Earthquakes in the Cyclades islands: Astypalaia and Naxos moved by 2 and 2.8 centimeters respectively. This was stated by Thanasis Ganas, Director of Research at the Geodynamic Institute of Greece at the scientific event “Dialogues on Santorini” focusing on the 2-month-long seismic activities in the area and organized by the Center for Natural Disaster Research of the Academy of Athens on Monday.
Evi Nomikou, Professor of Geological Oceanography at the University of Athens, stated on her part that the area of the submarine slope of Colombo volcano sank by 19 centimeters.
Referring to the seismo-tectonic processes in the wider region, Ganas said that “every year, Santorini and Amorgos move by 4.5 millimeters to the northeast, and Astypalaia and Anafi to the southwest, and at the same time they shift horizontally. Due to the February crisis, Astypalaia moved by 2 centimeters to the southeast, while Naxos moved by 2.8 centimeters to the north-northwest. Anhydros, as shown by satellite data, moved by 14 centimeters to the west and sank by 12 centimeters, as it was at the epicenter of volcanic-tectonic activity.” As he mentioned, the maximum earthquake in the area was 5.3 Richter, however the potential of the underwater faults can reach 7.1 Richter (+/- 0.3).
Margarita Segou, Director of Research at the British Geological Survey, described very succinctly the mechanism that led to the crisis of last February. She described how the Santorini crisis unfolded in four phases.
“In the first phase, until February 1, there were seismic events, but they were reduced. In the second phase, from February 2 to 5, there was a sharp increase in seismicity, with earthquakes up to 5 on the Richter scale. The reason is the fragmentation of rocks due to the pressure exerted by the magma from below. In the third phase, from February 6 to 10, there is movement of magma and increased seismic events. Finally, in the fourth phase, from February 11 to 14, it begins to become more noticeable from the seismicity rates that there is also involvement of the faults in the area.”
It is necessary to create a volcanic observatory with the participation of Greek and international scientists, Ganas emphasized
Collaborations with with foreign universities and oceanographic expeditions in Santorini helped the gathering of lots of data, even though we as a country do not favor marine research,” Nomikou told daily kathimerini.gr
The scientists from Greece and abroad who participated in the event analyzed how the magma chambers located in the wider area of Santorini worked.
“By combining all the data, we conclude that the recurring earthquakes were caused by a “feeder vein”, the movement of fluids from deeper magma chambers to the surface, a movement that moved the faults and caused the earthquakes. It is clear that the earthquakes were not purely tectonic.”
What is impressive in the case of the recent volcanic-seismic crisis in Santorini is that the scientists reached these conclusions within a few weeks, when in corresponding cases in the past it took months or even years. [full article in Greek here]
See also: Santorini Earthquakes on KTG.
it also seems as if naxos and amorgos also were lifted several cm higher up, from noticing the low-tide marks on rocks and the quays in town which now seem to be always well clear of the water.