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Reappraising the seismogenic potential of a low-strain rate region: active faulting in the eastern Siena Basin (southern Tuscany, Italy)
No full textWe investigated the active tectonics and earthquake potential of the eastern Siena Basin, a slowly deforming portion of southern Tuscany in the inner Northern Apennines. This region hosts several historical settlements and valuable cultural heritage, but also frequent background seismicity and rare damaging earthquakes in the Mw range 5.0-6.2. We describe in detail an active, capable, and seismogenic fault system that we identified in the eastern Siena Basin, a few kilometres south-east of the city of Siena, thanks to the presence of an active quarry (Cava Capanni) that exploits travertines of Middle Pleistocene-Holocene age. Travertines are unique rock masses that may preserve living evidence of active and seismogenic faulting, thus providing remarkable seismotectonic insight. The active fault system consists of at least two segments rupturing travertines younger than 45 ka, with a cumulative vertical displacement of 111 cm, and an estimated minimum slip rate of 0.02-0.03 mm/y. We maintain that this displacement is the result of at least three coseismic movements accompanied by clastic dykes injected within the fault damage zone due to liquefaction phenomena. The fault system is seen to extend east of the quarry, affecting Pliocene and Mesozoic deposits.
The Cava Capanni fault system is evidence of a poorly understood but potentially seismogenic tectonic mechanism of regional extent. Its orientation and kinematics are compatible with the activity of faults that are oriented obliquely or orthogonally to the main chain axis, in contrast with the setting of the axial and outer zone of the Northern Apennines, where extension and compression are accommodated by Apennines-parallel faults.230Th/238U dating was supported by grants from the Science Vanguard Research Program of the Ministry of Science and Technology (MOST), Taiwan, ROC (109-2123-M-002-001 to C.-C.S.), the Higher Education Sprout Project of the Ministry of Education, Taiwan, ROC (109L901001 to C.-C.S.), and the National Taiwan University (110L8907 to C.-C.S.).Published230423JCR Journa
Dynamics of the 2021 unrest at Changbaishan Tianchi volcano from ALOS-2/PALSAR-2 and seismic data
No full textThe Changbaishan Tianchi intraplate volcano is one of the most active and hazardous volcanoes of NE Asia,
characterized by a summit caldera formed after the 946 CE ‘Millennium’ Plinian eruption. From December 2020
to June 2021, the frequency and magnitude of earthquakes at Tianchi were significantly higher than during
background periods, with hundreds of earthquakes (46 events per month in average) and reaching a local
magnitude of ML 3.1. This study reports a comprehensive deformation analysis and geophysical inversion scheme
aimed to unveil the dynamics of this period. Multi-temporal InSAR analysis results of 32 ALOS-2 images from
2018 to 2022 show that the surface deformation is a combination of seasonal fluctuations (± 25 mm in average,
with a maximum ± 45 mm) and a long-term positive component. The least squares linear regression of the
deformation time series and temperature data, isolates the seasonal fluctuations, revealing a clear upliftsubsidence
process from June 2020 to July 2021 in the caldera area. To constrain the Tianchi plumbing system
dynamics, a combined inversion scheme consisting of three deformation sources is designed. The inversion
results and the seismic records indicate that Tianchi volcano has experienced a low-level unrest episode from
December 2020 to June 2021. The shallower plumbing system, located at about 5–9 km depth and modelled by
pressurized spheroids, underwent a cumulative volume increase of 26 × 106 m3 from November 2018 to April
2021, followed by a volume decrease of 9 × 106 m3 from April to July 2021. This suggests magma uprising from
the 14 km deep storage zone to the shallower plumbing system, followed by depressurization of the plumbing
system due to the escape of fluids. This research provides a comprehensive understanding of the magma and fluid
migration dynamics within the Tianchi multi-level plumbing system for the first time.Published103775JCR Journa
Stationary solutions to a hybrid viscous hydrodynamic model with classical boundaries †
No full textIn this paper we present a quantum-classical hybrid model based on the hydrodynamic equations in steady state form. The approach presented here, which has already been proposed in previous works, consists in considering an intrinsically hybrid version of the Bohm potential, which acts only in the region of the domain where quantum effects play an important role, while it disappears where the quantum contribution is essentially negligible and the operation of the device can be well described by using a classical model. Compared to previous results from the same line of research, here we assume that the device at the boundaries of the domain behaves classically, while quantum effects are localised in the central part of it. This is the case of greatest scientific interest, since, in real devices, quantum effects are generally localized in a small area within the device itself. The well posedness of the problem is ensured by adding a viscous term necessary for the convergence of the hybrid limit to an appropriate weak solution. Some numerical tests are also performed for different values of the viscous coefficient, in order to evaluate the effects of the viscosity, especially on the boundaries of the device.Published2640-3501JCR Journa
Campi Flegrei - Storia eruttiva
No full textI Campi Flegrei sono un'area vulcanica attiva che
include i comuni di Bacoli, Monte di Procida, Pozzuoli,
Quarto, Giugliano in Campania e parte della città di
Napoli.
