBES.…”

Tsunami risk management for crustal earthquakes and non-seismic sources in Italy

“…Two evident scars develop just from the continental platform at 200 m depth b.s.l., 30 km offshore the city of Gela, with the corresponding deposit laying at their toes [365]. These two failures are the final phase of a complex series of collapses, tentatively reconstructed by Kuhlmann et al [366], that repeatedly occurred in the last 10 thousand years. The Twin Slides volumes are estimated at about 0.5 km 3 each; the Northernmost one has been selected for scenario reconstruction and tsunami simulation [367].…”

Simulation of a Submarine Landslide Using the Coupled Material Point Method

“…Several predisposing factors contributed to the destabilization of this slope. e most obvious one is the steep slope itself, which can be a result of a relatively high sedimentation rate [42]. e rapid deposition of sediment will generate excess pore water pressure in the underlying sediments, resulting in an unstable state of the slope.…”