Saturday, March 23, 2013

El Hierro: Renewed earthquake activity

NOTE: Oldest posts are at the bottom of this page.

+New post Nov. 8th,  2015:
 3,7 quake close to El Hierro
+New post March 15th 2014:
+New post Dec. 29th, 2013:
+New post Dec. 28th, 2013:
+New post Dec. 27th, 2013:
+New post Dec. 24th 2013: 

+LINK TO ADDITIONAL POST of AUGUST 2013: Earth Tremor South of La Gomera and El Hierro

Original posts to April 2013:  
Note: Oldest posts at bottom of this page:

FINAL update of this post - Monday April 22nd 2013:
As there is hasn't been much activity for more than 10 days now and as this post is getting too long, there won't be any further updates here. 
In case of renewed or stronger activity I will post a new article, and a link to that will appear on top ^
Update Wednesday, April 17th, 1pm:
Still very little activity.
Update Friday, April 12th, 10am:
Very little activity again: Only 15 very minor earthquakes in the past 3 days.


Update Thursday, April 11th, 7pm:
Renewed stronger earthquake of M4,1 at about 4.30 pm in 19kms depth and about 12kms off the western tip of El Hierro.This shock was quite strongly felt by the population and caused some rockfalls.
After yesterdays cancellation of the alert the volcano seems to be saying 'I'm not dead yet'...


Update Wednesday, April 10th, 1.30pm:
Just now PEVOLCA,the cicil protection agency, has lifted the yellow alert and cancelled all measures that were taken during the recent 'swarm' of earthquakes. There was only minor activity during the past few days and now El Hierro is officially back to normal


Update Monday, April 8th:
Just 14 light tremors yesterday, only one of them of more than M2.
Interesting new graphics elaborated by AVCAN showing probable extent of magma chamber near El Hierro:


Update Sunday, April 7th:
Just five very minor quakes off the west coast of El Hierro last night.
There were two stronger shocks in the Atlantic about 100 miles to the North of Tenerife
of M3,3 and M4,0 just in great depths of 67 and 86 kms just after 3 am this morning.


Update Saturday, April 6th:
No more activity since last night.


Updates Friday, April 5th:
+ 9am
At El Hierro there was hardly any seismic activity last night, but deformation remains high. There were only 12 minor shocks yesterday.
Today is the last chance to vote for El Hierro again in the NASA image of the year final HERE.Soon we'll know the winner.


Updates Thursday, April 4th:
+ 9pm:
Deformation of the island of El Hierro is still increasing, but there was hardly any seismic activity today - just 9 minor quakes, the strongest a M 3,2 just after 3pm. According to some observers the magma system is still building pressure and tension and they expect more strong shocks in the near future.
+ 9.30am:
The were some strongly-felt earthquakes near Lorca in the province of Murcia in mainland Spain, but El Hierro had a quiet night and morning with very few minor shocks.
Don't forget to vote for El Hierro again in the NASA image of the year final HERE


Updates Wednesday, April 3rd: M 4,5 at 3.45am
+ 10.15pm:
Another M 3,3 quake just before 9pm and a M 3,1 an hour before that, but generally still decreasing activity (let's hope it isn't tension building up), see statistics below:

+ 1pm:
There was another earthquake of M 4,2 about 45 minutes ago 19 kms deep.
The quakes come very suddenly now after spells of hardly any activity. See excerpt of one seismograph (CHIE) at El Hierro below:

+ 8am:
There was less activity last night, but during the early hours of this morning there were four stronger earthquakes just west of El Hierro again: M4,5 + M3,5  +  M4,2 + M4,2 all in about 20kms depth. The 4,5 was felt lightly on Tenerife, La Palma and La Gomera, while it woke many people on El Hierro where windows and doors rattled in some houses.
Don't forget to vote for El Hierro again in the NASA image of the year final HERE
A phase of Sunday's 4,9 quake as it registered at a seismic monitoring station on Tenerife (MACI) was made audible by speeding the sound up 100 times, and you can hear the clip below:

Updates Tuesday, April 2nd: More than 2000 earthquakes in past 15 days
The more than 2000 quakes (most of them minor) in the past 15 days have released as much energy as 2400 metric kilotons of TNT. 
No change in the relatively low level of seismic activity today.
Don't forget to vote for El Hierro again in the NASA image of the year final HERE
+ 9am:
Activity continues, but at a reduced level of intensity. Strongest earthquake last night was a M 3,3.


