Coseismic Subsidence and Paleotsunami Run-Up Records from Latest Holocene Deposits in the Waatch Valley, Neah Bay, Northwest Washington, U.S.A.: Links to Great Earthquakes in the Northern Cascadia Margin

Peterson, Curt D.; Cruikshank, Kenneth M.; Darienzo, Mark E.; Wessen, Gary C.; Butler, Virginia L.; Sterling, Sarah L.

doi:10.2112/jcoastres-d-12-00031.1

Cited by 14 publications

(8 citation statements)

References 17 publications

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“…The modern vertical displacements measured via GPS in this study differ from those recorded during the ~200-year interval of tidal marsh emergence after the last co-seismic rupture [AD 1700, [9]]. These results bear directly on previously unexpected relations between paleo-inter-seismic interval durations and magnitudes of interseismic uplift [10] and paleo-tsunami runup [11] The subduction zone is bounded at transform triple junctions (opposing arrows) to the north and south. Offshore deformation belt by from [6].…”

Section: Introductionsupporting

confidence: 46%

“…(b) Map of coastal coseismic-subsidence records (0.3 -3 ka in age), zero-isobases, and summarized vertical displacement trends from 50-year geodetic releveling surveys [42]. Coseismic subsidence localities are named [10]. Geodetic survey segments are color coded by uplift rate (mm/yr) [42].…”

Section: Rates Of Vertical Displacementmentioning

confidence: 99%

“…The names of the E-W transects are in blue, and selected volcanoes are named. displacement during the current interseismic strain interval, relative to prior tidal marsh uplift records after the last Cascadia rupture at AD1700 [e.g., [10]]. …”

Section: Introductionmentioning

confidence: 99%

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Late Stage Interseismic Strain Interval, Cascadia Subduction Zone Margin, USA and Canada

Cruikshank¹,

Peterson²

2017

OJER

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Modern horizontal strain (2006)(2007)(2008)(2009)(2010)(2011)(2012)(2013)(2014)(2015)(2016) measured along 56 new and 108 previously published GPS station baselines are used to establish the length (800 km) and width (300 -400 km) of the central Cascadia convergent margin seismogenic structure. Across-margin (west-east) annual rates of shortening range from 10 −9 a −1 at the eastern (landward) limit of the central Cascadia seismogenic structure to 10 −7 a −1 along the western onshore portion of the interplate zone. Relatively high shortening strain rates (10 −8 a −1 to 10 −7 a −1) are also measured in western transects from the northern (Explorer plate) and southern (Gorda plate) segments of the convergent margin, demonstrating that the full length of the margin (1300 km length) is currently capable of sustaining and/or initiating a major great earthquake. Vertical GPS velocities are averaged over the last decade at 321 stations to map patterns of uplift (0 -5 mm yr −1 ) and subsidence (0 -9 mm yr −1 ) relative to the study area mean. Along-margin belts of relative uplift and subsidence, respectively, are approximately associated with Coast Ranges and the Cascade volcanic arc. However, the vertical velocity data are locally heterogeneous, demonstrating patchy "anomalies" within the larger along-margin belts. A large coastal subsidence anomaly occurs in southwest Washington where the modern shortterm trend is reversed from the long-term (~200 yr) tidal marsh record of coastal uplift since the last co-seismic subsidence event (AD1700). The modern vertical displacements represent a late stage of the current inter-seismic interval. If the horizontal strain is considered largely or fully elastic, extrapolating the modern strain rates over the last 100 years show the accumulated strains would be similar in magnitude to the observed co-seismic strains resulting from the Tōhoku, Japan, Mw 9.0 earthquake in 2011. We believe that the central Cascadia seismogenic structure has accumulated sufficient elastic strain energy, during the last 300 years, to yield a Mw 9.0 earthquake from a rupture of at least one-half (400 km) of its length.

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Section: Introductionsupporting

confidence: 46%

Section: Rates Of Vertical Displacementmentioning

confidence: 99%

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Late Stage Interseismic Strain Interval, Cascadia Subduction Zone Margin, USA and Canada

Cruikshank¹,

Peterson²

2017

OJER

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“…The largest ruptures (>300 km rupture lengths) in the central Cascadia margin [4] [5] should yield Mw 8.5 ± 0.5 earthquakes that reoccur every few hundred years [6]. The last event (circa AD 1700) is known to have produced widespread evidence of paleoliquefaction along the Washington and Oregon coasts [7]- [10] and in the lower Columbia River valley [11]- [13]. The reported lack of large-scale clastic dikes and sills (≥10 cm in width) in the Willamette Valley has contributed to informal speculation that the Oregon portion of the subduction zone megathrust might be aseismic, weakly coupled, or highly segmented [14], thereby precluding Mw 8 ruptures.…”

