Auxiliary material for Paper 2013ES004216 Application of Modern Multispectral Imaging to Track Explosive Eruptions A.J.L. Harris (1), S. Valade (1), G.M. Sawyer (1), F. Donnadieu (1), J. Battaglia (1), L. Gurioli (1), K. Kelfoun (1), P. Labazuy (1), T. Stachowicz (1), M. Bombrun (2), V. Barra (2), D. Delle Donne (3), G. Lacanna (3) (1)Clermont Université, Université Blaise Pascal, Laboratoire Magmas et Volcans, BP 10448, F-63000 Clermont Ferrand, France (2) Clermont Université, Université Blaise Pascal, LIMOS - UMR 6158 CNRS, Campus des Cézeaux, 63173 AUBIERE, France (3) Dipartimento di Scienze della Terra, Universita di Firenze, via G. La Pira, 4 – 50121 FIRENZE, Italy [A.J.L. Harris, S. Valade, G.M. Sawyer, F. Donnadieu, J. Battaglia, L. Gurioli, K. Kelfoun, P. Labazuy, T. Stachowicz, M. Bombrun, V. Barra, D. Delle Donne, G. Lacanna (2013), Application of Modern Multispectral Imaging to Track Explosive Eruptions, EOS, XXX, BXXXXX, doi:XX.XXXX/ 2013ES004216.] Introduction Auxiliary material for Paper 2013ES004216 contains this file, plus three AVI files. These files contain ancillary information that provide summary array technical detail and example output. Auxiliary material contents (1) File Name: Supplement 1 Format: PDF (this file, pages 4-7) Title: System Design: Contents: Technical details regarding the instruments that Brief Technical Detail comprise the array, plus logistical notes (2) File Name: Supplement 2 Format: PDF (this file, pages 8-10) Title: System output: Contents: Examples of parameters extracted, and brief Example information regarding methodologies applied for parameter extraction 1 (3) File Name: Video 1.avi Format: avi Title: Thermal camera 1: video Contents: Video of plume ascent using the “stand-off” thermal camera Camera: FLIR AC655sc View: NW from Pizzo to SW crater Location: 0518551 Date/time: 2012-09-27T13h33m02s740 Frame rate: 4293750 (WGS-84) 30 fps Image dimensions: 640 480 pixels (115 86 m) Pixel size: (4) 18 cm File Name: Video 2.avi Format: avi Title: Thermal camera 2: video Contents: Video of plume ascent using the “vent-staring” thermal camera Camera: FLIR SC655 View: NW from Pizzo to SW crater Location: 0518551 Date/time: 2012-09-27T15h49m09s740 Frame rate: 4293750 (WGS-84) 200 fps Image dimensions: 640 135 pixels (33 7 m) Pixel size: (5) 5.2 cm File Name: Video 3.avi Format: avi Title: Stereo camera 1: video Contents: Video of plume ascent one of the stereo cameras with 3D particle trajectories 2 Camera: IP Basler View: SW from Rocetta shelters to NE crater Location: 0518802 Date/time: 2012-10-05T21h39m00s569 Frame rate: 4294128 (WGS-84) 30 fps Image dimensions: 1280 960 pixels (128 96 m) Pixel size: 10 cm 3 Supplement 1 System Design: Brief Technical Detail Our aim was to: (i) characterize plume dynamics at the highest possible spatio-temporal resolution, (ii) test the combined deployment of a complete instrument package, and evaluate its potential for operational plume analysis with (iii) a special emphasis on extracting, in real-time, MDR, vent exit velocities and particle size distributions several times a second. The equipment package the comprised the array designed to achieve these goals involved the following instruments: (1) Two thermal infrared cameras (FLIR Systems cameras, 8-14 microns) One camera was deployed to provide imagery at 200 Hz of hot gas, ash and particles across a narrow (7-m high) window immediately above the vent (see supplement: Video 2.avi). The pixel instantaneous field of view (IFOV) for this vent-staring camera, which was fitted with a 3.6 magnification lens, was 0.19 mrad. This, over a 275 m line of sight, equates to pixels 5.2 cm across. A second camera stood off to image, at 30 Hz, the entire plume ascent history (see supplement: Video 1.avi). This camera had an IFOV of 0.65 mrad, equivalent to an 18 cm diameter pixel. Image dimensions were 640 120 and 640 480 pixels for the two cameras, respectively. (2) One Doppler radar (VOLDORAD2, 23.5 cm wavelength) Custom designed at OPGC, VOLDORAD was set to acquire at 24 Hz over 4-8 sampling 4 volumes (50 50 60 m deep) across the plume so as to quantify the ejection velocities of particles, as well as mass and mass fluxes, especially if the particle size and shape distribution can be simultaneously constrained from the thermal cameras. (3) One Sulfur-Dioxide (SO2) camera Custom designed and built at INGV-Pisa, the SO2 camera acquires 1600 1200 pixel images every 6 seconds in two channels near-simultaneously (at 310 and 330 nm) to quantify the mass of SO2. Calibration of the data is achieved using an Ocean Optics USB2000 spectrometer to continuously collect spectra through the plume at a point within the camera field of view, and also by placing a range of SO2 calibration cells in the field of view before and after the measurement. Total gas flux is obtained by using the cloud ascent velocity, as extracted from the imagery, and coupling with relative proportions