Over 53.000 seismic events were located in 2016 by the National Seismic Network (RSN) of theIstituto Nazionale di Geofisica e Vulcanologia (INGV). Compared to previous years, the number of earthquakes has increased significantly (with seismic events more than doubling compared to 2014 and more than tripling compared to 2015). The high number of earthquakes in 2016 is largely due to the Amatrice, Norcia, and Visso seismic sequence, which began on August 24th with a magnitude 6.0 earthquake, located in the province of Rieti, and continued with other events with magnitudes above 5.0, and, most notably, the magnitude 6.5 earthquake of October 30th, the strongest ever recorded by the National Seismic Network since the early 1980s.
The seismicity map recorded by the INGV National Seismic Network in 2016
Most of the earthquakes had a magnitude of less than 2.0, with over 42.000 occurring. If we limit ourselves to counting the earthquakes of 2016 with a magnitude equal to or greater than 2.5 (those for which INGV notifies the Department of Civil Protection), there are instead 3400 events, about 5 times those of 2015.
Graph of the temporal trend of seismicity (magnitude M>=1.5) throughout the national territory in the year 2016, according to the magnitude, from yellow (M<2) to red (M>=4.0). The time scale is non-linear and therefore the seismicity before August 24 is condensed into a small portion of the graph (left)
As shown by the graph of seismicity over time, there were several events with a magnitude greater than or equal to 5.0 during 2016 (none in 2014 and 2015): in total 6 events with a magnitude greater than 5.0; 2 of magnitude greater than or equal to 6.0 (the events of August 24, Mw 6.0 and October 30, Mw 6.5). Another 3 events of magnitude between 5.0 and 6.0, located in the area of the seismic sequence of Amatrice, Norcia, Visso (August 24, Mw 5.4, October 26, Mw 5.4 and Mw 5.9), while another of magnitude Mw 5.8 in Tyrrhenian Sea on 28 October.
Finally, there were numerous earthquakes of magnitude between 4.0 and 5.0: 64 events, over 50 of these located in the area of the sequence.
In the first months of the year seismicity was in line with the last months of 2015. In fact, the daily average of events recorded by the National Seismic Network was around 40 earthquakes, while from August this average increased to reach the value of about 300, with days where more than 600 events were logged. In the end, the daily average of events recorded in 2016 stood at 145, much higher than the 40 in 2015 and the 60 in 2014.
Link to the INGVterremoti blog article:
https://ingvterremoti.wordpress.com/2017/02/23/speciale-2016-un-anno-di-terremoti/