Tephra fallout hazards at Quito International Airport (Ecuador)

Abstract

Tephra fallout is the most widespread hazard posed by explosive volcanic eruptions. The 2010 explosive eruption of Eyjafjallajokull in Iceland significantly exposed the vulnerability of aviation operations to volcanic ash. The presence of fine ash in the atmosphere forced authorities to close most of European airspace for almost a week. A worldwide study of airport operations disrupted by volcanic eruptions (Guffanti et al., Nat Hazards 51:287–302, 2009) showed significant past exposure to tephra fall of the old international airport (OUIO) in Quito, Ecuador. A new international airport, Mariscal Sucre International Airport (UIO), located 15 km due east to OUIO, started operations on February 20, 2013. Given its location close to the old airport, UIO is also at risk for tephra fallout in the future. We identified five volcanoes capable of producing tephra hazard at UIO. Three (Guagua Pichincha, Reventador, and Tungurahua) are currently active and have recently disrupted aviation operations in Ecuador. The other two (Cotopaxi and Pululagua) are not currently active, but any future eruption from these two volcanoes would probably be explosive, hence capable of producing tephra hazard to UIO. As eruption parameters and wind profiles cannot be forecast in advance, we used a probabilistic approach to quantify the probability of tephra accumulation exceeding 1 mm and 1 cm (regarded as non-conservative and conservative bounds for airport disruption) following an explosive eruption from each volcano. Each eruptive parameter was randomly sampled within a predefined distribution, and wind profiles are randomly sampled within a 5-year dataset. The probability of tephra accumulation reaching 1 mm and 1 cm at UIO is 14.3–19.9 and 2.5–5.8 %, respectively, for Cotopaxi; 17.5–19.9 and 7–7.7 %, respectively, for Guagua Pichincha; and 44.3–44.8 and 18.8–24.9 %, respectively, for Pululagua. According to our results, Reventador and Tungurahua are not likely to yield tephra accumulations of 1 cm or greater, and the probability of tephra accumulation reaching 1 mm at UIO is 3.8–8.2 and 0.2 %, respectively. Our results show that the probabilities of tephra accumulation are mostly reduced at the new airport site with respect to OUIO (except for Reventador). The use of our probabilistic approach is not restricted to UIO, but it can certainly be applied to quantify tephra fall hazards at other airports worldwide, especially those identified as being potentially affected by future volcanic eruptions (e.g., Catania, Italy; Anchorage, USA; Kokopo, Papua New Guinea). Finally, the probabilistic method presented here can also be applied to other critical facilities (e.g., nuclear power plants) or to urban areas.