HR: 15:15h
AN: V33C-06    [Abstracts]
TI: Numerical modeling of debris avalanches at Nevado de Toluca (Mexico): implications for hazard evaluation and mapping
AU: * Grieco, F
EM: filippo.grieco@gmail.com
AF: Istituto per la Dinamica dei Processi Ambientali – sez. di Milano, CNR, via Mangiagalli, 34, Milano, 20133, Italy
AU: Capra, L
EM: lcapra@geociencias.unam.mx
AF: Centro de Geociencias, UNAM, Campus Juriquilla, Apdo. Postal 1-742 Centro, Queretaro, Qro 76001, Mexico
AU: Groppelli, G
EM: gianluca.groppelli@unimi.it
AF: Istituto per la Dinamica dei Processi Ambientali – sez. di Milano, CNR, via Mangiagalli, 34, Milano, 20133, Italy
AU: Norini, G
EM: norini@ct.ingv.it
AF: Centro de Geociencias, UNAM, Campus Juriquilla, Apdo. Postal 1-742 Centro, Queretaro, Qro 76001, Mexico
AB: The present study concerns the numerical modeling of debris avalanches on the Nevado de Toluca Volcano (Mexico) using TITAN2D simulation software, and its application to create hazard maps. Nevado de Toluca is an andesitic to dacitic stratovolcano of Late Pliocene-Holocene age, located in central México near to the cities of Toluca and México City; its past activity has endangered an area with more than 25 million inhabitants today. The present work is based upon the data collected during extensive field work finalized to the realization of the geological map of Nevado de Toluca at 1:25,000 scale. The activity of the volcano has developed from 2.6 Ma until 10.5 ka with both effusive and explosive events; the Nevado de Toluca has presented long phases of inactivity characterized by erosion and emplacement of debris flow and debris avalanche deposits on its flanks. The largest epiclastic events in the history of the volcano are wide debris flows and debris avalanches, occurred between 1 Ma and 50 ka, during a prolonged hiatus in eruptive activity. Other minor events happened mainly during the most recent volcanic activity (less than 50 ka), characterized by magmatic and tectonic-induced instability of the summit dome complex. According to the most recent tectonic analysis, the active transtensive kinematics of the E-W Tenango Fault System had a strong influence on the preferential directions of the last three documented lateral collapses, which generated the Arroyo Grande and Zaguàn debris avalanche deposits towards E and Nopal debris avalanche deposit towards W. The analysis of the data collected during the field work permitted to create a detailed GIS database of the spatial and temporal distribution of debris avalanche deposits on the volcano. Flow models, that have been performed with the software TITAN2D, developed by GMFG at Buffalo, were entirely based upon the information stored in the geological database. The modeling software is built upon equations solved by a parallel and adaptive mesh, that can concentrate computing power in region of special interest. First of all, simulations of known past events, were compared with the geological data validating the effectiveness of the method. Afterwards, numerous simulations have been executed varying input parameters as friction angles, starting point and initial volume, in order to obtain a global perspective over the possible expected debris avalanche scenarios. The input parameters were selected considering the geological, structural and topographic factors controlling instability of the volcanic cone, especially in case of renewed eruptive activity. The interoperability between TITAN2D and GIS softwares permitted to draw a semi-quantitative hazard map by crossing simulation outputs with the distribution of deposits generated by past episodes of instability, mapped during the field work.
DE: 8404 Volcanoclastic deposits
DE: 8488 Volcanic hazards and risks
SC: Volcanology, Geochemistry, and Petrology [V]
MN: 2007 Joint Assembly