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  • 1
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    A Reliable Procedure to Estimate the Rupture Propagation Directions from Source Directivity: The 2016–2018 Central Italy Seismic Sequence (2024)
    Seismological Society of America
    Details
    Publication Date: 2024-05-22
    Description: We present a new approach to estimate the predominant direction of rupture propagation during a seismic sequence. A fast estimation of the rupture propagation direction is essential to knowthe azimuthal distribution of shaking around the seismic source and the associated risks for the earthquake occurrence. The main advantage of the proposed method is that it is conceptually reliable, simple, and fast (near real time). The approach uses the empirical Green’s function technique and can be applied directly to the waveforms without requiring the deconvolution of the instrumental response and without knowing a priori the attenuation model and the orientation of the activated fault system. We apply the method to the 2016–2017 Amatrice-Visso-Norcia high-energy and long-lasting earthquake series in central Italy,which affected a large area up to 80 kmalong strike, withmore than 130,000 events of small-to-moderate magnitude recorded until the end of August 2022. Most of the selected events analyzed in this study have a magnitude greater than 4.4 and only four seismic events have a magnitude in the range of 3.3–3.7. Our results show that the complex activated normal fault system has a rupture direction mainly controlled by the pre-existing normal faults and by the orientation of the reactivated faults. In addition, the preferred direction of rupture propagation is also controlled by the presence of fluid in the pre-existing structural discontinuities. We discuss the possible role of fluids as a cause of bimaterial interface. Another important finding from our analysis is that the spatial evolution of seismicity is controlled by the directivity.
    Description: Published
    Description: 1912–1924
    Description: JCR Journal
    Keywords: directivity ; 04.06. Seismology
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 2
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    Editorial: Women in science: seismology 2022 (2024)
    Frontiers S.A.
    Details
    Publication Date: 2024-05-22
    Description: Seismology is the study of earthquakes and of the propagation of seismic waves within the Earth. Seismologists study the Earth’s—and other planets’ interiors; provide detailed information on the shallow subsurface composition, where they help find resources (e.g., oil, gas, and geothermal) or estimate the ground stability, an information that is nowadays widely used in building codes. Seismology is a relatively young science that profited enormously from the technological and computational improvements of the past 2 decades. The first analogue seismographs, weighing several tons, appeared in the late 19th century. It was not before the mid 20th century that seismometers were fully digital and of portable sizes, which resulted in much denser deployments and recordings and an explosion in research of various aspects of our Earth (Agnew, 1989; Shearer, 2019).
    Description: Published
    Description: 1328206
    Description: JCR Journal
    Keywords: 04.06. Seismology
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 3
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    Investigating Spectral Estimates of Stress Drop for Small to Moderate Earthquakes With Heterogeneous Slip Distribution: Examples From the 2016–2017 Amatrice Earthquake Sequence (2024)
    Wiley-Agu
    Details
    Publication Date: 2024-05-22
    Description: The stress release (or stress drop) during an earthquake is an important element of seismic hazard forecasting; high stress drop earthquakes radiate more high frequency energy, causing stronger ground shaking. The stress drop also provides information about the energy budget, and the size of fault ruptured, and consequently, earthquake triggering and rupture dynamics. Reliable estimates of stress release are difficult to make, largely because of the ambiguity in removing the distorting propagation effects experienced by waves traveling from earthquake to seismometer from recorded seismograms. Most measurements are made using frequency amplitude spectra. We use two methods to estimate earthquake stress drop for 30 of the larger earthquakes in central Italy (2016–2017) and compare them with the results of previous studies. We find that the variation between absolute values estimated in different studies is much larger than the reported formal inversion errors. The relative values are more reliable, with different studies consistently finding a particular earthquake has relatively high or low stress drop. Direct comparison of the similar-sized, damaging Amatrice and Visso earthquakes reveals that the relative spectral stress drop estimates reflect the relative strength of high-frequency ground motion, but may indicate more complex rupture rather than higher average stress release.
