A probabilistic assessment of tephra-fall hazards at Hanford, Washington, from a future eruption of Mount St. Helens

Mastin, Larry G.; Eaton, Alexa R. Van; Schwaiger, Hans F.

doi:10.3133/ofr20201133

Cited by 3 publications

(1 citation statement)

References 28 publications

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“…This approach has been used to simulate, via computer modeling: a) tephra fallout from one volcano on a local scale (e.g. Barberi et al, 1990;Connor et al, 2001;Bonadonna et al, 2005;Bebbington et al, 2008;Costa et al, 2009;Yamano et al, 2018;Mastin et al, 2020); and b) tephra fallout from multiple volcanoes on a regional to global scale (e.g. Yokoyama et al, 1984;Hoblitt et al, 1987;Smith, 2004, 2010;Jenkins et al, 2012a;Jenkins et al, 2012b;Bear-Crozier et al, 2016;Miller et al, 2016;Jenkins et al, 2018).…”

Section: Introductionmentioning

confidence: 99%

Creating a digital database of tephra fallout distribution and frequency in Japan

et al. 2022

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Tephra fallout is a potential hazard to livelihoods, critical infrastructure, and health, even in areas that are far from volcanoes. Therefore, it is important to quantitatively evaluate tephra fall hazards for both residents and infrastructure around hazardous volcanoes. Modern probabilistic volcanic hazard assessments of tephra fallout strongly rely on computer modeling; however, assessments based on isopach maps can also be also helpful in assisting decision-makers. To assess the tephra fall hazards in Japan, we created a digital database “Isopach map-Based Tephra fall Hazard Analysis (IB-THA)” and a tool to draw the cumulative number of tephra fallout events exceeding a specific thickness at a particular location. The database was re-digitized using an existing catalog of 551 tephra fall deposit distribution maps. The re-digitized datasets were utilized here to estimate the cumulative number of tephra fallout events exceeding a specific thickness at 47 prefectural offices for the last 150 kyr. This allowed the characterization of regional tephra fall hazards in Japan for the first time. High cumulative numbers (20) of tephra fall deposits > 0 mm were identified in the NE-E region (e.g., Maebashi), whereas low numbers (2) were recognized in the SW and W regions of Japan (e.g., Naha). The thickest tephra fall deposit (2850 mm) was observed at Kagoshima. We used IB-THA to create a hazard curve for Tokyo. This hazard curve provides the minimum frequency needed to exceed the tephra fall thickness at any location. To refine the digital database presented here, further studies are required to incorporate recent (i.e., 2003 or younger) tephra distributions, review questionable isopach maps, and improve the interpolation method for digitizing tephra fall distributions.

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Section: Introductionmentioning

confidence: 99%

Creating a digital database of tephra fallout distribution and frequency in Japan

et al. 2022

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Modelling the transport and deposition of ash following a magnitude 7 eruption: the distal Mazama tephra

et al. 2022

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Volcanic ash transport and dispersion models (VATDMs) are necessary for forecasting tephra dispersal during volcanic eruptions and are a useful tool for estimating the eruption source parameters (ESPs) of prehistoric eruptions. Here we use Ash3D, an Eulerian VATDM, to simulate the tephra deposition from the ~ 7.7 ka climactic eruption of Mount Mazama. We investigate how best to apply a VATDM using the ESPs characteristic of a large magnitude eruption (M ≥ 7). We simplify the approach to focus on the distal deposit as if it were formed by a single phase of Plinian activity. Our results demonstrate that it is possible to use modern wind profiles to simulate the tephra dispersal from a prehistoric eruption; however, this introduces an inherent uncertainty to the subsequent simulations where we explore different ESPs. We show, using the well-documented distal Mazama tephra, that lateral umbrella cloud spreading, rather than advection–diffusion alone, must be included in the VATDM to reproduce the width of the isopachs. In addition, the Ash3D particle size distribution must be modified to simulate the transport and deposition of distal fine-grained (< 125 µm) Mazama ash. With these modifications, the Ash3D simulations reproduce the thickness and grain size of the Mazama tephra deposit. Based on our simulations, however, we conclude that the exact relationship between mass eruption rate and the scale of umbrella cloud spreading remains unresolved. Furthermore, for ground-based grain size distributions to be input directly into Ash3D, further research is required into the atmospheric and particle processes that control the settling behaviour of fine volcanic ash.

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No evidence for tephra in Greenland from the historic eruption of Vesuvius in 79 CE: implications for geochronology and paleoclimatology

et al. 2022

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Abstract. Volcanic fallout in polar ice sheets provides important opportunities to date and correlate ice-core records as well as to investigate the environmental impacts of eruptions. Only the geochemical characterization of volcanic ash (tephra) embedded in the ice strata can confirm the source of the eruption, however, and is a requisite if historical eruption ages are to be used as valid chronological checks on annual ice layer counting. Here we report the investigation of ash particles in a Greenland ice core that are associated with a volcanic sulfuric acid layer previously attributed to the 79 CE eruption of Vesuvius. Major and trace element composition of the particles indicates that the tephra does not derive from Vesuvius but most likely originates from an unidentified eruption in the Aleutian arc. Using ash dispersal modeling, we find that only an eruption large enough to include stratospheric injection is likely to account for the sizable (24–85 µm) ash particles observed in the Greenland ice at this time. Despite its likely explosivity, this event does not appear to have triggered significant climate perturbations, unlike some other large extratropical eruptions. In light of a recent re-evaluation of the Greenland ice-core chronologies, our findings further challenge the previous assignation of this volcanic event to 79 CE. We highlight the need for the revised Common Era ice-core chronology to be formally accepted by the wider ice-core and climate modeling communities in order to ensure robust age linkages to precisely dated historical and paleoclimate proxy records.

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A probabilistic assessment of tephra-fall hazards at Hanford, Washington, from a future eruption of Mount St. Helens

Cited by 3 publications

References 28 publications

Creating a digital database of tephra fallout distribution and frequency in Japan

Creating a digital database of tephra fallout distribution and frequency in Japan

Modelling the transport and deposition of ash following a magnitude 7 eruption: the distal Mazama tephra

No evidence for tephra in Greenland from the historic eruption of Vesuvius in 79 CE: implications for geochronology and paleoclimatology

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