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Stochastic Risk Evaluation of Volcanic Ash Fallout from Large Eruptions of Sakurajima Volcano〇Haris RAHADIANTO, Hirokazu TATANO, Masato IGUCHIThe forthcoming decades present an escalating

To address these challenges, our study adopts a novel

challenge in the field of volcanic risk management,

approach, utilizing extreme value analysis on extensivewith a high probability of a major volcanic eruption inmonitoring data from continuous eruptions from 1955

Sakurajima volcano within the next 25 to 30 years. The

until now to derive a range of eruption scenarios. Thismagnitude and complexity of such an event necessitate

method is grounded in the statistical analysis of pasta reevaluation of countermeasure and response

volcanic activities, providing a basis for predicting

strategies. The anticipated eruption is not just afuture eruptions. The scenarios generated focusing in

geological phenomenon but a multi-faceted disastervariability of plume heights of large eruptions, offeringwith far-reaching implications. The primary concern

a spectrum of eruption intensities, each with its uniquestems from the massive ash fallout characteristic ofimplications. These heights are not arbitrary but aresuch large eruptions, which can have devastating

calculated based on historical data, current volcanic

impacts across various sectors, severely disrupting

activities, and geophysical modeling, providing asocio-economic activities and community well-being torealistic range of potential scenarios.

all Japan areas. The ash fallout from these eruptions
poses significant threats to public health, agriculture,

Building upon these scenarios, we conductedtransportation, and infrastructure, not just locally but

detailed ash dispersal simulations using a Monte Carlopotentially on a global scale.

procedure. This approach is particularly suited toaddressing the uncertainties inherent in volcanic ash

The challenges of preparing for these events are

dispersal. By incorporating randomness in thecompounded by the inherent uncertainties in predicting

simulation of various parameters - such as wind speed

eruption scenarios. Traditional models and historicaland direction, eruption start time, and duration - wedata provide some insights, but the unique nature ofsimulated a wide range of possible ash distribution

each eruption, coupled with varying geophysicalgivenconditions, makes precise prediction challenging. This

probabilistic approach allows us to capture the inherent

uncertainty significantly hinders the development ofvariability and unpredictability of ash dispersion

comprehensive preparation plans, as the range ofpatterns in a way that deterministic models cannot.

theobtainederuption

scenarios.

Thispossible scenarios is vast and the specific impacts ofeach are largely unknown due to its rarity in the last

The results of these simulations are comprehensivecentury. Therefore, there is a critical need forand multifaceted, offering significant insights into theinnovative

ourpotential impacts of different eruption scenarios. We

understanding of potential eruption scenarios and theirsynthesized these results into risk curves andcorresponding

probabilistic maps, which serve as effective tools forapproaches
impacts,

thatcanthereby

enhanceenabling

effective planning and mitigation strategies.

more

visualizing and quantifying the potential impacts.

These outputs illustrate not only the geographicalIn the realm of transportation, the simulation

distribution of ashfall but also the probability ofoutcomes highlight critical areas where road and airport

different levels of ash deposition under each scenario.

cleaning would be necessary, thereby aiding in

The risk curves provide a clear depiction of themaintaining supply chains and evacuation mechanisms.

likelihood of various impact levels, enabling a better

In agriculture, the results inform strategies for cropunderstanding of the most probable scenarios and theirprotection and livestock safety, essential for mitigating

potential consequences.

economic losses and ensuring food security.
In conclusion, our study represents an advancement

Furthermore,

profoundin the field of volcanic risk assessment andashfall

preparedness. By employing a Monte Carlo approachcountermeasure strategies. They provide a solid

to simulate ash dispersal for various eruption scenarios,

foundation upon which emergency response plans canwebe developed, ensuring that resources are allocatedcomprehensive understanding of the potential impacts

effectively, evacuation plans are sound, and protectiveof massive ash fallout from various large-scalemeasures are appropriately targeted. For instance, theeruptions. This approach enables more targeted andprobabilistic maps can inform the planning ofeffective planning and response strategies, ultimately

evacuation routes, the positioning of emergency

enhancing the resilience of communities, economies,

shelters, and the distribution of resources. They also

and ecosystems at risk of volcanic disasters. The

play a crucial role in informing public health advisories,

methodologies and findings of this study haveagricultural planning, and infrastructure protection

implications far beyond the immediate field ofstrategies.

volcanology, offering insights and approaches that can

implications

for

these
theresults

havedevelopment

of

aimed

to

provideamore

nuancedandbe applied to a broad range of natural disaster scenarios.