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Etna and Stromboli update, 24 November 2012

20121122-24_EMOH

Two frames extracted from video recorded by the monitoring camera of the INGV-Osservatorio Etneo (Catania) on the Montagnola (EMOH), on the morning of 22 November 2012, and on the evening of 24 November 2012, showing the glow visible at the New Southeast Crater.

Etna: glow at the New Southeast Crater. On the evening of 21 November 2012, a weak glow was observed coming from the interior of the New Southeast Crater (New SEC) of Etna, caused by the emission of high-temperature gas and/or weak Strombolian activity within the conduit. The glow was visible also during the following nights (see images at left), remaining always rather weak and discontinuous. During a summit visit by INGV staff on the morning of 23 November, no sounds characteristically associated with Strombolian activity were heard. Furthermore, the volcanic tremor amplitude shows no significant variations.

After the latest episode of lava fountaining on 24 April 2012 and a brief episode of Strombolian activity a few days later, the New SEC had remained essentially quiet. This quiescence was interrupted, at the end of August, by the formation of a new small pit crater, due to the caving in of a portion of the southwestern rim of the crater. During the past few weeks, degassing from the New SEC has been progressively increasing.

Seismic swarm below Etna's northwest flank. At 09:10 GMT (= local time -1) on 2 November 2012, a seismic swarm started near Monte Maletto, on the northwestern flank of Etna, between the towns of Maletto and Randazzo. Focal depths were around 25 km. Following the first M 3.9 event, further earthquakes with magnitudes larger than 3 occurred at 11:25 GMT (M 3.9) and 11.28 (M 3.5). The swarm ceased on the evening of 22 November, but five new events with a maximum magnitude of 2.6 occurred in the same epicentral area on the early morning of 25 November.

The area affected by this seismic sequence has previously been the site of other earthquake swarms. The most significant of these occurred during the second half of December 2009, when more than 400 earthquakes with magnitudes ranging from 1.0 to 4.8 were recorded.

Stromboli: increase in the explosive activity. On the evening of 22 November 2012, the persistent explosive activity of Stromboli showed a distinct increase, with episodes of spattering and minor lava fountaining from two vents in the northern and central portions of the crater terrace. At 20:57 GMT a major explosion occurred from the northernmost vent. The activity returned to normal levels during the following days.