Karuna Earthquake and Volcanic Ash: Evacuate or Shelter?
The island state of Karuna lies above a subduction zone. Its capital, Port Merida (population 420,000), is 18 km from Mt Sena, a stratovolcano now at alert level 3 after 11 days of shallow tremors. A magnitude 6.8 earthquake at 35 km depth has cracked the airport runway and closed the port. Forecasters expect 5–10 cm of ashfall within 24 hours. Official assessments show 62% of buildings are unreinforced masonry; one of two hospitals lies in a landslide-prone district; the only inland road has 14 unstable sections. There are 38 designated shelters with a combined capacity of 55,000, fuel reserves for three days, and intermittent mobile coverage. The national disaster agency must choose within 12 hours between mass evacuation to the inland plateau and shelter-in-place with vertical evacuation. Local officials report that many residents will not leave livestock or shops.
1. Using the evidence, evaluate which of the two strategies-mass evacuation or shelter-in-place-is more defensible in the first 24 hours.
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Mass evacuation looks attractive because ashfall of 5–10 cm can collapse weak roofs and the volcano may escalate. But the only inland road has 14 unstable sections, the airport is unusable, and fuel lasts three days, so moving 420,000 people in 12 hours is unrealistic. Shelter capacity is only 55,000, so pure vertical evacuation would leave most people in unreinforced masonry-the buildings most likely to fail. The stronger judgement is a hybrid: immediate shelter-in-place for the majority, prioritising the 55,000 shelter spaces for those in landslide-prone districts and near the volcano, plus targeted evacuation of the most vulnerable along the safest road sections. This fits the short warning window, limited fuel and patchy communications. A full mass evacuation would create congestion and expose people to landslides; pure shelter-in-place would leave too many in hazardous buildings. The decision should therefore be framed as selective evacuation plus vertical refuge, with ash-load monitoring and roof-clearing teams.
2. Explain how the concept of resilience could guide recovery planning, with two specific measures.
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Resilience means the ability to absorb a shock and recover core functions without permanent loss. Two measures follow from the scenario. First, retrofit critical facilities-the hospital, schools and designated shelters-to seismic and ash-load standards, and duplicate hospital capacity outside the landslide-prone district so health care survives an event. Second, build livelihood continuity: pre-register traders and provide temporary market spaces, cash transfers and livestock shelter, because residents said they would not leave shops or animals. If recovery plans ignore livelihoods, future evacuation compliance will fall. Community drills and decentralised communication such as radio and SMS also address intermittent mobile coverage. These measures reduce vulnerability rather than only preparing a response.
3. Identify two limitations of the data and explain how they affect the decision.
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First, the 62% unreinforced-masonry figure may not capture informal additions, roof condition or age, so ash-load collapse risk is uncertain. Wet ash is heavier than dry ash, so the 5–10 cm forecast could under- or over-state roof danger. Second, the 55,000 shelter capacity is nominal: some shelters may be damaged, inaccessible or lacking water, and the 12-hour window depends on a forecast that can change. These uncertainties make a rigid binary choice risky. A monitored hybrid approach-starting selective evacuation and vertical refuge while reassessing ashfall and road safety-is more defensible than committing all resources to one strategy.