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Active tectonics in the Calabrian Arc: Insights from the Late Miocene to Recent structural evolution of the Squillace Basin (offshore eastern Calabria)
No full textThe Calabrian Arc represents one of the most active sectors of the upper plate of the Tyrrhenian-Ionian subduction system. This research aims to reconstruct the evolution of the Squillace Basin (Ionian offshore of the Calabrian Arc) from the Late Miocene to Recent times and recognise active shallow and deep structures using a multiscale approach. The latter is based on interpreting high-penetration and high-resolution seismic reflection profiles, calibrated with well-log data coupled with bathymetric data and the distribution of instrumental earthquakes. Data highlight three steps in the evolution of the Squillace Basin. A Late Miocene extensional event led to the formation of WNW-ESE oriented horst and half-graben structures. During the Pliocene, deformation was localised in the central and northern sectors of the basin and expressed by a WNW-ESE oriented strike-slip fault and NW-SE normal to trastensional faults, respectively. A transpressional event started in the Early Pleistocene, causing the positive inversion of deep (> 3 km) extensional faults and the formation of NW-SE to WNW-ESE oriented transpressional/reverse faults and related anticlines. The kinematics of these faults agree with the NW-SE oriented left-lateral Albi-Cosenza, Lamezia-Catanzaro and Petilia-Sosti crustal fault zones developed in north Calabria. The results of this work suggest that the transpressional structures in the northwestern sector of the basin likely represent the offshore prolongation of the Albi-Cosenza fault zone. NW-SE to WNW-ESE trending, shallow ( 3 and depth <15 km located in the hanging wall of transpressional faults. The integrated data suggest that these structures are active and probably responsible for the major earthquakes that affected the Ionian offshore.Published2297722T. Deformazione crostale attivaJCR Journa
Principal component analysis on twenty years (2000-2020) of geochemical and geophysical observations at Campi Flegrei active caldera
No full textCampi Flegrei (CF) is an active and densely populated caldera in Southern Italy, which has manifested signs of significant unrest in the last 50 years. Due to the high volcanic risk, monitoring networks of the most sensitive unrest indicators have been implemented and improved over time. Precious database constituted by geophysical and geochemical data allowed the study of the caldera unrest phases. In this paper we retrace the caldera history in the time span 2000-2020 by analyzing displacement, seismicity and geochemical time series in a unified framework. To this end, Principal Component Analysis (PCA) was firstly applied only on geochemical data because of their compositional nature. The retrieved first three components were successively analyzed via PCA together with the geophysical and thermodynamical variables. Our results suggest that three independent processes relay on geochemical observations: a heating/pressurizing of the hydrothermal system, a process related to magmatic fluids injection at the hydrothermal system roots, and third process probably connected with a deeper magmatic dynamic. The actual volcano alert state seems mainly linked to the variation of the hydrothermal system activity. Our approach made it possible to explore the interrelation among observations of different nature highlighting the importance of the relative driving processes over time.Published18445JCR Journa
Reappraisal of Data of Hydrological Changes Associated with Some Strong Historical Italian Earthquakes
No full textHistorical seismology retrieves information about the effects of earthquakes that occurred
in the past, mostly regarding the damage, but also on environmental effects. In this paper, we describe
the methodology of our research on earthquake-induced hydrological effects, which have been long
observed and documented, and are among the most outstanding coseismic phenomena. The method
of research follows two distinct paths, depending on whether the investigated event occurred before
or after the end of the 18th Century. For the most ancient events, we present examples of historical
accounts, local reports, private letters, and diaries, in which the information of interest is often
hidden within broader descriptions and mentioned as a minor curiosity. On the contrary, for more
recent earthquakes, the research benefits from the growing interest in naturalistic observations that
marked the onset of the 19th Century, and is achieved through detailed descriptions, journals, seismic
postcards, and through the first systematic collections of instrumental data. Finally, we describe
a possible method of classification of the hydrological data and show an analysis of the potential
applications and outcomes of this type of research.Published55JCR Journa
Using machine learning for the classification of Seismic Signals at Vulcano, Italy
No full textA Vulcanian eruption is described as an eruptive style with strong explosive characteristics. The name derives from the island of Vulcano in Italy, the first place in which it was observed during the last eruptive activity between 1888 and 1890. In this paper we analyze the seismicity recorded at Vulcano during a seismic unrest starting in September 2021 and still present as of November 2022. The distinctive feature of this seismicity is the presence of a variety of signals, most of which have a very long period (\textasciitilde0.5 s) signature. Low frequency content is interpreted as due to fluid involvement. Therefore, the high occurrence rate of VLP seismicity is a potential indication of pressure buildup within the volcanic system, and may herald phreatomagmatic activity (usually the first stage of a Vulcanian eruption), with serious consequences for inhabitants and tourists.Our analyses exploit machine learning procedures, with particular reference to pattern classification, at the aim of identifying varying classes of seismic events and trace their evolution over time. This classification can be useful for surveillance purposes contributing, along with other early warning methods, to reduce the devastating consequences of eruptions for people and property.PublishedBerlino (Germania)OST5 Verso un nuovo Monitoraggi
Anomalies and transient variations of b-value in Italy during the major earthquake sequences: what truth is there to this?
