The monitoring of induced seismicity is extremely important for understanding the physical processes at the origin of a seismic phenomenon. Monitoring also allows the identification and mapping of potential active faults near industrial sites. Real-time seismic monitoring is the most widely used control tool in many areas of resource use for energy production.
A seismic monitoring network is a set of seismic stations distributed across a given area and connected in real time through data transmission systems to a collection centre. Seismic monitoring networks are implemented for scientific purposes and civil protection actions.
TThe seismic monitoring network records the ground vibrations caused by the passage of seismic waves. The network is very sensitive and detects all ground vibrations, both those of earthquakes and those generated by other sources such as the transit of vehicles (trains, trucks, etc.), the activities of industrial machinery, weather disturbances or explosions at quarries or of war ordnance.
The seismic monitoring network records the ground vibrations caused by the passage of seismic waves. The network is very sensitive and detects all ground vibrations, both those of earthquakes and those generated by other sources such as the transit of vehicles (trains, trucks, etc.), the activities of industrial machinery, weather disturbances or explosions at quarries or of war ordnance.
The seismograph is a tool that transforms the movement of the ground caused by a seismic event into a permanent record. It allows proper analysis and review of all seismic waves at any time.
The monitoring system continuously acquires signals from the stations of the network, analyses the signals to recognize any variations and, if these variations are found at more than one station, locates their origin and intensity. If the conditions are met, a so-called "seismic event" is declared. This entire process occurs in a few seconds from the moment the signal is recorded.
It may also happen that different events or false events due to random correspondence of signal changes are identified. Since the system is calibrated to be very sensitive (remember that the main purpose is to record microseismicity), there can be many false events. For this reason, all automatic determinations are reviewed by an experienced seismologist who analyses the detected events and confirms that they correspond to local earthquakes or events potentially related to the activity of the storage plant.
The motion of the ground recorded by the instruments is usually represented with graphs, called seismograms, which describe the movement of the ground over time. From the seismograms, it is possible to evaluate (both visually and through computer analysis) where a seismic event occurred, how strong it was and what are some of its other characteristics.
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In the seismogram, we can recognize the phases (i.e., particular traits of waveforms) related to specific wave fronts that are generated at the source or have traversed the geological structure of the Earth, which is complex, and the "seismic noise", i.e., the vibrations resulting from many processes with different origins (from atmospheric perturbations to oceanic motion, from human activities to earthquakes themselves); this noise continuously runs along the Earth's surface similar to the continuous wave motion of varying strength seen on the sea.
From the specific phases recognizable in the seismograms generated by a seismic event, it is possible to estimate (both visually and through computer analysis) where it happened, how strong it was and what are some of its other characteristics.
The structural works of the IGS Cornegliano Stoccaggio plant have been designed according to the technical standards for construction by adopting particularly strict and conservative parameters; the structures are therefore robust and certainly able to withstand the expected seismic events without sustaining damage.
In the case of hypothetical catastrophic events, much more violent and unlikely, the structures could experience localized damage but no collapse; in this case, the plant is equipped with intrinsic safety systems that, in the case of anomalies, interrupt the operations and place the plant under non-operational conditions.
Yes, the deposit can be safe in case of an earthquake. In fact, it does not consist of a large empty cavity filled with gas but porous rocks into which the gas infiltrates, a kind of large sponge located at a depth of approximately 1.5 kilometre. The rock that constitutes the reservoir, inside which the gas is stored, and the layer that seals it above (the so-called cap rock) behave elastically with the passage of seismic waves generated by an event. It must be remembered that the depleted gas reservoirs used in Italy for storage had contained gas formed naturally for millions of years and experienced and resisted all the seismic events that occurred in the area.
