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Analysis and preliminary results of the Mw 4.9, Marradi seismic sequence (September 18th, 2023), in the northern Apennines, carried out by the BSI working group.
No full textOn September 18, 2023, an earthquake with a magnitude of Ml=4.8 (Mw=4.9) occurred a few kilometers SW of Marradi (FI) at a depth of about 8 kilometers. The computed TDMT solution of the mainshock suggests a normal fault oriented NW-SE (Scognamiglio et al., 2006).
The earthquake, preceded by a foreshock with a magnitude of Ml=3.3 (Mw=3.4), triggered a seismic sequence characterized, in the first two months, by approximately 700 aftershocks localized by the staff on duty in the Seismic Monitoring Room of the INGV in Rome, including 6 events with a magnitude of Ml≥3.0 occurred in the first two days.
The sequence occurred in a high seismic hazard region. The two closest historical earthquakes occurred in the Mugello area about 30 km SW of Marradi (and about 25 km north of Florence): one, whose magnitude (Mw) is estimated to be about 6.0, occurred on June 13, 1542 while the other with estimated magnitude (Mw) of about 6.4 occurred on June 29, 1919. The second one is among the strongest (most significant) Italian earthquakes of the 20th century, and also one of the strongest known to date with its epicentre in the northern Apennines. The affected area was that of Mugello, with extensive damage both in the province of Florence and on the Romagna side of the Apennines.
The analysts of the BSI (Italian Seismic Bulletin) reviewed the initial three days of the sequence, paying special attention to the hours directly following the mainshock. The BSI work mainly consists in revising the picking of P and S phases and assigning them appropriate weights, retrieving previously unused phases, and evaluating the maximum amplitudes necessary for calculating the value of Ml. The latter is a critical aspect of the initial phases of a seismic sequence; in fact, the occurrence of events is very close in time, making it challenging to estimate the maximum amplitudes and, consequently, the magnitude automatically. Through this analysis, they have identified an earthquake with a magnitude of Ml=3.4, occurring approximately one minute after the mainshock and overlooked during the surveillance service. Furthermore, a comprehensive effort to recover smaller seismic events not initially analyzed in the Seismic Monitoring Room resulted in the localization of 498 earthquakes, nearly a 30% increase within the first three days. In Figure 1(a-d), hypocentral parameters and time readings of the 352 earthquakes detected in the Seismic Monitoring Room have been compared with those of the same events revised by the BSI. It is evident as both the horizontal and vertical errors, as well the seismic gap associated with the location decrease for the dataset analyzed from the BSI, while the number of P and S phases increases for the same dataset. Subsequently, the events revised from BSI were initially relocated by applying the NonLinLoc code (Lomax et al., 2000) using a 1D regional velocity model from Pastori et al. (2019). Following this, a double-difference technique (Waldhauser and Schaff, 2008) was applied to improve the geometries of the activated structures (see Figure 2).
Concomitantly, an analysis using the template matching technique was applied, for the period from September first to October 10th, to identify events overlooked by the Earthworm system in the Seismic Monitoring Room. The results are shown in Figure 3. It was found that the number of detections increased by approximately 60%. Furthermore, the figures 3c and 3d put in evidence as the larger number of new detected earthquakes is characterized by lower magnitude. This result highlights the value of integrating this type of analysis to complement the efforts of the Italian Seismic Bulletin (BSI).PublishedFerrara, ItalyOST3 Vicino alla fagli
The importance of on-request reports for the correct assessment of low macroseismic intensities: the experience of “Hai Sentito Il Terremoto”
