IAVCEI 2013 Scientific Assembly - July 20 - 24, Kagoshima, Japan
Forecasting Volcanic Activity - Reading and translating the messages of nature for society

4W_3E-P14

Date/Time: July 24 Poster

Eruptions on the fast track, part a): computational routines for processing visible andthermal high-speed videos of explosive eruptions
Damien Gaudin1 , Monica Moroni2 , Jacopo Taddeucci1 , Piergiorgio Scarlato1 , Luca Shindler21

Department of Seismology and Tectonophysics, HP-HT Lab, INGV Roma, Italy, 2 DICEA , Sapienza
Universita di Roma, Rome, Italy
E-mail: damien.gaudin@ingv.it

Recent advancements in the use of high speed thermal and visible cameras allowed a precise quantification of key
parameters of explosive eruptions. However, the large volume of video data poses several processing issues andhinders parameter extraction. In this methodological investigation we show how computing techniques based on
Particle Image Velocimetry (PIV, measuring the displacement of sub-areas of an image between successive frames
by correlating features identified in any sub-area) and Particle Tracking Velocimetry (PTV, detecting and tracking
single particles along a series of images) allows for the automatic processing of high-speed videos and explosion
parameterization.
We developed a 3-steps automatized routine for volcanic high-speed video processing. Step 1 pre-processes theimages, removing image background with different techniques to improve image contrast and possibly accounting
for camera shaking. Step 2 involves running the custom-made PTV and PIV softwares. Step 3 processes thesoftwares outputs while operating a first filtering for numerical errors, and then operates the post-processing of theresults, where several additional filters can be applied to the results and volcanologically-relevant parameters are
finally computed. A sensitivity study was used to define the best settings for each of the above steps and their effecton output parameters.
The overall suitability of our routine and its limitations have been tested on high-speed videos of explosions ofStromboli (Italy) and Yasur (Vanuatu) volcanoes, including a variety of recording conditions and styles of explosive
activity.
From the above videos, PTV enables us to construct, for each explosion, a database including the size andtrajectory of a large number (order of 10000) of cm-to m-sized pyroclasts. From the database a broad variety
of key parameters are then extracted, from single particle ones (e.g., temperature, drag coefficient, deviation fromtheoretical ballistic trajectories), through explosion evolution ones (e.g., time variation of mean exit velocity, angle,mass and related standard deviations), up to whole-explosion ones (e.g., grain-size distribution and total mass ofejecta, thermal to kinetic energy balance, depth of the explosion, geometry of the vent). PIV provides the velocity
vectors of diffuse features, i.e., gas and ash clouds, from which the time and space evolution of: 1) gas ejection
velocity; 2) total ejected volume of gas plus pyroclasts; and 3) plume buoyant rise can be assessed.
Automatized results are in general agreement with previous manual estimations on the same videos but on a limited
number (order of thousands) of particles, supporting the robustness of out procedure. An illustration of the varietyof the volcanological application of this routine is presented in the companion abstract Eruptions on Fast Track, partb.

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