How well do concentric radii approximate population exposure to volcanic hazards?

Area of Science:

• Geosciences
• Volcanology
• Risk Assessment

Background:

• Large-scale volcanic hazard exposure assessment commonly uses simplified circular footprints.
• These circular models do not account for hazard directionality or intensity distribution.
• Previous studies have not validated circular footprint accuracy against detailed hazard models.

Purpose of the Study:

• To compare population exposure estimates from circular radii with modelled volcanic hazard footprints.
• To evaluate the accuracy of different radii (10, 30, 100 km) in representing hazard extent and population exposure.
• To provide a benchmark for interpreting radii-derived volcanic hazard and exposure estimates.

Main Methods:

• Compared population exposure from 10, 30, and 100 km radii with simulated pyroclastic density currents (PDCs), large clasts, and tephra fall.
• Utilized Volcanic Explosivity Index (VEI) 3, 4, and 5 scenarios for 40 Indonesian and Philippine volcanoes.
• Modeled dome-collapse and column-collapse PDCs, alongside tephra fall and large clast dispersal.

Main Results:

• A 10 km radius generally overestimates hazard extent, except for column-collapse PDCs.
• A 30 km radius overestimates PDCs and large clasts but underestimates tephra fall.
• A 100 km radius captures most hazards, but exceptions exist; radii and model estimates correlate positively, except for dome-collapse PDCs.

Conclusions:

• Concentric radii can significantly under- or overestimate volcanic hazard extent and population exposure.
• The accuracy of radii estimates depends on the hazard type, VEI, and specific volcanic scenario.
• This study provides crucial insights for refining large-scale volcanic risk assessment methodologies.