@article {khan_relative_2022, title = {Relative sea-level change in South Florida during the past ~5000~years}, journal = {Global and Planetary Change}, volume = {216}, year = {2022}, month = {09/2022}, pages = {103902}, abstract = {A paucity of detailed relative sea-level (RSL) reconstructions from low latitudes hinders efforts to understand the global, regional, and local processes that cause RSL change. We reconstruct RSL change during the past ~5~ka using cores of mangrove peat at two sites (Snipe Key and Swan Key) in the Florida Keys. Remote sensing and field surveys established the relationship between peat-forming mangroves and tidal elevation in South Florida. Core chronologies are developed from age-depth models applied to 72 radiocarbon dates (39 mangrove wood macrofossils and 33 fine-fraction bulk peat). RSL rose 3.7~m at Snipe Key and 5.0~m at Swan Key in the past 5~ka, with both sites recording the fastest century-scale rate of RSL rise since ~1900~CE (~2.1~mm/a). We demonstrate that it is feasible to produce near-continuous reconstructions of RSL from mangrove peat in regions with a microtidal regime and accommodation space created by millennial-scale RSL rise. Decomposition of RSL trends from a network of reconstructions across South Florida using a spatio-temporal model suggests that Snipe Key was representative of regional RSL trends, but Swan Key was influenced by an additional local-scale process acting over at least the past five millennia. Geotechnical analysis of modern and buried mangrove peat indicates that sediment compaction is not the local-scale process responsible for the exaggerated RSL rise at Swan Key. The substantial difference in RSL between two nearby sites highlights the critical need for within-region replication of RSL reconstructions to avoid misattribution of sea-level trends, which could also have implications for geophysical modeling studies using RSL data for model tuning and validation.}, keywords = {Holocene, mangrove, Proxy reconstruction, Reproducibility, sea level}, issn = {0921-8181}, doi = {10.1016/j.gloplacha.2022.103902}, url = {https://www.sciencedirect.com/science/article/pii/S0921818122001692}, author = {Khan, Nicole S. and Ashe, Erica and Moyer, Ryan P. and Kemp, Andrew C. and Engelhart, Simon E. and Brain, Matthew J. and Toth, Lauren T. and Chappel, Amanda and Christie, Margaret and Kopp, Robert E. and Horton, Benjamin P.} } @article {2929, title = {A maximum rupture model for the central and southern Cascadia subduction zone{\textemdash}reassessing ages for coastal evidence of megathrust earthquakes and tsunamis}, journal = {Quaternary Science Reviews}, volume = {261}, year = {2021}, month = {Jan-06-2021}, pages = {106922}, abstract = {A new history of great earthquakes (and their tsunamis) for the central and southern Cascadia subduction zone shows more frequent (17 in the past 6700 yr) megathrust ruptures than previous coastal chronologies. The history is based on along-strike correlations of Bayesian age models derived from evaluation of 554 radiocarbon ages that date earthquake evidence at 14 coastal sites. We reconstruct a history that accounts for all dated stratigraphic evidence with the fewest possible ruptures by evaluating the sequence of age models for earthquake or tsunami contacts at each site, comparing the degree of temporal overlap of correlated site age models, considering evidence for closely spaced earthquakes at four sites, and hypothesizing only maximum-length megathrust ruptures. For the past 6700 yr, recurrence for all earthquakes is 370e420 yr. But correlations suggest that ruptures at-1.5 ka and-1.1 ka were of limited extent (<400 km). If so, post-3-ka recurrence for ruptures extending throughout central and southern Cascadia is 510e540 yr. But the range in the times between earthquakes is large: two instances may be-50 yr, whereas the longest are-550 and-850 yr. The closely spaced ruptures about 1.6 ka may illustrate a pattern common at subduction zones of a long gap ending with a great earthquake rupturing much of the subduction zone, shortly followed by a rupture of more limited extent. The ruptures of limited