Increased marine sediment suspension and fluxes following an earthquake

Earthquakes are commonly cited as one possible triggering mechanism for tur bidity hows-dense sediment-water plumes that can transport large volumes of sediment great distances down slope-in both marine and lacustrine settings (1-6). Heezen and Ewing(1) were the first to make such a suggestion, attrib uting breaks in a sea-floor telephone cable in the North Atlantic Ocean to turbidity flows generated by the 1929 Grand Banks earthquake. A number of w orkers have consequently used sedimentary turbidite records to reconstruct the earthquake histories of various regions(2,7,8). Here we present direct observations of a seismicallyinduced turbidity flow. Measurements of light scattering and sediment fluxes in the Cariaco basin indicate that the earth quake that occurred along the coast of northern Venezuela on 9 July 1997 re sulted in considerable downslope displacement of sediments-probably >10(5) 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 lar ge amounts of carbon initially deposited at shadow depths.