Updates April-August 2012: seismic swarm and tremor in June-July
Deflation recorded, few earthquakes
Update Wed 22 Aug 18:00
So far, only 4 quakes occurred at El Hierro today. In addition, some deflation of about 2 cm has been registered over the past few days, suggesting that magma is withdrawing from under the island.
Deformation charts of El Hierro (IGN)
Update Tue 21 Aug 17:37Only 5 very weak quakes have been recorded today so far. It seems that the swarm is ending.
Seismic swarm decreasing, but size of quakes increase
Update Mon 20 Aug 14:39
The seismic swarm at El Hierro continues, but the number of quakes has been decreasing. Yesterday, 8 quakes (all below M2) were recorded and today there have been 5 weak quakes so far. The strength of the earthquakes has however increased, and the latest quake was a M2.7 event at 20 km depth under the western tip of the island.
Location of recent quakes under El Hierro (IGN)
Update Sun 19 Aug 11:20
The earthquake swarm seems to be ending or is at least decreasing. No quakes have been listed so far for today (although a few seem to be visible on the seismic recording) while there were about 25 small quakes yesterday.
Location of the recent earthquake swarm at El Hierro (IG)
Update Fri 17 Aug 18:29The swarm continues in the same area at aroud 10 km depth beneath the western El Golfo coast, but seems to be decreasing. Yesterday, 58 quakes occurred, today so far 18 although this number is likely to rise.
Tremor is low.
New seismic swarm at 10 km depth near the coast of El Golfo
Update Thu 16 Aug 12:42
Seismic signal with a cluster of small quakes today (IGN)
A new earthquake swarm has started yesterday just north off the western El Golfo coast. So far, more than 50 (mostly very small around magnitude 1) quakes have been registered since yesterday. The quakes are clustered at around 10 km depth, i.e. only half the distance to the surface than the previous swarms. A small increase in tremor is visible as well.
Location of recent quakes under the El Golfo coast (IGN)
Update Mon 13 Aug 16:54A total of 5 earthquakes (between M1.3-2.4) at 10-19 km depth has occurred today so far. This is the highest number in many days.
Slightly increased number of earthquakes, M2.4 quake at 3 km depth on 8 Aug
Update Thu 09 Aug 12:26
During the past days, the number of quakes beneath El Hierro has shown an increase. Since 7 Aug, 10 small quakes have been recorded at depths mostly between 10-22 km, i.e. significantly shallower than during the seismic swarm in late June-early July. The largest quake was a M2.4 yesterday at only 3 km depth beneath the western ridge of the island under the Tanganasoga volcanic system.
Earhtquake locations during the past 2 days under El Hierro
There is currently no significant tremor signal visible suggesting magma movements.
Update Wed 25 Jul 15:35
El Hierro volcano (Canary Islands, Spain) reported 11 earthquakes today and yesterday mostly SW off the island. This is a significant number compared to the many preceeding days of relative calm.
Recent quakes on El Hierro (IGN)
Seismic swarm with about 50 quakes >M2.5 on 8 July
Update Sun 08 Jul 17:02
Another swarm of earthquakes with about 50 quakes between M2-3.3 occurred today under the Las Calmas Sea SW of El Hierro. The quakes were at depths mostly between 20-25 km, i.e. slightly deeper than most previous quakes and could indicate a new intrusion from depth. Also, the quakes are continuing to migrate now eastwards closer towards the area of the 2011-12 submarine vent south of La Restinga. It is also a clear sign that the seismic crisis on El Hierro is far from over.
Seismic swarm today between 9-13 am UTC (IGN)
Earhtquake locations during the past 2 days, showing the migration eastwards towards the former eruption area
Seismic activity decreases
Update Sat 07 Jul 15:06
The seismic activity has calmed down since 4 July, after several pulses of intense earthquake activity, sometimes accompanied by an elevated tremor signal, in particular during 29 June - 1 July, and 2-3 July. During 1-7 July, there were 680 earthquakes, mostly between M1.5-3, but also 56 quakes >M3 and 3 larger than M4, the largest a M4.4 on 2 July, were recorded.
Location of the quakes during the past 48 hours (IGN)
The epicenters have remained at about 18-21 km depth at or near the SW tip of the island, suggesting that magma has accumulated there.
Uplift of the island has continued and reached peak values of up to 10 cm total, but also stagnated in the past days.
The next days to weeks will show whether the magmatic process is coming to a halt or continues and still leads to a new eruption.
