Annals of Geophysics (INGV, Istituto Nazionale di Geofisica e Vulcanologia)
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Multidisciplinary investigation of the Salse di Regnano mud volcanoes (Northern Italy) using remote sensing and historical data
No full textThis study presents a multidisciplinary analysis of the Salse di Regnano, a significant mud volcanic area in the Emilia-Romagna Apennines, aiming to develop a comprehensive research strategy to investigate its morphological evolution and fluid emission dynamics. High-resolution 3D models generated through UAV-based photogrammetric surveys enabled detailed mapping and monitoring of morphological features, capturing changes over an extended historical period (1907‑2025) by integrating regional geological maps and archival topographical data. In-situ measurements of methane (CH4) and carbon dioxide (CO2) fluxes revealed localized methane emissions associated with vents characterized by high soil permeability, while CO2 fluxes likely reflect biogenic soil respiration near mud deposits. However, geochemical signatures, including δ13C-CH4 values and the presence of ethane, suggest a thermogenic component, highlighting the complex interplay between biological and geological processes governing gas emissions in the area. Complementary satellite imagery and spatial analyses additionally elucidated the spatial distribution of these processes. This multidisciplinary approach not only advances the understanding of mud volcano dynamics in this geologically active region, but also establishes a practical and scalable methodological framework. The proposed workflow, incorporating targeted geophysical surveys such as geomagnetic and passive seismic measurements, aims to enhance the characterization of subsurface structures. As a preliminary study, this contribution provides a valuable foundation for subsequent monitoring and risk assessment efforts of mud volcanic systems in similar geological contexts. In this view, comparing present-day observations with historical data may also offer critical insights for assessing long-term hazard potential
Three‑dimensional fast inversion of gravity and its gradient tensor data in wavenumber domain
No full textThe gravitational potential field plays a pivotal role in interdisciplinary geological exploration. Recently, significant progress has been made in inversion techniques for three‑dimensional gravity anomaly and its gradient tensor data in the spatial domain. However, in geoscientific research, gravity anomalies derived from models such as the Earth Gravitational Model (EGM) and othercharacteristic series models are prevalent. These spherical harmonic models have limitations due to their finite order, which can lead to truncation errors when traditional spatial domain inversion methods are applied. To address this problem, this paper presents a novel inversion method for three‑dimensional gravity and its gradient tensor data in the wavenumber domain. Unlike the spatial domain inversion, the Green’s function matrix in the wavenumber domain is sparse, resulting in substantial improvements in computational efficiency and reduced calculation time. Furthermore, to tackle the issue of multiple solutions often encountered in wavenumber domain inversions, regularization techniques commonly used in the spatial domain have been incorporated. This strategic integration stabilizes the inversion process and enhances the reliability of the results. To validate the effectiveness of the proposed method, rigorous testing using theoretical model data and field data has been performed. The inversion results clearly demonstrate the robustness of this novel approach, making it highly suitable for inverting three‑dimensional gravity anomaliesand their gradient tensor data
Crustal Thermal Structures Modeling Using Temperature-Depth Profiles in Northern Thailand
No full textThis study examines 1-D temperature-depth profiles (geotherms) in Northern Thailand by using computed compressional wave velocities () derived from shear wave velocities () models. These data, combined with various thermophysical parameters, are used to construct geotherms, focusing on thermal boundaries: the thermal brittle-ductile transition (thermal BDT), the thermal Curie point depth (thermal CPD), and the thermal uppermost mantle base (thermal lithospheric base). The study reveals relationships between geological boundaries, especially correlations between the depth of basin sediment-basement rock versus the thermal BDT and the upper-lower crust boundary versus the thermal CPD. The study also explores thermal BDT depth through crustal shear zone models based on frictional laws and quartzite flow assumptions. Additionally, assessing variability in crustal heat flow and strain rate informs understanding of crustal differential stress (3 – 1). Beyond geological insights, the study of geothermal energy evaluates hot-dry rock (HDR) potential. The study also correlates the crustal thermal gradient with the locations of regional hot springs
An improved methodology for lava flow hazard mapping at Etna volcano
