Scenarios of lateral collapses of the Vavilov seamount in the central Tyrrhenian sea

The strong EW asymmetry observed for the Vavilov seamount could be the result of an ancient collapse from its western flank. Two scenarios for the pre-collapse morphology of the seamount are built up by reshaping the western flank of Vavilov and modelling it as the eastern one. In scenario 1 the detached mass is assumed to slide down on the present bathymetry, i.e. the sliding surface outside the detachment niche is identified with the today’s abyssal plane to the west of Vavilov. Instead, in scenario 2 it is assumed that the difference between the depth of the western (less deep) and eastern (deeper) abyssal planes is due to the deposition and subsequent reworking of the collapsed material. Therefore, in scenario 2 the identified deposit is removed from the present bathymetry, while the western flank is reshaped approximately like in scenario~1. The motion of the landslide is simulated by the model UBO-BLOCK2, developed by the Tsunami Research Team of the University of Bologna, that treats it as a grid of blocks sliding under the effect of friction, drag forces and interaction forces. The influence of various parameters on the model's output is discussed for simulations that regard scenario 1. For scenario 2, the agreement between the hypothesised deposit and the one computed through the simulations is used to tune the model parameters, and in particular the sea bottom friction coefficient, that is the one that most affects the landslide motion. The conclusion of the thesis is that scenario 2 supports reasonably well the hypothesis that the Vavilov seamount experienced a collapse of the western flank, that the collapsed material filled the western abyssal plane causing an average decrease of the sea floor depth by hundreds of meters, that most of the material accumulated not too far from the feet of the Vavilov’s seamount, which is consistent with the available seismic lines.