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In the last decades, the scientific community has been focused on searching earthquake signatures in the Earth's atmosphere, ionosphere, and magnetosphere. This work investigates an offshore Mw 5.5 earthquake that struck off the Marche region's coast (Italy) on 9 November 2022, with a focus on the potential coupling between the Earth's lithosphere, atmosphere, and magnetosphere triggered by the seismic event. Analysis of atmospheric temperature data from ERA5 reveals a significant increase in potential energy (Ep) at the earthquake's epicenter, consistent with the generation of Atmospheric Gravity Waves (AGWs). This finding is further corroborated by the MILC analytical model, which accurately simulates the observed Ep trends (within 5%), supporting the theory of Lithosphere–Atmosphere–Ionosphere–Magnetosphere coupling. The study also examines the vertical Total Electron Content (vTEC) and finds notable fluctuations at the epicenter, exhibiting periodicities (7–12 min) characteristic of AGWs and traveling ionospheric disturbances. The correlation between ERA5 observations and MILC model predictions, particularly in temperature deviations and Ep distributions, strengthens the hypothesis that earthquake-generated AGWs impact atmospheric conditions at high altitudes, leading to observable ionospheric perturbations. This research contributes to a deeper understanding of Lithosphere–Atmosphere–Ionosphere–Magnetosphere coupling mechanisms and the potential for developing reliable earthquake prediction tools. [ABSTRACT FROM AUTHOR]

A passive seismic experiment is carried out at the non-volcanic highly degassing site of Mefite d'Ansanto located at the northern tip of the Irpinia region (southern Italy), where the 1980 MS 6.9 destructive earthquake occurred. Between 2020 and 2021, background seismic noise was recorded by deploying a broadband seismic station and a seismic array composed of seven 1 Hz three-component sensors. Using two different array configurations, we were allowed to explore in detail the 1–20 Hz frequency band of the seismic noise wavefield as well as Rayleigh wave phase velocities in the 400–800 m/s range. Spectral analyses and array techniques were applied to one year of data showing that the frequency content of the signal is very stable in time. High frequency peaks are likely linked to the emission source, whereas at low frequencies seismic noise is clearly correlated to meteorological parameters. The results of this study show that small aperture seismic arrays probe the subsurface of tectonic CO2-rich emission areas and contribute to the understanding of the link between fluid circulation and seismogenesis in seismically active regions. [ABSTRACT FROM AUTHOR]

We analyse and compare volcano-tectonic seismicity, rainfall, atmospheric pressure, ground deformation and Earth tide time series at the Campi Flegrei caldera (CFc) in the time interval 2005-2016, looking for possible tidal and hydrological triggers of hydrothermal and seismic activity. By applying statistical analysis, we show that the occurrence of clustered seismicity at the CFc has a cyclic behaviour on several time scales, from semidiurnal and diurnal to longer periods, such as fortnightly, monthly, semiannual and annual. The medium and long-period time scales match those of the main lunar and solar tidal constituents, while the exactly 24-h and 12-h periodicities can be ascribed not only to the Earth tides but also to other effects such as atmospheric pressure and temperature variations. In addition, a clear dependence on rainfall arises from the analysis of the hydrological parameters, indicating a strong seasonal periodicity along the entire observational interval, with the most numerous and energetic seismic swarm occurring in the wet season.We interpreted these observations in terms of a model linking magmatic degassing, ground deformation and seismicity. The proposed model considers the magmatic-hydrothermal fluid circulation system as a cascade hydraulic circuit, where in/out fluid flow and pressure condition of each segment are regulated by those of the contiguous ones. Our results suggest that volcano-tectonic seismicity at CFc is driven by both variations in the deep magmatic feeding system and exogenous phenomena, as rainfall or global inflation/deflation cycles of the Earth' s crust, controlled by the lunisolar interaction. Consequently, the role of exogenous triggers (combined with endogenous processes) in the evolution of the recent dynamics should be properly considered in the elaboration of volcanic risk scenarios. [ABSTRACT FROM AUTHOR]

We have analysed the wavefield of the background seismic noise at Ischia Island (Italy), recorded between 2017 and 2018. The Independent Component Analysis highlighted two persistent independent signals, with dominant frequency peak around 1 Hz and 3–4 Hz, respectively. The first signal is the most energetic and persistent. Its polarization shows preferential directions properties, with a shallow propagation that seems to be controlled by the tectonic-volcanic structures and the morphology of the Island. Moreover it is well correlated at all the stations in Casamicciola town. The second signal evidences similar polarization properties, but it is strongly affected by cultural noise and does not show any correlation. We interpret the 1-Hz wave-packets as the signature of the shallow hydrothermal system. Following a conceptual model of self-sustained musical instruments, the shallow hydrothermal system of Ischia can be seen as a solid structure constituted by a network of channels, continuously excited by the circulating hydrothermal fluids. In this framework the 1-Hz seismic signal and the eventual higher modes would be produced by persistent self-sustained oscillations. [ABSTRACT FROM AUTHOR]

The ability to image the underground structures of volcanoes is limited by the precision, resolution and penetration depth of each single geophysical method. In order to improve the knowledge of specific volcanic edifices and to better understand the general behavior of structures, the use of a combination of methods is strongly recommended to exploit and maximize their complementary capabilities of resolution and penetration depths. In this work a large dataset of seismic and electromagnetic measurements has been used to provide a more detailed and improved geophysical image of the shallower portion of the northern sector of Ischia Island (Campania region, Italy), severely hit by the August 21, 2017 earthquake (Mw 3.9). We analysed data by using different methodologies: Horizontal-to-Vertical Spectral Ratio (HVSR), seismic array technique (f-k), polarization analysis and Time Domain ElectroMagnetic (TDEM) survey. These methods are sensitive in a different way to tectonic features, lithologies, layer geometry and fluid distribution. Thus, their combination is useful for studying sites with complex crustal structures such as Ischia island, which is characterized by a well-developed geothermal system linked to the presence of a shallow magmatic body. Results of our study provides detailed information of the physical properties of the subsoil through: 1) the spatial distribution of the amplification parameters of ground motion, showing frequency peaks below 1 Hz and/or between 1 Hz and 5 Hz; 2) the definition of the velocity models up to 600 m depth, with shear wave velocities ranging from 150 m/s for the shallower layers to 2500 m/s for the half space; 3) the recognition of the correlation between the principal fault structures and polarization directions of the noise wavefield, mostly oriented along EW and NE-SW directions; 4) the resistivity models of the first 80 m depth with high resistivity values of the shallow layers in the range 50–100 Ω.m and low resistivity values of the bottom layers in the range 1–10 Ω.m. • Four 1D velocity models of Casamicciola area (Ischia, Italy) were obtained using a joint inversion of dispersion and spectral ratio curves • The polarization analysis, applied to seismic noise, highlights possible correlation with the major faults system direction • HVSR frequency peaks and amplification values were used to map possible site effects of the August 27, 2017 earthquake • 1D resistivity models of the first 100 m depth were obtained applying TDEM geophysical surveys. [ABSTRACT FROM AUTHOR]