    Description: Estimates of spectral stress drop are fundamental to understanding the factors controlling earthquake rupture and high frequency ground motion, but are known to include large, poorly-constrained uncertainties. We use earthquakes from the 2016–2017 sequence in the Italian Appenines (largest event at Norcia, Mw 6.3) to investigate these uncertainties and their causes. The similarly-sized events near Amatrice (Mw 6.0) and Visso (Mw 5.9) enable better constrained relative analysis. We calculate S wave source spectra, corner frequencies, and spectral stress drop for 30 of the larger events. We compare both empirical and modeling approaches to isolate the source spectra and calculate source parameters; we also compare our results with those from published studies. Both random and systematic inter-study variations are larger than the standard errors reported by any individual study. The reported magnitude dependence of stress drop varies between studies, being largest for generalized inversions and smallest for more individual event based approaches. The relative spectral estimates of inter-event stress drop are more consistent; all approaches estimated higher stress drop in the Amatrice earthquake than the similar-sized Visso earthquake. In contrast, finite fault inversions of these two earthquakes found that the Visso earthquake had the larger region of concentrated, higher slip, whereas the Amatrice earthquake had multiple, lower slip, subevents. The Amatrice spectra contain more high frequency energy than those of the Visso earthquake. This comparison suggests that consistent measurement of a higher spectral stress drop indicates greater high-frequency ground motion but may correspond to greater rupture complexity rather than higher stress drop.
    Description: Published
    Description: e2022JB025022
    Description: OST2 Deformazione e Hazard sismico e da maremoto
    Description: JCR Journal
    Keywords: Stress Drop ; 04.06. Seismology
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 4
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    Comment on “A Seismic Moment Magnitude Scale” by Ranjit Das, Mukat Lal Sharma, Hans Raj Wason, Deepankar Choudhury, and Gabriel Gonzalez (2024)
    Seismological Society of America
    In:  Das, R., M. L. Sharma, H. R. Wason, D. Choudhury, and G. Gonzales (2019). A seismic moment magnitude scale, Bull Seismol. Soc. Am. 109, no. 4, 1542–1555, doi: 10.1785/0120180338.
    Details
    Publication Date: 2024-05-21
    Description: Moment magnitude Mw was first defined by Hiroo Kanamori in the late 1970s, when the availability of new force balance seismometers made it possible to measure the seismic moment M0 with virtually no limits in the frequency passband. For this reason, Mw does not become saturated even for the largest earthquakes ever recorded. Mw has been chosen in such a way that it coincides best with the previous definitions of magnitude (Ms, ML, mb, etc.) on certain ranges of values but can deviate significantly from them within other ranges. A few years ago, Das and colleagues proposed a new moment magnitude scale Mwg with the aim of better reproducing the values of mb and Ms over their entire range and to better predict the energy ES radiated by earthquakes. We show that there was no need to define such a new scale and that Mwg is not even optimal to achieve the goal of matching ES.
    Description: In press
    Description: OST2 Deformazione e Hazard sismico e da maremoto
    Description: JCR Journal
    Keywords: earthquake magnitude ; moment magnitude scale ; 04.06. Seismology
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 5
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    Comment on “Earthquake Magnitude Conversion Problem” by Ranjit Das, H. R. Wason, Gabriel Gonzalez, M. L. Sharma, Deepankar Choudhury, Conrad Lindholm, Narayan Roy, and Pablo Salazar (2024)
    Seismological Society of America
    In:  "Earthquake Magnitude Conversion Problem” by Ranjit Das, H. R. Wason, Gabriel Gonzalez, M. L. Sharma, Deepankar Choudhury, Conrad Lindholm, Narayan Roy, and Pablo Salazar
    Details
    Publication Date: 2024-05-21
    Description: Similar to the previous ones, the latest paper by Das and Colleagues (Das et al.,2018) on the application of the general orthogonal regression (GOR) method (Fuller, 1987; Castellaro et al.,2006), for the conversions between different types of earthquake magnitudes, is a collection of incorrect or undemonstrated assertions, most of which have already been pointed out in several contributions that have been published in the last few years (Gasperini and Lolli, 2014a, b; Gasperini et al., 2015, 2018; Pujol, 2018). We recall below only some of them. According to the recent seismological literature, we use here the term “GOR” to indicate the errors-in variable regression method described by Fuller (1987), even if such term is not fully in line with mathematical statistics as orthogonality is only given for equal errors of the dependent and independent variables.
