The seismic activity in the sea area between Santorini and Amorgos is continuing, with two fairly strong tremors registered on Wednesday (12th February) of 5.0 Richter at 1.50 am and 4.9 at 8.30 am. The earthquakes have continued unabated over the past 12 days with no sign of a reduction either in their frequency or their magnitude.
As of midnight on Wednesday 12th February, the area had since January 31st experienced 176 earthquakes of magnitude 4.0 Richter or above, of which six were of magnitude 5.0 or above and 91 per cent were at a focal depth of 10 km or less. These figures are taken from the statistics published by the Seismological Laboratory of the University of Athens. It should be noted that these tend to he more conservative than those published in the media immediately after an earthquake, and some of them may also be downgraded in magnitude from the initial report, presumably following further analysis.
When will it end?
As the series of tremors fluctuates and continues, experts appearing in the national media are constantly asked the same questions: How long will it go on, have we reached the peak yet, what are the possibilities of a major quake of 6.0 Richter or over?
Speaking on ERT News on Monday, the seismologist Professor Kostas Papazachos of the Aristotelian University of Thessaloniki explained the difficulty of making any firm predictions about the outcome of the present series of earthquakes. He explained that the sequence will continue in the same fashion and everyone needs to show patience, until there is a final de-escalation of the phenomenon:
“When we say that something will last for some time, it creates a false impression in the public that something will change from day to day. Whether it’s a group of similar tremors or a series leading up to a major earthquake, it may last for weeks, sometimes for months. It’s a disagreeable message but that’s how it is. The sequence will continue, and will do so in the same fashion.
“There is a specific mechanism which creates episodic occurrences of earthquakes, that is to say they come in small groups. Four or five tremors may occur within two or three hours, and after that 12 -16 hours will pass, the activity will quieten down and then start up again, and each time we have the same misunderstanding. This may take weeks to pass. Both we and the local community have to adjust to the fact that this is how the de-escalation will take place. It’s not something which will happen suddenly tomorrow to end the sequence,” he added.
Asked whether there was any prediction as to the state of affairs by Easter, Mr Papazachos said: “Generally these sequences do not last for such a long time with such a frequency [of tremors]. We have to say, however, that there have been sequences which have lasted for two or three months. Unfortunately in Santorini, we just have to wait and see. We need to assess the seismicity on a weekly basis. There is no technical or scientific knowledge which enables me to tell you that it will end on 10th April or 10th May. We need inevitably to work on the scenario that the whole of February or a large part of it will pass in the same situation, and let’s hope that eventually we will have a gradual de-escalation.”
Increased monitoring of the area
The unusual nature and long duration of the sequence of earthquakes has prompted an increasing number of scientific bodies to take an interest in developments in the area. In one initiative, specialists are installing new ultramodern seismographs around Santorini’s undersea volcano. A scientific team led by Evi Nomikou, Assistant Professor in Geological Oceanography and Natural Geography at the Faculty of Geology and Geo-Environment of University of Athens, is on the island along with the Army’s Geographic Service to collect data from the portable devices. The ultra-modern seismographs are to be placed in the Caldera for a week, replacing two others which have been gathering data for the past seven days.
Explaining to reporters how the scientists would be collecting and analysing the data, Ms Nomikou said that the aim was to achieve a better understanding of the phenomenon. “We need to understand the changes which have taken place under the surface from 2011 to the present day,” she said.
Monitoring from an oceanographic ship
In addition a research mission will be undertaken in the next few days by the oceanographic ship Aegean of the Hellenic Centre for Marine Research (HCMR) in the area of Santorini and Amorgos. Starting its mission on 12th February the Aegean will aim to collect additional geological, geophysical, geochemical and oceanographic data for a fuller understanding of the seismic activity taking place in the area. As HCMR’s Director of Research, geologist Dimitris Sakellariou explained to APE-MPE, the aim is to take different measurements, beyond the undersea fissures, which to a large extent are already known, also examining whether there have been any changes in the seabed.
“We want to map the areas in which we know that there have been landslides in the past, and especially in 1956, that is in areas which have let’s say a high risk of undersea landslides, and to understand their nature. We shall also see whether there there have been some small landslides during the current period, and what the state of the cliff is,” Mr Sakellariou said.
Also, he noted, they will try to take measurements of any gases being emitted by the fissures, which may have been activated by the current seismic activity. “A lot of things are unknown; however, the more data we can acquire, the more we can contribute to knowledge of the area, so as to better understand what is happening with this seismic activity and the possible consequences we may face,” he said.
Installation of a tide gauge
As part of the multiplicity of monitoring activities under way, a tide gauge has been installed on the north-east shore of Santorini by the National Tsunami Warning Centre (NTWC) of the of the National Observatory of Athens. According to an announcement by the Centre, the specific location was chosen as close as possible to the epicentre of the ongoing seismic activity, so as to promptly record and monitor changes in sea level.
(Sources: Haniotika Nea, 11/02/25, www.ertnews.gr)