Alert system to mitigate tephra fallout hazards at Mt. Etna Volcano, Italy

Abstract

Volcanic eruptions may create a wide range of risks in inhabited areas and, as a consequence, major economic damage to the surrounding territory. An example of volcanic hazard was given between 1998 and 2001 by Mt. Etna volcano, in Italy, with its frequent paroxysmal explosive activity that caused more than a hundred fire-fountain episodes. In the period January-June 2000, in particular, 64 lava fountains took place at the Southeast Crater. During the most intense explosive phase of each episode, a sustained column often formed, reaching up to 6 km above the eruptive vent. Then, the column started to expand laterally causing more or less copious tephra fallout on the slopes of Etna; ash and lapilli, therefore, constituted a serious danger for vehicular and air traffic. A software and hardware warning system was developed to mitigate the volcanic hazard indicating the areas affected by potential ash and lapilli fallout. The alert system was mainly based on the good correspondence between the pattern of volcanic tremor amplitude and the evolution of explosive activity. When a fixed tremor threshold was exceeded, a semiautomatic process started to send faxes to Civil Defence and Municipalities directly affected by tephra fallout, together with information on wind directions from the Meteorological Office. The application of this methodology, during the last 14 eruptive episodes in 2000 and the 14 events occurred in 2001, demonstrated the good correspondence between the forecasts on the areas affected by tephra fallout and the effective tephra distribution on land. Despite the integrity of the performance provided by the alert system, small discrepancies occurred in the technical procedure of alerting, for which possible solutions have been discussed. The improvement of this type of system, could become basic for the Etnean region and be proposed for similar volcanic areas throughout the world.

Tephra hazard assessment at Mt. Etna (Italy)

“…2001 and 2002-2003) and its characterization is often difficult due to the high variability of eruptive phenomena and meteorological conditions that influence and scatter the fallout sedimentation (Andronico et al, 2008;Scollo et al, 2007). However, constant monitoring of the explosive activity at Etna has been performed during the last two decades (Alparone et al, 2007;Andronico et al, 2009). An exceptional amount of data was collected thanks to many field surveys that were carried out at the end of explosive activities (e.g.…”

Joint analysis of infrasound and seismic signals by cross wavelet transform: detection of Mt. Etna explosive activity

“…1). Furthermore, for the sake of comparison, we also applied detection methods based on fixed thresholds of seismic and infrasonic RMS (see Alparone et al, 2007a) and reported the results in Fig. 7b and c, respectively.…”

Monitoring and forecasting Etna volcanic plumes

“…Surveillance cameras are very useful for detecting the height of eruption columns and analyze the style of explosive activity. Analysis of these images is used routinely at INGV-CT during Etna explosive activities (Alparone et al, 2007;Andronico et al, 2008a, b;Scollo et al, 2007).…”

“…The constrain of these parameters is usually given by analysis of field data collected during the monitoring activities of INGV-CT (Alparone et al, 2007;Andronico et al, 2009). However, two different typologies of explosive activity have been identified at Etna (Scollo, 2006): one producing strong and short-lasting plumes and another producing weak and long-lasting plume.…”