Activity burst with strong tremor and frequent quakes
Update Fri 29 Jun 15:33
Since 12:40 UTC, a strong tremor signal and many stronger quakes have been recorded. A series of about 10 strong volcanic quakes (probably well >M2.5) occurred between about 13:00-13:10. Magma is moving again, but we have to wait to see the location of the quakes.
Burst of seismic activity after 12:40 (IGN)
As the quakes get listed, it seems that they are in the Las Calmas Sea south of the El Julan coast at about 20 km depth.
Seismic activity decreases
Update Fri 29 Jun 11:09
Decreasing seismic activity (IGN)
Since about 2am today, the seismic activity has dropped markedly. Quakes continue, but at lower rate and most of them are weak ( Animated visualization of the hypocenters of the recent earthquake swarm (www.avcan.org)
Depth of quakes during the past 10 days (AVCAN)
New shallower quakes (16 km), press release (PEVOLCA) admits strong deformation of up to 5 cm
Update Thu 28 Jun 18:29Some of the latest quakes were measured at 16 km depth. It becomes clearer and clearer that some magma has probably started to rise!
A new press release by the government admits that deformation of the island due to magma pressure is strong. It was kindly translated by Earthquake-Report:
"We have observed a deformation of the entire island. The center of the deformation originates in the present earthquakes area (see below)
The energy release and ground deformation show an acceleration of the active magmatic process on the island of El Hierro, according to information forwarded by the National Geographic Institute at the direction of the Civil Protection Plan for Volcanic risk (PEVOLCA)
The GPS network solution, measuring the surface strain on the island shows that there is a clear process of inflation, marking an apparent center of pressure in the area where the seismicity is located. The total cumulative displacement from 24 June to 24 hours yesterday, is about 3-4 cm in the horizontal components and 4-5 cm in the vertical component.
Since the beginning of the new magmatic process on June 24, there have been over 750 earthquakes. An earthquake with a Magnitude 4.0, occurred yesterday at 18:55 pm in the Las Calmas Sea, 2 km from the coast and 20 km deep.
Be remembered as the seismicity started in the El Golfo bay, then moved to the center of the island, coinciding with the point of intersection of the ridges, and later migrated to the west. Since the 25th of June the seismicity is concentrated in the west and El Julan. From 12:00 hours. On 27th of June, seismicity began to migrate towards the Las Calmas sea."
Quakes continue, often depths now at 17 km
Update Thu 28 Jun 16:20
Location of earthquakes today since 09:00 (AVCAN)
The intense quake swarm continues underneath the El Julan coast, with about 90 quakes > M1.5 so far today. Some of the quakes are now measured to be at 17 km rather than 19-20 km depth. It could indicate a weak trend of magma rising, but as for now, it is not very clear. Tremor is mostly relatively low, but increases in phases typically lasting a few hours before decreasing again.
Seismic recording (IGN) showing frequent quakes and a phase of elevated tremor (IGN)
Update Thu 28 Jun 07:18
Location of quakes during the first 3 hours on 28 June (AVCAN)
Earthquakes continue, but at slightly lower rate. In the first 3 hours, 19 quakes >M1.5 were recorded by IGN, all at 18-19 km depth beneath the El Julan coast.
Ongoing quakes but low tremor signal on 28 June
Tremor is low, suggesting magma might be blocked in this area for the time being.
Total earthquakes on 27 June: 197 above M1.3, most of them between M2-3, one at M4 which was felt by most people on the island. Quake depths still at 20 km.
Quakes migrate southwards into Las Calmas Sea
Update Wed 27 Jun 20:09
Seismic signal on 27 June (IGN)
Earthquakes are still at 20 km depth and continue at high rate (more than 150 >M1.5 today, mostly larger than M2). Accompanied by harmonic tremor, their location is migrating southwards into the Las Calmas Sea. In other words, magma continues to move southwards and the question is whether or not it will at some point start rising to the surface.
Location of the latest quakes (AVCAN)
Strong deformation detected, yellow alert for El Julan areaFinally, INVOLCAN has published the important information that during the last 2 days significant and rapdid inflation was measured in the southern part of the island: At the El Pinar station, there has been horizontal eastward displacement of 2 cm and northward of 3 cm. The vertical displacement was 2 cm.
This deformation is most likely caused by the accumulating magma underneath, and it is much faster than those observed last year 2011 prior to the eruption south of La Restinga.