Section: Introductionmentioning

confidence: 99%

“…Coseismic fluidization features in late Holocene deposits have been widely observed during investigations of coseismic subsidence and paleotsunami inundation along the coast (Figure 1; Table 1). The clastic sand dikes and sills (10 -30 cm width) in Sites 1, 3 and 4 were briefly examined in shallow trenches [7]- [9]. Only two of the coastal paleoliquefaction localities, Site 2 and Site 13, were discovered in river cutbanks [10] [22].…”

Section: Introductionmentioning

confidence: 99%

Large-Scale Fluidization Features from Late Holocene Coseismic Paleoliquefaction in the Willamette River Forearc Valley, Central Cascadia Subduction Zone, Oregon, USA

Peterson¹,

Kristensen²,

Minor³

2014

OJER

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A search of Willamette River cutbanks was conducted for the presence of late Holocene paleoliquefaction records in the Willamette forearc valley, located 175 ± 25 km landward from the buried trench in the central Cascadia subduction zone. Eight cutbank sites are reported that show evidence of large-scale fluidization features (≥10 cm width) including clastic sand dikes and intruded sand sills in Holocene overbank mud deposits. The targeted alluvial sequences, and hosted paleoliquefaction records, are of late Holocene age, as based on radiocarbon dating, flood silt thickness (≤4 m thickness), and minimal consolidation of dike sand (~1.5 ± 0.5 kg•cm −2 unconfined compressive strength). Two of the paleoliquefaction sites, which are separated by 150 km distance, overlap in age (175 -500 yr BP) with the last great megathrust rupture (Mw 8.5 -9.0) in the Cascadia margin, dated at AD 1700. The scarcity of exposed late Holocene paleoliquefaction sites in the Willamette River cutbanks motivated subsurface searches for thick basal sand deposits and overlying fluidization features, using floodplain geomorphological analyses, ground penetrating radar, and remote pole-camera scans of deep trench walls (3 -4 m depth). The onset of large-scale fluidization features occurred in overbank mud deposits (2 -3 m thickness) above unconsolidated sand bodies (≥2 m thickness) with unconfined compressive strengths of ~1.5 ± 0.5 kg•cm −2 . We recommend geomorphically-targeted subsurface explorations rather than traditional cutbank searches for evidence of coseismic paleoliquefaction in high-gradient river valley systems.

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Downdip landward limit of Cascadia great earthquake rupture

Hyndman

2013

JGR Solid Earth

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[1] This paper examines the constraints to the downdip landward limit of rupture for the Cascadia great earthquakes off western North America. This limit is a primary control for ground motion hazard at near-coastal cities. The studies also provide information on the physical controls of subduction thrust rupture globally. The constraints are (1) "locked/ transition" zones from geodetic deformation (GPS, repeated leveling, tide gauges); (2) rupture zone from paleoseismic coastal marsh subsidence, "paleogeodesy"; (3) temperature on the thrust for the seismic-aseismic transition; (4) change in thrust seismic reflection character downdip from thin seismic to thick ductile; (5) fore-arc mantle corner aseismic serpentinite and talc overlying the thrust; (6) updip limit of episodic tremor and slip (ETS) slow slip; (7) rupture area associations with shelf-slope basins; (8) depth limit for small events on the thrust; and (9) landward limit of earthquakes on the Nootka transform fault zone. The most reliable constraints for the limit of large rupture displacement, >10 m, are generally just offshore in agreement with thermal control for this hot subduction zone, but well-offshore central Oregon and near the coast of northern Washington. The limit for 1-2 m rupture that can still provide strong shaking is less well estimated 25-50 km farther landward. The fore-arc mantle corner and the updip extent of ETS slow slip are significantly landward from the other constraints. Surprisingly, there is a downdip gap between the best other estimates for the great earthquake rupture zone and the ETS slow slip. In this gap, plate convergence may occur as continuous slow creep.

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Coseismic Subsidence and Paleotsunami Run-Up Records from Latest Holocene Deposits in the Waatch Valley, Neah Bay, Northwest Washington, U.S.A.: Links to Great Earthquakes in the Northern Cascadia Margin

Cited by 14 publications

References 17 publications

Late Stage Interseismic Strain Interval, Cascadia Subduction Zone Margin, USA and Canada

Late Stage Interseismic Strain Interval, Cascadia Subduction Zone Margin, USA and Canada

Large-Scale Fluidization Features from Late Holocene Coseismic Paleoliquefaction in the Willamette River Forearc Valley, Central Cascadia Subduction Zone, Oregon, USA

Downdip landward limit of Cascadia great earthquake rupture

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