89-14 Revising the Holocene Paleoseismological History of the Teton Fault: Seismic and Core-Based Evidence for Two Earthquakes Younger than ~5 ka

Session: Advancing Earthquake Geology and Surficial Deformation from Geologic Provinces to Political Entities through Multidisciplinary High-Resolution Data

Presenting Author:

Ryan Thigpen

Authors:

Thigpen, Ryan¹, McGlue, Michael M.², Woolery, Edward³, Dilworth, John⁴, Cortese, Callia⁵, Rasbold, Giliane Gessica⁶, Yeager, Kevin Michael⁷, Whitehead, Samuel⁸, Brown, Summer Jasmine⁹, Johnson, Sarah¹⁰, Portwood, Abigail¹¹

(1) University of Kentucky, Lexington, KY, USA, (2) University of Kentucky Earth and Environmental Sciences, Lexington, KY, USA, (3) University of Kentucky, Lexington, KY, USA, (4) University of Kentucky, Lexington, KY, USA, (5) University of Kentucky, Lexington, KY, USA, (6) Western Kentucky University, Bowling Green, KY, USA, (7) Old Dominion University, Ocean and Earth Sciences, Norfolk, VA, USA, (8) Old Dominion University, Norfolk, VA, USA, (9) University of Kentucky, Lexington, KY, USA, (10) University of Kentucky, Earth and Environmental Science, Lexington, KY, USA, (11) University of Kentucky, Lexington, KY, USA,

Abstract:

Paleoseismology studies of active faults reconstruct the timing, magnitude, and recurrence intervals of paleo-earthquakes and are critical for assessing the potential for future large earthquakes. On the seismically active Teton fault in northwestern Wyoming, multiple terrestrial trench studies spanning the length of the Teton Range identified three ground rupturing slip events at ~10 ka, ~8ka, and ~5 ka. Lacustrine studies of turbidites in piedmont lakes have augmented this record with events at ~9.1 ka, 11.6 ka, ~12.9 ka, and ~14.0 ka. Most notably, no earthquakes younger than ~5 ka were recognized. Although at least two younger events at ~4.5 ka (3.7-5.5 ka; 95% confidence interval) and ~2.5 ka (1.7-3.6 ka) have been proposed based on archeological investigations of liquefaction features on Jackson Lake, these events have not yet been independently confirmed.

Here, we present results from a dense seismic reflection survey of Jackson Lake culminating in the aquisition of a ~31 m continuous long deepwater sediment core in September 2023. Seismic mapping of >100 km of high-resolution CHIRP seismic reflection data yield 7 mass transport deposit (MTD) “groups” that include at least 5 spatially independent MTDs per group at the same instantaneous stratigraphic interval. This characteristic, known as the “synchronicity criterion”, suggests that these events occurred synchronously in response to a singular seismic or catastrophic event (e.g., major flooding). Age modeling of radiocarbon and tephra dates from the long core, which spans the last ~11.5 ka, indicates that three MTD groups overlap with three seismic events recognized in trench studies (~10, ~8, and ~5 ka). Integration of seismic and core data distinguishes three individual and substantial shaking events at ~8 ka, potentially indicating the main seismic event and major fore- and aftershocks. Two other MTD groups overlaps with seismically-derived turbidites in Jenny Lake at ~12 ka. Critically, another two other MTD groups recognized in our data yield modeled ages of ~3.4 ka and 2.1 ka, significantly younger than the ~5 ka event traditionally considered to be the last event seismic event on the Teton fault. Notably, both events have uncertainties that overlap with the youngest two events proposed from liquefaction studies of Jackson Lake. If confirmed, these data necessitate considerable revision to the Holocene paleoseismological record for the Teton fault.

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-10971

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