Coastal erosion and recovery from a Cascadia subduction zone earthquake and tsunami

Simms, Alexander R.; DeWitt, Regina; Zurbuchen, Julie; Vaughan, Patrick R.

doi:10.1016/j.margeo.2017.08.009

Cited by 15 publications

(5 citation statements)

References 62 publications

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“…6A). A series of landwarddipping, flat-lying, channels mark the filling of erosional topography and coastal reworking of the irregular shoreline following inundation and erosion (Simms et al, 2017). Multiple canyons and thrust ridge along the inner slope of the Cascadia Trench cause active sediment transport from the continental slope, Vancouver Island and shelf through erosion and reflected in the asymmetric tilted seafloor (Davis et al, 2017).…”

Section: Resultsmentioning

confidence: 99%

Applying Automatic Mapping Processing By GMT to Bathymetric and Geophysical Data: Cascadia Subduction Zone, Pacific Ocean

Lemenkova

2020

Journal of Environmental Geography

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The Cascadia Trench is stretching along the convergent plate boundaries of Pacific Plate, North America Plate and Juan De Fuca Plate. It is an important geomorphological structural feature in the north-east Pacific Ocean. The aim of the paper is to analyse the geomorphology of the Cascadia Trench west of Vancouver Island (Canada and USA) using the GMT cartographic scripting toolset. The unique geomorphological feature of the Cascadia Trench is that the thick sediment layer completely obscures the subduction zone and abyssal hills. This results in the asymmetric profile in the cross-section of the trench. Bathymetric data were extracted from the GEBCO 2019 dataset (15 arc-second grid), sediment thickness by the GlobSed dataset. Due to the dominance of high sedimentary rate and complexity of the tectonic processes and geologic settings, Cascadia Trench develops very specific asymmetric geomorphic shape comparing to the typical V-form. The results of the geomorphic modelling show that eastern side of the trench has a gentle curvature (slope: 35.12°), partially stepped, due to the tectonic movements and faults. The opposite, oceanward side is almost completely leveled. The trench is narrow with maximal depth at the selected segment -3489 m and for the whole dataset -6201 m. The most repetitive depth is in a range -2500 to -2400 m (267 samples) and -2500 to -2600 m (261 samples). The bottom is mostly flat due to the high sedimentation rates indicating the accumulative leveling processes. Marine free-air gravity anomalies along the Cascadia Subduction Zone are characterized by weakly positive values (20 mGal) increasing rapidly in the zone of the continental slope (>200 mGal), which is associated with a decrease in thickness of the Earth’s crust.

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Section: Resultsmentioning

confidence: 99%

Applying Automatic Mapping Processing By GMT to Bathymetric and Geophysical Data: Cascadia Subduction Zone, Pacific Ocean

Lemenkova

2020

Journal of Environmental Geography

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“…Because the radiocarbon ages of plant fragments in the humic silt layers are within the range of radiocarbon wiggle in the calibration curve (Sawai, 2012; Table 3), other methods, such as optically stimulated luminescence dating (e.g. May et al, 2015;Simms, DeWitt, Zurbuchen, & Vaughan, 2017), should be applied for precise determination of sedimentation ages.…”

Section: Radiocarbon Agesmentioning

confidence: 99%

Seismic subsidence near the source region of the 1662 Kanbun Hyuganada Sea earthquake: Geochemical, stratigraphical, chronological, and paleontological evidences in Miyazaki Plain, southwest Japan

Niwa

Kamataki

Kurosawa³

et al. 2020

Island Arc

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To identify the subsidence induced by an offshore earthquake, chemical compositions, fossil assemblages, and radiocarbon ages of organic materials were analyzed for Holocene sediments in the Miyazaki Plain, southwest Japan. The lower sedimentary facies (SF1) composed of sand-and pumice-rich sediments and the upper sedimentary facies (SF2) composed of silt-rich sediments were identified by stratigraphical description. Sharp facies changes and sediment disturbances are observed in the boundary between SF1 and SF2. Diatoms of brackish and marine water origins, foraminifers, ostracods, and mollusks are common in SF2, while fossils are rare, and most of them are diatoms of freshwater origins in SF1. The stratigraphical and paleontological evidences suggest an environmental change from the lower terrestrial to the upper shallow marine. The change is laterally continuous and seems to be inconsistent with Holocene uplift trends in the Miyazaki Plain. Radiocarbon ages of organic matters and the occurrence of the Sakurajima-Bunmei tephra (1471-1476 AD) show that the environmental change could be attributed to local subsidence due to the 1662 Kanbun Hyuganada Sea earthquake shown in historical records. The chemical analysis shows clear contrast between SF1 and SF2 in terms of concentrations of cations and anions commonly rich in seawater (i.e. Na + , Mg 2+ , K + , Ca 2+ , Cl − , and SO 4 2−) in adsorbed water extracted from the sediments, and total S concentrations in bulk sediments, supporting the environmental change from terrestrial to shallow marine. However, the bulk chemical composition, except total sulfur, remains rather unclear for use as marine-derived chemical markers compared to the adsorbed water, because it is more affected by the composition of the source sediments.

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“…Localized submergence of a continental shelf during a subduction earthquake occurs when, during the earthquake itself, there is co-seismic stress release caused by the strain on the continental plate and uplift due to the subducting plate (e.g., Nelson et al 1996;Nelson et al 2006;Simms et al 2017) ( Figure 6). As a result, although the entire region experiences overall uplift in response to the regional subduction event, there is localized subsidence during the event.…”

Section: Neo-tectonicsmentioning

confidence: 99%

Framework geology of Cape Shoalwater and northwest Willapa Bay, Washington : assessing potential geologic impacts on recent shoreline change

Wadman¹,

McNinch²,

Smith³

2020

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The shoreline along Cape Shoalwater and northwest Willapa Bay has experienced the highest rates of erosion along the entire Pacific Coast of the United States, due in part to rapid northward migration of the navigation channel. Recently, channel migration and shoreline erosion in this region have slowed, but the cause of this relative stabilization, and thus the longevity of these new patterns, is unknown. Given the complex neotectonics and geologic framework of the southern coast of Washington, it is possible that underlying, erosion-resistant geologic units have become exposed along the channel and/or in the nearshore, and are acting to reduce or halt channel migration and/or shoreline erosion. Conversely, the apparent reduction may be due to subtle, short-term changes in regional hydrodynamics and/or sediment transport, and thus future rates of channel migration and/or shoreline erosion might increase back to historical rates. The purpose of this special report is to detail the geologic and neotectonic framework of the northern Willapa Bay region, and determine how the underlying framework geology might be impacting channel stability and adjacent shoreline erosion rates. Suggested research questions to quantify potential geologic control are also presented, including the potential benefits of the research to the district.

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Coastal erosion and recovery from a Cascadia subduction zone earthquake and tsunami

Cited by 15 publications

References 62 publications

Applying Automatic Mapping Processing By GMT to Bathymetric and Geophysical Data: Cascadia Subduction Zone, Pacific Ocean

Applying Automatic Mapping Processing By GMT to Bathymetric and Geophysical Data: Cascadia Subduction Zone, Pacific Ocean

Seismic subsidence near the source region of the 1662 Kanbun Hyuganada Sea earthquake: Geochemical, stratigraphical, chronological, and paleontological evidences in Miyazaki Plain, southwest Japan

Framework geology of Cape Shoalwater and northwest Willapa Bay, Washington : assessing potential geologic impacts on recent shoreline change

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