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Scaled analogue models explored the role of different boundary conditions in intra‐caldera resurgence processes. Models investigated the role of magma intrusion depth (Series 1), asymmetric and symmetric caldera collapse (Series 2), as well as the presence of existing discontinuities in the pre‐volcanic substratum (Series 3) on the style of caldera resurgence. Experimental results indicate that different intrusion depths resulted in different resurgence styles and structural patterns, which evolved from piston‐like resurgence, for deeper intrusions, to intra‐caldera resurgent domes for shallower intrusions. Asymmetric collapse was typically accompanied by a tilted roof block above the emptied analogue magma reservoir, while inherited faults influenced significantly the deformation pattern of piston‐like resurgence. Experiments simulate many of the principal characteristics of calderas. We compare our modelling results primarily to the Los Potreros caldera nested within the Los Humeros Volcanic Complex, where the largest Mexico’s Quaternary eruption occurred and which hosts an important geothermal field (eastern Trans‐Mexican Volcanic Belt). A structural field survey was conducted to identify the kinematics of faults within the caldera and outside the volcanic edifice. The Los Potreros caldera shows a sub‐orthogonal fault pattern strikingly similar to that of models deformed with shallow intrusion depth. We interpret this correlation as an evidence of similarity in dynamic processes, whereby modelling results would indicate a scaled intrusion depth of approximately 4.5 km. The Acoculco caldera complex, in Mexico, shows a fault pattern similar to the Los Potreros caldera, and geological information corroborates the attribution of renewed magmatic pressure to similar intrusion depths.

During the last decades, central Italy has been struck by severe seismic sequences. Some authors have suggested that inherited thrust faults may have played an important role in controlling the recent-to active extensional deformation in the area, particularly during the 2016 Central Italy seismic sequence. To explore this hypothesis, we performed an analogue modelling study that addressed the structural evolution of a composite, heterogeneous multilayer affected by polyphase deformation. The overall three-dimensional geometry resulting from the modelling consists of a flat-ramp extensional fault system, with flats being localised along the weaker stratigraphic units, and ramps locally reactivating the pre-existing thrust ramps at depth. At shallower levels, deformation can localize at newly-formed short-cut faults depending on the geometry of deeper structures. The experimental results provide further support to the hypothesis of a link between Quaternary normal faults and inherited thrust faults during the 2016 seismic sequences. Specifically, analogue modelling results suggest that the Quaternary fault pattern may be controlled by the interaction between the active stress field and the pre-existing compressional structures. This scenario bears significant implications regarding the empirical relationship between the geometry of surface faulting and the magnitude of earthquakes, with considerable repercussions on seismic risk assessment.

This study investigates the seismic activity occurring at the Larderello-Travale geothermal field, central Italy, from June 2017 to January 2018. We deployed a network composed of nine broadband stations around the Venelle 2 well drilling for supercritical fluids. During the experiment, we recognizetwo types of seismic events (type 1 and type 2). Type-1 events have clear P and S wave arrivals and occur in clusters both above and below the K-horizon, which is a seismic reflector marking a debated transition zone at depth. The distribution and evolution of the seismic sequences suggest that the K-horizon could be interpreted as a fluid-rich region at near-lithostatic pressures. Type-2 events usually occur in swarms and show a periodic pattern, a narrow frequency band, and almost identical waveforms. Their source is estimated to be located near the well, and their occurrence ceases after about 3 weeks from the conclusion of the drilling. We propose a causal link with the drilling operations where pressure fronts inside the well may promote phase changes and fluid flow across the drilled formations. Our study sheds light on the fluid-driven tectonic and anthropogenic seismic activity at the Larderello-Travale geothermal field. More generally, we show that microseismic activity occurring during drilling in high-pressure and high-temperature conditions can remain at low magnitudes and that geothermal wells targeting geothermal fluids in such systems may be handled safely despite the critical conditions encountered at depth. The drilling of the Venelle 2 well is an encouraging example for the development of geothermal energy in critical conditions.

The MIMA muon tracker, developed by the INFN Unit of Florence and the Department of Physics and Astronomy of the University of Florence, has been designed to test the application of muon radiography (or muography) to multidisciplinary case studies, to demonstrate its validity as an imaging tool in different fields and to develop dedicated data analysis strategies. The MIMA detector is a scaled-down version of the muon trackers developed for the "Mu-Ray" INFN R&D project and the MURAVES (MUon RAdiography of VESuvius) "Progetto Premiale", financed by the Italian government. Thanks to its compactness, MIMA allowed the use of slightly different technical solutions with respect to the other detectors. Its construction was completed in the first half of 2017 and since then it has been used for several different measurements. In the second half of 2017 the detector was installed in the Bourbon Gallery inside Mount Echia, a hill in the center of Naples containing a complicated system of tunnels and cavities that have been dug over many centuries. The installation of the MIMA tracker was required to validate with an independent detector the results obtained in two previous measurements by the Mu-Ray tracker. After this measurement, the detector has been used in the Tuscany region, mainly for investigating two possible fields of application: geo-hydrological risk assessment and mining activity. The preliminary results of these tests and the future perspectives are shortly presented in this paper.

A novel algorithm developed within muon radiography to localize objects or cavities hidden inside large material volumes was recently proposed by some of the authors (Bonechi et al. 2015 J. Instrum. 10, P02003 (doi:10.1088/1748-0221/10/02/P02003)). The algorithm, based on muon back projection, helps to estimate the three-dimensional position and the transverse extension of detected objects without the need for measurements from different points of view, which would be required to make a triangulation. This algorithm can now be tested owing to the availability of real data collected both in laboratory tests and from real-world measurements. The methodology and some test results are presented in this paper. This article is part of the Theo Murphy meeting issue 'Cosmic-ray muography'.