A new analysis of the seismic risk in the historic center of Catania obtained with the stations of the first urban seismic network in Italy
Through the 20 seismic stations of the first Urban Seismic Network in Italy, built in Catania, some historical-monumental buildings of the Sicilian city were monitored during the 4.3 magnitude earthquake of last December 23, 2021.
The Network, which constitutes the Urban Seismic Observatory of Catania (OSU-CT), was developed by the National Institute of Geophysics and Volcanology (INGV) as part of the PON eWAS project "an Early Warning System for cultural heritage".
Its purpose is to monitor the state of health of city structures and infrastructures, to test an automatic on-site early warning system for earthquakes, to quickly assess any damage to structures through the automatic generation of shaking (shakemaps) and, finally, enrich the studies on the seismic microzoning of the territory.
“On December 23, with the earthquake of Motta Sant'Anastasia (CT) of magnitude 4.3, the OSU-CT network allowed a particularly detailed analysis of the seismic risk on the response to the event of the structures in the historic center of Catania”, explains Domenico Patanè, project manager. “The network, in fact, is characterized by a high density of seismic-accelerometer stations, most of which are located in the historical center in correspondence with historical-monumental buildings".
“The Shake Maps (ShakeMap)”, continues the researcher, “They provide an immediate visualization of the shaking level of an area hit or affected by an earthquake. For several years INGV has been calculating ShakeMaps for earthquakes starting from magnitude 3.0. They report the peak values recorded by the accelerometers and seismometers of the National Accelerometric Network (RAN) of the Civil Protection Department and the National Seismic Network (RSN) of the INGV, present in the earthquake zone”.
“For the historic center of Catania”, adds Domenico Patanè, “the elaboration of the earthquake map on an urban scale has made it possible to highlight how in some areas of the town greater hardships have been recorded with respect to the values reported in the map elaborated on a larger scale which refers to the observations of the closest monitoring stations located in Paternò and south of the city in the Plain of Catania. The greater detail obtained by the OSU-CT is a consequence of the numerous accelerometric data obtained from the stations of the urban network".
The indication of the level of shaking observed, and therefore of the potential impact on buildings, represents particularly useful information for the Civil Protection for the coordination and organization of rescue teams in the event of major earthquakes.
"Another 20 seismic stations will be placed in the first months of 2022 and will optimize the current coverage of the historic centre, extending beyond the municipal belt of Catania. In fact, other pilot sites will be inserted in analogy to what has already been done for the inhabited center of the port of the island of Vulcano and the historic center of Ragusa, developing the OSU network in the territories with the greatest seismic but also volcanic risk in Sicily ", continues the researcher.
Investments aimed at increasing the resilience of the entire built heritage, with networks such as the OSU, can represent a modern and practicable change of pace in the complex problem of seismic risk mitigation and help government bodies to adopt the best choices in prevention policies to be adopted.
The recent earthquakes that hit densely populated urban centers such as that of Irpinia in 1980, Umbria-Marche in 1997, L'Aquila in 2009, Emilia in 2012 and a large area of central Italy in 2016-2017 , have shown that unawareness of the seismic performance of the buildings in which one lives or works and of the infrastructures of the territory has led to the collapse of communities which, in some cases, has also produced the destruction of entire towns.
“It is with that goal”, underlines Domenico Patanè, “that a low-cost monitoring network, potentially applicable in all buildings, consisting of standardized systems for dynamic monitoring has been developed. It allows you to acquire useful information for assessing the vulnerability and integrity of structures following a seismic event. These estimates, in the context of eWAS, are conducted in collaboration with Ivo Caliò and Francesco Cannizzaro of the Department of Civil Engineering and Architecture of the University of Catania and Giuseppe Occhipinti of the National Research Council Institute of Environmental Geology and Geoengineering, IGAG-CNR, through numerical modeling of monumental buildings and their calibration on the basis of advanced numerical models.
It is obvious that knowing the "state of health" of a structure (Structural Health Monitoring, SHM) in an area highly exposed to seismic risk, allows you to evaluate and adopt resilience policies well before a critical event occurs, thus allowing not only to reduce and/or optimize investments but, above all, to reduce the consequences associated with the event”. Bottom line, he says “Similarly, in a post-earthquake scenario, monitoring systems and networks will make it possible to obtain useful information to rapidly estimate (almost in real time) the level of damage to buildings and infrastructures (bridges, viaducts, etc.), thus accelerating the emergency management machine and reducing intervention and recovery times".
---
Historic buildings monitored with the Urban Seismic Network of Catania during the earthquake of 23 December 2021
A new seismic risk analysis in the area of the historic center of Catania obtained with the stations of the first Urban Seismic Network in Italy.
Through the 20 seismic stations of the first Urban Seismic Network of Italy, built in Catania, some historic-monumental buildings of the Sicilian city were monitored during the 4.3 magnitude earthquake on 23 December 2021.
The Network, which constitutes the Urban Seismic Observatory of Catania (OSU-CT), was developed by the Italian National Institute of Geophysics and Volcanology (INGV) as part of the PON eWAS "an Early WArning System for cultural heritage" project.
It aims to monitor the state of health of the structures and city infrastructures, to test an automatic rapid alert system on-site for earthquakes, to quickly assess any damage to the structures through the automatic generation of maps of shaking (shakemaps) and, finally , enrich the studies on the seismic microzoning of the territory.
