PDnet is an innovative infrastructure, designed with the aim of detecting any variations in seismicity to relate them to changes in other parameters, such as the conductivity of water, for example, thus increasing knowledge of the interior of the Earth. Installed on Lake Garda, it was designed within the Milan section of INGV. To understand its characteristics and potential, we interviewed Lucia Luzi, Director of the Section.
Lucia, the installation of the PDNet monitoring network has begun in Lake Garda. What is it exactly and what can it detect?
PDNet is a network which, in research jargon, is called multi-parameter. It is defined as such in that each measurement station sees the presence of various instruments for detecting and recording phenomena such as earthquakes, the level of the water table (i.e. the level of water stored inside the rocks), the presence of radon gas but also the temperature of the water and its conductivity.
It is therefore very different from the national seismometric network because it is equipped only with sensors aimed at recording earthquakes.
Who was this infrastructure designed by?
PDNet was designed within the Milan section of the INGV where there is a functional unit that deals with monitoring. This, within the Dynamic Planet project (a project that aims to improve knowledge of the interior of the earth in the Euro-Mediterranean area), has designed the innovative infrastructure as the area covered by the installations, logistically close to the Section , is central to densely populated cities such as Brescia, Verona, Bergamo, Milan, Trento, Vicenza where there is a fairly high level of seismicity for northern Italy.
What are its main features?
The main feature of the multi-parameter network is that of having different types of sensors installed in the various measurement stations, with the stations positioned a short distance from each other. This arrangement makes it possible to lower the minimum magnitude detectable by the network, as seismic activity in northern Italy is lower than in other areas. If the stations are close to each other, the minimum detectable magnitude increases and, in this case, the minimum magnitude threshold is lowered to about 1.5. This allows you to detect low-magnitude earthquakes more accurately.
Why was this area chosen for its installation?
Firstly, because seismicity is quite high in the area in question, several historic earthquakes have occurred, one of which was quite recent, in 2004 with a magnitude of 5.2.
It is an area close to densely populated cities and could in the future, although it is still early to tell, be used as a seismic Early Warning network to warn the main surrounding cities in the event of an earthquake.
What are the seismic characteristics of the area?
From a geological point of view, the area is characterized by faults, called inverse faults, which generate compression on the earth's crust.
Seismicity in this area is moderate, if compared to the national one, but it is high for an area in northern Italy. In fact, historically important earthquakes have occurred along this compressive structure. An example of this is the event in the Garda area on 3, with an estimated magnitude of 5.4, which affected the areas south of Salò (BS) with effects ranging between the VII and VIII degrees on the Mercalli-Cancani-Sieberg (MCS) scale.
The most recent earthquake, however, occurred on, located 5 km north-east of Vobarno (BS), with a magnitude of 5.2.
Considering instead the areas immediately south of Lake Garda, the most significant historical earthquake is that of January 3, 1117, which is associated with a magnitude, estimated from macroseismic data, equal to 6.5.
To conclude, how was the monitoring network installed and what made it possible to implement it?
The Dynamic Planet Project has made the funds available for the construction of the infrastructure and the collaboration with the University of Milan Bicocca has allowed us to contact the water managers of Brescia, Verona and Lake Garda. At the same time, a researcher from Palermo, an expert in geochemistry, moved to us temporarily. The union of these skills, together with the funds, has allowed the creation of the multi-parameter network.
The installation started in the summer of 2021, with the identification of eight suitable sites where the seismic stations have been installed. Subsequently, in six disused wells, sensors dedicated to the evaluation of the level of the water table, to the measurement of the water and its conductivity were inserted; the instrumentation for detecting radon gas was also implemented, with two dedicated stations.
Finally, we installed four weather stations in order to evaluate and relate the variation of parameters such as the groundwater level with seismicity, net of meteorological effects.
The final purpose of the PDNet network is precisely that of detecting any variations in seismicity to put them in relation with the variation of other parameters, such as for example the conductivity of the water or the height of the aquifer. This is an innovative infrastructure since until a few years ago monitoring was very sectoral and the seismological, geodetic or hydrogeological instruments were installed independently, making joint analysis difficult to carry out.
For further information, link to the article on the INGV Terremoti Blog: