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Seismic unrest at Santorini, Greece - part 2 (Jan-March 2012)

Update Wed 28 Mar 23:20
Earthquakes have dropped again, the swarm is over and the question is probably "when is the next one?"... A press conference was held today on Santorini, and Tobias Schorr is now on the island with a group and if anything important happens, we will be able to report first-hand.
Weak earthquake at Nea Kameni 1,3 R
Update Mon 26 Mar 19:20
The position of the weak earthquake of 26.3.2012
The position of the weak earthquake of 26.3.2012
The seismic activity on and around Santorini island goes on. Today there was a realtively weak earthquake between Athinios port and Nea Kameni island.
Update Sun 25 Mar 17:39
Earthquake activity at and near Santorini between 24 Dec and 25 March 2012
Earthquake activity at and near Santorini between 24 Dec and 25 March 2012
The seismic swarm at Santorini seems to have moved to the SW along the main tectonic fault zone crossing the island SW-NE. A swarm of quakes has been occurring about 45 km SW of the island. IN the past 48 hours, there were 9 quakes up to 2.3 magnitude at depths of around 30 km in this area which was the site of a major earthquake swarm in early January.
Update Wed 21 Mar 21:30
Earthquake activity at and near Santorini between 22 Dec and 21 March 2012
Earthquake activity at and near Santorini between 22 Dec and 21 March 2012
The earthquake swarm that had started 4 days ago continues with more small quakes inside the caldera at shallow depths of around 6 km. This could suggest another magmatic intrusion the volcanic system.
Small earthquake swarm at Santorini and near Kolombo submarine volcano
Update Mon 19 Mar 21:16
Earthquake activity at and near Santorini between 20 Dec and 19 March 2012
Earthquake activity at and near Santorini between 20 Dec and 19 March 2012
After 6 weeks of calm, another seismic swarm has started yesterday at Santorini, clustered in the NE sector of the island and near the submarine Kolumbo volcano. The quakes are very small and will not have been felt. The largest was a magnitude 2.0 quake on 18 March at 10:37 GMT at 11 km depth beneath Kolumbo.
Update Sun 11 Mar 10:40
No new earthquakes have been recorded at Santorini during the past days. This is probably one of the first intervals of more than 4 days without quakes since seismic unrest started last July. It is too early to conclude that the unrest is over based on this observation alone, but other data (inflation, gas chemistry etc) are currently not publicly available.
Seismic activity at Santorini remains calm
Update Tue 06 Mar 10:46
Earthquake activity at and near Santorini between 5 Dec and 6 March 2012
Earthquake activity at and near Santorini between 5 Dec and 6 March 2012
To the relief of Santorini's inhabitants, seismic activity under the volcano and near the island, which had experienced swarms and increased levels in recent months, seems to continue to remain calm.
Update Sat 03 Mar 13:38
Santorini remains relatively quiet. No indications we know of point towards any activity to be expected in an immediate future, but we'll continue to watch this volcano more closely.
Update Tue 28 Feb 09:38
Earthquake activity at and near Santorini between 30 Nov and 28 February 2012
Earthquake activity at and near Santorini between 30 Nov and 28 February 2012
Except for a small magnitude 1.9 earthquake near Kolumbo volcano NE of Santorini, seismic activity remains calm at Santorini.
Update Sun 26 Feb 09:09
Santorini remains calm. No unusual seismic activity during the past week.
Update Fri 24 Feb 23:19
Earthquake activity at and near Santorini between 26 Nov and 24 February 2012
Earthquake activity at and near Santorini between 26 Nov and 24 February 2012
Santorini volcano remains calm during the carnival (1 week later in the orthodox calendar).
Update Thu 23 Feb 12:55
In contrast to the political events here in the country, seismicity at Santorini has been rather calm over the past days.
