The recent eruptive activity of Mount Etna (Italy) monitored by a network of visible and thermal video cameras

Vienna, Austria

INGV, Sezione Catania

The recent eruptive activity of Mount Etna (Italy)
monitored by a network of visible and thermal video
cameras

E. Biale, S. Mangiagli, M. Neri, E. Pecora, D. Reitano and B. Behncke
Istituto Nazionale di Geofisica e Vulcanologia, Sezione di Catania, P. Roma, 2 - 95125,
Catania Italy (pecora@ct.ingv.it, neri@ct.ingv.it)


The recent eruptive activity of Mount Etna in Sicily (Italy) has been well documented
by multidisciplinary instrumental observations, and significantly improved the understanding
of the eruptive dynamics of this volcano. The monitoring networks are currently
developed and managed by the Catania Section of the Istituto Nazionale di
Geofisica e Vulcanologia (INGV). Video footage from the network of the monitoring
video cameras is analyzed to discriminate between different eruptive typologies and
to derive physical and dynamic properties of the eruptions. The cameras are located
in four different places around the volcano (Schiena dell’Asino, Milo, Nicolosi and
Catania), at respective distances of 5, 11, 15 and 27 km from the summit craters. Four
video cameras record in the visible band and one in the Long-wave infrared (LWIR)
over 24 hours/day. The images acquired by the Schiena dell’Asino camera are sent to
a receiver in Catania, through a 10 GHz microwawe transmitter, whereas the signals
from the other cameras are sent to Catania via 2 GHz video transmitters and/or cable.
All images are digitized on computer, and archived on video tape and in AVI format
with each clip representing 15 minutes compressed using 1 frame per two seconds,
which are posted on the intranet server of the institute. A GPS Time-Code ads date
and time to each frame before being digitized to 640 x 480 pixels. Meaningful frames
are selected for analysis from footage of significant eruptive events, through dedicated
software. The cumulative error regarding the measured parameters is estimated at up
to 20%. In 2006, a new FLIR Thermavision A40M infrared camera was installed at
Nicolosi. The camera detector is a 320 by 240 pixel uncooled microbolometer with a
spectral range from 7.5 to 13 micrometer. Vertical and horizontal viewing is 18° and
24 , respectively, with a spatial resolution of 1.3 mrad. Thermal sensitivity is 0.08°C at 30°C. Thermal images are converted on board the camera into a single value for
the peak temperature found in a region of interest centred on the active craters. This
value is transmitted with a frequency of 1 Hz to the acquisition centre in Nicolosi. If
a peak temperature value is less than 2°C than the preceding value then the relative
change is added to the cumulative temperature value. Consequently, when the curve
is near vertical the images registered by the thermal camera suggest increases in explosive/
effusive activity. On the contrary, if the curve is near horizontal the radiance
of the eruptive theatre is constant or in diminution. Thermal images and thermal data
are processed by dedicated software developed by LabVIEW 8.0 in detecting ash-rich
eruptive columns, explosive and effusive activity. All these data are available at the
INGV Control Centre and are used to alert on-duty staff in the early-warning procedures.
This network of cameras furnished fundamental data to the Italian Civil Defence
during the 2006 eruption, when ash-rich columns several km in height severely
threatened the functioning of the nearby International Airport of Catania.