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Evidence of Seismic, Climatic, and Volcanic Events in the Sedimentary Record at Chelatna Lake, Alaska Over the Past 11,000 Yrs.

Description: 

Chelatna Lake is located on the southern slope of the Alaskan Range and experiences strong ground motion from megathrust, intraslab, and crustal sources along the Alaska-Aleutian plate boundary. The lake is 11.8 km long, 1.3 km wide, 133 m deep, and occupies a glaciated valley with approximately 5% of the catchment under ice. To develop the paleoseismic record from Chelatna Lake we collected a comprehensive dataset of high-resolution Chirp, multibeam bathymetry, and sediment cores—the longest core reaches 17.5-meters beneath the lake floor.

Chirp and bathymetry data reveal evidence of widespread slope failures, including a buried landslide complex over 4 meters thick that extends across the entire lake basin. Several older mass transport deposits, also interpreted as slope failures, are imaged in the Chirp data. The sediment consists of varved stratigraphy interrupted by thicker anomalous beds—interpreted as either seismically or flood generated turbidites—as well as tephras. Two groups of interpreted earthquake-related deposits are revealed within the sediment record, 1) thin, light brown turbidites and 2) darker, sandy megaturbidites. Cs-137 activity in the lake sediment suggests that at least three thin turbidites record historical earthquakes, including the 2018 Mw7.1 Anchorage and the 1964 Mw 9.2 Great Alaska earthquakes. Core-to-seismic correlations reveal that the large subaqueous failures imaged in the Chirp data are represented in the cores as thick megaturbidites. We further sub-sample the sediment record to develop an age model informed by radiocarbon and tephrochronology data and to extract downcore physical properties (e.g., grain size, XRF, and geotechnical data). Initial observations indicate over 50 earthquake-related deposits are preserved over the past ~11,000 years in Chelatna Lake. The long sedimentary record in Chelatna Lake, variation in earthquake-related deposits, and abundant local and regional seismic sources presents an opportunity to investigate the relationship between seismically triggered deposit characteristics and quantitative estimates of strong ground motions.

Session: Subaqueous Evidence for Earthquakes, Coseismic Landslides, Tsunamis and other Cascading Hazards [Poster]

Type: Poster

Date: 4/15/2026

Presentation Time: 08:00 AM (local time)

Presenting Author: Drake M. Singleton

Student Presenter: No

Invited Presentation: 

Poster Number: 166

Authors