A "yellow alert" has been declared for the El Verodal or the western tip of the island and the southern area in the El Julan bay, where most quakes are located, and an eruption could be imminent.
Quakes continue beneath the El Julan coast
Update Wed 27 Jun 10:11
The quakes continue; up to now, 60 quakes (most of them between M2-3) were recorded and listed by IGN, still at around 20 km depth and in the EL Julan area. Tremor has decreased but is still present. Apparently, magma keeps moving somewhere.
Location of the latest quakes since midnight (AVCAN)
Summary of yesterday 26 June:
The location of quakes between 17:00 and 24:00 on 26 June (AVCAN)
A record number of 234 quakes >M1.4, most of them larger than M2 and 6 larger than M3, all at about 18-20 km depth. Since tremor set in again after 16:10, quakes migrated to the El Julan area.
Update Wed 27 Jun 01:29
No significant change to report. The volcanic tremor has subsided again, but earthquakes continue at about 20 km depth in the El Julan area. More than 200 quakes >M1.5 have occurred today.
Seismic signal on 26 June (IGN)
If what caused this activity is fresh magma rising from the mantle beneath El Hierro, it now has moved a few km more to the south, but still remains at relatively great depth (20 km). Whether it remains there or continues to move, and perhaps rises towards the surface = cause an eruption, is speculation.
Update Tue 26 Jun 20:11
Quakes (indicators of magma flowing) continue to migrate south and east at the El Julan coast towards the Las Calmas Sea.
Location of the latest quakes (AVCAN)
Strong quakes correlate with onset of tremor, located further to the south
Update Tue 26 Jun 19:59
Latest quakes as listed by IGN
IGN now lists the quakes faster it seems. At the onset of the tremor, a series of larger quakes (3 above M3) occurred in the southern area: there were 3 quakes of M3.1, and two of M3.5 at or near the El Julan coast west of El Pinar. So, it does seem that there is some southward migration of magma going on, although the depth remains at 20 km. One push further towards an eruption.
Location of the latest quakes - the 3 quakes at the south coast occured after 16h00 (AVCAN)
Update Tue 26 Jun 19:48To see whether the earthquake locations and their depth changes towards the surface, which would be the expected sign of an eruption to start, IGN will start listing the current quakes only with a delay of about 2 hours, unfortunately. You can check it at: www.01.ign.es/ign/layoutIn/volcaListadoCatalogoVer.do.
Volcanic tremor has reappeared
Update Tue 26 Jun 19:08
Seismic signal on 26 June (IGN) with the tremor reappearing
Spectrum of the seismic recording showing the tremor signal reappearig around 16h30 (IGN)
Some minutes ago, following a pause of about 24 hours, volcanic tremor has started again to be visible on the seismograms. What exactly this means is difficult to know, but most likely, this indicates that magma is moving again underneath the island. Where to and whether or not it might reach the surface and initiate a new eruption is difficult to know at the moment. It is essential to continue to monitor location and magnitude of earthquakes.
Seismic recording 16-17h00 with the onset of strong tremor (IGN)
More than 140 quakes so far
Update Tue 26 Jun 18:07The number of earthquakes continues to rise - more than 140 quakes at M1.5 and higher were recorded so far, most of them between M2 and M3, and at around 20 km depth beneath the central part of the island. No tremor signal accompanies the quakes, suggesting simply that magma for now is not moving much, but pressure is breaking lots of rocks underneath the island.
Quakes continue, but no harmonic tremor
Update Tue 26 Jun 10:58
Volcanic tremor (thought to correspond to flowing magma in the underground) is still absent, but earthquakes (probably rock fracturing caused by magma pressure and small injections) are continuing at a high rate. So far, there have been about 50 quakes above M1.5 today. Most quakes are in the central part of the island between El Golfo and El Julan, or beneath the Tangenososa volcanic system. It can be assumed that a significant volume of magma arrived in this area yesterday if that is what the tremor signal actually was caused by. If so, this magma seems to be blocked for now, probably until a larger quake opens a sufficiently large new path towards a new location.
Map of today's quakes on El Hierro so far (AVCAN)
Interestingly, a few quakes at slightly shallower depth (16 km vs 18-20 km) have appeared in the area of El Pinar, significantly more to the E and S and closer to the 2011-12 submarine vent at the new cone 88 meters below the Las Calmas sea. It is speculation at this point to say that this could be a first hint, that new paths towards the southern rift zone are beginning to be opened.
