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The seismic risk in Italy unfortunately it is high over a large portion of our territory. But decreasing the risk of collapses is possible by building in compliance with the laws and using modern anti-seismic technologies.
Seismic risk: what it means
The seismic risk is defined as the probability that seismic events of an entity equal to or greater than an average level will occur in a certain territory and within a certain period of time.
In Italy, theNational Institute of Geology and Volcanology (INGV), established in 1999, has the task of collecting the main national scientific realities in the fields of geophysics and volcanology and in particular the resources of five institutes operating in the field of geophysical and volcanological disciplines:
- the National Institute of Geophysics;
- the Vesuvian Observatory;
- the International Institute of Volcanology;
- the Institute of Geochemistry of Fluids;
- the Institute for Research on Seismic Risk.
The INGV has the mission of monitoring the geophysical phenomena of our national territory, collecting the data provided by an extremely advanced instrumentation network that flows into the operating rooms of Rome, Naples and Catania where experts and specialized researchers, present 7 days a week and 24 hours a day, they analyze them and evaluate possible risks.
Seismic risk in Italy: the INGV interactive map
In 2004 the INGV developed a seismic hazard map which shows the risk associated with the various areas of the Italian territory, highlighting them with different colors.
The light gray color indicates areas with moderate risk, the purple color indicates areas with high risk. The risk grows from gray to light blue, blue, green, yellow, orange, red up to purple.
The values that define the different seismic risk bands refer to the maximum expected acceleration on rigid ground with respect to the acceleration of gravity (g) with a probability of exceeding this value of 10% in 50 years.
For a better view of individual areas you can view the map in full screen in a new window of your browser by clicking on this link.
From the map it is thus possible to understand that the region with the lowest risk of seismic events and the Sardinia while I higher risks are expected in Calabria, south-eastern Sicily, Friuli-Venezia Giulia and throughout theCentral-southern Apennines, with ground accelerations exceeding 0.225 g.
A medium risk it is instead associated with the Salento Peninsula, to Tyrrhenian coast between Tuscany and Lazio, in Liguria, in central-eastern part of the Po Valley and along theentire arc of the Alps.
INGV seismic hazard map: how it was built
There map of the seismic hazard of the Italian territory was created by weighing and aggregating various data starting from the analysis of past earthquakes, considering the geological information available and interpreting on the basis of current scientific knowledge the way in which seismic waves propagate from the hypocenter of an earthquake to the surrounding area.
By comparing these data, the ground shaking values in a given place caused by an earthquake are determined, expressed in terms of the maximum horizontal acceleration of the ground with respect to the acceleration of gravity (g).
Building with anti-seismic criteria: the most effective way to limit the damage caused by the earthquake
Modern construction techniques make it possible to create buildings capable of withstanding seismic tremors of high entity: building respecting the strictest anti-seismic criteria, however, involves higher costs and in the case of our country it would imply having to tear down a large number of buildings of high historical and architectural value. created in the past when modern technologies were not yet available.
Transforming existing buildings in our country to make them resistant to earthquakes is therefore not at all simple but in the same way it must become an indispensable obligation that all new constructions make use of more modern technologies to drastically reduce the seismic risk.
One of the most advanced states inapplication of anti-seismic criteria in buildings and the Japan, precisely due to the very high seismic risk to which it is subject. Another area of the earth with a high seismic risk is California and for greater precision the whole territory located in correspondence with the Sant'Andrea fault which has also given rise to the creation of films of the "apocalyptic" genre in which a high magnitude earthquake causes a tsunami with gigantic and devastating waves.
Seismic risk associated with a tsunami or tsunami
The seismic risk in various parts of the world should also consider the consequences of a tsunami (tsunami) generated by an earthquake with an epicenter off the coast, such as those that occurred in Indonesia and Thailand in 2004 or the one that occurred more recently in Japan, in 2011, which in turn caused a nuclear risk, as the tsunami hit the present nuclear reactor in Fukushima.
Tsunamis are more likely on the coasts facing oceans and in particular on the coasts of the Indian Ocean and the Pacific Ocean because the wave generated offshore by the earthquake can propagate and strengthen over several hundreds or even thousands of kilometers.
The tsunami risk however, it is present also for the coasts of Mediterranean: the last tsunami occurred on 28 December 1908 and was generated by the devastating earthquake with its epicenter in the Strait of Messina, with a magnitude of 7.2.
Even more devastating according to scholars was the tsunami that occurred on 21 July 365 AD. following the 8.5 magnitude earthquake and epicenter near the island of Crete: gigantic waves hit the coasts of Italy, Greece and Egypt, causing thousands of deaths.
The researchers are therefore also engaged in the analysis of data to assess the risk associated with a possible tsunami, so as to try to implement preventive measures.
Is it possible to predict earthquakes?
The response of INGV and seismologists around the world is quite clear: NO, to date, with current knowledge it is not possible to predict with certainty when and where an earthquake will occur.
However, INGV itself identifies "possible anticipatory signals", defined as "seismic precursors”Such as the unusual variation in the velocity of seismic waves, the variations in the content of radon gas in the waters of deep wells, the changes in the water level of rivers and lakes and the crustal movements.
Unfortunately, these "precursors" are not, however, to date, able to provide us with reliable and precise information such as to be able to launch an alarm or a preventive evacuation.
Science has yet to make progress in seismology. Today the only way to "limit damage and bereavement" remains that of to prevent, building buildings that comply with the strictest anti-seismic criteria using the most modern technologies, especially in the areas most at risk that maps such as the one created by INGV are able to identify.
You may also be interested in the article "Earthquakes: CNR's early warning tools”
INGV official site for more information: http://istituto.ingv.it/
Official site created by the civil protection where it is possible to read information and good practices in relation to earthquakes, tsunamis and floods: http://iononrischio.protezionecivile.it/
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