of gas species measured by OP-FTIR spectroscopy. OP-FTIR spectroscopy, itself, yields information regarding the source depth of ascending bubbles that generate the explosive activity. Coupled with the thermal camera and radar data, this allows the relative masses of gas and solids to be estimated. (4) One very high frame rate camera (Photron Fastcam SA3 120K) A high speed camera was operated at up to 2000 frames per second (fps). Acquiring 1024 1024 pixel images spanning the visible and near-infrared allowed us to characterize the highest velocities for particles carried by the gas phase. (5) Two stereoscopic cameras (IP Basler, visible and near infrared) These were separated by a distance of 60-85 m and collected synchronous 1280 960 pixel images at a frame rate of 25-30 fps. These were used to reconstruct 3-D particle 5 trajectories and further constrain their sizes (see supplement: Video 3.avi). (6) Two thermal infrared radiometers (Minolta/Land Cyclops 300, 8-14 microns) These were coupled to a SETRA pressure sensor and sampled at 50 Hz to obtain thermal time series associated with the emission, and the associated pressure variations. Using velocities, cloud densities and temperatures (to estimate sound speed in the conduit) extracted from the synchronous thermal camera data, the time delay for the onset of the infrasonic and thermal waveforms associated with explosion and emission, respectively, can yield explosion depth. These data were supplemented by installation of a Guralp seismometer and the permanent geophysical monitoring array installed on Stromboli by the geophysical group of Dipartimento di Scienze della Terra, Universita di Firenze, led by Maurizio Ripepe. This array allows characterisation of the seismic signal associated with explosive activity, including location of the very long period (VLP) signal, and location of the vent responsible for the emission using infrasonic array location. The network also includes a continuously recording thermal camera and a radiometer. In addition, all particles landing in well-defined areas within the fall out zone during individual eruptions were collected. To do this, four 3 4 m plastic sheets were set out at a location 75 m SW of the active vent. All samples landing on these were retrieved for density and textural analysis at the textural laboratory of the Laboratoire Magmas et Volcans at the Université Blaise Pascal (Clermont Ferrand, France). Logistical Notes Due to the reliability of explosive activity, ease of access and generous operational 6 support from the Centro Operativo Avanzato (COA) on Stromboli, as well as the Dipartimento della Protezione Civile (DPC) in Rome, the volcano of Stromboli (Italy) was selected for a test deployment: Stromboli being a reliable particle emitter where experimental plume measurement approaches can be tested and refined before operational deployment. Deployment was carried out between September 27 and October 7, 2012 at a cost of 25 k€ (33 kUS$). This covered all transport, shipping, personnel and deployment costs for the 17 day deployment, including 2.5 hours of helicopter time at 6400 € (8400 US$) and support of 12 field personnel. Instruments took less than 48 hours to pack and ship to the eruption site, with field deployment taking 1 hour of helicopter time (8 trips, including 4 sling loads; the last of involving an airborne thermal survey of the vent area followed by personnel drop). Set up and targeting of all equipment then took less than an hour. Each of the 12 field specialists were specifically trained, briefed and designated for set up, targeting and operation of the piece equipment to which they were assigned, so that each instrument team worked independently to ensure fully integrated data acquisition of the total network within 45 minutes of on-site arrival. For our experiment, data were collected on-site using GPS-time synchronised data loggers, but data could easily be transmitted off-site for ingestion into a common acquisition and procession system at a central operations centre. 7 Supplement 2 System output: Example Two types of activity were sampled during the test deployment: (i) Type 1 eruptions dominated by gas and coarse (bomb and lapilli sized) ballistic particles, and (ii) Type 2 eruptions involving a mixture of ballistics and convecting clouds of gas and ash [Patrick et al., 2007]. These attained typical heights of around 100-150 m. By way of example of system output, thermal, radar and seismic derived waveforms for a Type 1 eruption at 14:01 on September 27 are given in Figure 1d of the main article. Sample infrared and ultraviolet images for the Type 1 eruptions that typified the afternoon of September 27 are given in Figures 1a and 1b. The video’s from which these stills are taken are given in two supplements: Video 1.avi and Video 2.avi. Muzzle velocities recorded by the vent-starting thermal camera for the 14:01 event were 80-156 m s-1, with