El Hierro – Day 2

The face of El Hierran politics, Alpidio Armas.

This will just be a short update with the information that has come at hand.

There seems to be a full on war between Pevolca, Involcan and José Luis Barrera VP of the ICOG (Spannish Association of Geologists). Pevolca has stated that there are some reneval of tectonic earthquakes, with no risk for the population or any need for any measurments to be taken. They also point out that there is no increase in gases. They do though mention that they will be watching things. They have also stated that there is no inflation at El Hierro (GPS).

Involcan has stated there is inflation after studying the GPS system of Professor Sagiya from Nagoya. They also point out that the reason for Pevolca not being able to see any heightened gas levels is that they have not measured the gas since April 5.

http://www.facebook.com/pages/INSTITUTO-VOLCANOLÓGICO-DE-CANARIAS/134042953295772

José Luis Barrera and the ICOG have issued a statement that the more than 350 earthquakes are tectonic, but that they might be a run-up phase for renewed volcanic eruption. They also note that the activity is unusual.

http://www.europapress.es/comunicados/noticia-comunicado-colegio-geologos-muestra-incertidumbre-repunte-actividad-simica-hierro-20120626152109.html

Meanwhile in the real World

While the Spannish authorities and organisations are involved in their usuall pissing contest there are some things worthy of comment.

A little tidbit on the earthquakes during the 48 last hours…
Yesterday had the fifth highest recorded number of earthquakes (241), the highest recorded number is close to 454, and that was in August as the former wad of magma had it’s peak of arrival.
But what is really interesting is that if one take a look at how those quakes break down into size…
Yesterday first, then August number-record.
0-2M 55 (448)
2-3M 180 (6)
3<M 8 (0)

And that would have made yesterday into releasing 5 times as much energy and destroying about 32 times as much rock. It was the record of all time energywhise. This leads me to believe that the amound and speed of arrival is higher this time around. So, the last two days have had the largest accumulated seismic energy release since onset of activity at El Hierro. Energy record in short. And that is note noteworthy according to Pevolca.

LP Earthquakes

The earthquakes today has long amplitude component to them normally associated with magmatic movement into the cracks. These LP earthquakes is considered to be magmatic. There has during the last 8 hours been at least 3 of them. The 17.16 is one of them.
I believe this is onset of movement upwards of magma into the actual system of Tanganasoga.

First LP

Image by IGN. The First LP Earthquake.

Second LP

Image by IGN. The Secong LP Earthquake.

Third LP

Image by IGN. Third LP Earthquake, and what is most likely onset of a heavy magmatic intrusion upwards.

The third LP seems to have opened a conduit somewhere, most likely from the crustal boundary (MOHO) up to the chamber under Tanganasoga, or directly towards Bob. The Long Periodicity Earthquake is caused by an initial earthquake that opens up a fissure, sill or dyke, after that magma moves in to fill the opening, and that creates and unusual type of earthquakes.

Conclusion

There is no reason that I should recant on what I wrote yesterday. I still believe that there is a rather high risk of a new eruption at El Hierro. I still see no reason to not believe it will be in the southern part of the island, or out in the ocean south of La Restinga. I still feel that La Restinga is not entirely safe for it’s population.

Update

While I was writing this post the signal changed sufficiently for me to believe that there is risk that the eruption is either about to start, or has already started. We are all waiting for news, and think about the unprotected civilians in El Hierro.

CARL

Askja – A brief update

Photograph by Herve 1993. In the foreground is Viti, in the background is Öskjuvatn.

After an initial spatter of information of the de-icing of Lake Öskjuvatn things are now coming to a full Easter stop.

After going through the records for earthquakes during the winter up until now one can easily see that there has not been any elevated level of earthquakes. Regarding harmonic tremor episodes, yes there have been a few short episodes that can be interpreted as such, but not a lot really. Also the GPS readings have been fairly consistent.

Image by IMO. The earthquake showing is in the Upptyppingar, and is considered to not be a part of the Askja swarm. It is an uncorrected 1.5M.

In reality there are not that many signs of an upcoming eruption. First of all Askja deflated from the onset of the Krafla eruption up until 2007 when an inflation started according to gravimetric readings. Together with GPS readings an inflation was spotted in the center of the old caldera, and a likely dyke intrusion trending towards (possible all the way into) Herdubreid volcano.

That inflation started a series of earthquake swarms, predominantly in the Herdubreid volcano. But, during the winter there seem to not have been a lot of activity, and this makes the de-icing of Öskjuvatn a bit surprising to say the least.

Most likely one of the quakes gave water a path down to a heated area closer to the magma or down to remnants from the 1875 eruption. This in turn most likely caused a new sub-surface geothermal source to heat up the lake. All we can say is that the amount of energy released into the water is substantial, and that it has been warming the lake rapidly during the last few weeks.

Askja erupting?

Image by IMO. The plot is showing fairly normal readings for this rather noisy SIL-station.

Currently there is not much pointing towards an eruption. There are no persistant earthquakes, there is no elevated tremor level, and there is no rapid movement in the GPS:s in the vicinity. The last thing should be taken with a large pinch of salt. The GPS:s of Iceland are really hard to interpret. More about the GPS:s and how to read them will be coming I hope in an upcoming post from someone who actually knows what she is talking about.

In conclusion

Anybody hoping for an Easter-eruption to cure their boredom should go and start painting eggs instead.  We will know when and if a final run-up phase starts, and then it is most likely weeks before the actual eruption starts. So, do not expect Askja to blow anytime soon. Otherwise all we can do is waiting, for Askja in general, and for the IMO report after their Tuesday visit.

CARL