"Last December 23 with the 4.3 magnitude earthquake in Motta Sant'Anastasia (CT), the OSU-CT network allowed a particularly detailed seismic risk analysis on the response of the structures in the historic center of Catania to the event", explains Domenico Patanè, project manager. “The network, in fact, is characterized by a high density of seismic-accelerometric stations, most of which are located in the historic center inside of important historical-monumental buildings".
“Shakemaps”, continues the researcher, “provide an immediate visualization of the shaking level affecting the area hit by an earthquake. The INGV has been calculating Shakemaps for earthquakes with magnitude higher than equal 3.0 for several years. They report the peak ground motion values recorded by the accelerometers and seismometers of the National Accelerometric Network (RAN) of the Department for Civil Protection and the National Seismic Network (RSN) of the INGV, deployed in the earthquake area".
"For the historic center of Catania", adds Domenico Patanè, "the development of the shaking map on urban scale has made possible to highlight how in some zones of the inhabited area greater resentments have been recorded with respect to the values shown in the map drawn up at a larger scale. The last are referred to the observations of the nearest survey stations located in Paternò and in the southern part of the city, that is in the Piana di Catania. The greater detail in terms of ground shaking obtained by the OSU-CT, is a consequence of the numerous accelerometric data obtained from the stations of the urban network".
The indication of the observed shaking level, and therefore of the potential impact on buildings, represents particularly useful information for the Civil Protection, for the coordination and organization of rescue teams in the event of significant earthquakes.
"Another 20 seismic stations will be located in the early months of 2022 which will optimize the current coverage of the historic center, extending beyond the municipal belt of Catania. In fact, other pilot sites will be included in analogy to what has already been done for the inhabited center of the port of the island of Vulcano and the historic center of Ragusa, developing the OSU network in the areas with the greatest seismic risk but also volcanic one in Sicily", continues the researcher.
Investments aimed at increasing the resilience of the entire built heritage, with networks such as the OSU, can represent a modern and practicable change of peace in the complex problem of seismic risk mitigation and help government bodies to adopt the best choices in prevention policies.
The recent earthquakes that hit densely populated urban centers such as the ones of Irpinia in 1980, Umbria-Marche in 1997, L'Aquila in 2009, Emilia in 2012 and the central Italy in 2016-2017, have shown that the unawareness of the seismic performance of the buildings and of the infrastructures has led to the collapse of entire communities.
"It is with this objective", emphasizes Domenico Patane, "that a low-cost monitoring network has been developed, potentially applicable in all buildings, consisting of standardized systems for dynamic monitoring of structures. It makes possible to acquire useful information for assessing the vulnerability and integrity of structures due to a seismic event. These issues are conducted, inside eWAS project, in collaboration with Ivo Caliò and Francesco Cannizzaro of the Civil Engineering and Architecture Department of the University of Catania and Giuseppe Occhipinti of the National Research Council Institute of Environmental Geology and Geoengineering, IGAG-CNR, through numerical modeling of monumental buildings and their calibration on the basis of advanced numerical models.
It is obvious that knowing the "state of health" of a structure (Structural Health Monitoring, SHM) in an area highly exposed to seismic risk, allows to well evaluate and adopt resilience policies before a critical event occurs. Additionally, it allows to reduce and / or optimize investments and to mitigate the consequences associated with the event too". In conclusion, he states “, in a post-earthquake scenario, networks and monitoring systems will allow to obtain useful information to quickly estimate (almost in real time) the level of damage to Similarly buildings and infrastructures (bridges, viaducts, etc.), thus accelerating the emergency management machine and reducing intervention and recovery times".
Fig 1 - Map (shakemap) of peak ground accelerations (PGA) of the magnitude 4.3 event recorded at 21:33 (UTC) on December 23, 2021 (http://shakemap.ingv.it/shake4/data/29284471/current/products/pga.jpg). The isolines show the PGA values in % g (acceleration of gravity).
Fig 1 - Map of the peak ground accelerations (PGA) of the 4.3 magnitude event recorded at 21:33 (UTC) on 23 December 2021 (http://shakemap.ingv.it/ shake4 / data / 29284471 / current / products / pga.jpg). The isolines report the PGA values in % g (acceleration of gravity).
Fig.2 – Location of the OSU stations in the historic center of the municipality of Catania (left) and map (shakemap) of the peak ground accelerations (Peak Ground Acceleration, PGA) of the magnitude 4.3 event recorded at 21:33 (UTC) on the 23rd December 2021. The isolines show the PGA values in cm/sec². 1 g (acceleration of gravity) = 980,665 cm/s². The table at the top right shows some PGA values (in %g and in cm/sec2) recorded at 3 of the OSU-CT stations.
Fig 2 - Location of OSU stations in the historic center of Catania (left) and relative map (shakemap) of the peak ground accelerations (PGA) of the 4.3 magnitude event recorded at 21:33 (UTC) of 23 December 2021. The isolines report the PGA values in cm / sec². 1 g (acceleration due to gravity) = 980.665 cm / s². The table on the top left shows some PGA values (in% g and in cm / sec2) recorded at 3 of the OSU-CT stations.
Fig 3 - Accelerometric recordings of the vertical component at different stations of the OSU-CT network.
Fig 3 - Accelerometric recordings of vertical components at different stations of the OSU-CT network.