Paleotsunami Inundation of a Beach Ridge Plain: Cobble Ridge Overtopping and Interridge Valley Flooding in Seaside, Oregon, USA

Peterson, Curt D.; Jol, Harry M.; Horning, Thomas; Cruikshank, Kenneth M.

doi:10.1155/2010/276989

Cited by 6 publications

(7 citation statements)

References 12 publications

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“…In Oregon, the age of a tsunami deposit from Cannon Beach 47 partly overlaps with that of UC4, with correlative evidence of coseismic subsidence also reported from Netarts Bay 48 , Yaquina Bay 49 , and Coos Bay 50 . Evidence from Necanicum River 48 , 51 and Siletz Bay 48 , 52 , which has been correlated with the 1700 CE earthquake in previous studies, could also be correlated with UC4. Overall, the geographical distribution of synchronous onshore evidence with UC4 includes Vancouver Island, northern Washington, and northern Oregon.…”

Section: Introductionsupporting

confidence: 54%

A new chronology for tsunami deposits prior to the 1700 CE Cascadia earthquake from Vancouver Island, Canada

Tanigawa

Sawai

Bobrowsky

et al. 2022

Sci Rep

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Coastal deposits at Tofino, Ucluelet, and Port Alberni in Vancouver Island along the Cascadia subduction zone were re-examined to improve the earthquake history of the southwest coast of Canada. We found sand sheets interbedded within peat and mud, suggesting deposition by strong flows in a low-energy environment. Based on limiting maximum and minimum ages derived from plant macrofossils, the age of one of the sand sheets below the tsunami deposits of the great Cascadia earthquake in 1700 CE was estimated to be 1330–1430 CE. Onshore paleoseismic evidence has been documented in Vancouver Island, northern Washington, and northern Oregon during this period. However, the newly constrained age is between those of coseismic subsidence Y and W events in southern Washington, which have been recognized as the 1700 CE and the penultimate Cascadia earthquakes, respectively. Moreover, the new age partly overlaps with the age of offshore paleoseismic evidence for T2, interpreted to have originated from the penultimate Cascadia earthquake, based on offshore turbidite records. The new chronology prior to the 1700 CE Cascadia tsunami deposit from Vancouver Island contributes to a better understand of the timing of the penultimate Cascadia earthquake.

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Section: Introductionsupporting

confidence: 54%

A new chronology for tsunami deposits prior to the 1700 CE Cascadia earthquake from Vancouver Island, Canada

Tanigawa

Sawai

Bobrowsky

et al. 2022

Sci Rep

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“…Carbonate shell fragments were observed but not routinely logged in proximal sand sheet deposits from the Crescent City freshwater lagoons (Figure ). Shell fragments from paleotsunami sand sheet deposits are now being used to confirm marine inundation in other proximal runup localities in the central Cascadia margin (Peterson et al , ), where windblown ocean spray could import marine diatoms by non‐surge mechanisms.…”

Section: Discussionmentioning

confidence: 99%

“…The results presented here demonstrate overland inundation records from tsunami that inundated stable shorelines of the southern Cascadia margin (Figure ). Such records have been reported from the central Cascadia margin (Peterson et al , ), but not from the southernmost Cascadia margin. Comparisons of inundation frequency from tsunami should help to direct mitigation strategies for vulnerable communities throughout the region (Dengler, ).…”

Section: Introductionmentioning

confidence: 97%

Evaluation of the use of paleotsunami deposits to reconstruct inundation distance and runup heights associated with prehistoric inundation events, Crescent City, southern Cascadia margin

Peterson

Carver²,

Cruikshank

et al. 2011

Earth Surf Processes Landf

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Historic-and prehistoric-tsunami sand deposits are used to independently establish runup records for tsunami hazard mitigation and modeled runup verification in Crescent City, California, located in the southern Cascadia Subduction Zone. Inundation from historic (1964) farfield tsunami (~5-6 m runup height) left sand sheet deposits (100-200 m width) in wetlands located behind a low beach ridge [3-4 m elevation of the National Geodetic Vertical Datum of 1988 (NAVD88)]. The most landward flooding lines (4·5-5 m elevation) in high-gradient alluvial wetlands exceed the 1964 sand sheet records of inundation by 1-2 m in elevation. The most landward flooding in low-gradient alluvial wetlands exceed the corresponding sand sheet record of inundation distance by 1000 m. Nevertheless, the sand sheet record is an important proxy for high-velocity inundation. Sand sheet deposition from the 1964 historic tsunami closely corresponds to the landward extent of large debris transport and structural damage in the Crescent City waterfront. The sand sheet deposits provide a proxy for maximum hazard or 'kill zone' in the study area.Six paleotsunami sand sheets (0·3-3 ka) are recorded in the back-ridge marshes in Crescent City, yielding a~450 year mean recurrence interval for nearfield Cascadia tsunami. Two paleotsunami sand deposit records, likely correlated to Cascadia ruptures between 1·0 and 1·5 ka, are traced to 1·2 km distance and 9-10 m elevation, as adjusted for paleo-sea level. The paleotsunami sand deposits demonstrate at least twice the runup height, and four times the inundation distance of the farfield 1964 tsunami sand sheet in the same marsh system. The preserved paleotsunami deposits in Crescent City are compared to the most landward flooding, as modeled by other investigators from a predicted Cascadia (~Mw 9) rupture. The short geologic record (~1·5 ka) yields slightly lower runup records than those predicted for the modeled Mw 9 rupture scenario in the same marsh, but it generally verifies predicted maximum tsunami runup for use in the planning of emergency response and rapid evacuation.

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“…8). The last two events (#5 and # 6) are attributed to large magnitude runups in other central Cascadia tidal basins, back-barrier wetlands, and beach plains (Peterson et al, 2010a;Peterson et al, 2010b;Schlichting, 2000). These two paleotsunami are correlated to long inundation events in the adjacent Beaver Creek floodplain (see Section 5.3 below).…”

Section: Event Runup Heightsmentioning

confidence: 96%

Proximal Records of Paleotsunami Runup in Barrage Creek Floodplains from Late-Holocene Great Earthquakes in the Central Cascadia Suduction Zone, Oregon, USA

Peterson¹,

Cruikshank²

2011

Tsunami - A Growing Disaster

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Paleotsunami Inundation of a Beach Ridge Plain: Cobble Ridge Overtopping and Interridge Valley Flooding in Seaside, Oregon, USA

Cited by 6 publications

References 12 publications

A new chronology for tsunami deposits prior to the 1700 CE Cascadia earthquake from Vancouver Island, Canada

A new chronology for tsunami deposits prior to the 1700 CE Cascadia earthquake from Vancouver Island, Canada

Evaluation of the use of paleotsunami deposits to reconstruct inundation distance and runup heights associated with prehistoric inundation events, Crescent City, southern Cascadia margin

Proximal Records of Paleotsunami Runup in Barrage Creek Floodplains from Late-Holocene Great Earthquakes in the Central Cascadia Suduction Zone, Oregon, USA

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