From the Gargano to Salento, the seismic and tidal network of the region is the subject of new instruments for the knowledge of the phenomena and the mitigation of risks
Rome, 7 June 2024 – Although Puglia is characterized by a peculiar seismicity in the Gargano area, it is less studied and therefore known than that of the Apennines. Furthermore, Puglia also presents a specific vulnerability to tsunamis, due to the extensive coastal surface of the Region and its centrality in the Mediterranean.
To improve the reduction of risks deriving from seismic activity, it is crucial to increase the monitoring of these phenomena to understand the deepest dynamics of the planet.
This activity, fundamental for the research itself and for the protection of the territory and communities from seismic and tsunami risk, was implemented through the increasingly close collaboration between the National Institute of Geophysics and Volcanology (INGV), the Department of Earth and Geoenvironmental Sciences of the University of Bari (DiSTEGEO), and the Higher Institute for Environmental Protection and Research (ISPRA) which has strengthened the seismic and tidal monitoring network in the area.
Through the PNRR project “Monitoring Earth’s Evolution and Tectonics” (MEET), in the localities of Manfredonia, Rignano Garganico, Chieuti and Ischitella, in the province of Foggia, some stations of the Otrions seismic network have been implemented with the installation of broadband seismometers , while in Lucera (FG) in continuity with the PON project “Geoscience Research INfrastructure of ITaly” (GRINT), the monitoring station was replaced and implemented, with the installation of a sensor at 30 m depth.
Important changes of pace to better understand how the territory moves on the surface, but also the most hidden characteristics of the earth’s crust.
“The earthquakes in the Gargano – explains Andrea Tallarico, professor of the University of Bari Aldo Moro and scientific director of the Otrions network – occur at greater depths, up to 25 km deep, compared to the seismicity that characterizes the Apennines, which usually it is confined to the first 12 km of the earth’s crust. The reason why this happens and the consequences, in terms of seismic danger, are still not clear and the hypotheses are different”.
Detailed seismic monitoring provides fundamental information on the Earth’s internal dynamics that can illuminate the reasons behind this particular seismicity.
Giulio Selvaggi, INGV researcher and scientific coordinator of the PNRR-MEET project specifies “The seismogenic layer, i.e. that part of the earth’s crust that behaves in a fragile way and responds to deformations giving rise to earthquakes, is influenced by what we call rheological characteristics that is, the characteristics of the materials, such as the thermal state of the rocks or their viscosity. The propagation of seismic waves is influenced by the same parameters and it is for this reason that we are improving our ability to see deep into the crust over time.” A seismograph, in fact, records wave amplitude and frequency and these two elements are the key clues to understanding what the earth’s crust that seismic waves pass through is made of.
“Thanks to the new broadband sensors – continues Selvaggi – it is possible to record a broad spectrum of wave frequencies. If we think about our voice, it emits different high and low frequencies, the same happens with the shaking of the crust. Broadband allows you to hear all the nuances of the earth’s voice and therefore provides more precise data on the source and travel of seismic waves.”
The monitoring of tsunamis in the Mediterranean is also fundamental for the Apulian territory. The tsunami risk, in fact, is high due to the exposure to seismogenic sources present in the Adriatic and Ionian Seas, but also to the vulnerability of civilian homes and tourist infrastructures close to the coastal strip, in close connection with the increase in density housing in the summer months.
For this purpose, the tide gauge stations of Monopoli and Barletta, managed by the Department of Earth and Geoenvironmental Sciences of the University of Bari, and the ISPRA tide gauges already active in Otranto, Vieste, the Tremiti Islands and Taranto have recently been installed. from ISPRA a new tide gauge in Santa Maria di Leuca.
“The more intensive the monitoring is in the area – explains Alessandro Amato, INGV researcher and Head of the INGV Tsunami Warning Center (INGV-CAT) – the more we are able to make predictions of future scenarios. The tide gauges located in coastal areas inform us not only about variations in sea level, due to earthquakes that occur off the coast, but also about variations in pressure due to meteotsunamis or any underwater landslides that can generate tsunamis”.
“Having a reliable data network – continues Amato – is crucial in cases of tsunami warnings in the Mediterranean Sea. For example, in 2018 an earthquake that occurred in Greece, near the island of Zakynthos, triggered a local Watch (red) alert and an Advisory (orange) alert for Calabria and Puglia. The end of alert signal was issued thanks to the data provided by the tide gauges.”
For tsunami monitoring, the next step envisaged by the PNRR-MEET project will be the installation of two DART (Deep-ocean Assessment and Reporting of Tsunamis) buoys in the southern Ionian Sea, whose sensors will be placed at depths of 2,500 and 3,000 meters, and will be used for the rapid detection, measurement and real-time reporting of tsunamis, thus being able to confirm or deny the arrival of tsunami waves already offshore, before they reach the network of tide gauges on the coast.
