Update on the earthquake swarm of Campi Flegrei of the 7 October 2015.
The swarm of October 7, 2015, consisted of about 33 events with a magnitude comprised between M 2.5 and M-0.9. The first event was recorded at 9:20 am and the last at 11:16. The largest scale event (M = 2.5) occurred at 11:10. All events were located on the eastern edge of the Solfatara at an average depth of about 2 km.
One of seismic stations closer to the epicenter (on the edge of the Solfatara) recorded the highest ground accelerations (PGA) which was equal to 1.8% g (g = acceleration of gravity). This roughly corresponds to an intensity of IV on the Mercalli scale.
Earthquake swarms are common under of Campi Flegrei. For example, in September 2012 there was a swarm with nearly 200 events recorded, with a magnitude of up to M 1.7 . The hypocenters of the swarm were below the town of Pozzuoli, at a depth of about 3 km. Similarly, in March 2010, it has been observed another swarm with nearly 150 events recorded in 40 minutes, with a maximum amplitude of M1,2. During the crisis bradiseismic of Campi Flegrei in 1982-1984, they have been affected by seismic activity. At that time, more than 16,000 earthquakes were recorded with values of up to magnitude 4.
Seismic activity of Campi Flegrei is accompanied of other geophysical phenomena, the most obvious is certainly rising ground. Between 1982 and 1984, the land has risen by about 180 cm. Years later, she has fallen on a regular basis until 2005. Since 2005, the earth was again high of about 32 cm, approximately 11 cm from January 2014.
Remember that in 2012, due to the geochemical and geophysical anomalies observed in recent years, the alert level of Campi Flegrei was raised from green (normal) to yellow (warning). For this reason, the area of surveillance has been continuously improved in recent years with the addition of new stations and innovative systems.
October 10 , 2015. Campi Flegrei, Italie :
Photo : Campi Flegrei news