The earthquake swarm northeast of the island of Santorini continues, and has been intensifying, with more than 2000 quakes having been recorded in the past 48 hours. While it consisted mainly of smaller quakes of magnitudes around 2-3, barely noticeable, in the first days of the ongoing crisis that had started on 27 January, it now includes frequent felt quakes reaching magnitudes 4 or higher, with a first magnitude 5 earthquake having occurred earlier this morning.
Seismologists from the local science institutes tend to interpret the series of shocks as the result of tectonic movements along the SW-NE trending fault lines that define a graben between Santorini and the island of Amorgos, with the potential scenario that the earthquakes right now could be fore-shocks of a larger earthquake yet to come. This brings to mind the devastating earthquake of magnitude 7.7 on 9 July 1956, which caused massive destruction and loss of life on Santorini, and triggered a large local tsunami that inflicted further damage.
Whether volcanic processes are involved or could be result of the seismic activity remains uncertain. The epicenters of the quakes are not immediately beneath the known volcanic centers, namely the submarine Kolumbos volcano (which had a large destructive eruption in 1650 A.D.), but located mostly 15-20 km further to the NE. This probably makes magma intrusions as primary cause of the quakes less likely. Still, uncertainly remains high.
Residents alarmed
By now, the seismic crisis on Santorini has reached international news,- no wonder given the celebrity of Santorini. It is causing enormous anxiety locally. News reported many inhabitants decided to temporarily leave the island, and ferries and planes from Santorini to Athens or other islands have been unusually full for this time of year.
Authorities closed schools and other public buildings, and advised hotel owners to empty the pools that could cause damage in case of stronger quakes. Civil Protection and other authorities have increased their presence on the island and the Greek government holds emergency meetings, advising residents to be on alert and follow instructions in case of an emergency. A major risk is from potential tsunamis in case of a strong earthquake (above magnitude 6), and thus people are advised to avoid the coasts.