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 Submarin e Canyon following the October 1989 Loma Prieta earthquake was documen ted by the movement of bottom-deployed acoustic transponders used to n avigate free-falling oceanographic instrumentation. Measuring sites lo cated along the Cayon at distances of 55, 130 and 190 km from the Cayo n head off Moss Landing, CA, all showed evidence of tectonically induc ed sediment transport. At the site 55 km from the Canyon head, one tra nsponder, located in the axis of the Canyon, was carried 1.9 km down t he axis and was deposited among a field of rocks. The other three tran sponders had been deployed on the sides of the canyon and showed evide nce of sediment slumping toward the Canyon axis. Circumstantial eviden ce from the site 130 km down the canyon suggests that sediment deposit ion occurred outside the channel axis. Sediment slumping or erosional cutting moved one transponder deeper at the site 190 km from the canyo n head.