Data Release for Luminescence: Paleoseismic liquefaction associated with Holocene earthquakes on the Wallula Fault zone, Southeast Washington, USA
Dates
Publication Date
2022-07-08
Time Period
2020
Citation
Mahan, S.A., Krolczyk, E.T., and Angster, S.J., 2022, Data Release for Luminescence: Paleoseismic liquefaction associated with Holocene earthquakes on the Wallula Fault zone, Southeast Washington, USA: U.S. Geological Survey data release, https://doi.org/10.5066/P94RCR1Z.
Summary
Observations of widespread liquefaction and stratigraphic and structural relationships in a trench across an ambiguous scarp are used to constrain the timing of Holocene earthquakes on the northwest-striking Wallula fault zone in southeast Washington and Oregon. Additional observations and age constraints from OSL analysis of samples collected from large-scale liquefaction features that crosscut the Mount St Helens J tephra (13.8-13.7 ka) exposed at a nearby outcrop suggest up to 3 Holocene regional liquefaction events, any of which were likely triggered by seismic shaking sourced from either the Wallula fault and/or faults of the Yakima fold and thrust belt. Our observations provide plausible evidence supporting that the scarp formed [...]
Summary
Observations of widespread liquefaction and stratigraphic and structural relationships in a trench across an ambiguous scarp are used to constrain the timing of Holocene earthquakes on the northwest-striking Wallula fault zone in southeast Washington and Oregon. Additional observations and age constraints from OSL analysis of samples collected from large-scale liquefaction features that crosscut the Mount St Helens J tephra (13.8-13.7 ka) exposed at a nearby outcrop suggest up to 3 Holocene regional liquefaction events, any of which were likely triggered by seismic shaking sourced from either the Wallula fault and/or faults of the Yakima fold and thrust belt. Our observations provide plausible evidence supporting that the scarp formed during the M6 1936 Milton-Freewater earthquake. In addition, stratigraphic relationships observed in this study indicate that the end of the Missoula Floods in the southeast Washington region occurred sometime between 13.8–13.5 cal. k.y. B.P., approximately 1,000 years earlier than prior estimates.
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Wallula_Metadata.xml Original FGDC Metadata
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Wallula_Data.csv
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Wallula_Data_Dictionary.csv
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Purpose
In this study, we investigate the origin of the Wallula scarp and occurrence of liquefaction within late Pleistocene and Holocene deposits exposed in a paleoseismic trench and road cut to address questions related to the timing and cause of liquefaction. Our observations and geochronological data indicate that the liquefaction features observed at both sites were seismically induced and suggest up to four Holocene seismically induced liquefaction events; with one liquefaction event likely associated with partial-length rupture of the Wallula fault zone, possibly the 1936 Milton-Freewater earthquake.
