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Low-Frequency Ground Penetrating Radar: A Versatile Tool for Multiscale Analysis in Active Tectonics, Geoarchaeology, and Urban Geology
No full textIn situ geophysical techniques are essential tools in geological and geotechnical research for characterizing tectono-stratigraphic settings. Since its introduction in the late 1970s, Ground Penetrating Radar (GPR) provides integrated information over a large subsoil volume, overcoming the limitations of conventional point-scale direct survey or measurements. In the last decade, advances in low-frequency GPR systems have made them efficient and affordable for multiscale investigations. Compact and lightweight monostatic antennas, such as the COBRA Plug-In SE 70 employed in this study, allow for rapid deployment, flexible parameter settings, and high-resolution data acquisition. Operating with a center frequency of 80 MHz, a frequency range of 20–140 MHz, and a maximum penetration depth of 50 meters, this system achieves vertical resolutions of approximately 30 cm with a sampling rate of 32,000 sample/s. This study presents the results of low-frequency GPR surveys conducted in different geological contexts in Southern Italy:1) active tectonics at Mt. Camposauro (Southern Apennine, Italy) an area of energetic historical seismicity with evidences of recent tectonic activity; 2) geoarchaeology and site characterization of subsurface caves at the ancient Capua, an Etruscan city (IX century BCE) lately conquered by Osci, then by Samnite (IV century BCE) and finally by Romans, becoming in the III century BCE the main city along the Via Appia, regina viarum; and 3) urban geology in Calitri Town (Avellino, Italy) an area with a complex tectono-stratigraphic setting, affected by seismically induced gravity-driven deformations. The results highlight the versatility and effectiveness of low-frequency GPR for investigating geological processes at varying spatial and temporal scales. Key findings are summarized and discussed, emphasizing the role of GPR as a preferred method for integrated subsurface analysis.Publishe
Paleoearthquakes modelling and effects of uncertainties on probability assessment of next fault ruptures: the case of Central Italy surface faulting earthquakes
No full textUsing the published paleoseismological trenching data for 16 faultsin Central Italy, we compile
a new data base of surface faulting earthquakes, having a quite stationary temporal distribution
since 6000 BCE. By applying a probabilistic aggregation method, we correlate the event ages
from distinct trenches on each fault, to construct all possible individual fault rupture scenarios,
consistent with geological constraints. These inferred fault time histories are the basis for both
individual fault and regional seismic hazard evaluation. We found that the mean recurrence
time of each fault goesfrom about 1 to 4 thousand yearsfor individual faults, whereasthe value
at regionalscale is close to 120 yr. The smallsize of individual fault data samples does not allow
us to infer straightforward information on the fault temporal behaviour, but only to evaluate
the reliability of a chosen occurrence model for each fault. Therefore, hazard assessment is
carried out by including the uncertainties related to both ages and probability distribution of
the interevent times. We find that both these have a large impact on the probabilities of next
rupture for individual faults: these depend on basic features of the temporal model and on
the relation between the elapsed time and the mean interevent time. At a regional scale, we
cannot exclude the simplest possible model, that is, the Poissonian behaviour, that provides
quite stable probabilities of future events, close to 27 per cent in the next 50 yr.PublishedJCR Journa
Magnetic and Paleomagnetic Characterization of the Ivrea-Verbano Lower Crust Body (NW Italy): Assessing the Magnetization of Variscan-Age Lower Crust
No full textThe source of high-intensity magnetic anomalies from (mostly Precambrian) lower crust of continent interiors has long been debated, as it requires speculative rocks yielding 2-6 A/m magnetization. We report on the magnetic and paleomagnetic investigation of the Ivrea-Verbano Zone (IVZ), Western Alps, where metamorphic and intrusive lower crust rocks of Late Variscan-Permian ages are exposed. We sampled 39 oriented sites along the Cannobina, Ossola, Strona, and Sesia valleys/sections. Low (0.27-2.1•10 3 SI) magnetic susceptibility (k) values were measured in metapelite-metabasite metamorphic rocks from the Ossola and Strona valleys. There only two metabasite (one amphibolite and one granulite) out of 25 metamorphic sites containing pseudo-single domain (PSD) magnetite yield 0.48-1.1•10 1 SI k values that remain constant until 550°C heating. K of gabbros-granodiorites from Sesia valley mimic low values from metamorphic rocks, whereas at Cannobina valley one gabbro and one mafic granulite display values comparable to the two strongly magnetic sites from Ossola/Strona valleys. Peridotite lenses at Balmuccia and Finero similarly yielded low (0.24-5.5•10 3 SI) k values, consistently with their low (600 Ma) continental areas, hide the source of high-intensity magnetic anomalies. Crustal magnetic anomalies are measured by airborne surveys and indicate that a certain rock is rich in strongly magnetic minerals (mainly magnetite) as to produce a local field that may add or subtract to (depending on magnetization direction of the source rock) to the local Earth's magnetic field. The source of such anomalies is a matter of debate as the potential sources are normally hidden at 20-40 km depths below continents. In the western Alps, one of the most complete lower crust sections has been exhumed due to Alpine orogenesis and is exposed in the Ivrea Verbano Zone. We sampled and measured the magnetic properties of Late Variscan-Permian metamorphic and intrusive lower crust rocks at 39 sites along the Cannobina, Ossola, Strona, and Sesia valleys/sections. Results indicate that the Ivrea Verbano lower crust body definitely could not yield lower crust magnetic anomalies.PublishedJCR Journa
