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
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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.
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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.
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