Ferro, Angelo

On February 6, 2023, at 01 : 17 UTC, a M = 7 8 earthquake struck the southern area of Turkey near Gaziantep town and was followed by a second earthquake of M = 7 5 at 10 : 24 UTC with the epicenter in Elbistan city. Both events were associated with the Anatolian Fault System and have claimed over 50,000 victims, as reported by the Disaster and Emergency Management Authority, and caused serious damage in the regions of southern Turkey and northern Syria. Seismic waves related to strong Turkey earthquakes have been recorded both by seismic stations throughout the globe and on other devices such as the ground deformation (GNSS, strainmeters, or tiltmeters) networks. In this paper, we show and analyze the earthquake signals recorded by bore-hole tilt stations that monitor seismic and volcanic activities at Mt. Etna. Tilt stations showed very large variations, despite their distance from the epicenter (approximately 1950 km) with a period between 10 and 25 seconds. We compared tilt and seismic data for a co–located station evidencing a very similar waveform that highlight how tiltmeters respond to translational acceleration rather than ground tilt during a teleseism, suggesting that, for waves with this period, they may behave as horizontal seismometers. By using these signals, we evidence the different behaviors of two of the most used models of tiltmeters on volcanoes (Lily and Pinnacle) and how they are useful for instrument calibration.

A sector of the San Marco Hospital (Catania, Italy) was the subject of a jacking test in order to demonstrate the substitutability of the seismic isolator. A monitoring system, included tiltmeters and strain gauges, was applied to one column. Two distinct behaviours have been identified during the unloading stage, the first in which the column and the roof are still attached and a second in which the detachment takes place. The jacking system caused the column to return to its original position, induced by the building structure for thermoelastic causes.

Over the last few years, three tilt deep stations (27-30 meters) have been set up in the summit area ofMount Etna volcano. The aim of this challenging project is to record the ground deformations of the summit craters activity with high precision.We considered data related to the August 23-26, 2018, Strombolian and effusive activity. In this case, tiltmeters recorded variations in the order of 10−7 radians, not observed at the other stations. These changes suggest a shallow contraction source just south of the Southeast Crater. This result, related to the volcanic tremor source, points to the presence of a gas/magma reservoir feeding the Strombolian activity at 1200 m above sea level.

Stromboli is an open conduit strato-volcano of the Aeolian archipelago (Italy), characterized by typical Strom-bolian explosive activity, lasting for several centuries, and by the emission of huge amounts of gas. The normalactivity of Stromboli is characterized by some hundreds of moderate explosions per day. Major explosions, whichlaunch scoria up to hundreds of meters from the craters, lava flows and paroxysmal explosions, which producelarge ballistic blocks, sometimes take place. During the effusive eruption in 2002 - 2003, which caused a tsunamiwith waves of about 10 meters high along the coasts of the Island, the monitoring system was enhanced. In 2006INGV has added two Sacks-Evertson borehole volumetric dilatometers to the surveillance system, in order to mon-itor changes in the local strain field by measuring areal strain. Today we have a large amount of geophysical dataand observations that allow us to better understand how this volcano works. After a period of low explosive activitystarted in mid-2014, Stromboli has shown a more intense explosive activity in the last few months. During the re-cent phase of increased activity, the geophysical monitoring system detected four major explosions occurred on 26July, 23 October, 1 November and 1 December 2017, respectively. The current phase of reawakening of Strombolivolcano has led the Italian civil protection authorities to decree the "attention" alert level (yellow) on the Island.

In recent years, seismological studies in Antarctica have contributed plenty of new knowledge in many fields of earth science. Moreover, acoustic investigations are now also considered a powerful tool that provides insights for many different objectives, such as analyses of regional climate-related changes and studies of volcanic degassing and explosive activities. However, installation and maintenance of scientific instrumentation in Antarctica can be really challenging. Indeed, the instruments have to face the most extreme climate on the planet. They must be tolerant of very low temperatures and robust enough to survive strong winds. Moreover, one of the most critical tasks is powering a remote system year-round at polar latitudes. In this work, we present a novel seismo-acoustic station designed to work reliably in polar regions. To enable year-round seismo-acoustic data collection in such a remote, extreme environment, a hybrid powering system is used, integrating solar panels, a wind generator, and batteries. A power management system was specifically developed to either charge the battery bank or divert energy surplus to warm the enclosure or release the excess energy to the outside environment. Finally, due to the prohibitive environmental conditions at most Antarctic installation sites, the station was designed to be deployed quickly.