For a great animation to see the spacial and temporary distribution of quakes, please visit the AVCAN page: www.avcan.org
Update Tue 26 Jun 08:36
During the first 4 hours, 26 quakes >M1.5 were recorded by the Instituto Geográfico Nacional (IGN) and they seem again to be getting stronger. While they still are at "safe" 20 km depth, yesterday, one quake near El Pinar (in the southern part of the island) was at only 11 km, today, one quake in this area is listed but without depth.
Quake list of early 26 June (IGN)
Seismic signal on 26 June (IGN)
Update Tue 26 Jun 06:20The earthquakes continue (so far 14 events > mag 1.5 today) in the SW part of the island at around 20 km depth, but the tremor signal has almost subsided. It might be a sign that pressure is building up without magma moving much at the moment.
Yesterday's earthquake count: 180 quakes larger than mag 2, including 4 events at mag 3.2, 3.5, 3.8 and 3.1.
Update Mon 25 Jun 23:31
So far, 136 m2+ earthquakes have been listed by IGN. The total number by the end of the day is likely to be bigger than that. The volcanic tremor has dropped and almost subsided after about 17h00 UTC; the intrusion of magma has probably stopped for now.
Seismic signal on 25 June (IGN)
Update Mon 25 Jun 20:12Today marks the day with the largest number of m2+ earthquakes since 30 September 2011. Julio del Castillo Vivero in cooperation with Avcan has published an animation showing the propagation of the quakes, corresponding to the magma movement underground, which is currently blocked at El Julan:
Update Mon 25 Jun 17:59
The intensity of the swarm has decreased during the past hours. The latest quakes were located in the SW at the EL Julan (south) coast and still at about 20 km depth. On the map below the gradual propagation is visible. The question is whether magma continues to push southward and/or upwards, or if the injection comes to halt.
Map of the quakes during the 24-25 earthquake swarm so far (AVCAN)
Seismic signal showing a decrease of tremor and quakes (IGN)
Update Mon 25 Jun 15:16
Recent quakes (old-recent = yellow-green-red-purple) showing the trend towards the south of the island (AVCAN)
The earthquake swarm continues as can be seen on the tremor signal. So far, IG lists more than 90 quakes above magnitude 2; the total number of quakes including smaller ones is probably in the hundreds, and the seismic signal shows quakes occurring 1-2 times per minute.
Seismic signal 12-13h on 25 June (note that the displayed time frame has been changed from daily to hourly view) (IGN)
The latest AVCAN graphic shows a trend that the quakes are slowly propagating towards the south, in a similar way as last year, first to the south to Los Llanillos, then towards the west under Tanganasoga and from there to El Julan until the Las Calmas Sea.
It is plausible that magma could be moving along similar paths as previously, using areas of already highly fractured rock. If the magma finds its way up to the surface, it might be able to reactivate the submarine vents near La Restinga, or it could erupt closer to land or even on land. Until now, this remains speculation, but an eruption in the near future is a real possibility. According to INVOLCAN, there is no significant deformation (inflation) detected in association with the ongoing quakes.
For further updates, please visit also these interesting websites:
Actualidad Volcánica de Canarias (AVCAN)
Eruption warning for El Hierro (VolcanoCafe)
Earthquake-Report (frequent updates)
ESPECIAL CRISIS SÍSMICA (Diario El Hierro)
INSTITUTO VOLCANOLÓGICO DE CANARIAS (INVOLCAN on facebook)
Update Mon 25 Jun 12:10
The earthquake swarm continues. So far, there have been 70 quakes, almost all at around 18-19 km depth according to the IGN. It seems that the quakes are becoming stronger. So far, no eruption is imminent, but if their depth decreases, as magma pushes upwards and finds new paths, this could change quickly.
Location of the seismic swarm 24-25 June (IG)
Update Mon 25 Jun 11:28The number of quakes has risen to 65, including a relatively large one at magnitude 3.8 at 19 km depth a few minutes ago. This is surely the most significant earthquake swarm in recent months.
Strong seismic swarm under the central part of the island
Update Mon 25 Jun 10:12
Localization of earthquakes during 24-25 June (IGN)
A seismic swarm, this time located under El Golfo and the central part of the island between Sabinosa village and Malpaso at 20 km depth under the crest of the El Golfo escarpment. The swarm started yesterday evening 24 June and is still ongoing as of morning 25 June. So far, there more than 50 quakes mostly around magnitude 2-3, including 3 at magnitude 3.0-3.1.