I Campi Flegrei sono un
campo vulcanico, con diversi
centri eruttivi situati
all'interno e in prossimità di
una caldera.PublishedNapoli - Piazza Dant
Campi Flegrei -Il bradisismo
No full textL’area dei Campi Flegrei è soggetta
a lenta deformazione del suolo nota
con il nome di bradisismo. Il
bradisismo è il lento abbassamento
o sollevamento del suolo che si
verifica in alcune aree vulcaniche
dove è presente una vasta caldera...Publishe
Magma Differentiation in Dynamic Mush Domains From the Perspective of Multivariate Statistics: Open‐ Versus Closed‐System Evolution
No full textOpen-conduit conditions characterize several of the most hazardous and active volcanic systems of basaltic composition worldwide, persistently refilled by magmatic inputs. Eruptive products with similar bulk compositions, chemically buffered by continual mafic inputs, nevertheless exhibit heterogeneous glass compositions in response to variable magma mixing, crystallization, and differentiation processes within different parts of the plumbing system. Here, we document how multivariate statistics and magma differentiation modeling based on a large data set of glass compositions can be combined to constrain magma differentiation and plumbing system dynamics. Major and trace elements of matrix glasses erupted at Stromboli volcano (Italy) over the last 20 years provide a benchmark against which to test our integrated petrological approach. Principal component analysis, K-means cluster analysis, and kernel density estimation reveal that trace elements define a multivariate space whose eigenvectors are more readily interpretable in terms of petrological processes than major elements, leading to improved clustering solutions. Comparison between open- and closed-system differentiation models outlines that steady state magma compositions at constantly replenished and erupting magmatic systems approximate simple fractional crystallization trends, due to short magma residence times. Open-system magma evolution is associated with magma storage crystallinities that are lower than those associated with closed-system scenarios. Accordingly, open-system dynamics determine the efficient crystal-melt separation toward the top of the reservoir, where eruptible melts continuously supply the ordinary activity. Conversely, a mush-like environment constitutes the bottom of the reservoir, where poorly evolved magmas result from mixing events between mush residual melts and primitive magmas injected from deeper crustal levels.Publishede2023GC011396OSV1: Verso la previsione dei fenomeni vulcanici pericolosiJCR Journa
Travelling ionospheric disturbances detection: A statistical study of detrending techniques, induced period error and near real-time observables
No full textDue to advances in remote sensing of the Earth's Ionosphere through Total Electron Content (TEC) estimates by Global Navigation Satellite System (GNSS) receivers, it is possible to detect and characterize Travelling Ionospheric Disturbances (TIDs) in both post-processing and, to some extent, in near real-time (NRT). A reliable and precise TEC filtering technique must be adopted to characterize waves accurately. Specifically, TEC detrending is widely adopted to extract the amplitude and period of the detected ionospheric waves from the background ionospheric conditions. Therefore, this study aims to understand and compare how different TEC detrending techniques and their settings impact the ability to extract such parameters. We highlight that the novel Fast Iterative Filtering (FIF) and the Savitzky-Golay filter (SGOLAY) techniques are the most reliable overall compared with moving average (MA), multi-order numerical difference (DD), polynomial detrending (POLY) and Finite Impulse response (FIR) band-pass filter (BUTF). Moreover, the impact of general algorithm settings on the exracted TID period is investigated, such as the Ionospheric Piercing Point (IPP) height and elevation cutoff angle, showing that such parameters drastically impact the retrieved period, especially for slower TIDs. Finally, due to the growing interest in real-time (RT) detection and classification of TIDs, the study proposes techniques for accurately estimating the TID amplitude in an NRT scenario. Such NRT techniques are then compared with the widely used post-processing products, such as the calibrated vertical TEC (vTEC), showing a difference that is mostly lower than the typical noise level of GNSS receivers (0.05 TECu).PublishedJCR Journa
Investigating Mt. Etna lava fountains by seismic and infrasonic signals: 14-21 February 2021 case study