No full textThis article has been accepted for publication in Geophysical Journal International ©: The Authors 2023. Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved. Uploaded in accordance with the publisher's self-archiving policy.The Gutenberg–Richter b-value is thought to be a proxy of stress conditions in the crust and therefore able to locate asperities as zones of stress concentration responsible for the nucleation of strong events. The scientific literature contains a broad range of case studies showing precursory drops of b, just before the occurrence of strong events, and subsequent rises, during the early part of aftershocks sequences. Translating these results into hazard assessment, the b-value has assumed the status of a candidate precursor to the occurrence of an imminent large event. This issue is analysed here for three major seismic sequences that occurred recently in Italy. In comparison to previous studies, this investigation indicates that the variability of b may not be a reliable indicator of stress or a significant precursor in these examples, and instead may be assigned to a combination of chance, inhomogeneities in the data and inefficiencies in estimation methodologies. Consequently, extreme caution is required when we interpret b-values both as a proxy of physical processes involved in a seismic sequence and as a precursor to the occurrence of imminent strong events.Published1545–15556T. Studi di pericolosità sismica e da maremotoJCR Journa
Experimental insights on the shear-induced crystallization of a phonotephrite magma
No full textIn active volcanic environments magmas that ascend within the conduit and erupt at the surface as lava flows experience physico-chemical perturbations related to temperature changes and variable degrees of deformation. We have conducted experimental investigations to examine the concurrent effects of undercooling and stirring on the crystallization kinetics of a leucite-bearing phonotephrite from Somma-Vesuvius (Italy). Two sets of undercooling experiments have been carried out within the same temperature range of 1300–1150 °C. The first set involved classical static undercooling (SU) experiments with no stirring applied to the melt, while the second set involved dynamic undercooling (DU) experiments with a shear strain rate of 1 s−1 applied. By comparing SU and DU results with previous data from literature obtained using the same experimental approach, we observe that the degree of crystallization and the textural evolution of leucite and clinopyroxene progress upon the effect of melt stirring by shortening the incubation time. As a result, the solidification process is markedly enhanced in DU experiments, accompanied by a substantial increase in the crystal nucleation density and growth rate. Thermorheological modeling indicates that stirring-induced crystallization increases the melt viscosity by a factor of ∼1.5–4.5 depending on the system temperature. At a given temperature, mass transport can therefore produce higher crystallinity and higher viscosity magmatic suspensions than static crystallization conditions. We document that if subsequent cooling occurs, the existing crystal cargo in such suspensions may promote the onset of non-Newtonian rheological response, causing a transition from homogeneous viscous flow to shear localization and magma/lava rupture.Published121682OSV2: Complessità dei processi vulcanici: approcci multidisciplinari e multiparametriciJCR Journa
Vents opening susceptibility map of the Colli Albani long dormant volcano
No full textDespite their protracted periods of inactivity, long-dormant volcanoes may be highly hazardous, as their reactivation can be characterized by violent explosive eruptions. An example of such volcanoes is the Colli Albani caldera, onto which deposits Rome Capital City is built, Italy. Its last volcanic activity was characterized
by voluminous maar-forming phreatomagmatic eruptions dated between 36 and 25ka, but the volcano has produced several maar lake overflows during the Holocene till historical times.
Presently, Colli Albani is affected by recurrent seismic events, anomalous heat flow, ground uplifts, hydrothermal circulation and gas emissions. For these reasons, the Italian Civil Protection has recently listed Colli Albani among the ten active volcanoes of Italy, but products for the evaluation of its volcanic hazards lacking.
