CONSTRAINTS ON EARTHQUAKE SOURCE MODELS OF THE 1700 CE TSUNAMI: MAPPING AND SEDIMENT TRANSPORT MODELING OF TSUNAMI DEPOSITS IMPLY &gt;1 M OF MEGATHRUST COSEISMIC SUBSIDENCE AT THE SALMON RIVER, OR

Selle, S. La; Coastal, Pacific; Nelson, Alan R.; Jaffe, Bruce E.; Witter, Robert C.; Walter, Wendy; Gelfenbaum, Guy

doi:10.1130/abs/2021am-369286

Cited by 2 publications

(6 citation statements)

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“…Maximum tsunami runup at the harbor and nearby beaches was estimated by well-preserved wrack lines of lightweight plant material and wood, measured with survey-grade GPS receivers. At Santa Cruz Harbor, the highest runup was 3.97 m above Mean Lower Low Water (MLLW), which is 2.22 m above the predicted high tide [15]. At beaches along Monterey Bay 10 and 13 km southeast of the harbor, tsunami runup markers were surveyed at 3.71 m and 4.28 m above MLLW.…”

Section: Tsunami Observations and Impactsmentioning

confidence: 96%

The Tsunamis Generated by the Hunga Tonga-Hunga Ha'apai Volcano on January 15, 2022

Lynett

2022

Preprint

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On the evening of January 15th, 2022 at approximately 5:15 pm local time (4:15 am Greenwich Mean Time), the Hunga Tonga-Hunga Ha'apai volcano unleashed a violent underwater eruption, blanketing the surrounding land masses in ash and debris (1). The eruption generated tsunamis observed throughout the globe. The last time such an event occurred was the 1883 Krakatau eruption (2), and thus here we have the first observations of a tsunami from a large emergent volcanic eruption captured with modern instrumentation. The mechanisms of tsunami generation here are rare and complex, but a wealth of observations permit a forensic analysis. With the use of oceanographic and meteorological data, post-event field survey observations, and high-order hydrodynamic modeling, we show that the event generated tsunamis at different times and from distinct mechanisms. There is evidence of a relatively small wave generated through a pre-cursor source approximately 10 minutes before the primary eruption; due to lack of observational data, it is difficult to specify the source of these waves, but a submarine landslide associated with an early eruption is possible. The main eruption appears to have generated waves through multiple mechanisms, including: 1) air-sea coupling with the initial and powerful shockwave radiating out from the explosion in the immediate vicinity of the eruption, 2) the collapse of the water-crater created by the underwater explosion, and 3) air-sea coupling with the air-pressure wave that circled the earth multiple times, leading to a global tsunami. In the nearfield, the tsunami impacts are strongly controlled by the shockwave and water-crater source, while the far-field tsunami, which was uncommonly persistent, can be largely described by the air-pressure wave mechanism. Catastrophic damage in some harbors in the far-field was averted by just 10’s of cm, implying that a modest sea level rise combined with a future, similar event would lead to a step-function increase in infrastructure impacts. Piecing together the complexity of this event has broad implications to the hazard in similar geophysical

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Section: Tsunami Observations and Impactsmentioning

confidence: 96%

The Tsunamis Generated by the Hunga Tonga-Hunga Ha'apai Volcano on January 15, 2022

Lynett

2022

Preprint

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“…Further descriptions of coring are provided in Text S1 in Supporting Information S1. Core locations, sand depths, and thicknesses have been published in an accompanying U.S. Geological Survey data release (La Selle et al., 2024).…”

Section: Field and Laboratory Methodsmentioning

confidence: 99%

“…Insightful reviews were provided by Bre MacInnes, Kate Clark, and two anonymous reviewers. Supporting data can be found in a U.S. Geological Survey data release (La Selle et al., 2024) and the attached Supporting Information S1 files. Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government.…”

Section: Acknowledgmentsmentioning

confidence: 99%

“…Tsunami deposit thickness and grain size data along with Delft3D‐FLOW model setup files used in this study are available in La Selle et al. (2024).…”

Section: Data Availability Statementmentioning

confidence: 99%

“…Here, we integrate legacy core logs from 1987 to 1988 (Nelson et al., 2004), recent core data (La Selle et al., 2024), and numerical tsunami sediment transport models to infer the minimum amount of slip and coseismic subsidence of a ca. 1700 CE earthquake at the Salmon River estuary, central Oregon (Figures 1 and 2).…”

Section: Introductionmentioning

confidence: 99%

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Testing Megathrust Rupture Models Using Tsunami Deposits

La Selle,

Nelson,

Witter

et al. 2024

JGR Earth Surface

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The 26 January 1700 CE Cascadia subduction zone earthquake ruptured much of the plate boundary and generated a tsunami that deposited sand in coastal marshes from northern California to Vancouver Island. Although the depositional record of tsunami inundation is extensive in some of these marshes, few sites have been investigated in enough detail to map the inland extent of sand deposition and depict variability in tsunami deposit thickness and grain size. We collected 129 cores in marshes of the Salmon River estuary in Oregon and reanalyzed 114 core logs from a 1987–88 study that mapped the inland extent of circa 1700 CE sandy tsunami deposits. The ca. 1700 CE tsunami deposit in the Salmon River estuary is easily recognized in cores ≤1 m deep in which a buried marsh peat is overlain by a well sorted sand bed with a sharp lower contact that thins and fines inland. We use tsunami deposit data and models of sandy tsunami sediment transport (using Delft3D‐FLOW) to test 15 rupture models that could represent a ca. 1700 CE earthquake. At least 12–16 m of slip offshore of the Salmon River, which results in 0.8–1.0 m of coastal coseismic subsidence, is required to match the ca. 1700 CE sand deposit's inland extent, which is consistent with models of heterogeneous megathrust slip in ca. 1700 CE. Our methods of detailed tsunami deposit mapping, combined with sediment transport modeling, can be used to test models of megathrust ruptures and their tsunamis to potentially improve earthquake and tsunami hazard assessments.

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CONSTRAINTS ON EARTHQUAKE SOURCE MODELS OF THE 1700 CE TSUNAMI: MAPPING AND SEDIMENT TRANSPORT MODELING OF TSUNAMI DEPOSITS IMPLY >1 M OF MEGATHRUST COSEISMIC SUBSIDENCE AT THE SALMON RIVER, OR

Cited by 2 publications

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The Tsunamis Generated by the Hunga Tonga-Hunga Ha'apai Volcano on January 15, 2022

The Tsunamis Generated by the Hunga Tonga-Hunga Ha'apai Volcano on January 15, 2022

Testing Megathrust Rupture Models Using Tsunami Deposits

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