    Description: Published
    Description: 1366-1369
    Description: OST2 Deformazione e Hazard sismico e da maremoto
    Description: JCR Journal
    Keywords: 04.06. Seismology
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 6
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    From ambient vibration data analysis to 1D ground-motion prediction of the Mj 5.9 and the Mj 6.5 Kumamoto earthquakes in the Kumamoto alluvial plain, Japan (2024)
    Springer-Nature
    Details
    Publication Date: 2024-05-21
    Description: We present horizontal ground motion predictions at a soft site in the Kumamoto alluvial plain for the Mj 5.9 and Mj 6.5 Kumamoto earthquakes of April 2016, in the framework of an international blind prediction exercise. Such predictions were obtained by leveraging all available information which included: (i) analysis of earthquake ground motions; (ii) processing of ambient vibration data (AMV); and (iii) 1D ground response analysis. Spectral analysis of earthquake ground-motion data were used to obtain empirical estimates of the prediction site amplification function, with evidence of an amplification peak at about 1.2 Hz. Horizontal-to-vertical spectral ratio analysis of AMV confirmed this resonance frequency and pointed out also a low-frequency resonance around 0.3 Hz at the prediction site. AMV were then processed by cross-correlation, modified spatial autocorrelation and high-resolution beamforming methods to retrieve the 1D shear-wave velocity (Vs) structure at the prediction site by joint inversion of surface-wave dispersion and ellipticity curves. The use of low frequency dispersion curve and ellipticity data allowed to retrieve a reference Vs profile down to few thousand meters depth which was then used to perform 1D equivalent-linear simulations of the M 5.9 event, and both equivalent-linear and nonlinear simulations of the M 6.5 event at the target site. Adopting quantitative goodness-of-fit metrics based on time–frequency representation of the signals, we obtained fair-to-good agreement between 1D predictions and observations for the Mj 6.5 earthquake and a poor agreement for the Mj 5.9 earthquake. In terms of acceleration response spectra, while ground-motion overpredictions were obtained for the Mj 5.9 event, simulated ground motions for the Mj 6.5 earthquake severely underestimate the observations, especially those obtained by the nonlinear approach.
    Description: stituto Nazionale di Geofisica e Vulcanologia (INGV), Rome, Italy.