Mount Melbourne (74821? S, 164843? E) is a quiescent volcano located in 20 northern Victoria Land, Antarctica. Tilt signals have been recorded on Mount Melbourne since early 1989 by a permanent shallow borehole tiltmeter network comprising five stations. An overall picture of tilt, air and permafrost temperatures over 15 years of continuous recording data is reported. We focused our observations on long-term tilt trends that at the end of 1997 25 showed coherent changes at the three highest altitude stations, suggesting the presence of a ground deformation source whose effects are restricted to the summit area of Mount Melbourne. We inverted these data using a finite spherical body source, thereby obtaining a shallow deflation volume source located under the summit area. The ground deformation observed corroborates 30 the hypothesis that the volcanic edifice of Mount Melbourne is active and should be monitored multidisciplinarily.

A review of the experience gained in the use of tiltmeters on Mt. Etna, Stromboli and Vulcano during the last 30 years is reported here. Tilt data represent a fundamental contribution towards understanding volcanic processes such as dike intrusions, fracture propagation, lava fountains and volume changes in magmatic or hydrothermal systems causing a deflation/ inflation of the edifice. Intrusive processes preceding lateral eruptions show large variations (up to over 100 microradians), while minor variations (not exceeding 2.5 microradians) are linked to lava fountains that form ash plumes and lead to fallout deposits that cause severe hazards to aviation. High precision tilt also allows detecting the slight ground deformation linked to strombolian activity (0.01–0.2 microradians) as well as co-seismic variations (0.1–1.5 microradians) and tidal effects (0.1–0.2 microradians) that may have a role in the evolution of a volcanic system. Time–amplitude tilt ranges linked to each process are generally different allowing to discriminate, in real time, between a signal associated to one process and another one. This fact is important in terms of early warning particularly during the first phases of dikes propagation that precede a lateral eruption by hours–days.

The Trecastagni Fault (TF) is a NNW-SSE tectonic structure inside Mt. Etna that is characterized by evident morphological scarps and normal and right-lateral type movements that directly affect roads and buildings. The TF has an important role in the instability that affects the southeastern flank of Mt. Etna, and it represents part of the southern boundary of the unstable sector. Starting from 2005, the TF has been monitored using continuous wire extensometers and by carrying out periodic direct measurements across the northern and central sectors. From 2005 to September 2009, the measurements show that the TF has undergone continuous extension of about 2-3 mm/yr. During the October 2009 to January 2010 period, the creep rate of the TF reached up to 5.5 to 7.0 mm/yr, and this was accompanied by several shallow, low magnitude earthquakes that were felt by local people. This episode appears to be linked to the increase in the sliding velocity of the eastern flank that occurred during 2009.

In 2007-2008, we installed on Mt. Etna two deep tilt stations using high resolution, self-leveling instruments. These installations are a result of accurate instrument tests, site selection, drilling and sensor positioning that has allowed detecting variations related to the principal diurnal and semidiurnal tides for first time on Mt. Etna using tilt data. We analyzed the tidal effects recorded on tilt signals and we removed tidal effects from signals, thereby allowing to detect changes of about 20 nrad with a considerable improvement in respect to the previous installation. Tilt changes have accompanied the Mt. Etna main eruptive phases and are generally related to the rapid rise of magma and formation of dikes and eruptive fissures. However, tilt changes may characterize lava fountains, earthquakes, and inflation-deflation phases. The 2008-2009 eruption represents an example of the potential of the tiltmeters we used, which provides new perspectives for highly precise monitoring of ground deformation on volcanoes.

In questo rapporto sono riportati i dettagli dell’installazione di un clinometro profondo effettuata nel 2010 in prossimità di Pedagaggi (SR) nel settore nord-orientale dell’altipiano ibleo. L'installazione è stata possibile utilizzando uno strumento digitale autolivellante modello AGI (Applied Geomechanics Incorporated) Lily, con sensibilità pari a 0.005 microradianti. Sono illustrati i dettagli dell’installazione ed i primi dati che evidenziano la loro ottima qualità, la presenza delle componenti mareali e la minima variazione di inclinazione ottenibile ripulendo il segnale dalle stesse.