Gian Marco Marmoni

High-resolution geological model of the gravitational deformation affecting the western slope of Mt. Epomeo (Ischia)

The recent geological history of Ischia Island is characterized by slope-scale gravitational deformations closely related to volcano-tectonic dynamics of the Mt. Epomeo resurgent caldera. This study focuses on the gravitational deformation that involves alkali-trachytic lava and trachytic ignimbrite flow-units of Mt. Nuovo, located in the western portion of Mt. Epomeo. A preliminary, high-resolution engineering-geological model was obtained through geological, geomorphological and geophysical surveys and reveals a complex morpho-structure with geomorphological evidence of gravitational instability. The complexity of the ongoing slope deformations is confirmed by field geo-structural evidences that led to the identification of a multiple compound mechanism with a main rupture surface which is about 200 m deep. This geometry was better constrained by passive seismic investigations consisting in noise measurements, focused on resonance frequencies of the soil (i.e. based on H/V Nakamura approach). In addition, a close relationship between the outcrop of Mt. Epomeo Green Tuff breccia layers and the distribution of hydrothermal emissions and gas vent can be inferred, as it is related to the higher permeability of the breccia layers with respect to the main Mt. Epomeo Green Tuff flow unit, where the ascent path of deep hydrothermal fluids developed along faults and fracture networks.

Thermal Response of Jointed Rock Masses Inferred from Infrared Thermographic Surveying (Acuto Test-Site, Italy)

The Mediterranean region is affected by considerable daily and seasonal temperature variations due to intense solar radiation. In mid-seasons, thermal excursions can exceed tens of degrees thus influencing the long-term behaviour of jointed rock masses acting as a preparatory factor for rock slope instabilities. In order to evaluate the thermal response of a densely jointed rock-block, monitoring has been in operation since 2016 by direct and remote sensing techniques in an abandoned quarry in Acuto (central Italy). Monthly InfraRed Thermographic (IRT) surveys were carried out on its exposed faces and along sections of interest across monitored main joints. The results highlight the daily and seasonal cyclical behaviour, constraining amplitudes and rates of heating and cooling phases. The temperature time-series revealed the effect of sun radiation and exposure on thermal response of the rock-block, which mainly depends on the seasonal conditions. The influence of opened joints in the heat propagation is revealed by the differential heating experienced across it, which was verified under 1D and 2D analysis. IRT has proved to be a valid monitoring technique in supporting traditional approaches, for the definition of the surficial temperature distribution on rock masses or stone building materials.