Characterization of an Active Fault through a Multiparametric Investigation: The Trecastagni Fault and Its Relationship with the Dynamics of Mt. Etna Volcano (Sicily, Italy)

Abstract

The Trecastagni Fault (TF) is an important tectonic structure in the middle-lower southern flank of Mt. Etna volcano. It is characterised by evident morphological slopes with normal dip-slip ruptures that directly affect roads and buildings. The TF plays a key role in the complex framework of the volcano dynamics since it represents part of the southern boundary of the unstable sector. Seismic surveys have been performed on three different areas of the fault to gain insights into the seismic stratigraphic structure of the subsoil. We considered the seismic activity of a sector of the territory affecting the surface evidence of the Trecastagni Fault in the period between 1980 and 2021 in order to highlight the main seismic release and define the space–time distribution of seismicity. Most of the seismicity is located in the north-western portion, while the central and southern sectors are characterised by low seismic activity. The strongest earthquakes occur mainly within the first 5 km of depth in the form of swarms and/or isolated shocks. Ground deformation techniques (levelling, In-SAR and two continuous extensometers) evidence a continuous aseismic slip of the TF that is interrupted by short accelerations accompanied by shallow seismicity. The Trecastagni Fault dynamics are strictly linked to magma pressurisation and intrusive episodes of Mt. Etna that induce additional stress and promote its slip along the fault plane. Multidisciplinary data analysed in this work, evidenced the dual behaviour of the fault, from aseismic creep to stick-slip, and the relation with magmatic activity, also suggesting the time delay in the response of the fault after the intense stress induced by dyke intrusion.

Extended Tromograph Surveys for a Full Experimental Characterisation of the San Giorgio Cathedral in Ragusa (Italy)

“…By integrating the data of the H/V spectra with the information on the shear waves velocity distribution, it was possible to reconstruct 2D seismic stratigraphic sections known as impedance contrast sections. These sections show the distribution of H/V spectral ratio amplitude values in the subsoil, allowing identifying any horizontal and vertical variations [ 43 , 44 , 45 ]. Impedance contrasts are determined by the variation of seismic impedance between different layers defined as the product between the density of the medium and the velocity of the shear waves.…”

Mt. Etna Tilt Signals Associated with February 6, 2023, M=7.8 and M=7.5 Turkey Earthquakes

“…The permanent seismic network located on Mt. Etna consists of about 30 digital broadband 3-component stations [29]. The February 6, 2023, M = 7 8 and M = 7 5 seismic events had been recorded by all the stations about 4 minutes later (01 : 21 : 30 UTC and 10 : 28 : 30 UTC, respectively) with respect to origin time with very high amplitudes.…”

Microtremor Recording Surveys to Study the Effects of Seasonally Frozen Soil on Site Response

“…Consequently, this approach can lead to inaccuracies in determining the predominant frequency of the microtremor spectrum, making it challenging to estimate the site amplification factor [ 11 ]. On the other hand, numerous studies have demonstrated that the microtremor horizontal-to-vertical spectral ratio method (HVSR) effectively eliminates the influence of the vibration source on the site dynamics analysis, resulting in predominant frequencies that are more representative of the actual site frequencies [ 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 ]. As a consequence, many recent studies have employed the microtremor HVSR method to determine the site characteristic parameters.…”