Evaluating relative tephra fall hazard and risk in the Asia-Pacific region

Jenkins, Susanna F.; Magill, Christina; Blong, Russell

doi:10.1130/ges01549.1

Cited by 13 publications

(22 citation statements)

References 41 publications

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“…Here, 1/λ an represents the return period (Jenkins et al, 2018). Table 2 Number of tephra fall events exceeding 0 and equal to or greater than 10, 100, 200, and 500 kg/m 2 for every 10,000 yr for Tokyo.…”

Section: Resultsmentioning

confidence: 99%

“…PVAHA was proposed by Stirling and Wilson (2002) and was adopted from the method for Probabilistic Seismic Hazard Assessment (PSHA: Cornell, 1968;McGuire, 1995), a four-step procedure for event-based. This procedure was developed by Simpson et al (2011), Jenkins et al (2012aJenkins et al ( , 2012b, Bear-Crozier et al (2016, and Jenkins et al (2018). The development of this procedure is particularly well documented in Bear-Crozier et al (2016).…”

Section: Probabilistic Volcanic Ash Fall Hazard Assessmentmentioning

confidence: 99%

“…1) rather than PVAHA because "ash" refers to a limited range of grain sizes (pyroclastic materials ner than sand). Generally, the probability for PVTHA is represented by the AEP (Jenkins et al, 2018).…”

Section: Probabilistic Volcanic Ash Fall Hazard Assessmentmentioning

confidence: 99%

“…Probabilistic methods have been increasingly used to evaluate tephra fall hazards through both computational techniques (Bonadonna et al, 2005;Magill et al, 2006;Marzocchi et al, 2010;Jenkins et al, 2012a, b;Miller et al, 2016) and the evaluation of geological records (Suto et al, 2007). Computational tephra fall models (e.g., TEPHRA2: Conner et al, 2001;FALL3D: Folch et al, 2009) are coupled with wind pro le data for individual eruptions (e.g., Bonadonna et al, 2005) and regional long-term eruptions (Bear-Crozier et al, 2016;Jenkins et al, 2018). However, evaluating the accuracy of calculations of these computational studies is di cult.…”

Section: Introductionmentioning

confidence: 99%

“…However, the database of Suto et al (2007) cannot be applied to directly calculate hazard curves because the isopach contours are provided in PDF format instead of shape le format. To evaluate regional tephra fall hazards, we calculated annual exceedance probabilities (AEPs;Jenkins et al, 2018) using Probabilistic Volcanic Ash fall Hazard Assessment (PVAHA; Stirling and Wilson, 2002). To do this, we traced and re-digitized the 551 PDF tephra fall distribution maps of Suto et al (2007) using Geographic Information System (GIS) mapping software.…”

Section: Introductionmentioning

confidence: 99%

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Probabilistic assessment of tephra fall hazards in Japan using a tephra fall distribution database

Uesawa

Toshida

Takeuchi

et al. 2020

Preprint

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Tephra falls can disrupt critical infrastructure, including transportation and electricity networks. Probabilistic assessments of tephra fall hazards have been performed using computational techniques, but it is also important to integrate long-term, regional geological records. To assess tephra fall load hazards in Japan, we re-digitized an existing database of 551 tephra distribution maps. We used the re-digitized datasets to produce hazard curves for a range of tephra loads for various localities. We calculated annual exceedance probabilities (AEPs) and constructed hazard curves from the most complete part of the geological record. We used records of tephra fall events with a Volcanic Explosivity Index (VEI) of 4–7 (based on survivor functions) that occurred over the last 150 ka, as the database contains a very high percentage (around 90%) of VEI 4–7 events for this period. We fitted the data for this period using a Poisson distribution function. Hazard curves were constructed for the tephra fall load at 47 prefectural offices throughout Japan, and four broad regions were defined (NE–W, NE–E, W, and SW Japan). AEPs were relatively high, exceeding 1 × 10 −4 for loads greater than 0 kg/m 2 on the eastern (down-wind) side of the volcanic front in the NE–E region. In much of the W and SW regions, maximum loads were heavier, but AEPs were lower (<10 −4 ). Tephras from large (VEI ≥ 6) events are the predominant hazard in every region. A parametric analysis was applied to investigate regional variability using AEP diagrams and slope shape parameters via curve fitting with exponential and double-exponential decay functions. Two major differences were recognized between the hazard curves from borehole data and those from the digitized tephra database. The first is a significant underestimation of AEP for frequent events using the tephra database, by one to two orders of magnitude. This is explained in terms of the lack of records for smaller tephra fall events in the database. The second is an overestimation of the heaviest tephra load events, which differ by a factor of two to three. This difference might be due to the tephra fall distribution contour interpolation methodology used to generate the original database. The hazard curve for Tokyo developed in this study differs from those that have been generated previously using computational techniques. For the Tokyo region, the probabilities and tephra loads produced by computational methods are at least one order of magnitude greater than those generated during the present study. These discrepancies are inferred to have been caused by initial parameter settings in the computational simulations, including their incorporation of large-scale eruptions of up to VEI = 7 for all large stratovolcanoes, regardless of their eruptive histories. To improve the precision of the digital database, we plan to incorporate recent (since 2003) tephra distributions, revise questionable isopach maps, and develop an improved interpolation method for digitizing tephra fall distributions.

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Section: Resultsmentioning

confidence: 99%

Section: Probabilistic Volcanic Ash Fall Hazard Assessmentmentioning

confidence: 99%

Section: Probabilistic Volcanic Ash Fall Hazard Assessmentmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Probabilistic assessment of tephra fall hazards in Japan using a tephra fall distribution database

Uesawa

Toshida

Takeuchi

et al. 2020

Preprint

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Characterising the wind-advected medial fall deposit from fissure 8 fountaining during the 2018 lower East Rift Zone eruption, Kīlauea

Watts,

Cockshell,

Houghton

2023

Bull Volcanol

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The 2018 eruption on the lower East Rift Zone, Hawaii, involved the opening of 24 fissures before the eruption focussed on a single point source, fissure 8 (F8). This study characterises the preserved medial F8 tephra deposit using an isopach map, maximum clast size data, and total grain size distribution analysis, shedding light on the tephra transport and dispersal mechanisms beyond the F8 cone occurring during the fountaining. The medial sheet-like deposit covers approximately 0.22 km2, best fit by a Power-Law thinning rate. The TephraFits model estimated the corresponding volume of the continuous medial tephra blanket to be ~ 2 $$\times$$ × 104 m3, just 0.02% of the total volume erupted from fissure 8. Samples from the preserved medial deposit have grain size modes of − 3.5 to − 4 Φ, compatible with Voronoi tessellation calculations. Maximum clast size did not show a ‘typical’ fining relationship with distance from the vent; instead, it shows no clear pattern. One factor was that the extremely low clast density, a function of a secondary vesiculation event, enabled the pyroclasts to be re-entrained, often repeatedly, by large eddies downwind of the vent. This should be considered in future studies of prolonged fountaining episodes as the clasts involved in the medial fall are rarely well preserved in the geologic record due to their fragile nature but their presence adds complexity to the inferred eruption dynamics.

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