No full textThe lower degrees of the macroseismic scales are estimated mainly using the diagnostic related to the percentage of people who felt the earthquake (“felt” percentage). However, estimating this percentage by examining only a sub-sample of people may be biased, as those who complete the questionnaires are predominantly those who have felt the earthquake. One way to solve this problem is to send a specific request to them when an earthquake occurs. The ‘Hai Sentito il Terremoto’ (HSIT) site began implementing this strategy in December 2008 by allowing users to register on the website. Thanks to contributions from registered users, the HSIT database has been populated with “not felt” reports, which since 2009 have outnumbered the “felt” ones. The diagnostics of registered and unregistered users were analyzed separately in a sample of municipalities, showing no difference between the two types of users with the exception of “not felt” reports number. Despite the availability of the “not felt” reports, the experimental “felt” percentage is still overestimated when compared to those indicated in the Mercalli-Cancani-Sieberg scale. To refine the intensity calculation, the number of ‘not felt’ reports was multiplied by a correction factor, estimated at 6, to correctly use the ‘felt’ percentage. The macroseismic intensity and event magnitude do not affect this correction factor. By using both on-request reports and a correction factor it is possible to overcome the problem of underreporting “not felt” reports, more accurately estimate low intensities, and better define the “felt”-“not felt” boundary.In pressJCR Journa
Constraining Between-Event Variability of Kinematic Rupture Scenarios by Empirical Ground-Motion Model: A Case Study in Central Italy
No full textThe region of central Italy is well known for its moderate-to-large earthquakes. Events such
as 2016 Mw 6.2 Amatrice, generated in the shallow extensional tectonic regime, motivate
numerical simulations to gain insights into source-related ground-motion complexities. We
utilize a hybrid integral–composite kinematic rupture model by Gallovič and Brokešová
(2007) to predict ground motions for other hypothetical Amatrice fault rupture scenarios
(scenario events). The synthetic seismograms are computed in 1D crustal velocity models,
including region-specific 1D profiles for selected stations up to 10 Hz. We create more than
ten thousand rupture scenarios by varying source parameters. The resulting distributions of
synthetic spectral accelerations at periods 0.2–2 s agree with the empirical nonergodic
ground-motion model ofSgobbaetal.(2021)forcentral Italy in terms of the mean and total
variability. However, statistical mixed-effect analysis of the residuals indicates that the
between-eventvariability of the scenarios exceeds theempirical one significantly. We quan
tify the role ofsourcemodelparametersinthemodelinganddemonstratethepivotalroleof
theso-called stress parameterthatcontrols high-frequencyradiation. Weproposerestricting
thescenariovariability tokeepthebetween-eventvariabilitywithintheempiricalvalue.The
presented validation of the scenario variability can be generally utilized in scenario model
ing for more realistic physics-based seismic hazard assessment.Published2138–2150OST3 Vicino alla fagliaJCR Journa
A novel algorithm for seismic events multiplets search
No full textA common practice of seismology is to analyze earthquake occurrence in terms of events catalogues, with the aim to either find useful correlations between internal mechanisms under study and their outcome in the spatial/temporal series of the events or, more directly, to assess some statistical rules from observations. With this approach, catalogues are often searched for some recognizable patterns or behaviors: in this work we present a software tool created to reveal a particular kind of events sequences.
The idea follows from the concept of multiplets, a well known events pattern often found in seismic series. A multiplet is defined as a sequence of events, all near in space and time and exhibiting similar magnitudes. The amount of multiplets in seismic series is related, as it is for other clustering mechanisms, to underlying correlations in the physics of the events.
The software, built from scratch, scans seismic catalogues in search of events clustered as “multiplets”: this is done through the thorough application of comparison tests whose parameters thresholds are both user defined and semi-automated. The tool is however more “general” in the sense that by varying values of the filtering parameters it can reveal other kind of patterns too.
While we think that this tool can be thought as a general purpose space–time series analyzer, we have found it particularly useful when applied to the results of a seismic simulator with the purpose of assessing their adherence with the observed seismicity. It can be used as a sort of metric to quantify the simulation predictions effectiveness in terms of presence of similar multiplets distributions in simulated vs. real catalogues.