The tremor signal accompanying the earthquake swarm (IGN)
A relatively strong volcanic tremor signal is visible as well. The swarm follows a series of similarly located swarms in the past few weeks, but is significantly stronger and most likely indicates that new magmatic intrustions are taking place. Whether or not this might lead to a new eruption, perhaps from a vent on land, is still matter of speculation.
Update Wed 20 Jun 12:44Yesterday (19 June), the number of quakes from the swarm increased to 17. Only one occurred today so far, and it seems the swarm is over. When will the next one occur?
New seismic swarm under El Golfo Bay
Update Tue 19 Jun 12:10
A new seismic swarm has started last night (18 June) under the El Golfo area. Until now, there were 22 quakes last night and 7 today, including 3 larger than magnitude 2. The depth of the new quakes is around 17.5 km, significantly shallower than during the swarm last week.
Location of earthquakes during 18-19 June (IG)
A plausible explanation could be rising magma underneath the island producing magmatic intrusions at decreasing depths. It will be interesting to follow the developments and see whether the number of quakes increases and their depths decrease, in which case a new eruption could be preparing itself for the near to medium future (weeks to months).
Seismic swarm on 14 June
Update Sun 17 Jun 12:23
Another seismic swarm with over 20 earthquakes at depths around 20-25 km under the El Golfo bay just north of the coast has occurred recently. 5 quakes were larger than magnitude 2, the largest being an mag 2.7 event.
Earthquake swarm at El Hierro during 14 June (IG)
Probably, this reflects a small magmatic intrusion at depth, but is far from the intensity of quakes preceding the submarine eruption in Oct 2011.
Update Sat 09 Jun 12:37After the recent swarm of earthquakes, seismicity has gone back to almost no activity in recent days.
Results of a recent research campaign aboard the Atlantic Explorer from the Universidad de Las Palmas de Gran Canaria have been published at: www.ulpgc.es/hege/almacen/download/7097/7097354/8pdf__rov2.pdf
The survey shows 2 vents of degassing (one very intense) on the submarine cone at depths >140 m. In addition, it appears that ash or occasional larger particles are still being ejected from the area as well.
W-E echosound profile of the submarine cone showing the degassing vents
Earthquake swarm continues - new magmatic intrusion ?
Update Tue 05 Jun 11:13
The earthquake swarm at El Hierro volcano continues. Yesterday, a total of 16 quakes including one of magnitude 2.9 were recorded. The quakes are clustered around the 15-20 km depth beneath the El Golfo bay, where a new magmatic intrusion could be taking place. The harmonic tremor signal has risen slightly as well.
Locaation of the latest earthquake swarm at El Hierro (IGN)
New minor earthquake swarm at El Hierro
Update Sun 03 Jun 16:43After weeks of almost no activity, a small earthquake swarm has started yesterday. During the past 36 hours, 12 mostly very small quakes have occurred at depths mostly around 10-20 km in the area NW of Frontera. This possibly indicates that magma is still occasionally moving under the volcano, but unless the intensity of earthquake swarms increases a lot, it is not likely that a new eruption is in the making.
Almost no more activity above background levels
Update Wed 23 May 19:56Almost no earthquakes have occurred since the last update, and intervals between the occasional weak quakes are becoming longer. In addition, degassing activity from the submarine vents has decreased and there are no more visible stain or jacuzzi reported from near La Restinga. We therefore decided to put El Hierro back to "green".
5 small earthquakes on 12 May
Update Mon 14 May 18:42A slight increase of seismic activity has been noted recently. On 12 May, 5 small quakes occurred in the western part of the island at depths of 2-17 km. It is unlikely that this is a precursor of a new eruptive phase, but rather reflects residual magma movements and minor tectonic adjustments at the recently emplaces dikes beneath the island.
Minor seismic activity and weak degassing continue
Update Fri 04 May 15:07
The overall decreasing trend of what is left of the volcanic activity at El Hierro continues. Still, a few, mostly very small quakes continue to occur focused in 2 areas SW and NW of the island. Occasionally, a weak stain and sometimes bubbling water is seen above the submarine vent near La Restinga. Measurements indicate that the vent is still degassing, but with very low SO2 content, suggesting that there is no more fresh magma moving towards to the surface.
Earthquakes at El Hierro during 21 April - 1 May 2012 (AVCAN)