    Description: Published
    Description: 105
    Description: OST4 Descrizione in tempo reale del terremoto, del maremoto, loro predicibilità e impatto
    Description: JCR Journal
    Keywords: 04.06. Seismology ; 04.02. Exploration geophysics
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 7
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    Giornata ONT 2023 - Proceedings Volume (2024)
    INGV
    Details
    Publication Date: 2024-05-16
    Description: The “Giornata ONT 2023” arises from the will to let know within INGV how many activities do people from the Osservatorio Nazionale Terremoti (ONT), and how strong is their contribution to the INGV missions: Research, Services, Education, Communication. In the nearly seven years of the current management the ONT has experienced a continuous evolutionary, sometimes complex, path. But it is always a straight path to pursue the objective of a continuous growth of the ONT. During these years the ONT has changed its name (from Centro Nazionale Terremoti – CNT, to ONT); it has experienced the coming out of some employees that moved to create the Irpinia new Section; it has lived the novelty of incoming people (example from the Centro Allerta Tsunami). It has also faced the need to overcome the limitations due to the worldwide pandemic emergency COVID19, either for the h24 services or for the research activities. Therefore in 2020 and 2021 we have only remotely attended the ONT days. The drive to be “in presenza” comes from this latter issue. We strongly want to meet, to talk face to face, to “Welcome” the young colleagues who are the injection of new ideas and perspectives, that are the necessary fuel to evolve the knowledge. As a matter of fact it emerges from the DNA of the ONT, i.e. the inclusiveness and the multidisciplinarity. This latter is widely testified by the ONT activities that are shared among the three Departments and their strategic objectives. The agenda of the “Giornata ONT 2023” has specifically emphasized the variety of the technical and scientific contents, that for sake of simplicity have been collected in the following themes: • Infrastructures, Data­Sharing and Laboratories • Analysis, Modelling, Interpretation of Geophysical Phenomena • National and International Projects (Research Results and Products from Completed Projects; Ongoing Projects) • Society ­ Communication, Dissemination, Emergency Management • Seismic Surveillance And Tsunami Warning Overall, the contributions have been 100, most of which are posters (77) and the remaining (23) in different exhibit formats. The wide interest about the proposed contents and the positive feedback from the attendance, pushed the decision to collect and publish the contributions in a Miscellanea INGV, where the documents can be easily found. And we are finally ready to make the Miscellanea available to the reader. I would warmly thank the Authors for their enthusiastic acceptance to contribute, the Conveners of the “Giornata ONT 2023” Sessions for their availability to organise and manage the submitted poster/exhibits, the Editorial Board members for their hidden work that led to this Miscellanea. In conclusion, let me spend a few words about my personal journey as Director of the ONT. After 2504 days it has come to an end and the “Giornata ONT 2023” and the Miscellanea are, somehow, the cherry on top. It is really difficult to say “Thanks” one by one to the people who helped me along this complex and long path. So, please, let me simply say Grazie a tutti voi! Salvatore Stramondo - Director ONT (2017-2023)
    Description: Published
    Description: 1-206
    Description: N/A or not JCR
    Keywords: Osservatorio Nazionale Terremoti ; GIORNATA ONT 2023 ; Research scientific and service ; 01.01. Atmosphere ; 04.06. Seismology ; 04.08. Volcanology ; 05.09. Miscellaneous ; ; Research scientific and
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 8
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    Vulnerability Assessment of Art Collections: The National Archaeological Museum “Gaio Cilnio Mecenate” in Arezzo (Italy) (2024)
    MDPI
    Details
    Publication Date: 2024-05-16
    Description: Artworks play a fundamental role in the cultural and economic assets of communities, enhancing their identity and helping with social integration. Despite their importance, they are not always adequately protected against degradation, which can be induced by aging, atmospheric and human-induced occurrences, and catastrophic events. Earthquakes certainly represent one of the main risks for art objects; however, traffic, construction works, and shipment can also represent a threat to art goods. Therefore, the assessment of the vulnerability of art collections to dynamic excitations plays a crucial role in their conservation, and it has been collecting increasing attention from researchers, academics, and museum managers. This work focuses on the vulnerability of the art collections exhibited at the “Gaio Cilnio Mecenate” museum in Arezzo. Namely, it aims to assess the effective dynamic loading experienced by the artworks, which is a function of the dynamic propagation played by the foundation soil, the building, and the displayers used for the exhibition. In this study, the dynamic properties of some of the displayers used for exhibiting the art collections are investigated by performing an experimental survey. The analysis of the experimental data led to the assessment of the proper frequencies of the displayers, which were compared to those of the building and the foundation soil of the museum.
