Sylvain J. Charbonnier

Vhub: a knowledge management system to facilitate online collaborative volcano modeling and research

Knowledge of volcanic systems and the hazards they produce is rapidly advancing as internet resources become more readily accessible, new and more sensitive field techniques are developed, and ever greater amounts of data are collected. Such rapid advances drive the need for an online collaborative knowledge management system that enables the sharing of volcanological information, and modeling and analysis tools. Vhub (http://vhub.org) is a community cyberinfrastructure platform designed for collaboration in volcanology research, education, outreach, and discovery that complements existing volcano databases and other cyberinfrastructure projects. Vhub is unique in its functionality as a nucleus for the creation of collaborative groups focused on issues such as code development, field research, education, and hazard mitigation. In addition, Vhub serves as a clearinghouse and virtual platform for computational tools relating to volcanic processes and data analysis, as well as documentation to aid in the use and understanding of these tools. By providing a means for scientists to easily disseminate data, models, and ideas, Vhub aims to promote collaboration amongst scientists and to provide resources for science education while advancing the state of understanding of volcanoes and the hazards they produce. This paper introduces the Vhub cyberinfrastructure and provides an overview of select hub features and resources.

Modeling the October 2005 lahars at Panabaj (Guatemala)

An extreme rainfall event in October of 2005 triggered two deadly lahars on the flanks of Tolimán volcano (Guatemala) that caused many fatalities in the village of Panabaj. We mapped the deposits of these lahars, then developed computer simulations of the lahars using the geologic data and compared simulated area inundated by the flows to mapped area inundated. Computer simulation of the two lahars was dramatically improved after calibration with geological data. Specifically, detailed field measurements of flow inundation area, flow thickness, flow direction, and velocity estimates, collected after lahar emplacement, were used to calibrate the rheological input parameters for the models, including deposit volume, yield strength, sediment and water concentrations, and Manning roughness coefficients. Simulations of the two lahars, with volumes of 240,200 ± 55,400 and 126,000 ± 29,000 m3, using the FLO-2D computer program produced models of lahar runout within 3% of measured runouts and produced reasonable estimates of flow thickness and velocity along the lengths of the simulated flows. We compare areas inundated using the Jaccard fit, model sensitivity, and model precision metrics, all related to Bayes’ theorem. These metrics show that false negatives (areas inundated by the observed lahar where not simulated) and false positives (areas not inundated by the observed lahar where inundation was simulated) are reduced using a model calibrated by rheology. The metrics offer a procedure for tuning model performance that will enhance model accuracy and make numerical models a more robust tool for natural hazard reduction.