Earthquakes: seismic swarm at Campi Flegrei, about 200 shocks caused by bradyseismus
Saturday Sep 08, 2012 09:00 AM | Age: 6 hrs
Location of recent earthquakes in the Campi Flegrei
A new swarm of earthquakes was recorded under the Phlegean Fields near Naples yesterday (8 Sep). The quakes are related to what is called bradyseismus, a slow periodic ground inflation and deflation, which make the
land of the Phlegraean Fields rise and sink over years.
On the morning of 8 September, about 200 earthquakes of magnitude up to 1.6 were detected by the Osservatorio Vesuviano (OV). Its director, Marcello Martini, said that this phenomenon repeats periodically and is linked to the process of deformation of the Phlegraean Fields.
Earthquakes today have not surprised the experts. Small earthquake swarms were already recorded in the Campi Flegrei very recently: on August 4 last year, when the shocks were only a few tens, and between 19 and 20 April, with 21 earthquakes of magnitude 1.4 maximum.
The process of deformation of this area (which is one of what often has been described as a "supervolcano") is continuous. The ground rises and falls periodically and changes in this movement are often accompanied by small earthquakes.
For example, Martini explains, "between 1982 and 1985 began a slow decline that ended in 2005. Since then, a slow rise of the land began that is still continuing today."
"What that past experience has taught us," says the expert," is that earthquakes can occur with the lifting process. Certainly, however, the phenomenon of today still has to be studied. There is also the fact, he added, that the peaks of speed in the movement caused by bradyseismus has been reduced by 10 times compared to the maximum of 15 cm per month measured 30 years ago. At present this is not a disturbing phenomenon, but we follow it very carefully."
According to OV there is no relationship between the swarm and the drilling recently launched as part of an international project on supervolcanoes led by Italy's INGV. "The drilling - says Martini - reached only 200 meters this time, while in the past drillings were made to up to 400 m depth, and second, the drilling is in the Bagnoli area, while the swarm is concentrated in the center of the caldera in the area of Pozzuoli." [link to www.volcanodiscovery.com