Full text linkLava flow hazard is a significant geological threat associated with volcanic activity. Understanding and quantifying this hazard is crucial for protecting communities, infrastructure, and the environment, especially in active volcanic areas like Etna. Here we propose a new probabilistic methodology for assessing the lava flow hazard at Etna volcano based on a 4,000 years-long dataset of eruptions and accurate statistical analyses. The methodology combines the probability of future vent opening, the probabilities of occurrence of individual classes of eruptions, and the weighted combination of lava flow simulations. These simulations are based on representative scenarios for each eruption class. The results are two maps, one for flank and one for summit eruptions, which provide the likelihood that a specific area will be affected by lava flow inundation during specific time intervals. Moreover, we present the first attempt to assess the hazard from both kinds of eruptions (flank and summit) that occur at Etna volcano. These hazard maps represent a fundamental support for local authorities, facilitating land-use planning, emergency management, and decision-making during eruptive crises at Etna volcano
Forecasting the evolution of the current unrest of Campi Flegrei by defining anomalies through experts’ elicitation
Full text linkThe Campi Flegrei caldera, Italy, is considered one of the most high-risk volcanic areas on the planet due to its location within the metropolitan area of Naples. Campi Flegrei caldera is currently undergoing unrest. The unrest is linked to an uplift phase that started in 2005, which is accompanied by gas emissions and volcano-tectonic seismicity. Owing to the limited knowledge of the plumbing system and the pre-eruptive processes, tracking the evolution of a volcanic unrest is often based on probabilities obtained by experts’ elicitation. In this work, we present the daily variation of the probability that the unrest is driven by a shallow magma movement and the monthly probability of eruption based on the Bayesian Event Tree for Eruption Forecasting (BET_EF) model calibrated for Campi Flegrei by means of the outcomes of the VI experts’ elicitation carried out in 2015. The results show that according to the interpretive framework provided by experts, the probability that the mechanism behind the current unrest is shallow magma movements is not negligible, but the monthly probability of eruption remained overall constant during the entire period
Analyzing Virtual Reference Station for GPS surveying: experiments and applications in a test site of the northern Apennine (Italy).
Full text linkThe availability of a GPS network of 10-20 km mean size, provides good topographical support for the measurement of ground displacements, even at a local scale such as a landslide. In particular, a series of multitemporal kinematic or rapid-static GPS acquisitions of a landslide allows a good characterization of its displacements if the measurements are referred to a GPS reference network. Nevertheless, a wider network formed by stations located at long distances, for example at several tens of kilometers, characterized by large spacing, can lead to results affected by high noise, degrading the accuracy of final point positions. In order to obtain an adequate GPS reference network, some virtual reference stations (VRSs) can be introduced, even if a network refinement based on VRS cannot reach the same accuracy of a real local network. Some experiments, including measurements on a real landslide, have been performed in order to evaluate the performance of this technique. The results point out that the standard deviation of the obtained solutions is about two or three times larger than those which can be reached using a real local network
Exploring Earthquake Depth variability through Between‑Event Residuals: Insights from Italy
Full text linkDespite the crucial importance of accurate event localizations, focal depths are generally poorly constrained, especially for very shallow events (depth <10 km), which are often mislocated. In this study, we investigate whether the event‑specific ground‑motion residuals, , are correlated with focal depth. In particular, we examine whether and to what extent the focal depth influencesthe spectral shape of the curves.The residual investigated in this study are derived from the ITACAext 1.0 flatfile, which is related to the ITalian ACcelerometric Archive (i.e., ITACA database) and collects waveforms of seismic events with magnitude greater than 3.0, recorded in Italy since 1972. The residual analysis is conducted using the latest predictive ground-motion model for shallow crustal earthquakes in Italy as a reference. To emphasize the differences for events with varying focal depths, the attenuation in the groundmotionmodel is measured using the Joyner-Boore distance.A cluster analysis is applied on the spectral curves, revealing systematic trends that can be related to different focal depths. In particular, a cluster of very shallow earthquakes (<10 km; VSE) is identified. This cluster is characterized by amplitudes that are systematically positive at long periods (>1 s) and negative at short periods (<1 s). Opposite features are observed for deeper earthquakes (>10 km), with amplitudes that are systematically negative at long periods (>1 s) and positive at short periods (<1 s). As expected, the overall amplitudes of deep events decrease as depth increases.The proposed method appears to be a promising tool for identifying mislocated events or detecting earthquakes erroneously classified as shallow crustal seismicity (i.e., very shallow earthquakes of volcanic origin or deep earthquakes in subduction areas). Improving the estimates of focal depths would lead to a reduction in the variability of the ground motion models in epicentral area, with significant implications on hazard estimates