extent support the continued inclusion of magnitude-8 earthquakes, with longer ruptures near magnitude 9, in assessments of seismic hazard in the region. }, issn = {02773791}, doi = {10.1016/j.quascirev.2021.106922}, url = {https://apps.webofknowledge.com/InboundService.do?product=WOS\&Func=Frame\&DestFail=http\%3A\%2F\%2Fwww.webofknowledge.com\&SrcApp=search\&SrcAuth=Alerting\&SID=6DMZZppDlBSzMpeHDG2\&customersID=Alerting\&mode=FullRecord\&IsProductCode=Yes\&AlertId=4d48b20a-7d27-4fa2-}, author = {Nelson, Alan R. and DuRoss, Christopher B. and Witter, Robert C. and Kelsey, Harvey M. and Engelhart, Simon E. and Mahan, Shannon A. and Gray, Harrison J. and Hawkes, Andrea D. and Horton, Benjamin P. and Padgett, Jason S.} } @article {2776, title = {Identifying the Greatest Earthquakes of the Past 2000 Years at the Nehalem River Estuary, Northern Oregon Coast, USA}, journal = {Open Quaternary}, volume = {6}, year = {2020}, month = {Feb-01-2021}, 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 {\textpm} 0.5 m); B, 942{\textendash}764 cal a BP (0.7 {\textpm} 0.4 m and 1.0 m {\textpm} 0.4 m); and D, 1568{\textendash}1361 cal a BP (1.0 m {\textpm} 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.}, keywords = {Bayesian transfer function, Cascadia subduction zone, Coseismic subsidence, earthquake hazards, Paleoseismology, salt-marsh stratigraphy, Sea-level changes, tidal foraminifera and diatoms}, doi = {10.5334/oq.70}, url = {http://www.openquaternary.com/articles/10.5334/oq.70/}, author = {Nelson, Alan R. and Hawkes, Andrea D. and Sawai, Yuki and Engelhart, Simon E. and Witter, Rob and Grant-Walter, Wendy C. and Bradley, Lee-Ann and Dura, Tina and Cahill, Niamh and Horton, Ben} } @article { ISI:000481723500018, title = {The application of delta C-13, TOC and C/N geochemistry of mangrove sediments to reconstruct Holocene paleoenvironments and relative sea levels, Puerto Rico}, journal = {MARINE GEOLOGY}, volume = {415}, year = {2019}, month = {SEP}, pages = {105963}, abstract = {We assessed the use of delta C-13, TOC and C/N values of bulk sedimentary organic matter (OM) to reconstruct paleoenvironmental and relative sea-level change from mangrove environments in Puerto Rico. The modern distribution of delta C-13, TOC and C/N values was described from 63 vegetation and 59 surface sediment samples collected from three sites containing basin and riverine mangrove stands, and was compared to microfossil (foraminiferal and thecamoebian) assemblages. Four vertically-zoned environments were identified: tidal flat (delta C-13: -18.6 +/- 2.8 parts per thousand; TOC: 10.2 +/- 5.7\%; C/N: 12.7 +/- 3.1), mangrove (delta C-13: -26.4 +/- 1.0 parts per thousand; TOC: 33.9 +/- 13.4\%; C/N: 24.3 +/- 6.2), brackish transition (delta C-13: -28.8 +/- 0.7 parts per thousand; TOC: 40.8 +/- 11.7\%; C/N: 21.7 +/- 3.7), and freshwater swamp (delta C-13: -28.4 +/- 0.4 parts per thousand; TOC: 42.8 +/- 4.8\%; C/N: 17.0 +/- 1.1). These environments had distinct delta C-13, TOC and C/N values, with the exception of the brackish transition and freshwater swamp zones that were difficult to distinguish on a geochemical basis alone. The foraminiferal assemblages were complicated by a group that did not show a relationship to elevation due to the presence of calcareous foraminifera occurring above mean higher high water (MHHW), likely resulting from washover or transport by storms. However, the ratio of foraminifera to thecamoebians (F/T) along with delta C-13, TOC and C/N values refines the distinction between brackish and freshwater environments. Using linear discriminant analysis, we applied the delta C-13, TOC, C/N and F/T distributions to a 1.7 m core containing a continuous sequence of Rhizophora mangle peat, which began accumulating at similar to 1650-1930 CE. Together, microfossils, delta C-13, TOC, and C/N values, and the core chronology from Cs-137 and radiocarbon dating revealed that sediments in the core likely accumulated in response to anthropogenic sediment delivery, making it unsuitable for relative sea-level reconstruction. We caution that in the absence of detailed litho-, bio-, chemo-, or chrono-stratigraphic analyses as presented here, care should be taken in interpreting sea-level histories derived from single dates on mangrove peats.