A new study by the University of Stanford, California, and directed by the Italian Tiziana Vanoriosheds light on what triggers the earthquakes and deformations of the ground in the Flegrei camps: the cause would be theIncrease in water and steam pressure within the sediments that make up the so -called geothermal tank Located to about 2 km deepabove the magmatic chamber. Based on the study, the increase in pressure occurs when large quantities of rainwater (i.e. due to rainfall) flow to Pozzuoli, infiltrate accumulating in porous sediments and are heated by the gases released by the magma. This conclusion was achieved with laboratory tests and analyzing the speed of propagation of seismic waves in the subsoil of the caldera. The researchers also suggest that Reduce the amount of fluids present It could help limit pressure and consequently related seismic phenomena.
The study of the causes of the seismicity of the caldera
In the past, geophysical studies have been carried out relating to the trend of seismic waves in correspondence with the Caldera dei Campi Flegrei. The new research, however, has related more precisely the speed of the seismic waves of the earthquakes that occurred during the Bradisismic crisis of 1982-1984 and that of current earthquakes. Were thus identified anomalies common to the two periodslinked to the presence of a geothermal tank about 2 km deep. In both cases, moreover, the lifting was accompanied by noises attributable to explosions due to the rapid transformation of liquid water into steam when during earthquakes, fractures in the rocks are created and the pressure decreases.
The researchers also analyzed 24 years of data relating to rainfall in correspondence of the area and integrated them with experiments conducted in the laboratory. These simulated the behavior of the geothermal tankconsisting of porous sediments. Meteoric water accumulates inside and is heated by the gases released by the magma, then expands. The presence of one Waterproof rocky layer above the tank makes the pressure increases enormously When the amount of high temperature fluids is high. As a result, the deformation rate and seismicity increase. The direct cause of the lifting would therefore not be magma, as confirmed by the speed of seismic waves.
The solutions proposed to reduce pressure to the Flegrei fields
Identifying these mechanisms that are repeated over time is important from the point of view of the prevention. Tiziana Vanio, driving the team of researchers, proposes some solutions for Reduce pressure in the geothermal tank adjusting the amount of water and steam inside. The problem, in fact, is that due to the conformation of the territory there is a large outflow of underground water to Pozzuoli. It would therefore be, for example, of intercept the meteoric water upstream to prevent their concentration downstream. Another important intervention would be to do Maintenance to the riverbedsoften obstructed, of the waterways that channerate rainwater towards the sea. Also take water from the wells In the Pozzuoli area to lower the level of the water table is indicated as a useful intervention. To escape the fluids from the tank, the reopening of geothermal wells made in the seventies, when the exploitation of that type of energy had been evaluated. In this case, however it is a very delicate operation because it could solicit seismic phenomena.
