Seismic unrest at El Hierro Island (Canary Islands): updates Jan-March 2013

New earthquake swarm

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.

Depth vs time of recent quakes under El Hierro

The number of earthquakes continues to be a bit above background with 1-6 small daily events.

Second submarine eruption during 2012 ?

Some new data suggest that a second submarine eruption might actually have occurred at El Hierro occurred at the sea floor SW off El Hierro Island during the strong seismic crises in end of June - July 2012.
Evidence of this claimed eruption were 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. However, some doubts about this evidence remain because while the earthquake swarm was very intense, there were no shallow earthquakes associated with the possible opening of a new eruptive vent. Read all.
Read more about the June-July 2012 seismic activity.
Slightly elevated earthquake activity continues.

New earthquakes

Map of recent earthquakes at El Hierro

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. Most of them were located at depths of 10-15 km depth under the central part of the island.
It seems that the swarm has already ended.

Inflation visible, suggesting magma intrusion

Earthquakes continue under in the eastern El Golfo area. GPS station HI00 in the NE part of the island shows a clear inflation, which suggests that some magma intrusion has been taking place. The tremor signal recorded by IGN is low.

New seismic swarm

A new swarm of earthquakes started on 31 Dec. Most quakes are located at 15-20 km depth under El Golfo and seem to propagate slowly towards the east. On 31, 57 quakes of magnitudes 1.4-2.4 were registered, on 1 Jan, 43 with magnitudes up to 2.6.