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Uplift and subsidence reveal a nonpersistent megathrust rupture boundary (Sitkinak Island, Alaska)
Author(s) -
Briggs Richard W.,
Engelhart Simon E.,
Nelson Alan R.,
Dura Tina,
Kemp Andrew C.,
Haeussler Peter J.,
Corbett D. Reide,
Angster Stephen J.,
Bradley LeeAnn
Publication year - 2014
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1002/2014gl059380
Subject(s) - geology , subsidence , boundary (topology) , seismology , oceanography , geomorphology , mathematical analysis , mathematics , structural basin
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, computerized tomography scans, and microfossil assemblages are consistent with rapid uplift circa 290–0, 520–300, and 1050–790 cal yr B.P. and subsidence in A.D. 1964 and circa 640–510 cal yr B.P. 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 A.D. 1788. The mixed uplift and subsidence record suggests that Sitkinak Island sits above a nonpersistent boundary near the southwestern limit of the A.D. 1964 M w 9.2 megathrust rupture.