Telecommunication resilience and geohazard characterisation

As global demand for communication links grows, so does our reliance on seafloor networks of fibre optic cables which transmit >98% of all digital global data traffic. Despite their importance, however, these networks are vulnerable to damage from tsunamis and sediment-laden seafloor flows (turbidity currents), and the remote location of many Small Island Developing States mean they are frequently reliant on individual connections to global networks making them especially susceptible to breaks (e.g. Tonga lost all internet access for 2 weeks in 2019 following a severed cable). The lack of detailed offshore surveys for such geohazards in many Small Island Developing States currently results in a geohazard ‘blindspot’ that limits the ability of government agencies and industrial stakeholders to ensure that the routing of cables and other infrastructure are resilient as possible.

Work conducted through this project enables these issues to be addressed by integrating detailed bathymetry data with a combination of terrestrial remote sensing data, onshore and offshore sediment sampling, and documented historical events. For example, by combining the bathymetric data collected by CME Programme partner the UK Hydrographic Office with seafloor environmental data obtained by the NOC’s habitat mapping team, this project was able to identify that  cascades of sediment released by non-volcanic events (including outburst floods and tropical cyclones) that may be separated by decades, were found to be more important for the preconditioning and triggering of offshore landslides and turbidity currents in oversupplied sedimentary regimes such as at Tanna, Vanuatu. This finding enabled a general model for how submarine landslides and turbidity currents are triggered at volcanic and other heavily eroding mountainous islands to be established, highlighting the often-ignored importance of outburst floods, non-linear responses to land-use and climatic changes, and the complex interactions between a range of coastal and tectonic processes that may overshadow volcanic regimes.

Outputs

• Geohazard assessment report that included (i) Qualitative and quantitative morphometric analysis of seafloor data; (ii) Geohazard assessment and inventory for potential seafloor structures offshore Tanna; (iii) Interpretative 3D figures and maps and supporting guidelines for future offshore/nearshore developments in the surveyed area.
• Particle size and mineralogical analysis of sediment samples collected from Tanna.

Publications

• Bedforms on the submarine flanks of insular volcanoes: New insights gained from high resolution seafloor surveys. D. Casalbore, M.A. Clare, E.L. Pope, R. Quartau, A. Bosman, F.L. Chiocci, C. Romagnoli and R. Santos (2020). Sedimentology.
• Complex and Cascading Triggering of Submarine Landslides and Turbidity Currents at Volcanic Islands Revealed from Integration of High Resolution Onshore and Offshore Surveys. M.A. Clare, T. Le Bas, D.M. Price, J.E. Hunt, D. Sear, M.J.B. Cartigny, A. Vellinga, W. Symons, C. Firth and S. Cronin (2018). Front. Earth Sci. 6:223. doi: 10.3389/feart.2018.00223