Heritage of Tethyan Oceanic Transform Faults Within Alpine Orogens: Paleomagnetic Evidence From the Shkoder-Peja Transverse Zone (Northern Albania)
No full textThe Shkoder-Peja transverse zone (SPTZ) of Northern Albania marks the boundary between the Dinarides and Albano-Hellenides and is marked by a ∼100 km SW-ward shift of the ophiolitic nappe front. The SPTZ has been variably interpreted as a paleogeographic inheritance, a dextral strike-slip fault, the hinge of the clockwise (CW) rotating Albano-Hellenides, and a Miocene normal fault. Here we report on the paleomagnetism of 23 Triassic-Cretaceous sites from the Krasta-Cukali and Albanian Alps domains, located both within and north of the SPTZ. Six sites yielded only a pre-tilt magnetization, 14 sites were found to be remagnetized after late Eocene-Aquitanian tilt, and 3 sites showed both pre-and post-tilt magnetizations. Both pre-and post-tilt paleomagnetic directions yielded a ∼70°CW rotation with respect to Adria/Africa, except 9 sites from the Koman zone at the boundary with the ophiolitic nappe, which record a 38°± 15°CW rotation. Thus, the well-known regional CW rotation of the Albano-Hellenides extends northward in the southern Dinarides, and the SPTZ is not a rotation boundary as previously assumed. The ∼70°CW rotation is interpreted as the sum of a 30°rotation associated with Late Oligocene-Aquitanian thrusting of the Krasta-Cukali nappe over the Kruja zone, plus the 40°Miocene-Pleistocene rotation well-documented in the external Kruja and Ionian zones of Albania. We suggest that the SPTZ is the heritage of a Lower-Middle Triassic transform fault of the Maliac Tethyan Ocean, later overprinted by the Lower Cretaceous obduction of the Vardar Ocean that rejuvenated Maliac since the Middle Jurassic.PublishedJCR Journa
Characteristics and modelling of slip-rate variability and temporal earthquake clustering across a distributed network of active normal faults constrained by in situ 36Cl cosmogenic dating of fault scarp exhumation, central Italy
No full textWe present a compilation of new and unpublished in situ 36 Cl cosmogenic isotope data recording the exhumation of 27 active normal fault planes by earthquake slip for the central Apennines, Italy. We do this to constrain the characteristics of slip-rate variability and temporal earthquake clustering and anticlustering across the entire extending orogen, and to assess why it occurs. From the 36 Cl observations we report(1) the long-term slip-rates averaged since 20 ka, (2) the percentage of sites with clusters and anticlusters in each 1 kyrs time-slice back to 20 ka, (3) regional maps showing cluster locations for every 1 kyr time-slice, (4) cluster and anticluster durations, and (5) the amounts of slip and slip-rates averaged over the duration of clusters and anticlusters. To study why this slip-rate variability has developed we conduct modelling of stress interactions between faults and underlying shear-zones, and between neighbouring fault/shear-zone structures. We show that the measured slip-rate variability and temporal clustering can be replicated by a model where the transfer of differential stress between faults and their underlying shearzones, and between neighbouring fault/shear-zone structures, produces changes in strain-rates on underlying viscous shear-zones which drive periods of rapid or reduced slip-rate on their overlying faults. We suggest that stress and hence strain-rate increase on an underlying shear-zone produced by coseismic slip on its overlying fault is the mechanism that initiates an earthquake cluster. Clusters progress because the increased strain-rate on the shear-zone reloads the overlying fault producing a positive feedback loop. The clusters also produce stress reduction on fault/shear-zones located across strike, initiating anticlusters in those locations. The durations of anticlusters will be set by the summed coseismic and interseismic stress changes through time, because although these shear-zones develop relatively low viscous strain-rates, eventually they will load their overlying fault to failure initiating a new cluster. These interactions cause the locations of clusters and anticlusters to migrate across and along-strike within the fault system. Such constraints on the processes producing clustering and anticlustering should allow observations of these phenomena to be included in probabilistic seismic hazard assessments (PSHA), and interpretations of the rheology of deforming continental crust.PublishedJCR Journa
Ionospheric tomography for SWARM satellite orbit determination using single-frequency GNSS data
