An earthquake is a natural phenomenon due to the continuous evolution of the earth's crust which occurs suddenly, with rapid shaking of the ground. Every year there are thousands of seismic events that affect Italy and the surrounding areas and, even if most of them are not perceived by people, they are located by the INGV National Seismic Network (RSN). Composed of over 350 permanent monitoring stations located throughout the territory, the RSN is able to detect every movement of the ground and sees its operational center in the Seismic Surveillance Room at the INGV headquarters in Rome. To comment on the seismicity that affected the national territory in 2018, we interviewed the geologist Maurizio Pignone of the INGV National Earthquake Observatory.
How many earthquakes were localized by the National Seismic Network in 2018?
In the past year, the National Seismic Network has located 23.180 seismic events in Italy and in neighboring areas. On average over 60 earthquakes a day, one every 20 minutes or so. However, it must be considered that, of these, only 10% could have been affected by people, as about 90% had a magnitude of less than 2.
How was the seismicity of 2018 compared to past years?
Wanting to make a comparison with the seismicity that has affected the Italian territory in the recent past, we can define 2018 "on average" with the past years (in the period 2013 - 2015). The exceptions are 2016 and 2017 which were characterized by a much higher number of events due to the significant contribution of the earthquakes of the seismic sequence in Central Italy which began on 24 August 2016. Consider that, compared to last year, in 2017 there are there have been over 45.000 earthquakes and in 2016 almost 60.000 (just under triple compared to 2018). The influence of seismic events located in the area of the central Italy sequence was, therefore, very strong in 2016 and 2017 and decreased by 2018% in 50.
What were the areas most affected by the seismic activity?
The extended area of Central Italy hit by the seismic sequence between 2016 and 2017 is certainly the one still with a higher number of localized events. In particular, two events with a magnitude greater than 4 occurred in the province of Macerata, on 4 April in Pieve Torina and on 10 April in the Municipality of Muccia. The other two areas most affected by significant events in 2018 are the province of Campobasso and the Etna area. In Montecilfone (in the province of Campobasso) a seismic sequence with hundreds of events began on August 14 with an earthquake of magnitude 4.6 and reached its peak with the earthquake of August 16 with a magnitude of 5.1. The latter was the strongest earthquake recorded in 2018 and was particularly felt both in the epicentral area and on the Molise, Apulian and Abruzzo coasts which were very popular in that period. In December, in conjunction with an eruptive phase of the volcano, a seismic sequence was recorded with numerous events in the Etna area which had its peak between 24 and 26 December, with earthquakes also with a magnitude of around 4. Among these, the most important event, of magnitude 4.9 occurred on December 26 and involved the south-east flank of Etna also producing an important superficial faulting.
Are there tools "within the citizen's reach" that allow for information on earthquakes in past years?
Every year in the INGVterremoti blog we publish an interactive map of the previous year's earthquakes with interaction tools and infographics that allow you to navigate between the earthquake locations and their characteristics. By querying the map anyone can select and view the earthquakes, identify the maximum magnitude in any area and observe the frequency distribution of the events month by month, through a dynamic graph. Furthermore, the more curious will be able to develop a space-time animation of the sequence, choosing the period and characteristics of the earthquake.