Uplift and subsidence reveal a nonpersistent megathrust rupture boundary (Sitkinak Island, Alaska)

Richard W. Briggs; Simon E. Engelhart; Alan R. Nelson; Tina Dura; Andrew C. Kemp; Peter J. Haeussler; D. Reide Corbett; Stephen J. Angster; Lee-Ann Bradley

doi:10.1002/2014gl059380

USGS · 70095612

Uplift and subsidence reveal a nonpersistent megathrust rupture boundary (Sitkinak Island, Alaska)

Richard W. Briggs·Simon E. Engelhart·Alan R. Nelson·Tina Dura·Andrew C. Kemp·Peter J. Haeussler·D. Reide Corbett·Stephen J. Angster·Lee-Ann Bradley

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Abstract

We report stratigraphic evidence of land-level change and tsunami inundation along the Alaska-Aleutian megathrust during prehistoric and historical earthquakes west of Kodiak Island. On Sitkinak Island, cores and tidal outcrops fringing a lagoon reveal five sharp lithologic contacts that record coseismic land-level change. Radiocarbon dates, 137 Cs profiles, CT scans, and microfossil assemblages are consistent with rapid uplift ca. 290-0, 520-300, and 1050-790 cal yr BP, and subsidence in AD 1964 and ca. 640-510 cal yr BP. Radiocarbon, 137 Cs, and 210 Pb ages bracketing a sand bed traced 1.5 km inland and evidence for sudden uplift are consistent with Russian accounts of an earthquake and tsunami in AD 1788. The mixed uplift and subsidence record suggests that Sitkinak Island sits above a non-persistent boundary near the southwestern limit of the AD 1964 Mw 9.2 megathrust rupture.

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Geophysical Research Letters Article

Source-reported bounding extent: 56.2112° to 56.8512° latitude; -154.3109° to -153.6709° longitude. This indicates report coverage, not an exact sampling location. View area on OpenStreetMap.

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Richard W. Briggs, Simon E. Engelhart, Alan R. Nelson, Tina Dura, Andrew C. Kemp, Peter J. Haeussler, D. Reide Corbett, Stephen J. Angster, Lee-Ann Bradley. 2014-04-14. Uplift and subsidence reveal a nonpersistent megathrust rupture boundary (Sitkinak Island, Alaska). https://doi.org/10.1002/2014gl059380

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