Joint Meeting Pacific Section, AAPG & Cordilleran Section GSA April 29–May 1, 2005, San José, California

Trans-Terrestrial Landslides Along the Northern Rim of the Circum-Pacific and the Impact on the Marine Environment: Big Sur Coastline, California

Lee Y. Murai¹, H. Gary Greene¹, and Steven Ward^2
1 Geological Oceanography, Moss Landing Marine Laboratories, 8272 Moss Landing Road, Moss Landing, CA 95039, [email protected]
² Univ of California, Santa Cruz, Santa Cruz, CA 96060

Recent investigation of the actively uplifting Circum-Pacific continental margin south of Point Sur, along the coastal area of the central Santa Lucia Mountain Range, using EM300 30 kHz multibeam bathymetry, 100 kHz side-scan sonar, and 3.5 kHz seismic reflection profile data indicate that extensive landslide deposits exist along the distal part of the continental shelf and upper slope within the Monterey Bay National Marine Sanctuary. Submersible dives using the Delta revealed that the deposits imaged in the remotely sensed data sets were composed of angular to sub-rounded boulders, cobbles and pebbles lying at a depth of 80 to 130m with little biological growth and sediment cover suggesting a fairly young age for the deposits. Based on preliminary aerial examination of the deposit we believe that the material originated subaerially from the coastal slope, progressed across the continental shelf and came to rest 2-3 km offshore of the Big Sur coastline. If such a deposit were to fail at one time it could produce a significant tsunami. We will present evidence that shows the distribution of the slide and a model of the possible impact wave that it could have generated.

Posted with permission of The Geological Society of America; abstract also online (http://gsa.confex.com/gsa/2005CD/finalprogram/abstract_85595.htm). © Copyright 2005 The Geological Society of America (GSA).