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Asperity size and neighboring segments can change the frictional response and fault slip behavior: insights from laboratory experiments and numerical simulations
No full textAccurate assessment of the rate and state friction parameters of rocks is essential for producing realistic earthquake rupture scenarios and, in turn, for seismic hazard analysis. Those parameters can be directly measured on samples, or indirectly based on inversion of coseismic or postseismic slip evolution. However, both direct and indirect approaches require assumptions that might bias the results. Aiming to reduce the potential sources of bias, we take advantage of a downscaled analog model reproducing megathrust earthquakes. We couple the simulated annealing algorithm with quasi-dynamic numerical models to retrieve rate and state parameters reproducing the recurrence time, rupture duration and slip of the analog model, in the ensemble. Then, we focus on how the asperity size and the neighboring segments’ properties control the seismic cycle characteristics and the corresponding variability of rate and state parameters. We identify a tradeoff between (a-b) of the asperity and (a-b) of neighboring creeping segments, with multiple parameter combinations that allow mimicking the analog model behavior. Tuning of rate and state parameters is required to fit laboratory experiments with different asperity lengths. Poorly constrained frictional properties of neighboring segments are responsible for uncertainties of (a-b) of the asperity in the order of per mille. Roughly one order of magnitude larger uncertainties derive from asperity size. Those results provide a glimpse of the variability that rate and state friction estimates might have when used as a constraint to model fault slip behavior in nature.Publishede2023JB026594OST4 Descrizione in tempo reale del terremoto, del maremoto, loro predicibilità e impattoJCR Journa
Variable plate kinematics promotes changes in back-arc deformation regime along the north-eastern Eurasia plate boundary
No full textThe stretching of the lithosphere leading to back-arc basins formation generally develops behind arc-trench systems and is considered the consequence of slab retreat relative to the upper plate. Here, we examine the deformation regime evolution within the overriding plate due to subduction processes, using thermo-mechanical numerical simulations. We explore the north-eastern Eurasia plate boundary and the mechanisms of subducting Pacific plate since 57 Ma. During this time interval, several extensional basins formed along the Eurasia margin, such as the East China Sea, the Japan Sea, and the Kuril basin. Here, we increased the simulation complexity, with the inclusion of (i) the kinematic variability of the Pacific plate over the geological past with respect to a fixed Eurasia, incorporating time-dependent (i.e., temporally evolving) velocities computed from plate motion reconstructions; (ii) a Low-Velocity Zone within the asthenosphere, and (iii) a horizontal eastward mantle flow. Our results show a crucial role of the mantle flow for the development of lithospheric extension and back-arc basin opening, and a main kinematic control of the subduction trench position, which advances and retreats, into distance intervals in the order of ∼ 100 km, and providing stages of compression and extension in a back-arc basin.Published7220OST1 Alla ricerca dei Motori GeodinamiciJCR Journa
Exploring Convolutional Neural Networks for the Thermal Image Classification of Volcanic Activity
No full textThis paper addresses the classification of images depicting the eruptive activity of Mount
Etna, captured by a network of ground-based thermal cameras. The proposed approach utilizes
Convolutional Neural Networks (CNNs), focusing on pretrained models. Eight popular pretrained
neural networks underwent systematic evaluation, revealing their effectiveness in addressing the
classification problem. The experimental results demonstrated that, following a retraining phase
with a limited dataset, specific networks such as VGG-16 and AlexNet, achieved an impressive
total accuracy of approximately 90%. Notably, VGG-16 and AlexNet emerged as practical choices,
exhibiting individual class accuracies exceeding 90%. The case study emphasized the pivotal role
of transfer learning, as attempts to solve the classification problem without pretrained networks
resulted in unsatisfactory outcomes.Supported by Italian Research Center on High Performance Computing Big Data and
Quantum Computing (ICSC), project funded by European Union—NextGenerationEU—and National
Recovery and Resilience Plan (NRRP)—Mission 4 Component 2 within the activities of Spoke 3
(Astrophysics and Cosmos Observations). Sonia Calvari also acknowledges the financial support of
