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|Title:||Identifying the greatest earthquakes of the past 2000 years at the Nehalem River estuary, northern Oregon coast, USA||Authors:||Nelson, Alan R.
Hawkes, Andrea D.
Engelhart, Simon E.
Grant-Walter, Wendy C.
Horton, Benjamin Peter
|Keywords:||Social sciences::Geography||Issue Date:||2020||Source:||Nelson, A. R., Hawkes, A. D., Sawai, Y., Engelhart, S. E., Witter, R., Grant-Walter, W. C., . . . Horton, B. P. (2020). Identifying the greatest earthquakes of the past 2000 years at the Nehalem River estuary, northern Oregon coast, USA. Open Quaternary, 6(1), 2-. doi:10.5334/oq.70||Journal:||Open Quaternary||Abstract:||We infer a history of three great megathrust earthquakes during the past 2000 years at the Nehalem River estuary based on the lateral extent of sharp (≤3 mm) peat-mud stratigraphic contacts in cores and outcrops, coseismic subsidence as interpreted from fossil diatom assemblages and reconstructed with foraminiferal assemblages using a Bayesian transfer function, and regional correlation of 14C-modeled ages for the times of subsidence. A subsidence contact from 1700 CE (contact A), sometimes overlain by tsunami-deposited sand, can be traced over distances of 7 km. Contacts B and D, which record subsidence during two earlier megathrust earthquakes, are much less extensive but are traced across a 700-m by 270-m tidal marsh. Although some other Cascadia studies report evidence for an earthquake between contacts B and D, our lack of extensive evidence for such an earthquake may result from the complexities of preserving identifiable evidence of it in the rapidly shifting shoreline environments of the lower river and bay. Ages (95% intervals) and subsidence for contacts are: A, 1700 CE (1.1 ± 0.5 m); B, 942–764 cal a BP (0.7 ± 0.4 m and 1.0 m ± 0.4 m); and D, 1568–1361 cal a BP (1.0 m ± 0.4 m). Comparisons of contact subsidence and the degree of overlap of their modeled ages with ages for other Cascadia sites are consistent with megathrust ruptures many hundreds of kilometers long. But these data cannot conclusively distinguish among different types or lengths of ruptures recorded by the three great earthquake contacts at the Nehalem River estuary.||URI:||https://hdl.handle.net/10356/145241||ISSN:||2055-298X||DOI:||10.5334/oq.70||Rights:||© 2020 The Author(s). This is an open-access article distributed under the terms of the Creative Commons Attribution 4.0 International License (CC-BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium,provided the original author and source are credited. See http://creativecommons.org/licenses/by/4.0/.||Fulltext Permission:||open||Fulltext Availability:||With Fulltext|
|Appears in Collections:||ASE Journal Articles|
Updated on May 20, 2022
Updated on May 20, 2022
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