}, issn = {0025-3227}, doi = {10.1016/j.margeo.2019.105963}, author = {Khan, Nicole S. and Vane, Christopher H. and Engelhart, Simon E. and Kendrick, Chris and Horton, Benjamin P.} } @article {2775, title = {Evidence for frequent, large tsunamis spanning locked and creeping parts of the Aleutian megathrust}, journal = {GSA Bulletin}, volume = {131}, year = {2019}, month = {Jan-05-2019}, pages = {707 - 729}, abstract = {At the eastern end of the 1957 Andreanof Islands, Alaska, USA, moment magnitude 8.6 earthquake rupture, Driftwood Bay (Umnak Island) and Stardust Bay (Sedanka Island) lie along presently locked and creeping parts of the Aleutian megathrust, respectively, based on satellite geodesy onshore. Both bays, located 200 km apart, face the Aleutian trench and harbor coastal evidence for tsunami inundation in 1957. Here we describe the evidence at Driftwood Bay, including eight sheets of landward-fining, normally-graded marine sand that extend up to 375 m inland and 23 m above mean tide level. Drift logs that corroborate historical accounts of 1957 tsunami runup on Umnak Island{\textquoteright}s Pacific coast overlie the youngest sand sheet, which 137Cs activity shows was deposited in the decade before 1963. The older sand sheets probably record tsunamis prior to 1957 because an emergent coastal terrace lacks evidence for storm-wave erosion and overwash since ca. 2 ka. Comparisons of the Driftwood Bay and Stardust Bay tsunami histories suggest that at least twice in the past 1700 years inundation occurred at one site but not the other. In contrast, Bayesian age-depth modeling suggests that the two bays may record five tsunamis like the 1957 tsunami, generated by earthquake ruptures that spanned the presently locked and creeping parts of the Aleutian megathrust. However, serial tsunamis occurring within days to centuries cannot be precluded. Our findings imply 164{\textendash}257-year recurrence intervals for large eastern Aleutian tsunamis and challenge the notion that creeping parts of the megathrust, inferred from geodesy onshore, pose lower earthquake and tsunami hazards than locked areas.}, issn = {0016-7606}, doi = {10.1130/B32031.110.1130/2018296}, url = {https://pubs.geoscienceworld.org/gsa/gsabulletin/article/131/5-6/707/566656/Evidence-for-frequent-large-tsunamis-spanning}, author = {Witter, Rob and Briggs, Rich and Engelhart, Simon E. and Gelfenbaum, Guy and Koehler, Rich D. and Nelson, Alan and Selle, SeanPaul La and Corbett, Reide and Wallace, Kristi} } @article {2774, title = {Testing the Utility of Geochemical Proxies to Reconstruct Holocene Coastal Environments and Relative Sea Level: A Case Study from Hungry Bay, Bermuda}, journal = {Open Quaternary}, volume = {5}, year = {2019}, month = {May-02-2019}, abstract = {On low-lying, tropical and sub-tropical coastlines freshwater marshes may be replaced by salt-tolerant mangroves in response to relative sea-level rise. Pollen analysis of radiocarbon-dated sediment cores showed that such a change occurred in Hungry Bay, Bermuda during the late Holocene. This well-established paleoenvironmental trajectory provides an opportunity to explore if geochemical proxies (bulk-sediment δ13C and Rock-Eval pyrolysis) can reconstruct known environmental changes and relative sea level. We characterized surface sediment from depositional environments in Bermuda (freshwater wetlands, saline mangroves, and wrack composed of Sargassum natans macroalgae) using geochemical measurements and demonstrate that a multi-proxy approach can objectively distinguish among these environments. However, application of these techniques to the transgressive sediment succession beneath Hungry Bay suggests that freshwater peat and mangrove peat cannot be reliably distinguished in the sedimentary record, possibly because of post-depositional convergence of geochemical characteristics on decadal to multi-century timescales and/or the relatively small number of modern samples analyzed. Sediment that includes substantial contributions from Sargassum is readily identified by geochemistry, but has a limited spatial extent. Radiocarbon dating indicates that beginning at {\textendash}700 CE, episodic marine incursions into Hungry Bay (e.g., during storms) carried Sargassum that accumulated as wrack and thickened through repeated depositional events until ~300 CE. It took a further ~550 years for a peat-forming mangrove community to colonize Hungry Bay, which then accumulated sediment rapidly, but likely out of equilibrium with regional relative sea-level rise.