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Sound velocities and single-crystal elasticity of hydrous Fo90 olivine to 12 GPa
No full textNominally anhydrous minerals (NAMs) may contain significant amounts of water and constitute an important
reservoir for mantle hydrogen. The colloquial term ‘water’ in NAMs is related to the presence of hydroxyl-bearing
(OH ) point defects in their crystal structure, where hydrogen is bonded to lattice oxygen and is charge-balanced
by cation vacancies. This hydrous component may therefore have substantial effects on the thermoelastic parameters
of NAMs, comparable to other major crystal-chemical substitutions (e.g., Fe, Al). Assessment of water
concentrations in natural minerals from mantle xenoliths indicates that olivine commonly stores ~0–200 ppm of
water. However, the lack of samples originating from depths exceeding ~250 km coupled with the rapid
diffusion of hydrogen in olivine at magmatic temperatures makes the determination of the olivine water content
in the upper mantle challenging. On the other hand, numerous experimental data show that, at pressures and
temperatures corresponding to deep upper mantle conditions, the water storage capacity of olivine increases to
0.2–0.5 wt%. Therefore, determining the elastic properties of olivine samples with more realistic water contents
for deep upper mantle conditions may help in interpreting both seismic velocity anomalies in potentially hydrous
regions of Earth’s mantle as well as the observed seismic velocity and density contrasts across the 410-km
discontinuity.
Here, we report simultaneous single-crystal X-ray diffraction and Brillouin scattering experiments at room
temperature up to 11.96(2) GPa on hydrous [0.20(3) wt% H2O] Fo90 olivine to assess its full elastic tensor, and
complement these results with a careful re-analysis of all the available single-crystal elasticity data from the
literature for anhydrous Fo90 olivine. While the bulk (K) and shear (G) moduli of hydrous Fo90 olivine are
virtually identical to those of the corresponding anhydrous phase, their pressure derivatives K′ and G′ are slightly
larger, although consistent within mutual uncertainties. We then defined linear relations between the water
concentration in Fo90 olivine, the elastic moduli and their pressure derivatives, which were then used to
compute the sound velocities of Fo90 olivine with higher degrees of hydration. Even for water concentrations as
high as 0.5 wt%, the sound wave velocities of hydrous and anhydrous olivines were found to be identical within
uncertainties at pressures corresponding to the base of the upper mantle. Contrary to previous claims, our data
suggest that water in olivine is not seismically detectable, at least for contents consistent with deep upper mantle
conditions. In addition to that, our data reveal that the hydration of olivine is unlikely to be a key factor in
reconciling seismic velocity and density contrasts across the 410-km discontinuity with a pyrolitic mantle.Published107011JCR Journa
Magma reservoir growth and ground deformation preceding the 79 CE Plinian eruption of Vesuvius
No full textThe 79 CE eruption of Vesuvius is the first documented Plinian eruption, also famous for the
archaeological ruins of Pompeii and Herculaneum. Although much is known regarding the
eruption dynamics and magma reservoir, little is known about the reservoir shape and
growth, and related ground deformation. Numerical modelling by Finite Element Method was
carried out, aimed at simulating the reservoir growth and ground deformation with respect to
the reservoir shape (prolate, spherical, oblate) and magma overpressure. The modelling was
tuned with volcanological, petrological and paleoenvironmental ground deformation con straints. Results indicate that the highest magma overpressure is achieved considering a
prolate reservoir, making it as the most likely shape that led to eruption. Similar deformations
but lower overpressures are obtained considering spherical and oblate reservoirs. These
results demonstrate that ground deformation may not be indicative of eruption probability,
style/size, and this has direct implications on surveillance at active explosive volcanoesPublished2112V. Struttura e sistema di alimentazione dei vulcani4V. Processi pre-eruttiviJCR Journa
Sacred plant impressions from Somma-Vesuvius volcanic ash deposits: A medicinal garden in Late Antique Acerra (Naples, Campania, Italy)?
