Probabilistic multi – hazard assessment at an active but under-monitored volcano: Ceboruco, Mexico

We conduct a probabilistic volcanic hazard assessment for Ceboruco volcano (Mexico) using PyBetVH, an e-tool based on the Bayesian event tree (BET) methodology. We use available information about the volcano, including eruptive history, numerical and theoretical models, to generate probability maps. Our hazard assessment accounts for the variability of eruption types expected at Ceboruco and the hazardous volcanic phenomena these eruptions generate. We create a generic event tree for Ceboruco to account for magmatic and amagmatic activity. For a magmatic eruption, we choose three scenarios: i) small (effusive), ii) medium (vulcanian/subPlinian) and iii) large (Plinian) based on the Holocene history of the volcano; with their related hazardous phenomena: ballistics, tephra fallout, pyroclastic density currents, lahars and lava flows. Despite numerous eruptions in the latest Holocene and efforts by several university and government groups to create and sustain a monitoring network, Ceboruco remains under-monitored, meaning that it is intermittently rather than continuously monitored by dedicated groups. With no consistent monitoring data available, we look at the geology and the eruptive history to inform our prior models. We estimate the probability of a magmatic eruption within the next time window (1 year) of ~ 0.002. We show how the BET creates higher probabilities in the absence of monitoring data. That is, there is a cost in terms of higher probabilities and higher uncertainties for having not yet developed a sustained volcano monitoring network. We present absolute probability maps (unconditional in terms of eruption size and vent location) for a magmatic eruption at Ceboruco volcano. With PyBetVH we estimate and visualize the uncertainties associated with each hazard map. Our intent is that hazard maps and uncertainties will be useful to local authorities who need to understand the hazard maps when considering the development of long-term urban and land-use planning and short-term crisis management strategies, and to the scientific community in their efforts to sustain monitoring of this active volcano.

Ceboruco hazard map: part I - definition of hazard scenarios based on the eruptive history

Of the 48 volcanoes in Mexico listed as potentially active by the National Center for Disaster Prevention (CENAPRED), Ceboruco, located in the western Trans-Mexican Volcanic Belt, is considered among the 5 most hazardous. Its recent eruptive history includes a large magnitude Plinian (VEI 6) eruption ~ 1000 years ago and the historical 1870–1875 vulcanian (VEI 3) eruption, as well as recent fumarolic and seismic activity.Ceboruco is a relatively young (< 400,000 years) stratovolcano characterized by abrupt changes in eruptive behavior. Individual eruptive episodes have great variations in style (effusive andesitic to highly-explosive rhyodacitic) and duration. These factors complicate hazard assessment.Three main eruptive scenarios of different magnitudes (large, intermediate, small) and eruption characteristics (likelihood of occurrence: high, medium, small) have been identified and will be presented as a background to build the volcanic hazard map for Ceboruco volcano (presented in part II of this work). Here, we report on the detailed eruptive history, with emphasis on the volcanic products of each of the eruptions, in order to identify those deposits that can serve as a reference for calibrating the modeling software (Tephra2 and Hazmap for ash fallout, Eject! code for ballistics, Etna Lava Flow Model for lava flows, Titan2D for pyroclastic density currents, and Flo-2D and LaharZ for lahars) that will be used in further steps to simulate different volcanic phenomena and lead to the construction of the hazard map.