This work presents the first study on vent opening susceptibility
mapping at Colli Albani. We explore the potential of an
available geological dataset for building, through geographic
information system analysis, an index that classifies areas at different
vents opening susceptibility (low, moderate and high). Such
result highlights as a solid geological mapping is a prerequisite
for the volcanic hazard assessment, especially in remote or poorly
studied long-dormant volcanoes such as caldera systems where
the location of new vents could occur in different volcano
sectors.Published2215905OSV1: Verso la previsione dei fenomeni vulcanici pericolosiJCR Journa
Deep-water hydrodynamic observations around a cold-water coral habitat in a submarine canyon in the eastern Ligurian Sea (Mediterranean Sea)
No full textA 2-year dataset of a stand-alone mooring, deployed in November 2020 down the Levante Canyon in the eastern Ligurian Sea, is presented. The Levante Canyon Mooring (LCM) is a deep submarine multidisciplinary observatory positioned at 608 m depth in a key ecosystem area. The Levante Canyon hosts a valuable and vulnerable ecosystem of deep-living cold-water corals (CWCs), studied and monitored since 2013 through integrated mapping of the seabed and water column. The 2-year dataset, acquired on the mooring and presented here (data from November 2020 to October 2022), includes measurements conducted with both current meters and conductivity–temperature–depth (CTD) probes and provides information about the hydrodynamics and thermohaline properties across almost the entire water column. The observatory is still ongoing, and the dataset is regularly updated. All the described data are publicly available from https://doi.org/10.17882/92236 (Borghini et al., 2022). They must therefore be preserved and are of considerable scientific interest.This research has been supported by the Distretto Ligure delle Tecnologie Marine (DLTM) through funding obtained from Regione Liguria (PAR-FSC 2007–2013 funds) and by institutional funds from Consiglio Nazionale delle Ricerche – Istituto di Scienze Marine (CNR-ISMAR), Agenzia nazionale per le nuove tecnologie, l’energia e lo sviluppo economico sostenibile (ENEA), Istituto Idrografico della Marina (IIM) and Istituto Nazionale di Geofisica e Vulcanologia (INGV).Published1933–1946OSA4: Ambiente marino, fascia costiera ed Oceanografia operativaJCR Journa
Twenty years of in-situ monitoring in the south-eastern Mediterranean Levantine basin: Basic elements of the thermohaline structure and of the mesoscale circulation during 1995-2015
No full textThe in-situ data gathered over two decades since mid-1990s in the South-Eastern Levantine Basin from 34 hydrographic campaigns and from 35 bi-weekly and monthly Voluntary Observing Ships (VOS) transects, after the pioneering POEM cruises, have provided insight on the dominant meso-scale coherent circulation features of this sub-basin. The most pronounced feature, the anticyclonic Cyprus Eddy, migrates over the broad region of the Eratosthenes seamount and exhibits significant seasonal and inter-annual spatial-temporal variability. Another prominent structure of the sub-basin is the anticyclonic Shikmona Eddy generated by instabilities of the strong northward flowing jet along the south-easternmost shelf and slope of the Levantine basin. Its evolution and co-existence with the Cyprus Eddy, cause the periodic re-establishment of the Shikmona Gyre, which was first observed during the POEM cruises in mid-1980s. The offshore, cross basin, eastward flowing Mid-Mediterranean Jet (MMJ) defines the northern and southern flanks of these sub-basin scale anticyclonic eddies and transports the lower salinity Modified Atlantic Water (MAW) in the subsurface layer, through the warmest and most saline waters of the Mediterranean. Periodically, the MMJ bifurcates and/or is diverted northward, along the western coast of Cyprus due to westward and northward spatial fluctuations of the Cyprus Eddy’s western boundaries. The current long term in-situ monitoring of the sub-basin provides an overview of the extent of the main water masses and characterizes their variability throughout the period considered. The analysis of the data indicates an increase of the temperature and salinity of the Levantine Surface Water (LSW) and of the subsurface MAW. The Eastern Mediterranean Transient Water (EMTW) is shown to occupy the deep cavities in the vicinity of the Eratosthenes seamount while its upper boundary was found to be lifted to shallower depths over a period of two decades.Published10745044A. Oceanografia e climaJCR Journa
Empirical correlations between a FAS non-ergodic ground motion model and a GIT derived model for Central Italy
No full textThis article has been accepted for publication in Geophysical Journal International ©:The Author(s) 2022. Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved. Uploaded in accordance with the publisher's self-archiving policy.In this study we investigate the correlation between the residuals of a neGMM (non-ergodic Ground Motion Model) and the physics-based parameters obtained using a non-parametric GIT approach (Generalized Inversion Technique) to lay the groundwork for the implementation of an ad-hoc FAS (Fourier Amplitude Spectra) neGMM for the Central Italy region.
This region is particularly suitable for data-driven methodologies as those applied in this work because of the large amount of available data due to the recent multiple mainshock-aftershock sequences occurred in this area.
Both neGMM and GIT models are developed for Fourier spectra in the frequency range between 0.5 and 25 Hz and using the same reference sites. The comparison of the non-ergodic terms with the source, path and site spectral parameters provides interesting results. First, we find a strong correlation between the source parameters, stress drop Δσ and decay ksource, and the source neGMM corrective terms (the combination of the between-event δBe and the location-to-location terms δL2L). This correlation is frequency dependent and, at high frequency, is remarkably positive for Δσ and negative for ksource. Concerning the attenuation terms, the path-to-path residuals (δP2P) are clearly associated with the deviations from the regional Q estimates obtained from GIT analysis. This indicates that the neGMM properly captures the properties of the anelastic attenuation and that the corrective terms δP2P can be used to account for differences in travel paths across different crustal domains.
Finally, adopting the same reference sites for neGMM and non-parametric GIT, we observe that the systematic site terms (δS2Ss) and the GIT-derived amplification functions are in good agreement. The next step for an appropriate modeling is to identify the physical parameters (for example VS,30 and k0) describing the empirical amplification curves to be introduced as explanatory variables in the ground motion model.Published51–685T. Sismologia, geofisica e geologia per l'ingegneria sismicaJCR Journa