Differences in coastal subsidence in southern Oregon (USA) during at least six prehistoric megathrust earthquakes

QUATERNARY SCIENCE REVIEWS

卷:142

Article

Milker, Yvonne^1,3  Nelson, Alan R.²  Horton, Benjamin P.^3,4,5,6  Engelhart, Simon E.⁷  Bradley, Lee-Ann²  Witter, Robert C.⁸ 

[1] Univ Leipzig, Inst Geol & Geophys, Talstr 35, D-04103 Leipzig, Germany

[2] US Geol Survey, Geol Hazards Sci Ctr, Golden, CO 80401 USA

[3] Rutgers State Univ, Dept Marine & Coastal Sci, Sea Level Res, 71 Dudley Rd, New Brunswick, NJ 08901 USA

[4] Rutgers State Univ, Inst Earth Ocean & Atmospher Sci, 71 Dudley Rd, New Brunswick, NJ 08901 USA

[5] Nanyang Technol Univ, Earth Observ Singapore, Singapore 639798, Singapore

[6] Nanyang Technol Univ, Asian Sch Environm, Singapore 639798, Singapore

[7] Univ Rhode Isl, Dept Geosci, Woodward Hall,9 East Alumni Ave, Kingston, RI 02881 USA

[8] US Geol Survey, Alaska Sci Ctr, 4210 Univ Dr, Anchorage, AK 99508 USA

关键词: Salt-marsh foraminifera;    Cascadia subduction zone;    Transfer functions;    Coseismic subsidence;    Megathrust earthquakes;    Paleoseismology;    Sea-level change;   

DOI  :  10.1016/j.quascirev.2016.04.017

来源: Elsevier

【 摘 要 】

Stratigraphic, sedimentologic (including Cr 3D X-ray tomography scans), foraminiferal, and radiocarbon analyses show that at least six of seven abrupt peat-to-mud contacts in cores from a tidal marsh at Talbot Creek (South Slough, Coos Bay), record sudden subsidence (relative sea-level rise) during great mega-thrust earthquakes at the Cascadia subduction zone. Data for one contact are insufficient to infer whether or not it records a great earthquake it may also have formed through local, non-seismic, hydrographic processes. To estimate the amount of subsidence marked by each contact, we expanded a previous regional modern foraminiferal dataset to 174 samples from six Oregon estuaries. Using a transfer function derived from the new dataset, estimates of coseismic subsidence across the six earthquake contacts vary from 0.31 m to 0.75 m. Comparison of subsidence estimates for three contacts in adjacent cores shows within-site differences of <= 0.10 m, about half the +/- 0.22 m error, although some estimates may be minimums due to uncertain ecological preferences for Balticammina pseudomacrescens in brackish environments and almost monospecific assemblages of Miliammina fusca on tidal flats. We also account for the influence of taphonomic processes, such as infiltration of mud with mixed foraminiferal assemblages into peat, on subsidence estimates. Comparisons of our subsidence estimates with values for correlative-contacts at other Oregon sites suggest that some of our estimates are minimums and that Cascadia's megathrust earthquake ruptures have been heterogeneous over the past 3500 years. (C) 2016 Elsevier Ltd. All rights reserved.

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