    Description: Published
    Description: 2701
    Description: JCR Journal
    Keywords: art collections ; seismic vulnerability ; seismic safety assessment ; experimental dynamic monitoring ; 04.06. Seismology
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 9
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    Monitoring sources of volcanic activity at Mount Etna using pattern recognition techniques on infrasound signals (2024)
    Oxford University Press on behalf of the Royal Astronomical Society and the German Geophysical Society
    Details
    Publication Date: 2024-05-10
    Description: Infrasound monitoring plays an important role in the framework of the surveillance of Mt. Etna, Europe’s largest active volcano. Compared to seismic monitoring, which is particularly effective for buried sources, infrasound signals mirror the activity of shallow sources like Strombolian explosions or degassing. The interpretation of infrasound signals is difficult to the untrained eye, as we have to account for volcanic and non-volcanic sources. The problem of handling large and complex data sets can be tackled with machine learning, namely pattern recognition techniques. Here, we focus on so-called ‘Unsupervised Learning’, where we identify groups of patterns being similar to each other. The degree of similarity is based on a metric measuring the distance among the features of the patterns. This work aims at the identification of typical regimes of infrasound radiation and their relation to the state of volcanic activity at Mt. Etna. For this goal, we defined features describing any infrasound pattern. These features were obtained using wavelet transform. We applied ‘Self-Organizing Maps’ (SOM) to the features projecting them to a 2-D representation space—the ‘map’. An intriguing aspect of SOM resides in the fact that the position of the patterns on the map can be expressed by a colour code, in a manner that similar patterns are assigned a similar colour code. This simplified representation of multivariate patterns allows to follow the development of their characteristics with time efficiently. During a training phase we considered a reference data set, which encompassed a large variety of scenarios. We identified typical groups of patterns which correspond to a specific regime of activity, being representative of the state of the volcano or noise conditions. These groups form areas on the 2-D maps. In a second step, we considered a test data set, which was not used during the training phase. Applying the same pre-processing as for the training data, we blindly assigned the test patterns to the regimes found before, identifying the one whose colour code is most similar to the one calculated to the test pattern. We are thus able to assess the validity of the prediction. The classification scheme presented provides a reliable assessment of the state of activity and adds useful and supplementary details to the results of the real-time automatic system in operation at Istituto Nazionale di Geofisica e Vulcanologia—Osservarorio Etneo. This is of particular importance when no visible information of the volcanic activity is available either for unfavourable meteorological conditions or during night time.
    Description: IMPACT PROJECT (INGV Department strategic Projects - 2019)
    Description: Published
    Description: 1-16
    Description: JCR Journal
    Keywords: infrasound ; volcano monitoring ; self-organization ; time-series analysis ; machine learning ; volcanic hazards and risks ; 04.06. Seismology ; 04.08. Volcanology
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 10
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    Low-strength shear zone in the western Makran subduction zone, southeastern Iran: insights from a receiver function analysis (2024)
    Oxford University Press
    Details
    Publication Date: 2024-05-09
    Description: To understand the seismic hazard of a subduction zone, it is necessary to know the geometry, location and mechanical characteristics of the interplate boundary below which an oceanic plate is thrust downward. By considering the azimuthal dependence of converted P-to-S (Ps) amplitudes in receiver functions, we have detected the interplate boundary in the Makran subduction zone, revealing significant seismic anisotropy at the base of the accretionary wedge above the slab before it bends down beneath the Jaz Murian basin. This anisotropic feature aligns with a zone of reduced seismic velocity and a high primary/secondary wave velocity ratio (Vp/Vs), as documented in previous studies. The presence of this low-velocity highly anisotropic layer at the base of the accretionary wedge, likely representing a low-strength shear zone, could possibly explain the unusually wide accretionary wedge in Makran. Additionally, it may impact the location and width of the locked zone along the interplate boundary.
    Description: Iranian National Science Foundation (INSF)
    Description: Published
    Description: 64-74
    Description: OST1 Alla ricerca dei Motori Geodinamici
    Description: JCR Journal
    Keywords: Earthquake hazards, Seismic anisotropy, Crustal structure, Subduction zone processes ; 04.06. Seismology
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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