The software has been entirely developed in the Wolfram Language (Mathematica), a commercial powerful environment for scientific calculus and results report, but the main computational routine has been also ported to python for open-source, copyleft usage.Published105496OST5 Verso un nuovo MonitoraggioJCR Journa
Marine Geohazards of the Bay of Naples (Southern Tyrrhenian Sea, Italy): A Review Integrating Morpho-Bathymetric and Seismo-Stratigraphic Analysis
No full textMarine geohazards in the Bay of Naples, an eruptive region during the late Quaternary,
have been assessed based on both morpho-bathymetric and seismic data. Previously identified areas
of high marine hazard with slide potential (northern Ischia slope, Naples canyons, and Sorrento
Peninsula–Capri slope) have been confirmed and integrated through the seismo-stratigraphic analysis
of selected seismic sections. We evaluated the occurrence of important fossil submarine landslides
in the stratigraphic record. Several kinds of submarine landslides have been individuated through
morpho-bathymetric and seismic interpretation, including creeping, debris avalanches, and debris
flows, among others, often controlled by volcanic eruptions. Submarine landslides of Naples Bay
are primary geohazards in the marine and coastal areas, which has been ascertained with significant
volcanic and tsunami hazards involving the gulf. Despite previous studies on these topics, much
work is still needed to compile a systematic database of the submarine landslides of the Bay of Naples,
representing a future step of this research.Published393–414OSA4: Ambiente marino, fascia costiera ed Oceanografia operativaJCR Journa
The interaction between the SEIS seismometer of the InSight Martian mission and a regolith simulant
No full textA detailed investigation has been conducted of the interaction between a Martian regolith simulant and the foot of a seismometer (SEIS) recently deployed on the surface of Mars within the NASA InSight mission. A specific device used to investigate the SEIS/ground interaction was improved to provide accurate measurements of low forces and displacements, with a higher system stiffness and appropriate thermal insulation. A series of tests was carried out with a 60 mm dia. disc and the SEIS foot (disc with a spike at its centre). The maximum disc penetration in the loose sand used as simulant under the SEIS weight (10 N) was between 400 and 600 μm, with a tiny effect of the spike. Load cycles under various forces were performed to investigate the elastic interaction, with good reversibility and a linear change of the Young's modulus with respect to the average vertical stress. The tests provided comparable values, showing that the Young's modulus was around 20 MPa – which is compatible with that of loose terrestrial sands – and agreed well with the seismic wave velocities at the surface (from laboratory experiments and from measuring on the surface of Mars the travel times of waves received by the SEIS seismometer).Published42-53OST5 Verso un nuovo MonitoraggioJCR Journa
The ShakeMap Atlas of Historical Earthquakes in Italy: Configuration and Validation
No full textItaly has a long tradition of studies on the seismic history of the country and the neighboring areas. Several archives and databases dealing with historical earthquake data—primarily intensity data points—have been published and are constantly updated. Macroseismic fields of significant events are of foremost importance in assessing earthquake effects and for the evaluation of seismic hazards. Here, we adopt the U.S. Geological Survey (USGS)‐ShakeMap software to calculate the maps of strong ground shaking (shakemaps) of 79 historical earthquakes with magnitude ≥6 that have occurred in Italy between 1117 and 1968 C.E. We use the macroseismic data published in the Italian Macroseismic Database (DBMI15). The shakemaps have been determined using two different configurations. The first adopts the virtual intensity prediction equations approach (VIPE; i.e., a combination of ground‐motion models [GMMs] and ground‐motion intensity conversion equations [GMICEs]; Bindi, Pacor, et al., 2011; Oliveti et al., 2022b). The second exploits the intensity prediction equations (IPE; Pasolini, Albarello, et al., 2008; Lolli et al., 2019). The VIPE configuration has been found to provide more accurate results after appraisal through a cross‐validation analysis and has been applied for the generation of the ShakeMap Atlas. The resulting maps are published in the Istituto Nazionale di Geofisica e Vulcanologia (INGV) ShakeMap (see Data and Resources; Oliveti et al., 2023), and in the Italian Archive of Historical Earthquake Data (ASMI; see Data and Resources; Rovida et al., 2017) platforms.Published21–37OST2 Deformazione e Hazard sismico e da maremotoJCR Journa
A novel, continuous high-resolution palaeoecological record from central Italy suggests comparable land-use dynamics in Southern and Central Europe during the Neolithic
No full textAlthough rare, temporally and taxonomically highly-resolved palaeoecological studies with high chronological precision are essential to perform
detailed comparisons with precisely dated independent evidence such as archaeological findings, historical events, or palaeoclimatic data. Using a new
highly-resolved and chronologically precise sedimentary record from Lago di Mezzano (central Italy), we reconstruct decadal-scale vegetation, species
diversity, and fire dynamics, aiming to better understand the linkages between climate, land use, fire, and plant communities from the Neolithic to
the Copper Age (c. 5100–3100 cal. BC). Closed, mixed beech-oak forests, including evergreen Quercus ilex, dominated the landscape around Lago di
Mezzano during the Neolithic and were disturbed by repeated opening phases, with important implications for lake biogeochemistry and mixing regimes.