Small earthquake swarm at Santorini
Update Mon 20 Feb 12:10
Earthquake activity at and near Santorini between 22 Nov and 20 February 2012
Earthquake activity at and near Santorini between 22 Nov and 20 February 2012
After a quiet period, a small (but not worrying) swarm of weak quakes have started to occur again under the caldera of Santorini during the past 48 hours.
Seismic activity calm during the past days
Update Wed 15 Feb 21:10
Earthquake activity at and near Santorini between 17 Nov and 15 February 2012
Earthquake activity at and near Santorini between 17 Nov and 15 February 2012
Almost no new earthquakes have occurred since the last update.
Seismic unrest continues
Update Sun 12 Feb 17:51
Earthquake activity at and near Santorini during the past weeks.
Earthquake activity at and near Santorini during the past weeks.
The frequency and number of (small) earthquakes at Santorini as well as in the fault zone about 45 km SW of the island has been increased in recent days.
Seismic activity remains calm
Update Thu 09 Feb 17:25
Seismic activity 11 Nov - 9 Feb 2012
Seismic activity 11 Nov - 9 Feb 2012
To the relief of many, the past week has been relatively calm, seismically, at Santorini. Few earthquakes continue to occur, but not on the scale as observed during January.
Update Sun 05 Feb 20:30
4_38.jpg
Seismic activity has picked up again, with more (but less intense) quakes in the area 50 km SW of the island (and a bit closer to the island itself) and a few small quakes under the caldera.
Seismic activity quiets down
Update Fri 03 Feb 00:08
4_37.jpg
During the past days, seismic activity has been relatively calm. We are curious to see if there will be more bursts of activity in the near future.
Quick add-on, to repeat what has been said before: to our knowledge, and after talking to several scientist involved in monitoring the situation, there is NO indication to believe that an eruption on Santorini is imminent (= likely in the next weeks or months).
We have no confirmation of any volcanic tremor. What can be seen on the seismograms, is most likely something else. Also, to stress out, the most likely scenarios of the next eruption is a minor event, that probably will cause no major damage to the island. There is no reason to be too afraid.
Update Tue 31 Jan 13:43
Dr. Euthimis Lekkas, geologist from the National Athens University, gave a TV interview this morning, essentially confirming what has been written here earlier and expressed by other scientists as well:
The current earthquakes in the Cretan Sea 50 km SW of Santorini are on a different fault lines than the volcanic system of Santorini itself, in an area of intersecting NW-SE and NE-SW faults. The seismic energy is being depleted with a lowering intensity and number of earthquakes.
About the volcano, Lekkas mentioned that there is small inflation in the caldera with a small fluctuation in the temperature of emitted gasses, pointing out that the current activity is SMALL and "shouldn't worry anyone". Under no circumstances we should expect a large eruption. And we should not be scared by one - there are many volcanoes that erupt for months (Etna, Stromboli) without hurting anyone. When asked by the reporter about the water discoloration in Santorini he answered that this is normal for volcanoes due to fluid emissions from the bottom of the caldera (which happen all the time). In his concluding remarks he said that in contrast with earthquakes, volcanoes provide ample warnings before an eruption, that scientists are monitoring the volcano and that they are not worried at all.
(Special Thanks to Chris P. for helping follow the news!)
Seismic swarm 50 km SW of Santorini decreases
Update Tue 31 Jan 12:21
The "red waters" of the warm iron-spring at Agios Nikolaos on Palea Kameni
The "red waters" of the warm iron-spring at Agios Nikolaos on Palea Kameni
Earthquake swarm in the Aegean Sea 50 km SW of Santorini
Earthquake swarm in the Aegean Sea 50 km SW of Santorini
The swarm of earthquakes in the Cretan Sea 50 km SW of Santorini seems to be decreasing. Talking with Dr. Athanassios Ganas, head of the Athens Geodynamic Institute, and others, there is a consensus that the quakes are tectonic in origin and not related to volcanic activity (after all, their location is far from the Santorini volcanic system).
