Determination of volcanic hazards applying Multicriteria Evaluation and SIG techniques in the Nevado de Toluca area, central Mexico
Studies of short- and long-term volcanic hazards by means of geographic technologies generate useful knowledge for the analysis, planning and handling of the volcanic crises. The Nevado de Toluca is a stratovolcano that throughout its geologic history has had very violent eruptions accompanied by piroclastic flows (blocks and ash flows, pumice and ash flows, surges), lahars, debris avalanches and ash fall which have covered and modified in several occasions the relief of the Toluca basin. Eight vesuvian eruptions, four plinian, one ultraplinian eruptions, and at least three events of dome destruction occurred in the last 50,000 years; besides two sector collapses were identified in the last 100,000 years. The Toluca basin is one of the most important industrial and agricultural centers of Mexico, including the city of Toluca, capital of the State of Mexico. On the basis of previous studies about the volcanic products, it was determined that the emission of piroclastic flows represents the most important hazard in the area because of its frequency and the area covered during the last eruptions. Lahars represent the next hazard in importance, followed by ash fall, and finally debris avalanches. This work presents a methodology to integrate information of the Nevado de Toluca volcanic hazards in order to obtain a map of total hazards by applying Multicriteria Evaluation (MCE) and GIS techniques. This methodology includes the evaluation and combination of criteria applying decision rules, based on the analysis and hierarchization of alternatives, with the purpose of generating reliable information to determine the potential susceptible areas and to support the decision process. The map of total hazards shows that the most susceptible areas would be the Toluca city, and the Toluca-Lerma-San Mateo Atenco and Ocoyoacac-Tianguistengo industrial complexes, all of them economically important and situated on the areas most subject to piroclastic flows, lahars and ash fall.
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