}, keywords = {mangrove, radiocarbon, Rock-Eval pyrolysis, Sargassum, δ13C}, doi = {10.5334/oq.49}, url = {http://www.openquaternary.com/articles/10.5334/oq.49/}, author = {Kemp, Andrew C. and Vane, Christopher H. and Khan, Nicole S. and Ellison, Joanna C. and Engelhart, Simon E. and Horton, Benjamin P. and Nikitina, Daria and Smith, Struan R. and Rodrigues, Lisa J. and Moyer, Ryan P.} } @article {2773, title = {Reconstructing Common Era relative sea-level change on the Gulf Coast of Florida}, journal = {Marine Geology}, volume = {390}, year = {2017}, month = {Jan-08-2017}, pages = {254 - 269}, abstract = {To address a paucity of Common Era data in the Gulf of Mexico, we reconstructed ~ 1.1 m of relative sea-level (RSL) rise over the past ~ 2000 years at Little Manatee River (Gulf Coast of Florida, USA). We applied a regional-scale foraminiferal transfer function to fossil assemblages preserved in a core of salt-marsh peat and organic silt that was dated using radiocarbon and recognition of pollution, 137Cs and pollen chronohorizons. Our proxy reconstruction was combined with tide-gauge data from four nearby sites spanning 1913{\textendash}2014 CE. Application of an Errors-in-Variables Integrated Gaussian Process (EIV-IGP) model to the combined proxy and instrumental dataset demonstrates that RSL fell from ~ 350 to 100 BCE, before rising continuously to present. This initial RSL fall was likely the result of local-scale processes (e.g., silting up of a tidal flat or shallow sub-tidal shoal) as salt-marsh development at the site began. Since ~ 0 CE, we consider the reconstruction to be representative of regional-scale RSL trends. We removed a linear rate of 0.3 mm/yr from the RSL record using the EIV-IGP model to estimate climate-driven sea-level trends and to facilitate comparison among sites. This analysis demonstrates that since ~ 0 CE sea level did not deviate significantly from zero until accelerating continuously from ~ 1500 CE to present. Sea level was rising at 1.33 mm/yr in 1900 CE and accelerated until 2014 CE when a rate of 2.02 mm/yr was attained, which is the fastest, century-scale trend in the ~ 2000-year record. Comparison to existing reconstructions from the Gulf coast of Louisiana and the Atlantic coast of northern Florida reveal similar sea-level histories at all three sites. We explored the influence of compaction and fluvial processes on our reconstruction and concluded that compaction was likely insignificant. Fluvial processes were also likely insignificant, but further proxy evidence is needed to fully test this hypothesis. Our results indicate that no significant Common Era sea-level changes took place on the Gulf and southeastern Atlantic U.S. coasts until the onset of modern sea-level rise in the late 19th century.}, issn = {00253227}, doi = {10.1016/j.margeo.2017.07.001}, url = {https://linkinghub.elsevier.com/retrieve/pii/S0025322716303346}, author = {Gerlach, Matthew J. and Engelhart, Simon E. and Kemp, Andrew C. and Moyer, Ryan P. and Smoak, Joseph M. and Bernhardt, Christopher E. and Cahill, Niamh} } @article {2597, title = {Differences in coastal subsidence in southern Oregon (USA) during at least six prehistoric megathrust earthquakes}, journal = {Quaternary Science Reviews}, volume = {142}, year = {2016}, month = {Jan-06-2016}, pages = {143 - 163}, abstract = {Stratigraphic, sedimentologic (including CT 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 megathrust earthquakes at the Cascadia subduction zone. Data for one contact are insufficient to infer whether or not it records a great earthquake{\textemdash}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 {\textpm}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{\textquoteright}s megathrust earthquake ruptures have been heterogeneous over the past 3500 years.