A short side note: fortunately, the large amount of energy released in the recent quakes was spread over hundreds of quakes of various sizes, and did not manifest itself in one large earthquake.
Another short side note about rumors going on that the "sea has turned red" in the caldera: not true, or nothing new. There are iron-bearing hydrothermal springs in the area that produce an orange stain at the surface level. These have always been there and are one of the main attractions of the caldera, known as the "hot springs".
Comment on internet tremor rumors
Update Tue 31 Jan 00:41
SANT.active_01.gif
Short comment for those looking at real-time seismogramms, such as this one (station HL_SANT from the Geodynamic Institute, NOA) located on top of the mountain Profitis Ilias. The weather clearly influences the signal (or the station is malfunctioning) - right now, wind is probably blowing at force 10-12 beaufort up there, and produces what many of you now call "tremor". If it was volcanic tremor, caused by magma movements, that would mean that magma tries to erupt from the peak of the non-volcanic marbles more than 1100 m higher than the base of the ruptured base of the caldera (the magma probably thinks "why taking the easy path, when I can erupt from the possibly most unlikely and hard to reach place at all?")
Seismic swarm continues, scientist admit it is no normal event, but claim it has nothing to do with the volcano
Update Mon 30 Jan 17:28
The seismic swarm SW of Santorini, and the absence of quakes under Santorini itself during the past 48 hours.
The seismic swarm SW of Santorini, and the absence of quakes under Santorini itself during the past 48 hours.
The seismic swarm 50 km SW of Santorini continues with a smaller number of quakes than in the first 2 days. 10 Quakes were recorded in the past 24 hours, including a 3.9 magnitude last night at 31 km depth at 22h46:33 GMT.
Interestingly, no quakes seem to occur inside the caldera or in the immediate vicinity of Santorini since the swarm to the SW has started. This clearly shows that there is some relationship. What nature this has, is speculation.

In a TV interview earlier today, a seismologist from the Athens Observatory confirmed the widespread (public) opinion that these earthquakes 50 km SW are no longer normal, and that "everything could happen" (not mentioning what), and criticized fellow scientists who have been saying that the quakes were normal.
At the same time, Dr. Houliaras said that these quakes have nothing to do with the volcano (which we don't agree, since there is a correlation between the absence of quakes under the volcano and the seismic swarm off the island). He said that before June 25, 2011, only earthquakes magnitude 4 and above where recorded on Santorini (!) and that the increase in the seismic activity was due to the presence of more seismographs on the island. We leave it to the reader to interpret this statement...
Update Mon 30 Jan 02:22
A big question is what to expect in the case of a new eruption. It is more difficult to look into the future than to look back, but sometimes this helps to get an idea. Here is a detailed description of the last eruption of Santorini, which was in 1950. By no means this should be taken as a prediction of the next eruption, which might or might not be close (months to years from now), but it is a scenario of a typical small-scale eruption that would represent a highly interesting attraction rather than devastation to Santorini.
Santorini volcano (Greece): strong seismic swarm 50 km SW of the volcano continues
Update Sun 29 Jan 16:47
The seismic swarm 50 km SW of Santorini, at the end of the fault zone
The seismic swarm 50 km SW of Santorini, at the end of the fault zone
The highly unusual swarm of earthquakes SW of Santorini on the main fault zone that also defines the volcanic vents of the region continues with about 10 quakes larger than magnitude 2 during the past 24 hours. 2 of the quakes were magnitude 4 and 4.7, respectively.
Greek media start to pick up the story and become increasingly interested:

Today the wall of silence seems to be falling as a major Sunday newspaper has exclusive interviews with a number of Greek seismologists and geologists on the matter and some information is now public.
1. Inflation
From 1993 until 2010 there was deflation in the caldera of about 1cm/year, since the beginning of 2011 that has changed to inflation centered at a radius of 15 km on the north part of the caldera, rapid episodes of inflation have been recorded at intervals that coincide with bursts in seismic activity. Since August the intensity of the phenomenon warranted a rise to alert level 4 (red), where it has remained ever since.

