Evidence of a turbidity current in Monterey Submarine Canyon associated with the 1989 Loma Prieta earthquake

Evidence of a turbidity current sweeping through the Monterey Submarine Canyon following the October 1989 Loma Prieta earthquake was documented by the movement of bottom-deployed acoustic transponders used to navigate free-falling oceanographic instrumentation. Measuring sites located along the Canyon at distances of 55, 130 and 190 km from the Canyon head off Moss Landing, CA, all showed evidence of tectonically induced sediment transport. At the site 55 km from the Canyon head, one transponder, located in the axis of the Canyon, was carried 1.9 km down the axis and was deposited among a field of rocks. The other three transponders had been deployed on the sides of the canyon and showed evidence of sediment slumping toward the Canyon axis. Circumstantial evidence from the site 130 km down the canyon suggests that sediment deposition occurred outside the channel axis. Sediment slumping or erosional cutting moved one transponder deeper at the site 190 km from the canyon head.