a mean and standard deviation for all particles passing through the radar range gates being 55 and 30 m s-1 (from 191 measurements). The maximum radial velocity recorded by the radar of 156 m s-1 matched perfectly that obtained by the thermal camera. A type 1 event at 15:50 gave thermal camera derived a maximum velocity of 288 m s-1, with a mean and standard deviation of 43 and 27 m s-1. This maximum value approaches the anomalously (compared with past measurements) high values recently found by Taddeucci et al. [2012] and Harris et al. [2012] and is probably due to small particles being carried by the gas phase, and is thus a proxy for the velocity of the gas jet [Harris et al., 2012]. For the stand-off thermal camera, the method of Harris et al. [2012] was applied to obtain the 2-D areas of hot sub-pixel particles. Following Chouet et al. [1974], the image with the greatest number of particles was selected for volume estimation. A shape assumption 8 was applied to each particle in this image to convert to particle volume. Volumes of all particles were then summed to estimate total volume. For the 14:01 event, 5.7 m3 of bombs were emitted, which should be considered as a lower bound. Bomb and lapilli densities were obtained from field samples. This data set comprised 53 bombs whose densities were measured using the Archimedes principle to give a mean of 1810 kg m-3, a standard deviation of 180 kg m-3 and a range of 1370-2300 kg m-3 [Gurioli et al., 2013]. For lapilli we have a range of 900-1700 kg m-3, with a mean and standard deviation of 990 and 110 kg m-3. Using the average bomb density, the bomb volume obtained for the 14:01 event converts to a mass of ~104 kg. For a 7-8 second emission duration, this gives an MDR of 1375 kg s-1. For the vent-staring camera, the optical flow equation for particle detection and velocity tracking of Shindler et al. [2012] was coupled with the method of Bai et al. [2011] to allow all particles to be identified and tracked. For the 15:50 event a preliminary version of the algorithm detected 1033 bombs with a total volume of 7-30 m3 (depending on the shape assumption used in the volume conversion), which gives a maximum bound on the bomb mass of 5 104 kg. For an emission duration of 7 s this, in turn, gives a maximum bound on MDR of 7750 kg s-1. Our current estimate for the total mass of lapilli is between 1.5 and 5.9 kg. We are in the process of refining the methodologies, and thus also these masses; however, they currently give a ball-park estimate with which to work. Over one 3 4 m in-situ sample collection sheet (which had been cleaned just prior to the fall out event) 5.27 g (or 0.44 g m-2) of ash, lapilli and Pele’s hair arrived during a 10 second-long fall event. Assuming that deposition was similar across the 4000-8000 m2 fall out area identified using the thermal imagery, this multiplies up to a total ash and lapilli mass of 1.8-3.5 kg; falling within the range of our thermal camera estimate. Deposition was highly discontinuous, with only 48 particles landing in the 12 m2 collection area; all of which were collected. 9 References Bai, X., Zhou, F., and H. Xue, 2011, Infrared image enhancement through contrast enhancement by using multiscale new top-hat transform, Infrared Physics & Technology, 54, 61-69. Chouet, B., N. Hamisevicz, and T.R. McGetchin, 1974, Photoballistics of volcanic jet activity at Stromboli, Italy, J. Geophys. Res., 79, 4961-4976 Harris, A.J.L., Ripepe, M., and E.E. Hughes, 2012, Detailed analysis of particle launch velocities, size distributions and gas densities during normal explosions at Stromboli. J. Volcanol. Geotherm. Res, 231-232, 109-131 Gurioli L., Harris A.J.L., Colò L., Bernard J., Favalli M., Ripepe M., and D. Andronico, 2013, Classification, landing distribution and associated flight parameters for a bomb field emplaced during a single major explosion at Stromboli, Geology, DOI 10.1130/G33967.1 Patrick. M.R., Harris, A.J.L., Ripepe, M., Dehn, J., Rothery, D., and S. Calvari, 2007, Strombolian explosive styles and source conditions: Insights from thermal (FLIR) video. Bulletin of Volcanology, 69, 769-784. DOI: 10.1007/s00445-006-0107-0 Shindler, L., Moroni, M., and A. Cenedese, 2012, Using optical flow equation for particle detection and velocity prediction in particle tracking, Applied Mathematics & Computation, 218, 8684-8694 Taddeucci, J., P. Scarlato, A. Capponi, E. Del Bello, C. Cimarelli, D. M. Palladino, and U. Kueppers, 2012, High-speed imaging of Strombolian explosions: The ejection velocity of pyroclasts, Geophys. Res. Lett., 39, doi:10.1029/2011GL050404. Full Details of Figure 1. (a-c) Visible and thermal images of a plume associated with the explosive event recorded at 14:01 UT on 27 September 2012, and SO2 camera (optical depth) image for a plume active at 15:35 UT on the same day. (d) Thermal, radar and seismic data for an explosive event recorded at 14:01:15 UT on 27 September 2012. 10