UTILIZING LANDSLIDES ON LAKE CHAMPLAIN AS PALEOSEISMIC AND PALEOHAZARD INDICATORS: PREDICTIVE HAZARD REGIONS FOR FUTURE SLOPE FAILURE

In Lake Champlain, many landslides have been identified via Mutlibeam and CHIRP (compressed high intensity radar pulse) seismic profile imagery. Previous studies (Ghosh, 2012, Rosales-Underbrink, 2015, Manley and Manley, 2015) have shown that these landslides are coeval and were most likely triggered by a large earthquake ~4500 – 5500 years ago. These landslides also correlate with surficial landslides in Ottowa, for which a M6.5 earthquake trigger has been determined (Brooks, 2015). It has also previously been recognized that older landslides have also occurred, but no further investigation has been done. This study focuses on a series of overlapping landslide deposits in an area between the Bouquet River Delta and Essex, NY in the main section of Lake Champlain, where nearly the entire slope has had failure, with the exception of a few locations where blocks of sediment remain intact. Core studies show that sedimentation rates are much higher on the west side of the lake than the east side because of sediment flux from the Bouquet River. Using this sedimentation rate and the thickness of sediment accumulation above slumped material in seismic imagery, we have identified three failure events, each having a distinct age. As demonstrated by Manley and Manley (2015), lake tsunami models can be generated from the landslides. Utilizing the failure and timing of the failed slopes, a lake tsunami has been made. Future lake tsunami models are also determined for the unfailed sections of the western slope.