High-resolution seismic characterization of post-glacial subaqueous mass movements in the Beagle Channel (Tierra del Fuego, Argentina): dynamics and tsunami hazard implications

Abstract

Analysis of high-resolution seismic profiles from the central Beagle Channel enabled the recognition and characterization of several post-glacial subaqueous mass transport deposits in the subsurface of Bahía Ushuaia, offshore the city of Ushuaia (Argentina). These deposits are located at different stratigraphic levels and are embedded in the stratified sedimentary sequence within a deep trough, suggesting a recurrent occurrence. Up to eleven deposits have been identified, with four major events that involved estimated sediment volumes ranging from 12 to 57 million m3. The latter are associated with megaturbidite deposits up to 10 m thick. Two of the largest events postdate the early Holocene unconformity of marine transgression. The seismic data suggest a different dynamic behaviour of these four main events, with erosional, strongly disintegrating and longer-lasting pre-marine transgression mass transport events compared to the post-early Holocene deposits. Several of the deposits appear to have a common origin due to earthquake-induced failures of submerged glaciofluvial deposits or from tributary deltas. In addition, a preliminary analysis of the potential generation of tsunami waves associated with the largest submarine failures was carried out using numerical models. The results show that at least three of them would have the potential to generate dangerous waves with maximum heights of up to 1–2 m in the port of Ushuaia and estimated run-up heights between 2 and 8 m. Although further detailed analysis is recommended, particularly with regard to a more sophisticated modelling approach and refinement of the resolution of bathymetric and topographic data for strategic areas.