}, keywords = {Cascadia subduction zone, Coseismic subsidence, Megathrust earthquakes, Paleoseismology, Salt-marsh foraminifera, Sea-level change, Transfer functions}, issn = {02773791}, doi = {10.1016/j.quascirev.2016.04.017}, url = {https://doi.org/10.1016/j.quascirev.2016.04.017}, author = {Milker, Yvonne and Nelson, Alan R. and Horton, Benjamin P. and Engelhart, Simon E. and Bradley, Lee-Ann and Witter, Robert C.} } @article {2536, title = {Unusually large tsunamis frequent a currently creeping part of the Aleutian megathrust}, journal = {Geophysical Research Letters}, volume = {43}, year = {2016}, month = {Apr-01-2017}, pages = {76 - 84}, abstract = {Current models used to assess earthquake and tsunami hazards are inadequate where creep dominates a subduction megathrust. Here we report geological evidence for large tsunamis, occurring on average every 300{\textendash}340 years, near the source areas of the 1946 and 1957 Aleutian tsunamis. These areas bookend a postulated seismic gap over 200 km long where modern geodetic measurements indicate that the megathrust is currently creeping. At Sedanka Island, evidence for large tsunamis includes six sand sheets that blanket a lowland facing the Pacific Ocean, rise to 15 m above mean sea level, contain marine diatoms, cap terraces, adjoin evidence for scour, and date from the past 1700 years. The youngest sheet and modern drift logs found as far as 800 m inland and >18 m elevation likely record the 1957 tsunami. Previously unrecognized tsunami sources coexist with a presently creeping megathrust along this part of the Aleutian Subduction Zone.}, doi = {10.1002/2015GL066083}, url = {http://doi.wiley.com/10.1002/2015GL066083}, author = {Witter, Robert C. and Carver, Gary A. and Briggs, Richard W. and Gelfenbaum, Guy and Koehler, Richard D. and La Selle, SeanPaul and Bender, Adrian M. and Engelhart, Simon E. and Hemphill-Haley, Eileen and Hill, Troy D.} } @article {25, title = {Beach ridges as paleoseismic indicators of abrupt coastal subsidence during subduction zone earthquakes, and implications for Alaska-Aleutian subduction zone paleoseismology, southeast coast of the Kenai Peninsula, Alaska}, journal = {Megathrust Earthquakes and Sea-level Change: a Tribute to George Plafker}, volume = {113}, year = {2015}, pages = {147-158}, abstract = {The Kenai section of the eastern Alaska-Aleutian subduction zone straddles two areas of high slip in the 1964 great Alaska earthquake and is the least studied of the three megathrust segments (Kodiak, Kenai, Prince William Sound) that ruptured in 1964. Investigation of two coastal sites in the eastern part of the Kenai segment, on the southeast coast of the Kenai Peninsula, identified evidence for two subduction zone earthquakes that predate the 1964 earthquake. Both coastal sites provide paleoseismic data through inferred coseismic subsidence of wetlands and associated subsidence-induced erosion of beach ridges. At Verdant Cove, paleo-beach ridges record the paleoseismic history; whereas at Quicksand Cove, buried soils in drowned coastal wetlands are the primary indicators of paleoearthquake occurrence and age. The timing of submergence and death of trees mark the oldest earthquake at Verdant Cove that is consistent with the age of a well documented \~{}900-year-ago subduction zone earthquake that ruptured the Prince William Sound segment of the megathrust to the east and the Kodiak segment to the west. Soils buried within the last 400{\textendash}450 years mark the penultimate earthquake on the southeast coast of the Kenai Peninsula. The penultimate earthquake probably occurred before AD 1840 from its absence in Russian historical accounts. The penultimate subduction zone earthquake on the Kenai segment did not rupture in conjunction with the Prince William Sound to the northeast. Therefore the Kenai segment, which is presently creeping, can rupture independently of the adjacent Prince William Sound segment that is presently locked.