Sponsor
This research was supported by the U.S. Geological Survey (USGS), Department of the Interior, under USGS Award Number G16AP00142 to Portland State University, and G16AP00141 to the Oklahoma Geological Survey and Oklahoma University.
Published In
Bulletin of the Seismological Society of America
Document Type
Article
Publication Date
2-1-2020
Subjects
Geology -- Oklahoma -- Comanche County, Meers Fault (Okla.) -- Geomorphology, Paleoseismology -- Holocene
Abstract
The Meers fault (Oklahoma) is one of few seismogenic structures with evidence for Holocene surface rupture in the stable continental region of North America. The 37‐kilometer‐long southeast section of the full 54‐kilometer‐long Meers fault is interpreted to be Holocene active. The 17‐kilometer‐long northwest section is considered Quaternary active, but not Holocene active. We reevaluate surface expression and earthquake timing of the northwest Meers fault to improve seismic source characterization. We use airborne light detection and ranging and historical stereopaired aerial photos to evaluate the fault scarp and local fault‐zone geomorphology. In the northwest, complex surface deformation includes fault splays, subtle monoclinal warping, and a minor change in fault strike. We interpret that the along‐strike transition from surface faulting on the southeast Meers fault to surface folding on the northwest Meers fault occurs at the lithologic contact between Permian Post Oak conglomerate and Hennessey shale. We excavated a paleoseismic trench to evaluate the timing of surface‐deforming earthquakes on the northwest section of the fault. The excavation revealed weathered Permian Hennessey shale and an ∼1–2∼1–2‐meter‐thick veneer of Holocene alluvial deposits that were progressively deformed during two surface‐folding earthquakes likely related to blind fault rupture beneath the site. Repeated onlapping to overlapping stratigraphic sequences and associated unconformities are intimately related to folding events along the monocline. OxCal paleoearthquake age modeling indicates that earthquakes occurred 4704–3109 yr B.P. and 5955–4744 yr B.P., and that part of the northwest section of the Meers fault is Holocene active. We find the Holocene‐active section of the Meers fault should be lengthened 6.1 km to the northwest, to a total Holocene‐active fault length of 43 km. Empirical scaling relationships between surface rupture length and magnitude reveal that the fault could generate an MwMw 7.0 earthquake.
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DOI
10.1785/0120180148
Persistent Identifier
https://archives.pdx.edu/ds/psu/32609
Citation Details
Hornsby, K. T., Streig, A. R., Bennett, S. E., Chang, J. C., & Mahan, S. (2020). Neotectonic and Paleoseismic Analysis of the Northwest Extent of Holocene Surface Deformation along the Meers Fault, Oklahoma. Bulletin of the Seismological Society of America, 110(1), 49-66.
Description
© Seismological Society of America
This work was authored as part of the Contributor's official duties as an Employee of the United States Government and is therefore a work of the United States Government. In accordance with 17 U.S.C. 105, no copyright protection is available for such works under U.S. Law