IAVCEI Commission on Tephra Hazard Modelling

FIRST-MEETING REPORT

Tephra fall is one of the main products of explosive eruptions and forms after material has been explosively ejected from a vent producing an eruption column, which is a buoyant plume of tephra and gas rising high into the atmosphere. Tephra fall can cause respiratory problems to human and animals, serious damage to buildings and can affect several economical sectors such as agriculture and tourism. The study of fall dispersal gives fundamental insights on eruptive dynamics, but it also represents an important aspect of hazard mitigation necessary in those populated area which have developed close to active volcanoes and those area characterized by significant aviation traffic. In an attempt of mitigating tephra-fall hazards several dispersal models have been developed to respond to different volcanic scenarios and fulfill different user needs (e.g. aviation operations, building constructions). We felt that it is important to “join the effort” and gather together scientists with different background to implement our models and make our models more accessible for model users. This is why the IAVCEI Working Group on Modeling Volcanic Tephra-Fall Hazards was born.

The first meeting of the IAVCEI Working Group on Modeling Volcanic Tephra-Fall Hazards took place in Hilo (Hawaii) on July 2003 within the Cities on Volcanoes 3 conference. This first meeting was convened to bring together scientists with different tephra-fall hazard experiences in order to integrate and improve current approaches and tephra-dispersal models. It was open to everyone interested in tephra-fall hazard and therefore it involved computer modelers, model users and field volcanologists. The main issues that were identified during this first meeting are:

1) Development of a model calibration protocol to compare the results of numerical models with observations from well-characterized eruptions.

2) Identification of model parameters to develop a common understanding of model requirements, and appropriate data needs from characterized eruptions.

3) Discussion of well-characterized tephra fall eruptions that could be used to evaluate model accuracies. These eruptions need to have appropriate field or lab measurements to successfully parameterize the models.

4) Outline of a working-group webpage useful for computer modelers, model users and field volcanologists. This webpage will include: description of the working group, description of existing tephra-fall models with corresponding links, shared database of open-source codes and data to facilitate rapid development and use of dispersion models, protocol for tephra sampling and analysis.

5) Identification of specific hazards from tephra, needs of different organizations for hazards analyses (e.g., aircraft alerts, facilities designs, evacuation likelihoods), and appropriate models to meet these information needs.

6) Need to develop a standard protocol for tephra sampling and determination of deposit volume and total grain size distribution to make the studies of different deposits comparable. This sampling protocol should also provide data needed for input parameters for tephra-fall modeling.

7) Likely need to incorporate particle aggregation processes in models for tephra-dispersal.

8) Eventual integration of calibrated models into useable hazard analysis tools that can be widely distributed. This could be done within the MAPGAC program of the Geological Survey of Canada.

The working-group web page is under construction and will be hosted by the IAVCEI main page (www.iavcei.org). This web page will include a brief description of existing models, with corresponding links to home pages. The web page will also contain a database for model parameters from well-characterized eruptions, for use in calibration of existing and future models. Plans are for working-group members to put their codes on-line in order to build a shared database of open-source codes that are useful for rapid development of tephra-fall modeling.

We plan to hold the second meeting of the working group on November 14, 2004 within the IAVCEI General Assembly 2004 (Chile). During this second meeting, we will compare results from model calibration runs and present new data if available. We will also discuss and finalize the protocol for tephra-deposit sampling and analysis. Depending on the results of the model calibration exercise, additional work in model development may be warranted. Alternatively, models may be found suitable for general use in hazards analyses, in which case the working group will proceed in developing a hazard analysis tool supported by resources from the Geological Survey of Canada and other organizations (e.g. Multinational Andean Project; see also presentation by Mark Stasiuk).