No full textIonospheric tomography offers three-dimensional (3D) description of the electron density distribution, enabling the direct incorporation of electron density data into the slant total electron content (STEC) computation. As a result, STEC derived from tomography helps mitigate the ionospheric delay experienced in the line of sight between global navigation satellite systems (GNSS) and satellites positioned in low Earth orbits (LEO). Tomography can therefore be effectively employed to correct single-frequency GNSS observations and allow enhanced positioning of spaceborne platforms. We demonstrate the accuracy and performance of a global-scale ionospheric tomography method for determining satellite orbits, utilizing single-frequency GNSS measurements combined with a precise point positioning (PPP) algorithm. We compare the tomographic outcomes against orbit determination derived from the GRoup and PHase ionospheric correction (GRAPHIC) observable and based on an ionospheric climatological model. Near the peak of solar cycle 24, the overall accuracy achieved with tomography was around 3.8 m. notably, compared to the background climatological model, tomography demonstrated improvements ranging from 15 to 20%. The GRAPHIC method outperformed tomography, achieving an accuracy of 0.7 m, whereas we obtained around 7 m accuracy when no ionospheric model is employed. Although the developed ionospheric tomography has yet to match the precision of GRAPHIC, our results bring us relatively closer to this objective.Published26OSA3: Climatologia e meteorologia spazialeJCR Journa
HSIT system: Citizen Participation in Seismology for Data Collection and Enhanced Understanding of Earthquake Effects
No full textHai Sentito Il Terremoto (HSIT: Did You Feel the Earthquake?) is one of the longest-running citizen science projects on the web. Launched experimentally in 1996 and fully operational since 2007, HSIT has collected data on over 16,800 earthquakes felt in Italy through more than 1,500,000 questionnaires submitted by citizens. Of these, nearly 30,000 participants are registered with HSIT, ensuring continuous engagement across the national territory. The results of this collaboration are bidirectional: citizens contribute their experience of earthquake perception, forming a core dataset that provides localized information. In return, they receive real-time feedback on the earthquake's effects on their region, represented in macroseismic intensity using the Mercalli (MCS) and European (EMS) scales. This partnership enables seismologists to access high-resolution data for analyzing territorial responses to seismic events, including attenuation laws, identifying amplification and/or attenuation zones, and perception patterns based on urban characteristics and behavioral factors. Citizen involvement has expanded the scope of the investigation to include moderate-to-low magnitude earthquakes and distant areas affected by stronger quakes. Registered participants, in particular, gain awareness of earthquakes as ongoing, active phenomena, shifting from a perception of rare catastrophic events to a continuous focus on regional seismic risks. The HSIT project bridges the gap between scientific knowledge and common understanding, fostering a shared experience of living in earthquake-prone regions with awareness and respect for associated risks and preventive measures.Published1-20OS: Terza missioneOST4 Descrizione in tempo reale del terremoto, del maremoto, loro predicibilità e impattoN/A or not JC
The Qixiangzhan Lava Flow at the Tianchi Volcano: Eruptive Dynamics, Emplacement Mechanism and Implications for the Formation of Long‐lived Magmatic Systems Prior to Caldera‐forming Eruptions
No full textPublishedJCR Journa
Low-Frequency Ground Penetrating Radar for Active Fault Characterization: Insights from the Southern Apennines (Italy)
No full textGround Penetrating Radar (GPR) is a powerful tool for imaging shallow stratigraphic and structural features. This study shows that it is particularly effective also in detecting near-surface evidence of active faulting. In the Southern Apennines (Italy), one of the most seismically active regions of the Mediterranean area, the shallow expression of active faults is often poorly constrained due to limited or ambiguous surface evidence. Low-frequency GPR profiles were acquired in the Calore River Valley (Campania Region), an area historically affected by large earthquakes and characterized by debated seismogenic sources. The surveys employed multiple antenna frequencies (30, 60, and 80 MHz) and both horizontal and vertical acquisition geometries, enabling penetration depths ranging from ~5 m to ~50 m. The acquired GPR profiles, integrated with high-precision georeferencing, were able to reveal the presence of shallow steeply dipping active normal faults striking E–W to ENE–WSW, here named the Postiglione Fault System. Therefore, this study highlights the methodological potential of low-frequency GPR for investigating active faults in carbonate substratum and fine-to-coarse-grained sedimentary units and thus contributing to refining the seismotectonic framework and improving seismic hazard assessment of seismically active areas such as the Southern Apennines.PublishedJCR Journa
Dynamic management of uncertainty in rapid tsunami forecasting
No full textIssuing a tsunami warning rapidly is crucial to maximize the lead time for evacuation and other response actions. However, in the first minutes after an earthquake, no tsunami observations are available, and forecasts rely on rapid but uncertain estimates of earthquake location and magnitude. As more data become available, forecasts can be updated for more distant coastlines or near-source immediate post-event assessments. Here we present a method for real-time updating of Probabilistic Tsunami Forecasting that continuously integrates new seismic and tsunami observations. We apply it to the 2010 Mw8.8 Maule event and to several synthetic and real Mw 6.5-8.5 events in the Mediterranean Sea, demonstrating that it consistently preserves accuracy and generally reduces uncertainty, especially when using local tsunami data rather than focal mechanisms. Based on reweighting the initial scenario ensemble, this evolutionary approach enables fast updates and synchronization of forecast uncertainty with evolving information.PublishedOST2 Deformazione e Hazard sismico e da maremotoJCR Journa