Pitfalls and opportunities in estimating the volumes of small, young submarine landslides

Submarine landslides have the potential to be major geohazards as they can destroy seafloor infrastructure such as communication cables and cause tsunamis. The volume of material displaced during the landslide is one factor that determines its hazard and is typically estimated using bathymetric and/or seismic data. Here, we use various established methods to determine the initial failed volume based on a well-constrained case study, the Ana Slide, a small slope failure in the Eivissa Channel off the eastern Iberian Peninsula. We find that, not only, the availability and quality of marine-geophysical data, but also the emplacement mechanism affects how precisely the volume can be estimated. In general, the volume estimation based on comparison of recent and reconstructed pre-failure seafloor topographies yields conservative, yet robust estimates for the volume mobilized. In contrast, volumes estimated from seismic data may be overestimated if the nature of the chaotic, transparent, or disrupted seismic facies commonly used to identify landslide material is unknown.