Updates Monday, April 1st: Water temperature has risen 3ºC near submarine volcano
+ 9.45 pm:
There was a quake of M 2,5 in only 2 kms depth this evening.
Overall, the activity has decreased significantly during the second half of today.
+ 3pm: 
Ten earthquakes of M3 to M3,2 were registered since my last update and generally the activity is much lower than on previous days.
Scientists aboard the research vessel which is investigating the waters around El Hierro have found 'abnormal parameters' around the site of the 2011/12 submarine eruption when results are compared to last December's research data. Most interesting is the change of the water temperature: It has risen by three degrees Celsius at the new submarine crater which had pushed up to just 87 metres below the sea surface during the eruption.
In all 40 different physiochemical factors were measured in the new study and most showed significantly altered values. CO2 levels in the air remain very elevated, too.
Meanwhile the online diagrams of the El Hierro seismograph appear to have been scaled down after yesterday's 4,9  - probably because the stronger quakes didn't fully fit into the dimensions.
... and (added 30 mins. later) PEVOLCA, the civil protection agency has stated in a press conference just now (after a lengthy meeting) that there is no chance of an imminent eruption, while not ruling out the possibility of one completely. Well, that's what they said in 2011,too.
+ 9am:
Less activity last night with the same pattern of periods of relative calm and spells of stronger activity. Early this morning were about a dozen earthquakes of M3 to M4, the strongest were two of M 3,8 at around 5.17am. 
Below are the statistics for the past month of March, showing hardly any activity in the first half of the month and then the sudden increase in seismic energy released from March 17th: 

+1 am: 
Up to now a relatively quiet night with less quakes, strongest a M 3,5 at 11.30pm.
When you look at the IGN graphs and statistics remember to add one hour to the given time as we've changed the clock this weekend and IGN stays with UTC in most bulletins.
More confusingly the time is one hour ahead of the Canaries on the Spanish mainland and here we've got the same time as in Ireland and the UK which in winter is the same as UTC, but now UTC+1. A lot of press reports on yesterdays 4,9 quake got the local time wrong.


Updates Sunday, March 31st: M 4,9 quake
+ 9.30pm:
No change in level of activity.
The deformation of El Hierro island is still considerable and the shift of the terrain to the East is about 4 inches, while the elevation is even higher as this interesting map elaborated by  Nahúm Méndez Chazarra and Julio del Castillo Vivero (C) shows:
+ 7pm:
Now the Instituto Geografico Nacional (IGN) has corrected the strength of the noontime earthquake again and the originally given strength of M 4,9 has been finally confirmed.A different scale was used for this quake for a while and had reduced the strength. Now the same scale as for all the other shocks has been applied and this makes it a 4,9 again.
Maybe this confusion is due to the heavy workload over the past fortnight, understaffing and Easter holidays ?
Again I have changed my posts accordingly.
The activity has increased a little bit in the past 2 hours after a relatively quiet period this afternoon. Most of the last earthquakes were of between M2,2 and M3,2 in 16-19 kms depth in locations a little bit closer to El Hierro.
The Instituto Geografico Nacional (IGN) has revised the strength of the noontime earthquake from M 4,9 down to M 4,6 even though this was strongest-felt quake on El Hierro for years. I have corrected my posts accordingly, however.
Still relatively quiet but activity continues. Below I've posted a video showing several rockfalls/landslides in the El Golfo area on El Hierro caused by the 4,9 shock at noon:

© Guillermo Rodriguez Pulido
The activity has become less again. It seems that the longer the quieter period lasts the stronger the erthquakes that follow when the activity increases again. Lots of rockfalls are still being reported (see image of one on right >)

+12 noon:
Less activity today, but another earthquake of magnitude M 4,5 was felt on El Hierro at 10.40am this morning. The hypocentre was in 20kms depth off the western tip of the island about 10 kms from the lighthouse at Orchilla.
Just now a very strong quake which IGN has put at M 4,9  
(the strongest earthquake in the Canary Islands for years)
in 20 kms depth and again in the sea off the western tip of El Hierro, about 8 miles west of Orchilla lighthouse.
 This shock was widely felt all over the western Canary Islands including La Gomera, and obviously more strongly on El Hierro. Two quakes of M 3 and M 3,6 followed the strong quake a few minutes later.
There were no reports of damages, but rocks fell in several places.
Nothing much new just now. Seismic activity continues at lowered intensity and there were a few minor shocks closer to El Hierro and a few at a lesser depth.
Statistics for yesterday show 'only' just over 100 quakes, of which 'only' 29 were of magnitude 3 or more, while the day before (Good Friday) had 100 of M 3 to M 4,7 alone - but that was an exceptionally active day and slightly worrying. 
Here's a new cleverly done animation of all events from March 18th to late Good Friday, March 30th :


