Vulkaanuitbarsting bij Canarische Eilanden #4

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SPECIAL NOTE AVCAN 038 - 11/07/2012 - 11:15 pm Peninsula. - EVOLUTION AND MONITORING EARTHQUAKE SWARM-VOLCANIC ISLAND OF HIERRO.

The seismicity map updated today, now carry 2 earthquakes located by the IGN in the spectrogram are not located many more .... and yesterday we had 70 that draw more or less the area of the swarm, especially yesterday's gains as yesterday afternoon and seismic activity is concentrated in the coastal area between the lighthouse and Julan Orchilla. GPS data and INVOLCAN IGN indicate that the vertical deformation somewhat low, not so the horizontal, which appears to increase their rate of deformation .. Enrique)

http://www.avcan.org/mapas/AVCAN3749.jpg?d=1341997116

Earthquake of July 11 from 00:00 to 06:00 h UTC - Light Blue (2)

Earthquake of July 10 - Yellow (70)

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[bron AVCAN]
Events for absolute share of the tide. This is to check how seismic events occur when the tides reach their ends, ie, high tide or low tide. In this graph, therefore, does not distinguish between high or low tides. The Y, is 100 for both high tide or low and 0 for the "mean tide". For each tidal height, we calculated the extent of their corresponding tide and it calculates the percentage on it without distinguishing whether low or high. It can be seen, the greater concentration of points representing events to the value 100, which means that high tides and low tides in more seismic activity in the "mean tide" and the fact that the most significant events in general and at this stage of the crisis, also occur in high or low tides.

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To complement the above graph, which has generated some questions to be hardly understandable. I think the following is quite explicit and reflects: The number of seismic events and the energy accumulated by absolute share of the tide. Remember, that percentage represents 0 in the "Half Tide" and 100 represents the high tide or low tide. In summary, the graph, accounts of what happens to the mean tide, as opposed to extreme values. For its calculation, computed the actual extent of each trip and we calculated the absolute percentage of tidal height on the amplitude, so that (insist), the value 0 of the abscissa represents the mean tide and the value 100 represents tidal peaks of both the high tide as low tide. Not the subject of this graph, draw conclusions, but to present a statistical study.

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Julio says:
July 11, 2012 at 12:33 pm
There have been strong winds at the Island for the past days as you can see in Joke’s Photographs. This results in an increase tremor line in the graphs.

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Progression of the average depths of the hypocentres of seismic events per hour, since the beginning of the crisis. Although there are fewer earthquakes per hour, the latest trend appears to be rising with some shallow earthquakes. (JR)

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SPECIAL NOTE AVCAN 043 - 07/15/2012 -22:15 h peninsular. - EVOLUTION AND MONITORING EARTHQUAKE SWARM-VOLCANIC ISLAND ON El Hierro.

The seismicity map updated today, now carry 2 earthquakes located by IGN, although in the spectrogram are located but not enough, yesterday we had 10 between the lighthouse area Orchilla south on the Mar de las Calmas. The small rally yesterday morning was further east in the sea area near the coast between the lighthouse and Julan Orchilla. The truth is that the last of yesterday and today have an alignment NW - SE and NS, in addition to other alignments of other days.

The truth is that it should be noted that it was lightning fast with this phenomenon of volcanic reactivation, with a plume of horse, something has put the brake, but far from stopped, be an earthquake of 3.4 shows yesterday or the deformations are rising, especially in the vertical, albeit more slowly.

The truth is that it happens, that seismic activity in the volcanic islands can last for years before finding a way to the surface to form a mouth eruption. In the recent past Canarian volcanism, this has already happened, as was the case of Chinyero or San Juan or the actual eruption of Timanfaya, this specifically, according to the writings of the priest of Yaiza, had in pulses or periods of moderate seismicity strong that when he was stopped by that opened a new mouth, which threw up a time and then stop everything and spend some quiet time until after a month or less started a new seismic pulses that opened up another mouth other and after a while expelling material was returning to stop and so on several times, we shot 6 years is repeating this behavior (Enrique)

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Update 16/07 – 07:38 UTC
- There were finally 2 earthquakes at El Hierro yesterday : a M2,1 and a M1.7 at 21 and 22 km depth.
- 2 earthquakes so far today:
03:01:09 Depth 20 km 2.0mbLg SW EL PINAR
05:42:25 Depth 21 km 1.8mbLg SW FRONTERA
- Vertical deformations are down from 1 to 2 cm (one of the biggest deflations so far).
- We expect Pevolca to announce a further normalization of the situation and to change the Yellow alerts on some parts of the island soon to Green again.

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Update 17/07 – 08:07 UTC
-A new strong earthquake occurred 21 minutes ago. IGN has not listed this earthquake yet. Based on what we see on CHIE we estimate the quake to be in the M3 to M3.5 range.

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Update 19/07 – 08:30 UTC
- NO earthquakes so far today
- The uplifting from PINA and FRON as reported yesterday and the day before yesterday has reversed into a strong decrease of approx. 0.5 to 1 cm
- The conclusion of the current non-events is that the new swarm episode seems to be completely over

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Update 07/08 – 10:21 UTC
An article in Diario El Hierro reports about some findings of the University of La Laguna. The professor indicates that eruption material from El Hierro is among the strongest eruption radioactive material known so far. Click here to read this (Spanish) article.
- Pevolca has changed the alertt level of the south western tip of the island again to green. It was changed into Yellow after the many strong earthquakes. Yellow is maintained at the vent in the Las Calmas sea.

