news20 ottobre 2011

Foreshocks in the province of Siracusa

In-depth and information on the ongoing phenomena and seismic risk prevention

Over the past few weeks, the Department has been receiving requests of information from the citizens regarding the shocks perceived in Sicily.

On the base of data received from Ingv National Institute of Geophysics and Volcanology and Seismic and volcanic risk Office of the Department of Civil Protection, we publish in depth examination of the phenomena. With the occasion, we present again the test on seismic risk prevention and remind our readers some rules of behaviour.

East Sicily is currently affected by a seismic sequence, or swarm: it is not possible to say that there is a main quake followed by aftershocks of minor intensity, but only shock of the same energy, casually distributed in time. The swarm has been affecting the central ans south area of the province of Siracusa for about a month: the area of Iblei Mountains, among the municipalities of Noto, Avola, Canicattini Bagni, Buscemi, Solarino. As of today, some twenty shocks have been registered, with an MI magnitude grade between 1.5 and 3.3 (9 October 2011). The average depth of hypocentres is about 10 km.

The area of Siracusa has a medium-high seismic dangerousnees, according to the seismic dangerousness map of our country created by the National Institute of Geophysics and Volcanology. Municipalities affected by the on-going swarm are claasified in seismic zone: they are territories where specific building regulations need to be applied.
Sicily - as well as other seismic areas of our country - in particular the east part, has been affected, throughout history, also by the effect of seaquakes in conjunction with the strongest earthquakes, among which the ones of 4 February 1169, of 10 December 1542 and of 11 January 1693, as described in the technical file of Siracuse's seismicity.

Dangerousness maps and seismic classification show which areas of Italy are affected by a high seismicity, thus where an earthquake is more likely to occur, although the exact time cannot be defined. Studies on foreshocks, like the ones ongoing in Montefeltro and Messina areas, doesn't allow to assume the occurrence of a stronger shock. As of today, in fact, there are no recognized scientific methods to predict time and place where a quake will occur. The map of seismic dangerousness is still the most effective tool that the scientific community provides for the prevention politics. Prevention is still the best defence from earthquakes and the only wat to reduce any consequence.

In Italy each year there are over 10,000 eathquakes, an average of thirty a day, which cannot be predicted. It is thus important to be aware of the danger on the territory and be informed on how buildings where we live, study and work are constructed.

On 22 and 23 October, the "Earthquake - I don't risk" initiative will be carried out in Siracusa and Solarino, and at the same time in other seven municipalities at high seismic risk of Basilicata, Calabria, Campania, Puglia, and Tuscany. The national campaign aims at sensitizing on the seismic risk reduction and diffusing awareness among the population on seismic risk and prevention themes.