the Project FIRST ForecastIng eRuptive activity at Stromboli volcano (Delibera n. 144/2020; Scientific
Responsibility: S.C.) Vulcani 2019.Published124-137OSV3: Sviluppo di nuovi sistemi osservazionali e di analisi ad alta sensibilitàJCR Journa
Statistical models of the variability of plasma in the topside ionosphere: 2. Performance assessment
No full textStatistical models of the variability of plasma in the topside ionosphere based on the Swarm data have been developed in the “Swarm Variability of Ionospheric Plasma” (Swarm-VIP) project within the European Space Agency’s Swarm+4D-Ionosphere framework. The models can predict the electron density, its gradients for three horizontal spatial scales – 20, 50 and 100 km – along the North-South direction and the level of the density fluctuations. Despite being developed by leveraging on Swarm data, the models provide predictions that are independent of these data, having a global coverage, fed by various parameters and proxies of the helio-geophysical conditions. Those features make the Swarm-VIP models useful for various purposes, which include the possible support for already available ionospheric models and proxy of the effect of ionospheric irregularities of the medium scales that affect the signals emitted by Global Navigation Satellite Systems (GNSS). The formulation, optimisation and validation of the Swarm-VIP models are reported in Paper 1 (Wood et al. 2024. J Space Weather Space Clim. in press). This paper describes the performance assessment of the models, by addressing their capability to reproduce the known climatological variability of the modelled quantities, and the ionospheric weather as depicted by ground-based GNSS, as a proxy for the ionospheric effect on GNSS signals. Additionally, we demonstrate that, under certain conditions, the model can better reproduce the ionospheric variability than a physics-based model, namely the Thermosphere-Ionosphere-Electrodynamics General Circulation Model (TIE-GCM).Published4OSA3: Climatologia e meteorologia spazialeJCR Journa
Groundwater-rock interactions and mixing in fault-controlled karstic aquifers: A structural, hydrogeochemical and multi-isotopic review of the Pontina Plain (Central Italy)
No full textKarstic aquifers represent crucial water resources and are categorized as either stratigraphically or fault-controlled. This study investigates groundwater-rock interactions and mixing processes within one of the largest fault-controlled karstic aquifers in Central Italy, adjacent to the Pontina plain, which is a highly populated area where agricultural activities and climate change challenge the groundwater assessment of a complex aquifer. We conducted structural, hydrogeochemical, and multi-isotopic screening of ten selected springs with different degrees of mineralization (ranging from Ca-HCO3 to NaCl hydrofacies), incorporating new analyses and modeling of δ34S(SO4), δ18O(SO4), 87Sr/86Sr, and δ11B. Additionally, the reinterpretation of a seismic section provides a more detailed framework extending to depths of approximately 5-7 km that allows the identification of the geometry of normal faults, which act as pathways for upwelling fluids. Our findings reveal that hydrogeochemical compositions result from multiple interactions between karstic water and deeper fluids that have interacted with different rocks. Concentration (Na/Li) and isotope (SO4-H2O) geothermometers, coupled with geochemical modeling and trace element analysis, enabled the estimation of a water temperature equilibrium of approximately 95.5 °C, with Triassic evaporites generally corresponding to a depth of approximately 3 km and a temperature of 40 °C with magmatic rocks at approximately 1 km depth, which is likely associated with ongoing tectonics and the Quaternary tectonically controlled Volsci Volcanic Field. To obtain the latter estimate, we used a new geothermometer activity based on the equilibrium between analcime and pollucite. Furthermore, this multidisciplinary approach enhances the understanding of groundwater behavior in fault-controlled karstic aquifers, where mantle-derived CO2 dissolved in groundwater is the driving force behind water-rock interactions. Given the potential for further variations in mixing, which may worsen water quality and increase aquifer vulnerability, periodic monitoring of these processes is essential in a human-impacted environment amidst ongoing climate change.Published175439JCR Journa
High-Precision and High-Reliability Positioning, Navigation, and Timing: Opportunities and Challenges
No full textThe research scope of the papers published in this Special Issue mainly focuses on high-precision and high-reliability positioning, navigation, and timing (PNT) with Global Navigation Satellite System (GNSS) or multi-source sensors, resilient PNT with GNSSs or multi-source sensors in challenging environments, integrated PNT with GNSSs and multi-sensor systems, applications of PNT with GNSSs or multi-source sensors, etc.Published4403OSA5: Energia e georisorseJCR Journa
