In search of the reasons why earthquakes happen

Greek scientists are heading two new, pioneering programs

By Giorgos Lialios - Kathimerini

Greek scientists are looking for the key to understanding earthquakes that are the result of tectonic plate movements by examining distortions in the earth’s outer shell (lithosphere). In observing the rhythm of changes to the surface, seismologists are hoping to better understand the mechanisms that give rise to earthquakes, in order to be in a position in the future where they may be able to predict occurrences. Two such programs are currently being run by the Geodynamics Institute and the University of Athens in the eastern Corinthian Gulf and western Greece.

The program in the Corinthian Gulf encompasses the fault line at Kapareli in Viotia, which was responsible for a strong March 1981 earthquake measuring 6.3 on the Richter scale. The area was not selected because it is considered risky, “but, as uncouth as may it sound, because of its proximity to Athens,” admits the program’s scientific director, Giorgos Drakatos, who is also director of research at the Geodynamics Institute. “The earthquake at Parnitha [in September 1999], which we scientists did not rate highly in magnitude, was destructive because it occurred near the country’s biggest city. So we are studying a fault line that is considered dormant but is very near the capital.”

Scientists from other European countries are participating in the program, which is funded by the General Secretariat for Research and Technology and the European program COST (European Cooperation in the Field of Scientific and Technical Research). Monitoring the distortions of the earth’s surface is the main way to observe seismic activity. “If we squeeze anything from both ends, it will break. That is what is happening at the earth’s surface. The stress waves signify a concentration of energy, which at given times is released through a shift in the tectonic plates,” explains Thanassis Ganas, researcher at the Geodynamics Institute and a member of the program’s research team. “We measure these distortions in the area by applying the method of tectonic geodesy, which means measuring the distance between specific points. Our aim is to be able to evaluate future activity, not in the form of prognosis, but to better understand the phenomenon.”

The network comprises three stations, running from Kapareli to the village of Erythres, while next week it will be extended to Aghios Thomas and Asopos, covering the full 60-kilometer belt from Kapareli to Oropos. What is innovative in this program is the extensive use of GPS (Global Positioning System) technology “to pinpoint specific areas prone to stress.”

A similar program, being run in cooperation with Athens University’s Department of Geophysics-Geothermics (headed by Professor Vangelis Lagios) and with Ganas as its scientific director, has been under way since the beginning of the year in western Greece. “We have installed a pioneering network that allows us to constantly monitor shifts in Cephalonia and the prefecture of Achaia. The difference with Kapareli is that in Kapareli, the system is not permanent and measurements are taken once a year, while in Cephalonia-Achaia, the installations are permanent, though spaced further apart, and are able to send measurements every second via the network to Athens,” explains Ganas. “Cephalonia is some 77 kilometers away from Patras. The two areas belong to different ‘packages,’ but they are both shifting southeast, at different speeds. What we are trying to understand is what is happening between these two plates, and what is happening under the seabed. The GPS will help us understand this in the next tremor, because it will record the actual movement; something a conventional seismograph cannot do.”