Increased marine sediment suspension and fluxes following an earthquake

Earthquakes are commonly cited as one possible triggering mechanism for turbidity flows—dense sediment–water plumes that can transport large volumes of sediment great distances down slope—in both marine and lacustrine settings1,2,3,4,5,6. Heezen and Ewing1 were the first to make such a suggestion, attributing breaks in a sea-floor telephone cable in the North Atlantic Ocean to turbidity flows generated by the 1929 Grand Banks earthquake. Anumber of workers have consequently used sedimentary turbidite records to reconstruct the earthquake histories of various regions2,7,8. Here we present direct observations of a seismically induced turbidity flow. Measurements of light scattering and sediment fluxes in the Cariaco basin indicate that the earthquake that occurred along the coast of northern Venezuela on 9 July 1997 resulted in considerable downslope displacement of sediments—probably >105 tonnes into the deep part of the basin. In such a seismically active region, this mechanism of sediment transport may be responsible for a significant component of the long-term sediment accumulation in the basin. Furthermore, this process may result in the sequestration in deep sea sediments of large amounts of carbon initially deposited at shallow depths.