Des scientifiques de l'IGN ont déclaré qu'ils ne sont pas 100 % certain encore si une éruption est en cours ou pas, bien que des gaz volcaniques du côté sud de l'île ont été détectés et il n'y a pure tremblements volcaniques harmonique, typique des éruptions volcaniques.
Distribution of the recent earthquakes under El Hierro (IGN) - note the distinct two layers at about 20 and 10 km depth
The recent seismic crisis could be over: No further significant earthquake activity has occurred since the last pulse on Wednesday. It becomes more and more likely that the crisis (or, if that is was what caused it, the magmatic intrusion under western El Hierro) has ended. ...plus
Deformation (inflation and horizontal displacement to the east) has eased a lot. For the vertical movement, the strong inflation has stopped or even began to show a trend of deflation. [moins]
The situation has not changed much. Pulsating tremor and strong earthquakes up to magnitudes 4.3 continued throughout the night and have intensified this morning. A further small migration towards the south can be noted. Most quakes remain in the layer at 18-20 km depth. ...plus
Deformation (uplift and eastwards displacement) continue as well, although at somewhat reduced rate, and have have reached 12 cm in the parts of western El Hierro. [moins]
After a day of weakened activity, the seismic swarm has increased with higher energy tremor and stronger earthquakes than ever. Hundreds of earthquakes have occurred so far, including about 25 > magnitude 3 and no less than 4 felt earthquakes above magnitude 4 (M4.1-4.6). ...plus
The likelihood of a new eruption in a possible near future thus once again increased. [moins]
The likelihood of a new submarine eruption in the near future is increasing. Earthquakes and pulsating strong tremor continued with little changes, and a trend towards stronger quakes (a magnitude 4 event this morning), and shallower quakes as well (many at around 11-12 km depth today).
The scenario of an eruption in the near future is becoming increasingly likely. ...plus
Volcanic tremor continues, suggesting magma is still moving although mostly laterally for the time being to an area just northwest off the western tip of the island. Earthquakes continue at high frequency and increasing magnitudes (33 quakes today above magnitude 2 including 3 above magnitude 3 so far). Their epicenters have remained at 14-16 km depth mostly, with some shallower events as well. [moins]
A third, intense pulse of quakes and harmonic tremor started late last night and is going on at the moment. A magnitude 3.8 quake early today marks the so far largest event. ...plus
The location of the latest quakes moved again a bit further to the west, and is now clustered at about 15-17 km depth beneath the western tip of the island. If the earthquakes are indeed caused by magma moving opening new cracks and moving at depth, they indicate that pressure has been building up during the calmer intervals and that now magma has continued to migrate and is now below the western rift zone. Interestingly, this is also very near the vent of the (probable) last historic subaerial activity of the volcano, at Volcano de Lomo Negro, in 1793. [moins]
A powerful new earthquake swarm accompanied by volcanic tremor has started under the western part of the island. So far, the quakes are mostly at about 20 km depth. A plausible cause is that another magma intrusion from the mantle into the crust under the island has just started.
The detected submarine volcanic plume as evidence for an eruption (INVOLCAN)
Depth vs time of quakes at El Hierro during the June-July 2012 seismic crisis
Some new data suggest that a second submarine eruption occurred at El Hierro last year. Spanish scientist have published what they claim evidence that a second submarine eruption actually occurred at the sea floor SW off El Hierro Island during the strong seismic crises in end of June - July 2012. ...plus
Evidence of this claimed eruption was detected by the oceanographic vessel Hesperides using sonar images which, according to the researchers showed volcanic material erupted in an area less than 2 NM from the coast and at depths of 64 to 88 meters. The material formed a plume that rose up to a depth of 48 meters. Involcan claims that the strong deformation and increased gas emissions at that time confirm this hypothesis. However, as earthquake-report mentioned, no earthquakes at shallow depths occurred. But exactly this would have to be expected if new eruptive vents opened there. All in all, it is fair to keep some doubts about the presented conclusion. [moins]
Small earthquakes have started to occur again in increased numbers. Following a period of calm with many days without any quakes, about 9 small quakes in the range of magnitude 1-2 have been recorded over the past 48 hours.
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