No full textThe AD 472 eruption of Somma-Vesuvius widely impacted the northern and eastern territory around the volcano, laying down a complex sequence of pyroclastic fallout and pyroclastic current deposits. During archaeological test excavations conducted in the Acerra locality, Pollena eruption (AD 472) fallout and lahar deposits composed of fine ash containing traces of plant impressions were found. These deposits were sampled and carefully frac tured in order to recover the plant imprints. Features of the ash impressions were compared with those of live plants and dried Herbarium specimens. Species identification was based on the characteristics of leaves (maximum width, type of leaf margin, size of midrib, angle of formation of the secondary veins) and fruits. Impressions of Mandragora officinarum L., Rosa canina L. and Hedera helix L. were recognized. This is the first documented discovery of subfossil mandrake specimens. The use of mandrake plants for healing and psycho tropic purposes is referred to by Classical authors such as Pliny the Elder and Dioscorides; it was sometimes used mixed with rose. In addition, rose and ivy plants were symbolically important to the ancient Romans and were employed together as medicinal plants. The coexistence of these plants in a restricted area suggests the presence of a garden dedicated to sacred/medicinal plants. In addition, it is interesting to note that the discovery of mandrake plants with fruits supports the hypothesis that the eruptive event took place between the end of summer and the autumn.Published1038025V. Processi eruttivi e post-eruttivi6V. Pericolosità vulcanica e contributi alla stima del rischioJCR Journa
ANALYSIS OF 20-YEAR TERRESTRIAL GRAVITY AND GROUND DEFORMATION CHANGES COLLECTED AT MT. ETNA: COMPARISON WITH SATELLITE DATA
No full textWe present a preliminary comparison between satellite and terrestrial gravity and GNSS data collected in a twenty-year period (2002-2022) at Mt. Etna volcano, with the aim of investigating the capabilities of this integrated approach to study the dynamics of volcanic phenomena over time-scales of months to years.
The terrestrial gravity data were collected through absolute and relative spring gravimeters in the framework of almost monthly campaigns. Instead, GNSS measurements are continuously collected for monitoring purposes.
Regarding satellite data, we used the Gravity Recovery and Climate Experiment (GRACE) data and GRACE Follow-On L3 solutions, that can provide high-quality information about mass distribution at regional and global scales in a long-term interval.
After being corrected for the known effects, reduced terrestrial gravity and GNSS height variations were compared with satellite data. The comparison reveals long-term correlations between the analyzed time series which could represent volcano-scale variations.PublishedBerlin, Germany7A. Geofisica per il monitoraggio ambiental
Towards a monitoring system of the sea state based on microseism and machine learning
No full textIn this work, we exploited the ubiquitous seismic noise generated by energy transfer from the sea to the solid
Earth (called microseism) to infer the significant wave height data, with the aim of developing a microseismbased
monitoring system of the Sicily Channel. We used a combined approach based on statistical analysis
and machine learning by using seismic and sea state data (provided by the hindcast maps), recorded between
2018 and 2021.Through spectral and amplitude analysis, we observed that microseism was influenced by the
conditions of the seas surrounding Sicily. Correlation analysis demonstrates that microseism mostly originates
from sources located up to 400 km from the coastlines. Moreover, employing machine learning algorithms, we
successfully reconstruct spatial and temporal sea wave distributions using microseism data. Among the tested
methods, the Random Forest algorithm yields the best results, with an R2 value of 0.89 and a mean prediction
error of about 0.21 m.Published1057814A. Oceanografia e climaJCR Journa
Mapping and chronological classification of marine terraces along the southern side of the Sibari Plain (northern Calabria, Italy) by means of digital and analogue tools
No full textWe study the marine terraces of the southern side of the Sibari Plain in Northern Calabria (Italy)
through the use of traditional and quantitative analyses of the Digital Terrain Model (DTM). The
main aim of the present work consists in the extensive use of GIS tools that were never used
before in the area, and in checking the applicability of this procedure. The terraced surfaces
identified using photo interpretation and those recognized semi-automatically through the
GIS tools were compared to finally produce a consensus map. In the final map, we identified
272 terraced surfaces and 62 morphological features associated with inner margins (i.e.
paleoshorelines). The main map shows a well-developed flight of seven orders of marine
terraces with elevation ranging from 45 to 360 m asl and age ranging from Marine Isotope
Stage (MIS) 5a to 11.Published2243983OST3 Vicino alla fagliaJCR Journa
Kahramanmaraş - Gaziantep Türkiye M7.7 Earthquake, 6 February 2023 (04:17 GMT+03:00) Large historical earthquakes of the earthquake-affected region: a preliminary report
No full textThe region where the 2023 February 6 earthquakes took place is known to have been very active in the past; it is part of the contact between the Eurasian and the Arabic plate, an area where seismic activity was relatively low in the 20th century (Figure 1). It is a “border zone” also from the historical point of view; therefore, although many earthquakes are known to most earthquake catalogues and compilations, the relevant information is often rather poor and affected by chronological and place-names problems. As a consequence, earthquake parameters given in the catalogues are often based on a poor dataset; the situation is even more complicated by chronological issues and careless compilations, which lead to earthquake duplications.