2. Magma column
A displacement of 10 million cubic meters has been located 1 km north of the central island of Nea Kameni at a depth of 4 km, it is hypothesized that it is a magma intrusion, located right at the center of the most seismically active part of the caldera.
Note: 10 million cu meters sound like a lot, but it is a small volume for volcanic inflations. To visualize the volume: it corresponds roughly to a cube of 200 m length, or a typical cinder cone about 100 m high and a base diameter of 600 m.

3. CO2.
Co2 levels have jumped to 39 tonnes/day along with the emission of other gasses, a rising gas column has been observed outside the port of Thirassia in the caldera (the island on the west rim).

4. Water temperature.
The rise in sea water temperature in the caldera has been confirmed.

Most of the Greek scientists have brushed any concerns saying that conditions are normal and that has happened before, Euthimios Lekkas, geologist from Athens University, even said on TV that there is no danger even of a large earthquake in the vicinity of the island, the next day there were 3 earthquakes magnitude 5 and above, 50 km to the SW at the other end of the fault line.
Noticable exception, foreign geologists have a very different opinion, Michelle Parks, a geologist from Oxford, mentioned that the evidence points to something important, there is volcanic activity and the volcano is now potencially active at depth.
Consencus is that the volcano has woken up in early 2011, but opinions differ mainly on the lines of nationality of the scientists.
(Thanks to Chris P. for the help in updating this!)

Sources and more reporting in the news:
http://www.espressonews.gr/default.asp?pid=79&la=1&artid=1488030&catID=16
http://www.ethnos.gr/article.asp?catid=22768&subid=2&pubid=63607339
http://www.star.gr/ellada_kosmos/127965/ (with a stolen picture from us)
http://www.tanea.gr/latestnews/article/?aid=4690103
http://www.protothema.gr/greece/article/?aid=173430
Strong seismic swarm continues 50 km SW of Santorini Island, Greece
Update Sat 28 Jan 16:29
Map of the quakes near Santorini as of 28 Jan 2012 (note that the depths below 15km indicated here are from automatic calculations. The list of manually revised locations results in depths around 30 km for all of the quakes in the cluster of quakes SW of Santorini). (Source: Institute of Geodynamics, Athens)
Map of the quakes near Santorini as of 28 Jan 2012 (note that the depths below 15km indicated here are from automatic calculations. The list of manually revised locations results in depths around 30 km for all of the quakes in the cluster of quakes SW of Santorini). (Source: Institute of Geodynamics, Athens)
The unusual seismic swarm in progress at a location ca. 50 km SW of Santorini is continuing. Up to now, 22 quakes between 2 and 4.9 magnitude have been recorded by the Hellenic Seismic networks for 28 January 2012.
What exactly is happening is unclear, but it is almost certain that it is not a normal tectonic earthquake with aftershocks.