Updates Saturday, March 30th:
No news is good news ! Much weaker activity continues... Happy Easter to all !
Nothing to report, but that the seismic activity has died down considerably.
The night saw slightly weaker activity than the night before, but there were 4 earthquakes of magnitude M 4 to M 4,3 and more than 30 of M 3 to M 4 until now.
Locations and depths similar to yesterday's. Continuing activity, but weaker than yesterday.
According to scientific estimates the total amount of energy released by the El Hierro earthquakes over the past 2 weeks is greater than the total amount of energy liberated on and around the island from summer 2011 (when the current active phase began) until March 17th 2013 !
Last night's seismograph:

+ 1am:
The calm was short-lived as another M 4,3 quake shook El Hierro half an hour ago (depth: 19kms). The stronger quakes are still about 10 miles well out to sea and most are happening in depths of 17-20 kms, but there were some weaker ones last night in 10-11 kms depth and one in only 5 kms.
Total number of earthquakes of M 4 to M 4,7 was 14 (!) in 24 hours yesterday.


Updates Friday March 29th:
+10.30pm: Relative calm has returned again since my last update. Let's hope the people of El Hierro will have a more undisturbed rest than last night.
The pattern of spells of relative calm followed by periods of strong activity is continuing. There were several more earthquakes of between 3 and 4 on the Richter scale, and about an hour ago one of M 4,3 followed by one of M 3,8 and M 4,1 and some more strong shocks that haven't been listed yet. The IGN website is frequently not working due to the high demand and there have been appeals from the Canary Islands to those interested from abroad to give the site a rest so that the locals can get the information they desperately seek. More rockfalls have been reported from El Hierro and strong activity is continuing. There is a palpable tension in the air felt by many on El Hierro and neighbouring islands, including La Gomera.
Below a graph of of the curve of liberated energy since March 17th 2013 : 
©Actualidad Volcanica de Canarias

Just in time with the end of the afternoon siesta the seismic activity came back     
with a bang (literally) just after 5pm. This was by all accounts the strongest felt shock on El Hierro so far and there are lots of reports of rockfalls and landslides. This quake was felt all over the western Canaries, but to a much lesser degree than on El Hierro. There is no official classification yet and the IGN server is down, probably due to capacity problems. I'll put an image of the shock (green) as it registered on El Julan's seismograph on the right margin:>>>>>>>>>>>>>>>>>
...just now the IGN server is working again, and yes that was the strongest quake so far: M 4,7 ! 
Compared to the first half of today this afternoon's activity is relatively quiet. Below is a visualisation video of all the hypocentres since March 17th, 2013 which was published on Youtube by geologist Nahúm Méndez Chazarra  today:

The activity is a little less intense since lunchtime. There were a remarkable 11 (!) earthquakes of M 4 to M 4,6 so far today - the last of these a M 4,1 event just before 1pm.
The updated and revised IGN statistics for yesterday show a total of 203 quakes of which 62 were M 3 or stronger.
There's no let-up: Several strong shocks up to M 4,4 that were widely felt by the population on El Hierro and to a lesser extent on neighbouring islands since my last update. On Hierro doors and windows rattled and there were noises and rumblings with the quakes. Here the seismograph at El Julan (closest to hypocentres):

The strong activity continued on and off during the night and there were about 35 earthquakes of magnitude 3 or higher up to now, culminating in two shocks of M 4,3 around 3am this morning and lots of quakes were felt by the people of El Hierro. The two 
4,3 quakes woke me during the night without knowing why I woke up,  and I could feel a very slight 'slow' vibration (this has now been independently corroborated and is confirmed). Some of the stronger seismic activity over the past 48 hours was felt as far away as Gran Canaria.
--Just now at 8.15am a quake of magnitude 4,6.
Yesterday 188 earthquakes were recorded, 58 of them of M 3 to M 4,1.
Nearly 1700 earthquakes were recorded since the beginning of the current seismic crisis just two weeks ago. There seems to be a gradual migration of the activity to the South and further away from the island of El Hierro, and to the deeper 18-21 kms level, as the location map shows:


Update Thursday March 28th, 11pm:
Just before 10pm the seismic activity increased sharply again with a series of earthquakes of magnitude 3 to 4,1. There were 14 of these stronger shocks in less than one hour. As I write this spell of stronger quakes seem has weakened considerably again.
There were reports of short power outages and rockfalls from some areas in the West of El Hierro.
Activity on the spectrogram for 10-11pm