This was in conjunction with increasing fire activity to promote agro-pastoral practices, as inferred from increasing charcoal, Cerealia type, Triticum type,
Hordeum type, Plantago lanceolata type, and Urtica pollen. Fires, on their turn, augmented species diversity (richness and evenness). The comparison
of the Mediterranean record from Lago di Mezzano with available continuous and high-precision submediterranean and cool-temperate palynological
sequences suggests comparable land use pulses across Southern and Central European regions, most likely in connection with climate change. The
outcomes of this study are not only of palaeoecological and archaeological interest; they may also help to improve projections of ecosystem dynamics
under future global change.Published1009-1024OSA2: Evoluzione climatica: effetti e loro mitigazioneJCR Journa
New chronology for submerged relict paleoshorelines and associated rates of crustal vertical movements offshore the Marzamemi village, Sicily (Southern Italy)
No full textWe investigated the Late Pleistocene-Holocene crustal vertical movements off the coast of Marzamemi village in SE Sicily, Italy. By using a Synchronous Correlation Approach (SCA), we analysed terraced landforms that characterize a submerged sector within one of Southern Italy's most seismically active regions. In this area, the emerging portion of the NE-SW oriented bulge of the African foreland structurally shapes the coastal and marine regions off Marzamemi village.
Based on a newly created 17 km2 high-resolution bathymetric map generated from a Multibeam Echosounder (MBES) survey conducted in June 2021, we identified and examined four main paleo-shorelines identifying four submerged terraces. Terraced landforms play a crucial role in reconstructing Quaternary glacial and interglacial stages, offering insights into associated sea level fluctuations. Through the application of the SCA, our goal is to refine the chronology of these recently mapped and submerged marine terraces off the Marzamemi village, thereby contributing to the calculation of associated rates of crustal vertical movements. We demonstrate that these rates persist constantly throughout the Late Pleistocene-Holocene epoch, suggesting overall tectonic stability, with a slight and likely local fault-related subsidence. We explore a few chronology scenarios, raising questions about whether these submerged marine terraces are indeed recording the Late Pleistocene-Holocene limit or not. This research contributes to a better understanding of the geological dynamics in this region and sheds light on the potential factors influencing coastal landscape development over time.Published107326OST2 Deformazione e Hazard sismico e da maremotoJCR Journa
Editorial
No full textEditorial to Special issue Embracing the past, empowering the present, envisioning the future, 25th INGV AnniversaryDear AG Readers, It is with great pleasure and pride that I introduce to you this special volume of Annals of Geophysics titled “Embracing the past, empowering the present, and envisioning the future”. As Editor-in-Chief, I am thrilled to present a collection of articles that celebrates 25 years of INGV excellence, within the realm of geophysical disciplines. This volume showcases the outstanding contributions of our esteemed colleagues who have made themselves available to participate as authors in the compilation of this volume. Their participation is rooted in the numerous projects, collaborations, and cultural exchanges they have had over time with all the personnel of our Institute, which have allowed the advancement of knowledge in the various scientific disciplines covered. I extend my heartfelt gratitude to all authors, reviewers, and editorial board members whose dedication has made this milestone possible. Over the past 6 months we have worked hard to curate this special issue of Annals of Geophysics. I would like to acknowledge the generous help of A. Grazia Chiodetti, who has been consistently present in every stage of editing the papers, and not least Emanuela Bagnato, Felicia Corsale and M. Chiara Piazza in following up with the authors and compiling the papers into the special issue. Without their assistance, the production of this volume would have been significantly more difficult, if not impossible. I'd like to finally thank Enrico Rocchetti, Simone Vecchi and Barbara Angioni for helping us have a well-made and always up-to-date website. I would like to thank all the referees for their excellent work in reviewing the scientific papers in such a short time. I invite you to explore these pages and delve into the diverse insights and discoveries that define our field. May this volume inspire further exploration and collaboration in the years to come. Warm regards, Editor-in-ChiefINGVPublishedOS: Terza missioneJCR Journa