Seismic risk activity
The Civil Protection Department carries out activity to assess, prevent and mitigate seismic risk in Italy, Centres of Competence or operating units.
Science today is not yet able to forecast the exact time and place for future earthquakes. The only forecast possible is of a statistical kind, based on knowledge of past seismicity in Italy therefore on the recurrence of earthquakes. We know which areas in the country run a high seismic risk, for earthquake frequency and intensity and therefore where it is most likely that a big seismic event will happen, but it is not possible to exactly determine when it will happen.
Probabilistic forecasting allows hazardous areas to be identified and classified according to the probability of strong earthquakes and their expected frequency. For greater accuracy when calculating the interval of time in which a given location will most probably be hit by an earthquake, we would need to know how much energy is accumulated in the seismogenic structure, which may trigger off an earthquake in that place and the way in which the energy is released, in other words, a little at a time with many low magnitude shakes or with a few very strong events. But even in-depth study of seismogenic structures will not enable us to establish the exact moment the next earthquake will strike.
Over recent years science has made considerable progress in the study of seismic precursors, in other words the chemical and physical parameters of the ground and underground subject to the variations that can be observed before an earthquake happens. In the future, systematic study of these precursors could allow the initial moment of the earthquake to be fixed, even if false alarms must be avoided, which could prove to be even more harmful.
Research into earthquake precursors has concentrated on:
• Seismological precursors: before a big seismic event a series of microtremors may occur, only detectable by instruments.
• Geophysical precursors: anomalies in the P and S wave speeds, variations in magnetic and electric characteristics of rocks.
• Geochemical precursors: variation in underground waters of the concentration of some chemical elements, in particular of radon, a radioactive gas.
• Geodetic precursors: alterations in the level and slope of ground surface.
Despite comprehension of the phenomenon and confirmation of the validity of the genetic model for earthquakes advanced by seismologists, forecasting of earthquakes based on precursors has so far brought disappointing contradictory results. No precursor happens regularly before each important earthquake, for this reason research is moving towards simultaneous observation of different phenomena. For example, while it is true that animals behave unusually before a seismic event, it is not always true that an earthquake will occur when cats or dogs behave in a certain way. To prevent the effects of a seismic shake, the risk factors must be reduced, acting in particular on the quality of building. Prevention in the form of building well is therefore still the only effective way of reducing the consequences of an earthquake.