Inversion of Rayleigh wave dispersion databased on variational modal decomposition football team training algorithm
Full text linkIn view of the triple challenges in the Rayleigh wave dispersion curve inversion algorithm, which has strong sensitivity, low convergence efficiency and poor noise robustness, The Football Team Training Algorithm (FTTA) is applied to the problem of dispersion curve inversion,; and proposes a Variational Football Team Training Algorithm, VFTTA)’s Rayleigh wave dispersion curve inversion method, which introduces variational modal decomposition (VMD) into the FTTA to build a hybrid inversion framework. The core innovation lies in: i) Constructing a three‑stage mapping mechanism for football training – to achieve efficient parameter space search through global collaborative collective training, regional optimization group training, and individual reinforcement additional training; ii) Design a VMD‑FTTA joint preprocessing system, FTTA is used to adaptively optimize VMD parameters to achieve optimal decomposition of the original signal and accurate extraction of the target mode, fundamentally suppressing noise interference and providing high‑fidelity input signals for inversion. This study first tested the performance of FTTA and VFTTA through two complex benchmark functions and then applied it to the inversion of noise‑containing and noise‑free base‑order and higher‑order dispersion curves designed under different geological conditions. The results show the effectiveness and reliability of VFTTA in dispersion curve inversion. Finally, the measured micro‑motion dispersion data in Nanjing area further verified that VFTTA has smaller fitting errors and higher stability compared with FTTA and PSO
The use of the inversion of single-station Rayleigh wave ellipticity curve in routine site investigation: numerical inversion and case-studies
No full textNon-invasive single-station ambient vibration recordings have become very common nowadays for
microzonation studies. Usually, these records are processed using Nakamura’s method to determine
the horizontal-to-vertical spectral ratio (H/V) curve, but the Rayleigh waves’ ellipticity curve can
also be determined and inverted alone or combined with data acquired using other surface wave
methods. Since single-station ambient vibration-based analyses are a very cost-effective technique,
this paper studies the reliability of the shallow ground structure that results from the ellipticity
curve inversion, with prior knowledge on the ground profile characteristics, as is common in urban
areas. The inversion of the ellipticity curve of a large set of shear wave velocity profiles (Vs-profiles)
was simulated numerically to characterize the uncertainty. Three normally dispersive case studies
in Lisbon County were used to evaluate the technique. RayDec was used to obtain experimental
ellipticity curves inverting the right flank and the complete curve. It is shown that the Rayleigh
wave ellipticity curve inversion can be a valuable and cost-effective preliminary site investigation
technique, adopting a constrained inversion (based on some prior knowledge), to support the
preliminary design stage of geotechnical works)
Offshore Shear Wave Velocity Measurements for the Assessment of Soil Sampling Quality
No full textShear wave velocity Vs is a critical soil parameter for several geotechnical and geophysical engineering applications including seismic site response analysis, liquefaction risk assessment and design of shallow and deep foundations. Moreover, the comparison of shear wave velocity between laboratory and in situ measurements has become a standard acceptance criterion for the assessment of sampling quality.
Offshore in situ shear wave velocity testing is considerably more challenging than onshore, due to the difficulties in the correct deployment of the instrumentation as well as of the wave source, in absence of direct visibility of the ground level below water. This paper describes the methodology employed for offshore shear wave velocities (Vs) measurements in the harbour of Barcelona in September 2022. Medusa SDMT tests were performed in sea depths ranging between 15-17 m from a jackup and employing a drill rig to penetrate the probe down to 40 m below the seafloor. The paper includes examples of recorded S-wave seismograms, analyses of Vs repeatability for the same depth measurements and Vs profiles with depth.
In the same test locations, carefully prepared specimens of undisturbed samples were tested after reconsolidation to the estimated in situ stress states in stress path triaxial cells with bender elements transducers. The obtained lab shear wave velocities were compared with the in situ values obtained with the Medusa SDMT tests to assess sample quality