Pierre Gehl, MIAVITA team member,
Risks and Prevention Division, BRGM, Orléans, France
A proof-of-concept software has been developed in order to perform automated impact assessments of a volcanic eruption on a series of exposed elements, ranging from built areas to crops or network infrastructures. This software is an adaptation to the case of volcanic risk of the previous development of a toolbox (Cavalieri et al., 2012) for the seismic risk assessment of interdependent systems (SYNER-G European project). The modified version of this toolbox performs the vulnerability assessment of the following systems of exposed elements, all of them being described in an object-oriented framework (UML diagrams):
- Built areas
- Cultivated areas (crops)
- Road network
- Utility networks (water, electric power supply)
- Critical facilities (decision centers, hospitals…)
Figure 1 – (a) UML diagram of the road network system (b) Example of a road network modeling, from the GIS information to the object oriented framework
This proof-of-concept software needs deterministic scenarios as input (e.g. intensity maps of volcanic hazards, such as the thickness of tephra layers or the position of lava flows) as well as GIS files representing the inventory of exposed elements. The multiplicity of volcanic phenomena that are likely to happen during a given volcanic eruption require the software to operate with a great variety of vulnerability models, depending on the type of damaging mechanism and the elements at risk. For each volcanic phenomenon, a damage table is generated by the software (at component- or system-level). Finally, a global damage table is computed in order to account for the damage accumulation due to the successive volcanic phenomena threatening the exposed elements throughout the volcanic eruption.
Figure 2 – Flowchart of a multi-hazard scenario computation
This software has been tested and applied to an arbitrary volcanic eruption scenario in the Mount Cameroun area. The chosen scenario consists of an explosive eruption resulting in two successive phenomena (ballistic blocks and tephra accumulation). The use of the developed toolbox has enabled the computation of the proportion of buildings with collapsed roofs and the area of damaged crops, as well as the estimation of disrupted or disturbed lifelines (e.g. road segments, power lines...).
Figure 3 – (a) Projection of the Mount Cameroun built areas in the toolbox mesh (b) Damage to built areas due to both ballistic rocks and tephra accumulation in the hypothetical scenario
Cavalieri F., Franchin P., Gehl P., Khazai B. (2012) – Quantitative assessment of social losses based on physical damage and interaction with infrastructural systems. Earthquake Engineering and Structural Dynamics, Special Issue on Seismic Damage and Loss Assessment in Buildings.
SYNER-G (2009-2012) – Systemic Seismic Vulnerability and Risk Analysis for Buildings, Lifeline Networks and Infrastructures Safety Gain. European Collaborative research Project.
We are indebted to MINIMIDT (Ministry of Industry, Mines and Technological Development in Cameroun) for sharing their database of exposed elements in order to conduct the case study on Mt Cameroun. This study has been made possible thanks to the results of previous work carried out within the collaborative research project SYNER-G (www.syner-g.eu), coordinated by Prof. Kyriazis Pitilakis from Aristotle University in Thessaloniki and funded by the European Commission within Framework Programme 7. Regarding the first version of the toolbox for seismic risk assessment, the authors gratefully acknowledge the support from the research groups from University of Roma – La Sapienza (Paolo Franchin and Francesco Cavalieri) and Karlsruhe Institute of Technology (Bijan Khazai).