In the frame of a larger investigation effort underway (Sesetyan et al., 2020; Stucchi et al. 2022) we first considered the available information from the main earthquake catalogues and compilations in the time-window 1000-1900. The volume by Ambraseys (2009) summarizes and sometimes updates the knowledge already proposed in previous works such as Ambraseys and Jackson (1988), Ambraseys (1989), Ambraseys and Finkel (1995). We also considered the works by Soysal et al. (1981), Guidoboni et al. (2019), Sbeinati et al. (2005), some recent historical earthquake investigations and the parametric catalogues by Shebalin and Tatevossian (1997), Tan et al. (2008), Sesetyan et al. (2013). Next, we assessed - when possible - macroseismic intensities at the mentioned localities and, from them, we assessed earthquake parameters by making use of the so-called “Boxer” method by Gasperini et al. (1999).
For some of the main earthquakes in the region we briefly summarise here the earthquake parameters from our investigation and from the main catalogues. In the Appendix we summarise the available information.Boğaziçi University Kandilli Observatory and Earthquake Research Institute Department of Earthquake Engineering, Istanbul (Turkey)
Istituto Nazionale di Geofisica e Vulcanologia, ItaliaPublished3T. Fisica dei terremoti e Sorgente Sismic
Volcanic Clouds Characterization of the 2020–2022 Sequence of Mt. Etna Lava Fountains Using MSG-SEVIRI and Products’ Cross-Comparison
No full textFrom December 2020 to February 2022, 66 lava fountains (LF) occurred at Etna volcano (Italy). Despite their short duration (an average of about two hours), they produced a strong impact on human life, environment, and air traffic. In this work, the measurements collected from the Spinning Enhanced Visible and InfraRed Imager (SEVIRI) instrument, on board Meteosat Second Generation (MSG) geostationary satellite, are processed every 15 min to characterize the volcanic clouds produced during the activities. In particular, a quantitative estimation of volcanic cloud top height (VCTH) and ash/ice/SO2 masses’ time series are obtained. VCTHs are computed by integrating three different retrieval approaches based on coldest pixel detection, plume tracking, and HYSPLIT models, while particles and gas retrievals are realized simultaneously by exploiting the Volcanic Plume Retrieval (VPR) real-time procedure. The discrimination between ashy and icy pixels is carried out by applying the Brightness Temperature Difference (BTD) method with thresholds obtained by making specific Radiative Transfer Model simulations. Results indicate a VCTH variation during the entire period between 4 and 13 km, while the SO2, ash, and ice total masses reach maximum values of about 50, 100, and 300 Gg, respectively. The cumulative ash, ice, and SO2 emitted from all the 2020–2022 LFs in the atmosphere are about 750, 2300, and 670 Gg, respectively. All the retrievals indicate that the overall activity can be grouped into 3 main periods in which it passes from high (December 2020 to March 2021), low (March to June 2021), and medium/high (June 2021 to February 2022). The different products have been validated by using TROPOspheric Monitoring Instrument (TROPOMI) polar satellite sensor, Volcano Observatory Notices for Aviation (VONA) bulletins, and by processing the SEVIRI data considering a different and more accurate retrieval approach. The products’ cross-comparison shows a generally good agreement, except for the SO2 total mass in case of high ash/ice content in the volcanic cloud.Published20555V. Processi eruttivi e post-eruttiviJCR Journa
Voices of Foreign Residents in Yokohama and Tokyo at the Time of the 1923 Kanto Earthquake
No full textWhen the Kanto earthquake struck on Saturday the 1st of September 1923 at a few minutes to noon, the foreign residents from western countries in the harbour city of Yokohama reached 2,500, and a similar presence was in Tokyo, which as the capital hosted the officers of embassies, consulates, and trade companies. These foreign residents left impressive records of the earthquake occurrence, as well as the fire that started immediately after. To add a different viewpoint to the overall understanding of this earthquake disaster, we concentrated on the considerable quantity of documents now stored at the National Archives (Kew Gardens, UK) and at the Affaires Etrangéres-Archives diplomatiques (La Courneuve, France). These documents were produced by British and French diplomats and naval commanders as well as foreign residents of different nationalities who were in Yokohama and Tokyo at the time of the earthquake. The immediacy of the descriptions they contain and the details they supply about the earthquake, the fire, and the rescue and relief actions bring us back to the shaking and shocking moments experienced by the people living in Yokohama and Tokyo one hundred years ago.Published598-610OST2 Deformazione e Hazard sismico e da maremotoJCR Journa
Improving the quality of the seismic catalogue by updating outdated or preliminary reference studies: case histories
No full textThe Parametric Catalogue of Italian Earthquakes CPTI15 [Rovida et al., 2022] includes 241 earthquakes whose epicentral parameters are based on studies marked AMGNDT95 [Archivio Macrosismico GNDT, 1995]. These are preliminary (or, in some cases, extremely basic) studies, that were carried out in the early 1990s by the GNDT/CNR (Gruppo Nazionale per la Difesa dai Terremoti of the Consiglio Nazionale delle Ricerche of Italy) in the frame of the “Hazard Project”, whose aim was making available the basic data required for preparing an updated hazard model, as quickly as possible and in the form of a parametric catalogue.