No full textInfrasonic and seismic tremor are signals released by active volcanoes. These signals play a crucial role in monitoring volcanic activity and providing insights into volcanic dynamics and hazards. Between December 2020 and February 2022, Mount Etna was characterized by an intense eruptive period, during which monitoring efforts were employed to investigate the characteristics and source signals. Our work focuses on analyzing volcanic tremors in both seismic and infrasound signals to understand their behavior and relationship with the volcano’s dynamics. In particular, the interval 14‐21 February 2021, comprising 4 lava fountain episodes, was taken into account. Concerning the data analysis, amplitude, spectral content, seismic volcanic tremor and infrasonic explosion‐quakes source locations have been computed. The results reveal that the seismic amplitude is closely related to emitted magma volume during the lava fountains. The study finds that most of the energy in volcanic tremors is concentrated below 5.0 Hz. During eruptive episodes, both seismic and infrasound signals exhibit lower frequencies, with variations between different stations due to propagation effects. Finally, two different source mechanisms of the seismic tremor were suggested: i) flow of gasses through a shallower permeable solid layer is likely to be responsible for the generation of volcanic tremor during non‐eruptive periods; ii) magmatic flows along the shallow plumbing system and the consequent impact of particles on the walls of the conduit during eruptive periods.PublishedJCR Journa
Geophysical evidence of large-scale silica-rich fluid flow above the continental subduction interface
No full textFluids in subduction zones can have major effects on subduction dynamics. However, geophysical constraints on the scale and impact of fluid flow during continental subduction are still limited. Here we analyze the V P /V S ratios in the Western Alpine region, hosting one of the best-preserved fossil continental subduction zones worldwide, to investigate the impact of fluid flow during continental subduction. We found a belt of high V P /V S ratios >1.9 on the upper-plate side of the subduction zone, consistent with a partially serpentinized upper-plate mantle, and a belt of unusually low V P /V S ratios <1.7 on the lower-plate side, at depths shallower than 30 km. We propose that these low V P /V S ratios result from a widespread network of silica-rich veins, indicating past fluid flow along the continental subduction interface. Our results suggest that past fluid flow may have reduced the effective stress along the subduction interface thus favoring continental subduction.PublishedJCR Journa
Early results of a systematic revision of Ferrarese seismicity of the 13th-15th centuries
No full textWithin the PRIN 2020 project NASHA4SHA [Fault segmentation and seismotectonics of active thrust systems: the Northern Apennines and Southern Alps laboratories for new Seismic Hazard Assessments in northern Italy] and in order to improve our general knowledge of the seismic record of the Ferrara area, we are proceeding to examine the ancient local narrative sources, not only to find information on “unknown” or “forgotten" earthquakes, but primarily to improve the understanding of earthquakes already known through a comprehensive study of the original texts which are relied on by the reference studies of the CPTI15 catalogue (Rovida et al., 2022).
Far from limiting ourselves to searching for “earthquake news” and taking them out of context, as we tended to do in the "heroic" days at the dawn of modern historical seismology, we attempted here a more ambitious undertaking. Our aim is to examine original earthquake news in their cultural framework, to check their intrinsic quality and "authoritativeness", and thus to improve the quality of general knowledge on historical earthquake observations. Using data extrapolated from narrative written sources (such as chronicles and annals) to compile earthquake catalogues sometimes risks isolating the data themselves and undermining their evaluation. Indeed, news taken out of the context that reports them, while useful in itself, remain impoverished, like archaeological findings whose site, location and circumstances of discovery are unknown.
Up to now our study has considered some dozen earthquakes with M ≥3.5, dated between 1234 and 1495, of which 11 are located by the CPTI15 catalogue (Rovida et al., 2022) in Ferrara, 3 in Modena, while a couple of cases are unknown to the CPTI15 catalogue. A couple of these earthquakes were never studied at all, in several cases epicentral parameters are derived from reference studies that are almost 20 years old, and in 5 cases even 40 years old. The informative basis for these earthquakes, as summarized in Locati et al. (2022) and Rovida et al. (2022) is rather poor. In many case information on a single locality is available from a single source, whose intrinsic value and reliability are also questionable.
The preliminary results of the revision work are generally an improvement of the intensity estimates. In a few cases, the studied earthquakes turned out to be doubtful or completely fakeUnpublishedFerraraOST1 Alla ricerca dei Motori Geodinamic