}, issn = {0277-3791}, doi = {10.1016/j.quascirev.2015.01.006}, url = {http://www.sciencedirect.com/science/article/pii/S0277379115000220}, author = {Kelsey, Harvey M. and Witter, Robert C. and Engelhart, Simon E. and Briggs, Richard and Nelson, Alan and Haeussler, Peter and Corbett, D. Reide} } @article {2596, title = {A sea-level database for the Pacific coast of central North America}, journal = {Quaternary Science Reviews}, volume = {113}, year = {2015}, month = {Jan-04-2015}, pages = {78 - 92}, abstract = {A database of published and new relative sea-level (RSL) data for the past 16 ka constrains the sea-level histories of the Pacific coast of central North America (southern British Columbia to central California). Our reevaluation of the stratigraphic context and radiocarbon age of sea-level indicators from geological and archaeological investigations yields 600 sea-level index points and 241 sea-level limiting points. We subdivided the database into 12 regions based on the availability of data, tectonic setting, and distance from the former Cordilleran ice sheet. Most index (95\%) and limiting points (54\%) are <7 ka; older data come mainly from British Columbia and San Francisco Bay. The stratigraphic position of points was used as a first-order assessment of compaction. Formerly glaciated areas show variable RSL change; where data are present, highstands of RSL occur immediately post-deglaciation and in the mid to late Holocene. Sites at the periphery and distant to formerly glaciated areas demonstrate a continuous rise in RSL with a decreasing rate through time due to the collapse of the peripheral forebulge and the reduction in meltwater input during deglaciation. Late Holocene RSL change varies spatially from falling at 0.7 {\textpm} 0.8 mm a-1 in southern British Columbia to rising at 1.5 {\textpm} 0.3 mm a-1 in California. The different sea-level histories are an ongoing isostatic response to deglaciation of the Cordilleran and Laurentide Ice Sheets.}, keywords = {Cascadia subduction zone, Glacial isostatic adjustment, Holocene, Pacific North America, Sea-level database}, issn = {02773791}, doi = {10.1016/j.quascirev.2014.12.001}, url = {https://doi.org/10.1016/j.quascirev.2014.12.001}, author = {Engelhart, Simon E. and Vacchi, Matteo and Horton, Benjamin P. and Nelson, Alan R. and Kopp, Robert E.} } @article {2593, title = {Uplift and subsidence reveal a nonpersistent megathrust rupture boundary (Sitkinak Island, Alaska)}, journal = {Geophysical Research Letters}, volume = {41}, year = {2014}, month = {Apr-04-2015}, pages = {2289 - 2296}, 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, 137Cs profiles, computerized tomography scans, and microfossil assemblages are consistent with rapid uplift circa 290{\textendash}0, 520{\textendash}300, and 1050{\textendash}790 cal yr B.P. and subsidence in A.D. 1964 and circa 640{\textendash}510 cal yr B.P. Radiocarbon, 137Cs, and 210Pb 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 Mw 9.2 megathrust rupture.}, doi = {10.1002/2014GL059380}, url = {http://doi.wiley.com/10.1002/2014GL059380}, author = {Briggs, Richard W. and Engelhart, Simon E. and Nelson, Alan R. and Dura, Tina and Kemp, Andrew C. and Haeussler, Peter J. and Corbett, D. Reide and Angster, Stephen J. and Bradley, Lee-Ann} } @article {2590, title = {Heterogeneous rupture in the great Cascadia earthquake of 1700 inferred from coastal subsidence estimates}, journal = {Journal of Geophysical Research: Solid Earth}, volume = {118}, year = {2013}, month = {Jan-05-2013}, pages = {2460 - 2473}, abstract = {Past earthquake rupture models used to explain paleoseismic estimates of coastal subsidence during the great A.D. 1700 Cascadia earthquake have assumed a uniform slip distribution along the megathrust. Here we infer heterogeneous slip for the Cascadia margin in A.D. 1700 that is analogous to slip distributions during instrumentally recorded great subduction earthquakes worldwide. The assumption of uniform distribution in previous rupture models was due partly to the large uncertainties of then available paleoseismic data used to constrain the models. In this