Investigating Equatorial Plasma Depletions through CSES-01 Satellite Data
No full textIonospheric plasma density irregularities, which are one of the primary sources of disturbance for the Global Navigation Satellite System, significantly impact the propagation of electromagnetic signals, leading to signal degradation and potential interruptions. In the equatorial ionospheric F region after sunset, certain plasma density irregularities, identified as equatorial plasma bubbles, encounter optimal conditions for their formation and development. The energy spectra of electron density fluctuations associated with these irregularities exhibit a power-law scaling behavior qualitatively similar to the Kolmogorov power law observed in fluid turbulence theory. This intriguing similarity raises the possibility that these plasma density irregularities may possess turbulent characteristics. In this study, we analyzed electron density, temperature, and pressure data obtained from the China Seismo-Electromagnetic Satellite (CSES-01) to delve into the spectral properties of equatorial plasma depletions in the ionospheric F region at an altitude of about 500 km. This research marks the first exploration of these properties utilizing CSES-01 data and focuses on 14 semi-orbits that crossed the equator after midnight (01:00–03:00 LT), characterized by a geomagnetic quiet condition (Kp < 1). The analysis of electron temperature, density and pressure within equatorial plasma depletions revealed power-law scaling behavior for all the selected parameters. Notably, the spectral index values of these parameters are different from each other. The significance of these findings in terms of investigating plasma depletions via magnetic field signatures, as well as their relationship to the occurrence of Rayleigh–Taylor convective turbulence, is examined and discussed.Published868OSA3: Climatologia e meteorologia spazialeJCR Journa
Temporary Seismic Network in the Metropolitan Area of Rome (Italy): New Insight on an Urban Seismology Experiment
No full textThis study presents data and preliminary analysis from a temporary seismic network (SPQR), which was deployed in the urban area of Rome (Italy) for three months in early 2021. The network was designed to investigate the city’s subsurface while evaluating the feasibility of a permanent urban seismic network, and consisted of 24 seismic stations. Despite significant anthropogenic noise, the SPQR network well recorded earthquake signals, revealing clear spatial variability referable to site effects. In addition, the network’s continuous recordings allowed the use of seismic noise and earthquake signals to derive spectral ratios at sites located in different geological and lithological settings. During the experiment, there were periods of activity restrictions imposed on citizens to limit the spread of COVID‐19. Although the observed power spectral density levels at stations may not show visible noise reductions, they do cause variations in calculated spectral ratios across measurement sites. Finally, a statistical noise analysis was conducted on continuous seismic station data to evaluate their performance in terms of detection threshold for earthquakes. The results indicate that all network stations can effectively record earthquakes with a good signal‐to‐noise ratio (≥5 for P and S phases) in the magnitude range of 1.9–3.3 at distances of 10 km and 80 km, respectively. In addition, the network has the potential to record earthquakes of magnitude 4 up to 200 km, covering areas in Central Italy that are far from the city. This analysis shows that it is possible to establish urban observatories in noisy cities such as Rome, where hazard studies are of particular importance due to the high vulnerability (inherent fragility of its monumental heritage) and exposure.The experiment was financed with funds of the Istituto Nazionale di Geofisica e Vulcanologia (INGV) dedicated to the institution’s open research projects (RicercaLibera) to promote free research within the INGV (Research Project: Three-dimensional shear-wave velocity imaging by ambient seismic noise tomography in the urban area of Rome city - Central Italy)Published2554–2569OST5 Verso un nuovo MonitoraggioJCR Journa
Crustal root shapes the plumbing system of a monogenetic volcanic field as revealed by magnetotelluric data
No full textThe plumbing systems of subduction-zone volcanoes consist of magma reservoirs with different degrees of
evolution at multiple depths. The geometries of plumbing system of intraplate monogenetic volcanic fields are
generally characterized by basaltic magma ascending from the mantle and/or a shallower reservoir along dikes.
