Reconnaissance Implies a Potentially Complete Record of Holocene Earthquakes in Esther Lake Above the Alaska-Aleutian Megathrust
Description:
We investigated Esther Lake, Alaska, to evaluate its potential for lacustrine paleoseismology, specifically for its likelihood to yield a record of megathrust earthquakes. The lake is trenchward of prior lacustrine paleoseismology studies in southcentral Alaska, and it lies in the epicentral region of the 1964 Mw9.2 earthquake. Esther Lake is located in north-central Prince William Sound, formed after deglaciation around 12.9 kya, and lies in a mountainous region dominated by high precipitation and perennial headwater snowfields. Despite such hydrologic conditions, Esther Lake hosts no significant stream deltas, and thus little sediment enters the lake. We collected multibeam echosounder (MBES) bathymetry data, 2-16 kHz Compressed High-Intensity Radar Pulse (CHIRP) seismic data, and 20 short (<2 m) percussion-driven gravity cores that we scanned via computerized tomography (CT) and multi-sensor core logger.
The bathymetry and CHIRP data reveal sediment (<12m thick) is deposited in 9 isolated basins no more than 100 m across. The distinctive seismic stratigraphy of each basin is nearly identical, showing a succession of acoustically transparent ~1 m-thick packages separated by high-amplitude reflections. We divide the sediment, which is generally organic-rich and mineral-poor (<5%) into two main types: “event deposits” and “intra-event deposits”. The intra-event deposits are typically dark brown fine-grained organic rich material, in which we find no identifiable macrofossils, and almost no mineral matter except distinctive light-colored tephras that display high radiodensity and magnetic susceptibility. We interpret these horizons as the high-amplitude CHIRP reflectors. The event deposits are brown organic-rich turbidites that fine upward and commonly contain organic macrofossils and granite-derived micas at the base. Initial radiocarbon samples have been submitted for dating. We infer that Esther Lake has the potential to have a nearly complete record of Holocene earthquakes dominated by megathrust events.
Session: From Faults to Fjords: Earthquake Evidence in Terrestrial and Subaqueous Environments [Poster Session]
Type: Poster
Date: 5/1/2024
Presentation Time: 08:00 AM (local time)
Presenting Author: Peter
Student Presenter: No
Invited Presentation:
Authors
Peter Haeussler Presenting Author Corresponding Author pheuslr@usgs.gov U.S. Geological Survey |
Robert Witter rwitter@usgs.gov U.S. Geological Survey |
Drake Singleton dsingleton@usgs.gov U.S. Geological Survey |
Rachel Marcuson rmarcuson@usgs.gov U.S. Geological Survey |
Daniel Brothers dbrothers@usgs.gov U.S. Geological Survey |
Darrell Kaufman darrell.kaufman@nau.edu Northern Arizona University |
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Reconnaissance Implies a Potentially Complete Record of Holocene Earthquakes in Esther Lake Above the Alaska-Aleutian Megathrust
Session
From Faults to Fjords: Earthquake Evidence in Terrestrial and Subaqueous Environments