Los fondos marinos de El Hierro vuelven a recuperar su belleza

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Important Update 13/08 – 16:26 UTC
After a period of relative weak to very weak seismic activity, the magma below El Hierro looks to start another episode as we cannot relate the 6 earthquakes today as stress phenomena. The epicenter of the earthquakes were in between 10 and 14 km, which means that if seismicity today is generated by magma, we have a totally different situation than at the end of June when we constantly has epicenters below 20 km. The location of the epicenters today where also different as the majority was located in the El Golfo Bay and a few others below the island and in the Las Calmas sea.
6 earthquakes so far today is not revolutionary, but at least interesting to give it a close watch
- The seismogram at CHIE does not confirm an increase of the activity, but this can change swiftly as we know from the recent past
- The deformation data from Involcan and the Nogoya University also show an uplifting from a little less than a cm in both PINA and FRON (Ultra Rapid and we trust that the GPS data are still refreshed as it is hard to see on the graph.
- If deformation data and seismicity would continue to increase the following hours and days, we might have a new phase in the El Hierro volcano activity

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Update 14/08 07:50 UTC
After the update with 6 earthquakes yesterday, everything went silent again.
Deformation data (vertical) have stabilized again.

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Important Update 15/08 – 08:14 UTC
- We have to add 5 new earthquakes in only 2 hours time. As written yesterday and earlier today, these are certainly no stress related earthquakes. Not powerful at all, but they have a trending which puts some action (magma action ?) at a depth of 10 to 12 km. These quakes are not powerful enough to be dangerous at the short term as well as the depth is still deep enough to not be alarmed, but something is going on down there !
The epicenter locations of these earthquakes are almost all of them in the Sabinosa part of the El Golfo bay
The latest depth of 6 km may be updated later today as this happened often in the past.

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Important Update 15/08 14:50 UTC
- Another 5 earthquakes have to be added by the already 6 mentioned earlier on, bringing the total to 11. Depth 11 to 12 km and the depth of the 06:46 quake still stands at 6 km ! Epicenters : close to Sabinosa or in the El Golfo Bay just north of Sabinosa.

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Very important Update 16/08 – 08:19 UTC – A new earthquake swarm has started below El Hierro
- For the 3th day in a row the number of earthquakes are fundamentally increasing below El Hierro. Although not official, we think that speaking of a new earthquake swarm is the only right way of describing the current set of earthquakes.
- No less than 26 earthquakes occurred this morning (from midnight UTC until 07:00 AM)
- The majority of the earthquakes are still weak, but the M2.2 from early this morning was the strongest in a while and the Magnitude pattern tends to become stronger every couple of hours.
- The CHIE seismogram is not showing a lot of action, but the M2.2 can well be seen. CHIE is not the best station at the moment to show the seismic events at his best.
- The depth is continuing around the 10 to 12 km which is a complete difference from the July swarm, but still far away from an eruption. More seismicity at lesser depths is needed to create a pre-eruptive condition. Newt to seismicity, we have also the gas analysis, the deformation, etc who will have to confirm if the present swarm will end in an eruption. The magma pressure should be powerful enough to find his way up.
- We do not know how many University of Nagoya GPS stations are still working, but we know for sure that FRON station still works and shows a vertical increase of many mm, which sounds normal after the present set of increasing earthquakes in the area.
- A reason for concern at this time should be the location of the seismicity (El Golfo Bay and Sabinosa area – including the cliffs south of Sabinosa). Landslides and rockfall may become dangerous at Magnitudes from M4 and up.

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Update 16/08 13:37 UTC
- 5 more earthquakes in between M0.6 and M1.2 and at depths in between 10 and &é km

Image courtesy Avcan
Update 16/08 11:53 UTC
- We have to continue bringing updates on the seismicity below the island.
4 more earthquakes bringing the total on 32 today. Magnitudes from M1.0 until M1.5. Depths 10-11 km. IGN has updated his list up to 08:30 UTC
- At right a small map with the epicenters of a number of the latest earthquakes.

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Update 16/08 – 23:31 UTC
- So far IGN has listed 45 earthquakes today. We see on the seismogram that there are definitely some more quakes later on. They will probably be listed tomorrow morning.
Update 16/08 – 19:42 UTC
- 4 more earthquakes from M0.6 to M1.4 at a depth of 10 to 12 km (15:29 to 16:18 UTC)
Update 16/08 – 16:25 UTC
- 3 more earthquakes from M0.9 to M1.1 at a depth of 11 to 12 km (12:25 to 13:47 UTC)
- Maybe IGN could take a few courses in press reporting at GNS Science New Zealand. If an important new swarm starts, like the one today (even with weak earthquakes), an experienced volcanologist may write 5 sentences in explaining what the opinion of the organization is. Why does a body like Pevolca is to be used for volcanology ? If i would live in Sabinosa, i would love to hear a few words if continuous quakes are occurring below my house.

Update 17/08 07:37 UTC
- A little bit to our surprise, there were no more earthquakes listed yesterday after 18:11. This brings yesterdays total on 45.
- The quakes continued though after midnight and so far today we have noticed 7 volcanic earthquakes (see list below). Epicenters are still in the same perimeter.
- Vertical deformation both at El Pinar and Frontera stations is slightly higher which corresponds with the many, mostly weak earthquakes in the El Golfo area. The SABI station (Sabinosa) of the University of Nagoya does not seem to report data anymore, a pity as almost all the current action takes place in that sector.