Which earthquakes trigger damaging submarine mass movements: Insights from a global record of submarine cable breaks?

Submarine landslides, debris flows and turbidity currents are significant geohazards for seafloor infrastructure in many locations around the world. Their deposits potentially provide a valuable record of major earthquakes, which extends further back in time than most terrestrial earthquake records. It is therefore important to determine their frequency and triggering mechanisms, and what types of earthquake trigger submarine slides and flows in different settings. Submarine cable breaks provided the first evidence of submarine mass movements, as shown by the 1929 Grand Banks earthquake. Even now the global network of subsea telecommunication cables provides our only means to monitor flows globally. Here, we present the first global analysis of the occurrence of submarine mass movements caused by earthquakes using cable break data. Using a global database of subsea fibre-optic cable breaks we identify earthquakes that triggered (and did not trigger) submarine mass movements from 1989 to 2015. We note that cable breaks are not a perfect record of submarine mass movements, and may only record more powerful (>~ 2 m s− 1) flows. However, our results show, in contrast to previous assertions, that there is no specific earthquake magnitude that systematically trigger mass flows capable of breaking a cable. Some earthquakes with magnitudes > 7.0 Mw triggered cable breaking flows, but many > 7.0 Mw earthquakes have failed to break nearby cables. We also show that some very small (3.0-4.0) magnitude earthquakes are capable of triggering cable breaking flows. The susceptibility of slopes to fail as a consequence of large and small earthquakes is dependent on the average seismicity of the region and the volume of sediment supplied annually in addition to other preconditioning factors such as slope architecture and mechanical sediment properties.