However, the shape and vertical extent of these plumbing systems are largely unknown due to the rareness of
robust geophysical data. The possible role of faults and mountain chains in controlling the geometry of magma
reservoirs is also poorly understood. To address these limitations, we present a three-dimensional resistivity
structure beneath the Holocene Jingpohu Monogenetic Volcanic Field (JMVF) in the Zhangguangcai Range
(ZGC), northeastern China. The resistivity model was derived from the magnetotelluric data in a dense net-like
array. We identified an inverted cone-shaped high-resistivity (~10,000 Ω m) anomaly below the ZGC. This
anomaly traverses almost the entire crust. We interpret this high-resistivity anomaly to be the stiff basement of
the ZGC. At the base of the resistive volume, we resolved a sill-like, low-resistivity anomaly that occurs at the top
of the lithospheric mantle. Sheet-like low-resistivity anomalies surrounding the high-resistivity body depart from
the lithospheric mantle. We interpret these sill- and sheet-like anomalies as a trans-crustal saucer-shaped magma
plumbing system beneath the JMVF. This system involves multi-level magma reservoirs, including basaltic
magma at its base, basaltic dikes/sills swarms in the middle and sill intrusions in the upper crust. We propose
that the stiff crustal root and the topographic loading of the ZGC work together to deflect the upward magma
propagation towards the edges of the ZGC. The magma ascent to the surface is probably controlled by preexisting,
lithospheric faults. Our data show how mountain chains, together with the crustal structure, play a
key role in controlling the geometry of multi-level plumbing systems of intraplate monogenetic volcanic fields.Published118523OSV2: Complessità dei processi vulcanici: approcci multidisciplinari e multiparametriciJCR Journa
RELACIÓN EMPÍRICA ENTRE EL PARÁMETRO DE MOVIMIENTO FUERTE PGA Y LA INTENSIDAD MACROSÍSMICA PARA SISMOS EN COLOMBIA EMPIRICAL RELATIONSHIP BETWEEN THE STRONG-MOTION PARAMETER PGA AND THE MACROSEISMIC INTENSITY FOR EARTHQUAKES IN COLOMBIA
No full textUnderstanding the relationship between different ground motion parameters (GMPs) and
macroseismic intensity (I) is essential for applications in seismology and earthquake engineering.
This study presents empirical relationships between Peak Ground Acceleration (PGA) and
macroseismic intensity (I) for seismic events in Colombia, using historical earthquake data
processed by the Colombian Geological Survey. Ten historical earthquakes across the country,
occurring between 1994 and 2016, with magnitudes ranging from Mw 5.3 to 7.2, were analyzed.
From the cross-analysis between municipalities with recorded intensity (I) and nearby PGA
measurements, 62 I-PGA pairs with an average distance of 3.6 kilometers were obtained. These
pairs were manually validated based on distance and topographic similarity criteria and used to
establish the proposed empirical relationships. The final relationships employed the geometric
mean of the horizontal components of the PGA and the European Macroseismic Scale EMS-98.
Additionally, analyses were conducted using the Modified Mercalli Scale and varying the
acceleration records, including the vertical component and the highest of all components. During
the analysis, linear, exponential, polynomial, and power functions were calibrated with intensities
ranging from II to VIII on the EMS-98 scale and PGA values ranging from 1.16 to 527.36 cm/s².
The relationships that best represented the seismicity in Colombia were selected through the
calculation of standard deviations and determination coefficients. Finally, residuals of
observed/predicted intensity and acceleration were analyzed as a function of variables such as
magnitude and epicentral distance.PublishedCentro Cultural Metropolitano de Convenciones de Armenia, Armenia, ColombiaOST2 Deformazione e Hazard sismico e da maremot