ENVIRONMENTAL EFFECTS OF EARTHQUAKES

For the population of this indicator, the 19 earthquakes that occurred in 2022 with a magnitude of 4.0 or higher (see Table 1 of the "Seismic Events" indicator) were considered to check if they induced any significant environmental effects. Of the 19 events, 7 occurred at a depth of over 20 km, which is too deep to induce environmental effects, given that the magnitudes did not exceed Mw 5.5. Of the 12 events that occurred at a hypocentral depth of less than 20 km, the only one for which environmental effects were reported is the earthquake of December 4, 2022, in the Aeolian Islands with a magnitude of Mw 4.5, which occurred at a depth of 3.1 km (source: https://terremoti.ingv.it/event/33554561), with the epicenter located approximately 9 km southwest of Vulcano Island (epicentral coordinates 38°31'7.20''N; 14°51'23.40''E).

This earthquake induced secondary effects on the ground in various locations on the islands of Lipari and Vulcano, including collapses and landslides. These were reported in a report following an INGV field survey (Tuvè T., Manni M., Pruiti L., Azzaro R., Bottari C., Giampiccolo E., Musumeci C., 2023. Macrosismic Survey of the 4th December 2022 Aeolian Earthquake – 08:12 local time. Internal INGV Report, http://hdl.handle.net/2122/16122) and from the local Civil Protection Service of Lipari (ME). In the Capistello area, located in the southern part of the island, a rock collapse of several cubic meters occurred. The fallen rocks blocked a paved path above the so-called Villaggio Francese (Figures 1, 2, 3). Other collapses were recorded in the Mendolita area, just west of the town of Lipari, as well as in the Falcone area and at Valle Muria Beach, where part of a rock slope collapsed into the sea. The earthquake did not cause any fatalities and resulted in minor damage in various inhabited areas, including Lipari. Except for the blockage of the pedestrian road at Capistello, the landslides induced by the earthquake did not cause damage to buildings. On Vulcano Island, the aforementioned INGV report also documented two rockfalls on Monte Lentia.

From the overall picture of the environmental effects induced by the seismic sequence, it is clear that the maximum ESI intensity reached is IV-V, as the environmental effects were sporadic and of small size.

The various areas of Italy have different susceptibilities to the environmental effects of earthquakes, depending on local seismic, geomorphological, and geological characteristics. To represent this diversity, the maximum intensities (MCS, Mercalli Cancani Sieberg) reached throughout the seismic history of the country were considered and converted into ESI intensities (Environmental Seismic Intensity), according to the ESI2007 Scale. Figure 4 shows the ESI intensities related to known historical earthquakes that occurred from the year 1000 to 2022, with MCS intensities of VI or higher. Since both the ESI and MCS scales are based on 12 degrees, the MCS intensities were directly converted into ESI without changes. This empirical correspondence is based on comparisons between events where both scales have been applied. However, it is statistically possible that there may occasionally be a one-degree difference between the two scales, and in very rare cases, a two-degree difference. Each ESI intensity corresponds to a defined environmental effects scenario, which is described in terms of primary and secondary effects in the ESI scale. Environmental effects become clearly appreciable starting from degree VI, and they manifest more visibly as intensity increases. For degrees VIII to X, environmental effects are a characteristic component of the intensity of the earthquake; for degrees XI and XII, they are the most reliable tool for evaluating intensity.

Figure 5 provides a graphical representation of the environmental effects that can be induced by earthquakes of varying intensities. Given that the intensities of past earthquakes are indicative of the potential damage that could occur again in the future, the data presented in Figure 5 represent possible scenarios, in terms of environmental effects, that could occur in different parts of the country in the case of earthquakes similar to those that happened in the past. This type of knowledge is relevant, among other things, for achieving the long-term goal of the 8th Environment Action Program to 2030, which aims to achieve greater resilience to environmental risks by 2050. Knowing the potential effects that may occur in a territory following an earthquake can help take necessary precautionary measures to prevent significant damage to the environment and to sensitive structures and infrastructures (such as appropriately protecting facilities at risk of major accidents, pipelines, gas lines, etc.)