Update Thursday March 28th, 7pm:
El Hierro still remains relatively quiet. Less quakes and of lower intensity. There is a minor migration of the hypocentres to the South.
Update Thursday March 28th, 1pm:
There was a quieter phase since my last update. New data released today reveal that levels of diffuse CO2 have risen far above what is considered normal, and the deformation of the island is continuing upwards and eastwards at most GPS stations.
Update Thursday March 28th, 11.30am:
Very strong activity since last update, with a quake of M 3,8 at 10.30am and one of M 4,1 at 11am. A total of 16 shocks of between M3 and M4,1 were registered in just two hours ! Here the spectrogram for the time 10-11am:

Update Thursday March 28th, 9.30am:
The activity continues. Last night saw strong activity at around 5.30am when the strongest quake was a M 3,7. Up to now over 50 shocks were listed, of which 20 were between magnitude 3 and 3,7. The hypocentres were located a bit deeper on average than yesterday, and still 7-10 kms out to sea. After a much quieter phase this morning there was another wave of quakes culminating in two M 3,6 just now, continuing...


Update Wednesday March 27th, 9.30am:
The activity today continues at about the same slightly lower rate as yesterday, when 200 quakes were recorded, with the strongest a M 3,6. Today about 70 earthquakes have been counted up to now (the strongest  a M 3,3) most of them at the shallower 12-15 kms level, but one of M 2,5 was  only 3 kms deep at 7.22am this morning. Today's action has shifted slightly to the east towards the island of El Hierro. The deformation of the terrain is continuing to rise, but at a slower rate.
El Hierro eruption seen from space 2012. This image has now made it into
 the finals of the NASA Earth Observatory tournament for image of the year
and you too can vote for it! Click:
Keep voting (you can vote several times!) for the image seen on the  right which has now made it into the final four. This round of voting closes on Friday night.
Important update 6pm:
There has been a series of stronger earthquakes @ El Hierro this afternoon, some above magnitude 4 and lots above  M 3. just after 3pm the action culminated in a M 4,6 quake which was preceeded by a M 4,3 and about an hour later followed by a 4,5 shock. All of these and lots more over mag. 3 were strongly felt by the popuation. There is no danger  ensuing the quakes themselves - but the abrupt terrain on El Hierro suffers regular landslides and rockfalls in the best of times and now the loose material is getting an extra rattle. Here the 'dirty-looking' graph of today's El Julan seismograph:
Some of the stronger quakes today registered all over the Canaries - and La Gomeras mostly 'silent' station had this impressive register on the spectrogram this afternoon:


Another strong earthquake just before 8pm of M 4,1 making it half a dozen shocks of M 4 to M 4,6 since lunchtime.
Civil protection and Canarian government have decreed a yellow alert level and closed some roads on El Hierro just now. Click bulletin. Some rockfalls and landslides were caused by today's earthquakes, thankfully without harm.

+ just after midnight: 
Activity has decreased again since last update. I hope El Hierro will have a quiet night after today's rattling train of quakes which caused some (harmless) rockfalls and landslides. 


Update Tuesday March 26th, 8.30am:
Yesterday the largest number of earthquakes this year was recorded: 227 quakes, of which 46 were between magnitude M3 and M4,1. This morning the series of shocks continues a bit weaker than yesterday in about the same sea area off the western tip of the island. The only change is that more earthquakes are now occurring in the shallower 10-15 kms depth, indicating magma intrusion at this level. Overall during the current period of activity the epicentres seem to be gradually moving further out to sea, away from El Hierro. The location map of the epicentres for the past 15 days at the bottom of today's updates clearly shows this trend. 
+ 1.30pm:
After several meetings today both scientists and government organisations have concluded that there is no danger and that the magma movements and associated seismic activities are normal and within the safe boundaries. Accordingly they state that there is no threat to the population and no special measures are needed. A report by the scientists on the research vessel investigating the area has stated that 'nothing abnormal' has been detected. They will further investigate three possible degassing vents in the area where the 2011-12 eruption took place.
By lunchtime about 100 earthquakes had been counted today, the strongest a M 3,6 at around 4am this morning. The average strength of the shocks was lower than yesterday however.


