Sedimentological Analysis of an Ancient Sand Sheet of Multiple Origins at Lynch Cove, Puget Sound, Washington

Jovanelly, Tamie J.; Moore, Adam D.

doi:10.2112/07-0892.1

Cited by 3 publications

(12 citation statements)

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“…Thorough work by Martin and Bourgeois (2012) at Lynch Cove ( Fig. 1C) led them to reinterpret sandy beds as liquefaction features rather than tsunami deposits, as had been concluded by Hemphill-Haley (1996) and Jovanelly and Moore (2009).…”

Section: Strong Shaking In the Seattle Fault Zonementioning

confidence: 75%

Diverse rupture modes for surface-deforming upper plate earthquakes in the southern Puget Lowland of Washington State

et al. 2014

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Earthquake prehistory of the southern Puget Lowland, in the north-south compressive regime of the migrating Cascadia forearc, refl ects diverse earthquake rupture modes with variable recurrence. Stratigraphy and Bayesian analyses of previously reported and new 14 C ages in trenches and cores along backthrust scarps in the Seattle fault zone restrict a large earthquake to 1040-910 cal yr B.P. (2σ), an interval that includes the time of the M 7-7.5 Restoration Point earthquake. A newly identifi ed surface-rupturing earthquake along the Waterman Point backthrust dates to 940-380 cal yr B.P., bringing the number of earthquakes in the Seattle fault zone in the past 3500 yr to 4 or 5. Whether scarps record earthquakes of moderate (M 5.5-6.0) or large (M 6.5-7.0) magnitude, backthrusts of the Seattle fault zone may slip during moderate to large earthquakes every few hundred years for periods of 1000-2000 yr, and then not slip for periods of at least several thousands of years. Four new fault scarp trenches in the Tacoma fault zone show evidence of late Holocene folding and faulting about the time of a large earthquake or earthquakes inferred from widespread coseismic subsidence ca. 1000 cal yr B.P.; 12 ages from 8 sites in the Tacoma fault zone limit the earthquakes to 1050-980 cal yr B.P. Evidence is too sparse to determine whether a large earthquake was closely predated or postdated by other earthquakes in the Tacoma basin, but the scarp of the Tacoma fault was formed by multiple earthquakes. In the northeast-striking Saddle Mountain deformation zone, along the western limit of the Seattle and Tacoma fault zones, analysis of previous ages limits earthquakes to 1200-310 cal yr B.P. The prehistory clarifi es earthquake clustering in the central Puget Lowland, but cannot resolve potential structural links among the three Holocene fault zones.

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Section: Strong Shaking In the Seattle Fault Zonementioning

confidence: 75%

Diverse rupture modes for surface-deforming upper plate earthquakes in the southern Puget Lowland of Washington State

et al. 2014

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“…, 2007); 2004 Phra Thong Island, Thailand (Jankaew et al. , 2008); 2006 Kuril Islands (MacInnes et al , 2009); 1998 Papua New Guinea (Gelfenbaum & Jaffe, 2003); 1992 Nicaragua (Higman & Bourgeois, 2008); Gorst, this study; Cultus Bay (Moore, 1994); Snohomish delta (Bourgeois & Johnson, 2001); Skokomish delta, this study; Issaquah Creek, this study; Lynch Cove (M), this study; Lynch Cove (J) (Jovanelly, 2006); New Madrid (Tuttle & Schweig, 1996). The deposit at Gorst was not traced to its inland extent and the average thickness therefore may be over‐estimated.…”

Section: Characteristics Of Tsunami Deposits and Vented Sedimentsmentioning

confidence: 84%

“…Vented sediments are documented in primarily deltaic settings around the lowland (Bourgeois & Johnson, 2001; Sherrod, 2001). A sediment deposit in Lynch Cove on Hood Canal previously was interpreted primarily as a tsunami deposit with local sand venting (Hemphill‐Haley, 1996; Jovanelly & Moore, 2009), but herein it is reinterpreted as being solely vented sediment.…”

Section: Puget Lowland Case Studymentioning

confidence: 96%

“…1998 Papua New Guinea tsunami, earthquake Mw 7·7 (Gelfenbaum & Jaffe, 2003); 1992 Nicaragua tsunami, earthquake Mw 7·7 (Higman & Bourgeois, 2008); 1997 Kamchatka tsunami, earthquake Mw 7·8; 2006 Kuril Island tsunami, earthquake Mw 8·3 (MacInnes et al. , 2009); Sediment unit from Lynch Cove, Washington – topography is on the top of mudflat deposits inferred to be the surface at the time of the event (Jovanelly & Moore, 2009).…”

Section: Characteristics Of Tsunami Deposits and Vented Sedimentsmentioning

confidence: 99%

“…This study focuses in particular on a sandy deposit in the marsh at Lynch Cove, previously identified primarily as a tsunami deposit (Hemphill‐Haley, 1996; Jovanelly & Moore, 2009). Lynch Cove was chosen as an area for detailed study because widespread outcrops allowed documentation of details in sedimentary characteristics of the deposit, and because this interpretation of the deposit as being generated solely by sediment venting (no tsunami evidence) contradicts previous work at this location.…”

Section: Introductionmentioning

confidence: 99%

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Vented sediments and tsunami deposits in the Puget Lowland, Washington – differentiating sedimentary processes

Martin

Bourgeois

2011

Sedimentology

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The sandy deposits produced by tsunamis and liquefaction share many sedimentary features, and distinctions between the two are important in seismically active coastal zones. Both types of deposits are present in the wetlands bordering Puget Sound, where one or more earthquakes about 1100 years ago caused both tsunami flooding and sediment venting. This cooccurrence allows an examination of the resulting deposits and a comparison with tsunami and liquefaction features of modern events. Vented sediments occur at four of five wetland field localities and tsunami deposits at two. In comparison with tsunami deposits, vented sediments in this study and from other studies tend to be thicker (although they can be thin). Vented sediments also have more variable thickness at both outcrop and map scale, are associated with injected dykes and contain clasts derived from underlying deposits. Further, vented sediments tend to contain a greater variety of sedimentary structures, and these structures vary laterally over metres. Tsunami deposits compared with vented sediments are commonly thinner, fine and thin landward more consistently, have more uniform thickness on outcrop and map scales, and have the potential of containing coarser clasts, up to boulders. For both tsunami deposits and vented sediments, the availability and grain size of source material condition the characteristics of the deposit. In the cases presented in this paper, both foraminifera and diatom assemblages within tsunami deposits and vented sediments consisted of brackish and marine species, and no distinction between processes could be made based on microfossils. In summary, this study indicates a need for more careful analysis and mapping of coastal sediments associated with earthquakes to avoid misidentification of processes and misevaluation of hazards.

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Implications of Physics-Based M9 Ground Motions on Liquefaction-Induced Damage in the Cascadia Subduction Zone: Looking Forward and Backward

Rasanen,

Grant,

Makdisi

et al. 2023

Preprint

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Sedimentological Analysis of an Ancient Sand Sheet of Multiple Origins at Lynch Cove, Puget Sound, Washington

Cited by 3 publications

References 24 publications

Diverse rupture modes for surface-deforming upper plate earthquakes in the southern Puget Lowland of Washington State

Diverse rupture modes for surface-deforming upper plate earthquakes in the southern Puget Lowland of Washington State

Vented sediments and tsunami deposits in the Puget Lowland, Washington – differentiating sedimentary processes

Implications of Physics-Based M9 Ground Motions on Liquefaction-Induced Damage in the Cascadia Subduction Zone: Looking Forward and Backward

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