Below is the list of quakes as of today:
Date and time UTM Lat Lon depth(km) magnitude location
12/01/28_11:49:31 36.0498 24.9993 27.0 3.0 ML 54 Km SW from Santorini
12/01/28_11:13:45 36.0355 25.0027 30.7 3.2 ML 54 Km SW from Santorini
12/01/28_10:56:38 36.0472 25.0145 20.7 3.3 ML 53 Km SW from Santorini
12/01/28_10:56:05 36.0437 24.9902 31.4 3.1 ML 55 Km SW from Santorini
12/01/28_10:50:54 36.0555 25.0243 31.1 4.9 ML 4.7 Mw 52 Km SW from Santorini
12/01/28_10:26:54 36.0362 25.0225 29.4 2.5 ML 53 Km SW from Santorini
12/01/28_10:17:39 35.9963 25.0880 29.8 3.0 ML 53 Km SW from Santorini
12/01/28_09:40:33 36.0020 25.1448 31.2 2.1 ML 50 Km SSW from Santorini
12/01/28_09:30:42 36.0267 25.0478 31.7 2.4 ML 52 Km SW from Santorini
12/01/28_09:27:31 35.9957 25.0843 29.9 2.9 ML 53 Km SW from Santorini
12/01/28_07:34:07 36.0567 25.0515 31.1 2.6 ML 50 Km SW from Santorini
12/01/28_07:28:50 36.0390 25.0042 31.0 2.8 ML 54 Km SW from Santorini
12/01/28_07:15:40 35.9947 25.0933 30.5 3.1 ML 53 Km SW from Santorini
12/01/28_06:48:14 36.0498 25.0317 28.9 2.3 ML 51 Km SW from Santorini
12/01/28_03:40:49 36.0433 25.1175 28.5 2.8 ML 47 Km SW from Santorini
12/01/28_02:35:53 36.0263 25.0317 29.1 2.6 ML 53 Km SW from Santorini
12/01/28_02:01:18 36.0273 25.0778 30.7 2.6 ML 51 Km SW from Santorini
12/01/28_01:50:44 36.0490 25.0170 30.5 2.6 ML 52 Km SW from Santorini
12/01/28_00:55:17 36.0465 25.0285 31.8 3.1 ML 52 Km SW from Santorini
12/01/28_00:45:11 36.0842 25.1137 29.7 2.8 ML 44 Km SW from Santorini
12/01/28_00:43:29 36.0545 25.0065 25.3 2.6 ML 53 Km SW from Santorini
12/01/28_00:42:16 36.0803 25.0430 28.3 2.2 ML 48 Km SW from Santorini
Magnitude 5.3 tectonic earthquake 50 km SW of Santorini on 26 Jan
Update Fri 27 Jan 12:22
The location of the earthquake of 26 Jan and its many aftershocks
The location of the earthquake of 26 Jan and its many aftershocks
A 5.3 magnitude earthquake hit about 50 km SW of Santorini on 26 Jan at 04:24:58 GMT. The quake was 28.7 km depth and most likely of tectonic origin. The location is 48 km SW of Santorini at the end of a tectonic fault defining a graben SE of Santorini and the eastern boundary of the volcanically active SW-NE zone comprising the volcanic vents of the Christiania Islands, Santorini itself, the submarine Kolumbo volcano and several minor submarine vents NE of Kolumbo.
About 50 aftershocks have been occurring so far, the largest being 3 of magnitudes 4 and higher.
Seismologist Filippos Vallianatos from the Technological Educational Institute of Crete is cited in an radio interview that he believes that the quakes are related to magma movements beneath Santorini and could be precursors to a new eruption and/or another larger earthquake such as the devastating 7.8 magnitude quake on 9 July 1956, which had also been preceded by increased seismic activity over years.
Such large quakes are not common on the seismically relatively inactive plateau of the Cyclades, which favors this interpretation. Another interpretation is to assume that the current quakes SW of Santorini, although unusually strong, are purely tectonic due to a release of extensional stress in the Aegean plate.
The next months or years will probably give the answer to what is happening.
Update Fri 20 Jan 17:34
Seismic activity 22 Oct - 20 Jan 2012
Seismic activity 22 Oct - 20 Jan 2012
No significant quakes at Santorini during the past days. A small M1.5 from 18 Jan at 10 km depth beneath Kolumbo volcano is shown on the map NE of Santorini.
Update Wed 18 Jan 20:26
Seismic activity 18 Oct - 18 Jan 2012
Seismic activity 18 Oct - 18 Jan 2012
No significant events to report. If you check the seismogramms, you can see the daily rise in noise at Fira during daytime (cars etc.) and the changes of noise at the Profitis Ilias station with the changing weather. NO volcanic tremor.
Update Tue 17 Jan 01:43
Seismic activity 18 Oct - 16 Jan 2012
Seismic activity 18 Oct - 16 Jan 2012
In the past days, seismic activity seems completely normal.