UPDATE Monday March 25th, 9.30am:
There was strong activity early this morning with about 75 earthquakes above magnitude 2 already reported until 9am. Of these 18 were between strength 3 and 4 and for the first time this year one quake reached 4,0. The locations remain in the same area as yesterday, but a good few quakes have reached a shallower level at a depth of 10 - 14 kms. A research vessel is at sea in the area, and a team of scientists is on its way to El Hierro to measure air quality, looking for indicative gases. The population is reporting the same type of sensations as yesterday, but with a noticeable increase. 
+11.30am: A committee of scientists and the authorities called PEVOLCA will meet tomorrow to evaluate and discuss the current situation. They have already stressed that there is NO risk to the population at present.
Meanwhile the activity has decreased somewhat.
+8.30pm: ... and then the activity much increased again with the strongest quake measured so far at M 4,1 just before 3pm. Total number of shocks is at about 150 at this time, of which around 40 (!) were above magnitude M 3. 
The graphs for deformation of the island at some GPS stations had to be re-calibrated because the rate of deformation had reached the limits.
Note: There is some sensationalism turning up in the media and some doomsayers on the internet are drawing wildly over-dramatized and unsubstantiated conclusions from this activity (well, it's the year '13), but let me stress again that according to ALL experts there is NO danger to human life anywhere pertaining to this natural phenomenon.


UPDATE Sunday March 24th, 2pm:
The activity continues unabated. Yesterday there were 170 earthquakes registered, of which only two were below magnitude 2, the rest were between 2 and 3, while 15 were between 3 and 3,5. Today there were already 100 shocks of between 2 and 3,4 in strength. Most of the quakes took place in depths of between 13 and 18 kms in an area just off the western tip of the island where the Atlantic is 1000 -1800 metres deep. This is why the activity is considered 'safe' by the authorities. However the people of El Hierro have reported vibrations, rumblings, minor shaking, noises and strange smells.
Deformation of the island continues to increase indicating mounting pressure.
Location of quakes in past 3 days
The red dots are today's events until 12 noon.
Main post:
(Note: I'm not an expert and I'm just trying to report my personal experience, quoting the sources I trust)
After a longer spell of relative calm the neighbouring island of El Hierro has experienced a new 'swarm' of earthquakes this week. Well over 500 quakes have been recorded since Sunday, March 17th, and most of these were of magnitude 2 to 3 on the Richter scale with just a few quakes of between 3 and 3,8. A good few earthquakes were felt by the population however. Nearly all the quakes occurred in relatively safe depths of between 12 and 18 kilometres near the unpopulated western tip of the island. Deformation of the island has grown recently and at some GPS stations a sideways motion and a lifting of the island's terrain measuring several inches has been observed, indicating mounting magma pressure.
In the past hour the activity has increased as this seismograph at El Hierro shows:
You can follow the seismograph by clicking the following link:
This is an on-going volcanic event on (and off the coast of) the island of El Hierro, the smallest and farthest south of the Canary Islands. The island is also the geologically youngest in the island chain. The October 2011 - March 2012 eruption took place underwater, with a fissure of vents located approximately 2 km to the south of the small town of La Restinga on the southern coast of the island. As of June 2012, increased seismicity to the north-west of the vent indicated another phase in the area's volcanic activity and further vents were discovered underwater just off the west coast. There are deep-seated magma movements with associated earthquakes and deformation of the island under way. A new phase of eruptive activity has not yet occurred, and it does not necessarily follow that it will.
La Gomera will not be affected in any event, as our island is volcanically extinct and has not experienced any volcanic activity for much longer than a million years and is one of the oldest islands. La Gomera existed long before El Hierro was even born.
Generally volcanic activity in the Canaries is of a 'mild nature' and the last spectacular eruption took place on the westernmost island of La Palma in 1971 which lasted just a few weeks, left a small new crater and died down again without doing harm.
The current phase of activity on El Hierro started in July 2011 and culminated in November of that year in the underwater eruption just about a mile off the fishing harbour of La Resting and could even be spotted from space. Due to rising gases and the uncertainty of the eruption possibly entering an explosive phase, the area was evacuated a few times. In the end the eruption died down again and life continued as before, but economically it was a disaster for El Hierro because many holidaymakers did not return.
Below is a chart of all of the more than 17.000 El Hierro earthquakes since July 19th
2011. Most of them were very minor, but strong ones up to magnitude 4,6 were recorded as well:
...and as a reminder I add a video of the peak of the 2011/12 eruption in the sea about 1 mile off La Restinga, El Hierro, which rose up to 60 feet above sea level, taken in November 2011:


Ut på tur said...

Is it possible that these quakes can start an tsunami ?

La Gomera said...

According to all the experts this is highly unlikely. The quakes are not caused by tectonic movements (often the cause of tsunamis), but by magma movements. There are NO fault lines in the Canaries. Further, the seismic and volcanic activities in the Canaries are mostly of a 'mild' nature, albeit worrying for the people of El Hierro. A 4,9 quake is 'minor' by international standards.
To understand tsunami generation you may read: