Bayesian event tree for long‐term volcanic hazard assessment: Application to Teide‐Pico Viejo stratovolcanoes, Tenerife, Canary Islands

[1] In modern volcanology one of the most important goals is to perform hazard and risk assessment of volcanoes near urbanized areas. Previous work has been done to assess volcanic hazard in the form of event tree structures containing possible eruptive scenarios. Probability methods have been applied to these structures to estimate the long term probability for each scenario. However, most of these event tree models show restrictions in the eruptive scenarios they consider and/or on the possibility of having volcanic unrest triggered by other forces than magmatic. In this paper, we present a Bayesian event tree structure which accounts for external triggers (geothermal, seismic) as a source of volcanic unrest and looks at the hazard from different types of magma composition and different vent locations (as opposite to a central vent only). We apply the model to the particular case of Teide-Pico Viejo stratovolcanoes, two alkaline composite volcanoes that have erupted 1.8–3 km3 of mafic and felsic magmas from different vent sites during the last 35 ka, situated on a densely populated island, one of the biggest tourist destinations of Europe, and for which limited geological and no historical data exist. Hence, the importance of volcanic hazard assessment for risk-based decision-making in land use planning and emergency management. A previous attempt to estimate the volcanic hazard for Teide-Pico Viejo has been done using an event tree structure based on Elicitation of Expert Judgment. The new method overcomes some limitations of the previous method, including human decision bias, epistemic and aleatoric uncertainties, restrictions on the segmentation complexity of the event tree structure, and automatically updating. The main steps are the following: (1) Design an extensive tree-shaped Bayesian network with possible eruptive scenarios following the case of Teide-Pico Viejo volcanic complex. (2) Build a Bayesian model to estimate the long term volcanic hazard for each scenario. (3) Apply the model to Teide-Pico Viejo stratovolcanoes. Finally, we compare the results with those from the Elicitation method applied before, as well as previous Bayesian event tree structures developed for other volcanoes.

[1]  Alicia García,et al.  The seismic noise at Las Cañadas volcanic caldera, Tenerife, Spain: Persistence characterization, and possible relationship with regional tectonic events , 2008 .

[2]  Russell Blong.  Volcanic Hazards and Risk Management , 2000 .

[3]  Ramón Ortiz,et al.  On the predictability of volcano-tectonic events by low frequency seismic noise analysis at Teide-Pico Viejo volcanic complex, Canary Islands , 2006 .

[4]  Joan Martí,et al.  Stratigraphy, structure, and volcanic evolution of the Pico Teide–Pico Viejo formation, Tenerife, Canary Islands , 2000 .

[5]  W. Aspinall,et al.  Developing an Event Tree for probabilistic hazard and risk assessment at Vesuvius , 2008 .

[6]  Warner Marzocchi,et al.  A quantitative model for volcanic hazard assessment , 2006 .

[7]  Devin L. Galloway,et al.  Response plan for volcano hazards in the Long Valley Caldera and Mono Craters Region, California , 2002 .

[8]  J. Gottsmann,et al.  Oscillations in hydrothermal systems as a source of periodic unrest at caldera volcanoes: Multiparameter insights from Nisyros, Greece , 2007 .

[9]  Willy P Aspinall,et al.  Structured elicitation of expert judgment for probabilistic hazard and risk assessment in volcanic eruptions , 2006 .

[10]  G. Woo.  The Mathematics of Natural Catastrophes , 1999 .

[11]  Christopher G Newhall,et al.  Constructing event trees for volcanic crises , 2002 .

[12]  Joan Martí,et al.  Assessing the potential for future explosive activity from Teide–Pico Viejo stratovolcanoes (Tenerife, Canary Islands) , 2008 .

[13]  Christopher R. J. Kilburn,et al.  Multiscale fracturing as a key to forecasting volcanic eruptions , 2003 .

[14]  J. Martí,et al.  Central vs flank eruptions at Teide–Pico Viejo twin stratovolcanoes (Tenerife, Canary Islands) , 2009 .

[15]  Ramón Ortiz,et al.  A long-term volcanic hazard event tree for Teide-Pico Viejo stratovolcanoes (Tenerife, Canary Islands) , 2008 .

[16]  J. C. Carracedo,et al.  Dataciones radiometricas ( 14 C y K/Ar) del Teide y el Rift noroeste, Tenerife, Islas Canarias , 2003 .

[17]  P. Schnegg,et al.  Multiple caldera collapses inferred from the shallow electrical resistivity signature of the Las Cañadas caldera, Tenerife, Canary Islands , 2008 .

[18]  Roger M. Cooke,et al.  Expert Judgement and the Montserrat Volcano Eruption , 1998 .

[19]  J. Gottsmann,et al.  Hazard assessment during caldera unrest at the Campi Flegrei, Italy: a contribution from gravity–height gradients , 2003 .

[20]  Alicia García,et al.  Characterising unrest during the reawakening of the central volcanic complex on Tenerife, Canary Islands, 2004–2005, and implications for assessing hazards and risk mitigation , 2009 .

[21]  Joan Martí,et al.  Stratigraphy, structure and geochronology of the Las Cañadas caldera (Tenerife, Canary Islands) , 1994, Geological Magazine.

[22]  W. Marzocchi,et al.  BET_EF: a probabilistic tool for long- and short-term eruption forecasting , 2008 .

[23]  Willy P Aspinall,et al.  Evidence-based volcanology: application to eruption crises , 2003 .

[24]  Joan Martí,et al.  The Las Cañadas caldera (Tenerife, Canary Islands): an overlapping collapse caldera generated by magma-chamber migration , 2000 .

[25]  Paolo Gasparini,et al.  Quantifying probabilities of volcanic events: the example of volcanic hazard at Mount Vesuvius , 2004 .

[26]  Hervé Guillou,et al.  Eruptive and structural history of Teide Volcano and rift zones of Tenerife, Canary Islands , 2007 .