Update Fri 13 Jan 20:36
Seismic activity 15 Oct - 13 Jan 2011
Seismic activity 15 Oct - 13 Jan 2011
Seismic activity at Santorini - indicator of a possible reawakening?
Update Wed 11 Jan 19:23
Seismic signal from Fira town (11 Jan 2011), Natl Observatory
Seismic signal from Fira town (11 Jan 2011), Natl Observatory
Seismic signal from Nea Kameni (11 Jan 2011), Univ. of Thessaloniki network
Seismic signal from Nea Kameni (11 Jan 2011), Univ. of Thessaloniki network
Seismic signal from Prof. Ilias mountain station (11 Jan 2011), Natl Observatory
Seismic signal from Prof. Ilias mountain station (11 Jan 2011), Natl Observatory
Up to now, the seismic activity beneath Santorini is elevated, but not much. Small earthquakes beneath an active volcano (which Santorini has always been, not to forget) are quite normal. The recent modest swarms might simply indicate small intrusions beneath the caldera and the volcano-tectonic SW-NE zone that also comprises the large submarine volcano Kolumbo. Up to now, we have not observed significant tremor either. During daytime, stations located in towns (such as Fira) typically show increased noise, and during days of strong wind (such as now), the station at the summit of the mountain seems to generate more noise as well, or could be malfunctioning. Whether it is volcanic tremor or not what is seen on the seismograms is speculation. The more reliable signal from Nea Kameni, the most likely location of renewed activity, shows no indication of such strong volcanic tremor.
Update Mon 09 Jan 20:27
Earthquakes between 11 Oct and 9 Jan 2012
Earthquakes between 11 Oct and 9 Jan 2012
Seismic recording on Santorini on 9 Jan, showing the 3.3 earthquake and increased tremor in the morning
Seismic recording on Santorini on 9 Jan, showing the 3.3 earthquake and increased tremor in the morning
A new swarm of earthquakes occurred at Santorini. During the past 48 hours, 7 quakes between 1.1 and 3.3 magnitude occurred at depths between 5-7 km under the island. The largest was quake of 3.3 magnitude this morning at only 5.7 km depth beneath Santorini's caldera at 08h39 local time. Tremor was increased before and after the quake, suggesting a volcanic origin of the earthquake.
Santorini - seismic activity going on
Update Thu 05 Jan 10:51
Seismic activity at Santorini until 5 January 2012
Seismic activity at Santorini until 5 January 2012
It seems that the seismic activity on the main faults and below the active volcanic island Nea Kameni is still going on. Is this a sign of moving magma? Perhaps. It could also be caused by small tectonic movements caused by changes in the hyrdothermal system. The earthquakes are still small (mostly 0,5-2 R), but they are increased in numbers and concentrated at Nea Kameni. The last eruption took place in 1950. Maybe we can see the evolution of an new eruption circle in a near future? Most likely, no. At least, that's the most realistic answer now. In most cases, seismic swarms whether caused by magma intrusions or not, are not followed by an eruption.
Seismic swarm at Santorini volcano, Greece
Update Mon 02 Jan 13:10
Seismic swarm at Santorini volcano 1-2 Jan 2012 (source: Department of Geophysics, Aristoteles University of Thessaloniki)
Seismic swarm at Santorini volcano 1-2 Jan 2012 (source: Department of Geophysics, Aristoteles University of Thessaloniki)
The seismic unrest beneath Santorini which had started in July 2011 continues into 2012, greeting the world with a small swarm of quakes beneath the caldera.
The slightly increased number of quakes is concentrated on the volcano-tectonic Kameni line, which stretches SW-NE through the caldera and extends outside, especially to the NE where the submarine volcano Kolumbo is located 8 km off the coast. The alignment defines a tectonic graben structure underlying Santorini and has been used for rising magma for nearly all past eruptions of the volcano.
 

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