work, we use more precise estimates of subsidence in 1700 from detailed tidal microfossil studies. We develop a 3-D elastic dislocation model that allows the slip to vary both along strike and in the dip direction. Despite uncertainties in the updip and downdip slip extensions, the more precise subsidence estimates are best explained by a model with along-strike slip heterogeneity, with multiple patches of high-moment release separated by areas of low-moment release. For example, in A.D. 1700, there was very little slip near Alsea Bay, Oregon (~44.4{\textdegree}N), an area that coincides with a segment boundary previously suggested on the basis of gravity anomalies. A probable subducting seamount in this area may be responsible for impeding rupture during great earthquakes. Our results highlight the need for more precise, high-quality estimates of subsidence or uplift during prehistoric earthquakes from the coasts of southern British Columbia, northern Washington (north of 47{\textdegree}N), southernmost Oregon, and northern California (south of 43{\textdegree}N), where slip distributions of prehistoric earthquakes are poorly constrained.}, doi = {10.1002/jgrb.50101}, url = {http://doi.wiley.com/10.1002/jgrb.50101}, author = {Wang, Pei-Ling and Engelhart, Simon E. and Wang, Kelin and Hawkes, Andrea D. and Horton, Benjamin P. and Nelson, Alan R. and Witter, Robert C.} } @article {98, title = {Sea-level change during the last 2500 years in New Jersey, USA}, journal = {Quaternary Science Reviews}, volume = {81}, year = {2013}, pages = {90-104}, abstract = {Relative sea-level changes during the last \~{}2500 years in New Jersey, USA were reconstructed to test if late Holocene sea level was stable or included persistent and distinctive phases of variability. Foraminifera and bulk-sediment δ13C values were combined to reconstruct paleomarsh elevation with decimeter precision from sequences of salt-marsh sediment at two sites using a multi-proxy approach. The additional paleoenvironmental information provided by bulk-sediment δ13C values reduced vertical uncertainty in the sea-level reconstruction by about one third of that estimated from foraminifera alone using a transfer function. The history of sediment deposition was constrained by a composite chronology. An age{\textendash}depth model developed for each core enabled reconstruction of sea level with multi-decadal resolution. Following correction for land-level change (1.4 mm/yr), four successive and sustained (multi-centennial) sea-level trends were objectively identified and quantified (95\% confidence interval) using error-in-variables change point analysis to account for age and sea-level uncertainties. From at least 500 BC to 250 AD, sea-level fell at 0.11 mm/yr. The second period saw sea-level rise at 0.62 mm/yr from 250 AD to 733 AD. Between 733 AD and 1850 AD, sea level fell at 0.12 mm/yr. The reconstructed rate of sea-level rise since \~{}1850 AD was 3.1 mm/yr and represents the most rapid period of change for at least 2500 years. This trend began between 1830 AD and 1873 AD. Since this change point, reconstructed sea-level rise is in agreement with regional tide-gauge records and exceeds the global average estimate for the 20th century. These positive and negative departures from background rates demonstrate that the late Holocene sea level was not stable in New Jersey.}, issn = {0277-3791}, doi = {10.1016/j.quascirev.2013.09.024}, url = {http://www.sciencedirect.com/science/article/pii/S0277379113003740}, author = {Kemp, Andrew C. and Horton, Benjamin P. and Vane, Christopher H. and Bernhardt, Christopher E. and Corbett, D. Reide and Engelhart, Simon E. and Anisfeld, Shimon C. and Parnell, Andrew C. and Cahill, Niamh} } @article {277, title = {Spatial variability of late Holocene and 20th century sea-level rise along the Atlantic coast of the United States}, journal = {Geology}, volume = {37}, year = {2009}, note = {id: 1872Y}, pages = {1115-1118}, issn = {0091-7613 1943-2682}, doi = {10.1130/G30360A.1}, author = {Engelhart, Simon E. and Horton, Benjamin P. and Douglas, Bruce C. and Peltier, W. Richard and T{\"o}rnqvist, Torbj{\"o}rn E.} }