Those AMGNDT95 studies that we define as “preliminary” derived the epicentral parameters of each studied earthquake from a data base reconstructed starting from the bibliographic references of the PFG catalogue [Postpischl, 1985] and going back, wherever possible to their original sources, according to a procedure called “Analysis Through Catalogues” [Stucchi, 1993]. The AMGNDT95 studies that we define as ‘extremely basic’, limited themselves to parameterizing the information provided by the bibliographic references of the PFG catalogue, i.e. in most cases the Baratta [1901] earthquake compilation or the seismological bulletins of the 19th-20th centuries.
The AMGNDT95 studies remained unpublished and on paper only until the year 2017, when they were digitized within the framework of Annex B2 of the DPC-INGV 2016-2017 Convention, and made public via the ASMI platform [Rovida et al., 2017].
In the framework of the following triennial DPC-INGV Convention, an operation was then launched to update AMGNDT95 studies with revision priorities established according to the relevance of each earthquakes and to the potential margins for improving knowledge on each of them. As the operation was under way, the revision was extended to another 8 damaging earthquakes whose parameters in the CPTI15 catalogue were derived straight from the PFG catalogue. These earthquakes had never been studied and macroseismic data were lacking for them. The CPTI15 catalogue includes several hundred records derived directly from other parametric catalogues. In most cases they are related to earthquakes outside the national borders and their parameters are taken from the seismic catalogues of neighbouring countries (Switzerland, Austria, Slovenia, and Croatia). Only 56 of them are original records derived from the PFG catalogue [Postpischl, 1985] and mainly related to instrumental aftershocks of Italian earthquakes of the first decades of the 20th century. The 8 earthquakes mentioned above can be classified, on the contrary, as major events that had never been studied probably because the extreme poverty of the available source information made it difficult to improve in the short time allotted within the “Hazard Project” frame.
A first selection of studies, related to earthquakes occurred in the 1949-1971 time window, was the subject of a communication at the 40th GNGTS conference in 2022 and was recently published [Bernardini et al., 2022]. Here we continue the presentation and discussion of the results of our work, taking into account a wider selection of AMGNDT95 studies related to earthquakes occurred from the 14th to the 20th century. These earthquakes belong to a very numerous category in the CPTI15 catalogue, i.e. they are damaging earthquake of moderate energy, with a very narrow base of data, often reduced to 1 or 2 intensity data only. The problem of the consistency of the information base from which to derive the epicentral parameters of earthquakes is very serious in the CPTI catalogue, which is nevertheless the result of an enormous amount of work carried out during more than thirty years of research. For instance, the current version of the catalogue, includes as many as 65 earthquakes with Mw≥ 5.5 (‘strong earthquakes’) that are documented by less than 11 intensity data points each ((or even, in about 20 cases, one intensity data point only). In the energy class Mw≥ 4.5, there are no less than 221 earthquakes documented by a single intensity data point only. For this reason, it is both necessary and important to improve the quality of the catalogue by producing new and better quality studies of the moderate-energy earthquakes.
The results of the work are not all equally satisfactory. Overall, the revision has improved both the consistency of the intensity data that can be used to calculate epicentral parameters, and the individual intensity estimates, thanks to the availability of original sources and testimonies that allow to considerably refine the previous assessments, based as they were on second-hand seismological compilations only.
Among the most significant results we include the exclusion from the catalogue of some earthquakes that turned out to be non-existent. One of them is the alleged Ischia earthquake of 1767, that was demonstrated to be a forgery generated by a 19th century local history which attributed the collapse of a small church to an earthquake, citing as its source an epigraph that does not mention any earthquake at all. The information of the local historian had been accepted ‘on trust’ by 19th century seismological compilations, and for this reason the news of this non-existent earthquake did continue to circulate - resurfacing even in recent scientific assessments and elaborations produced after the Ischian event of 21 August 2017. Now, a careful critical analysis has led to its recognition as a fake earthquake.
Last but not least, it is important to know that our revision allows public and free access to all the information retrieved for each of the studied earthquakes. All available records of macroseismic effects that were retrieved during the study were transcribed and made available to the public through the Archivio Storico Macrosismico Italiano web platform [Rovida et al., 2017]. In this way, anyone wishing to take on the study of single earthquakes or groups of earthquakes will be able to start from a base of data organized in a homogeneous and transparent manner.PublishedBolognaOST1 Alla ricerca dei Motori Geodinamic