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Fast Ice Thickness Distribution in the Western Ross Sea in Late Spring
No full textWe present a 700 km airborne electromagnetic survey of late-spring fast ice and sub-ice platelet
layer (SIPL) thickness distributions from McMurdo Sound to Cape Adare, providing a first-time inventory
of fast ice thickness close to its annual maximum. The overall mode of the consolidated ice (including snow)
thickness was 1.9 m, less than its mean of 2.6 ± 1.0 m. Our survey was partitioned into level and rough ice,
and SIPL thickness was estimated under level ice. Although level ice, with a mode of 2.0 m and mean of
2.0 ± 0.6 m, was prevalent, rough ice occupied 41% of the transect by length, 50% by volume, and had a
mode of 3.3 m and mean of 3.2 ± 1.2 m. The thickest 10% of rough ice was almost 6 m on average, inclusive
of a 2 km segment thicker than 8 m in Moubray Bay. The thickest ice occurred predominantly along the
northwestern Ross Sea, due to compaction against the coast. The adjacent pack ice was thinner (by ∼1 m)
than the first-year fast ice. In Silverfish Bay, offshore Hells Gate Ice Shelf, New Harbor, and Granite Harbor,
the SIPL transect volume was a significant fraction (0.30) of the consolidated ice volume. The thickest 10%
of SIPLs averaged nearly 3 m thick, and near Hells Gate Ice Shelf the SIPL was almost 10 m thick, implying
vigorous heat loss to the ocean (∼90 W m −2). We conclude that polynya-induced ice deformation and
interaction with continental ice influence fast ice thickness in the western Ross Sea.Publishede2022JC019459OSA2: Evoluzione climatica: effetti e loro mitigazioneJCR Journa
Spectral and norm estimates for matrix-sequences arising from a finite difference approximation of elliptic operators
No full textWhen approximating elliptic problems by using specialized approximation techniques, we obtain large structured matrices whose analysis provides information on the stability of the method. Here we provide spectral and norm estimates for matrix-sequences arising from the approximation of the Laplacian via ad hoc finite differences. The analysis involves several tools from matrix theory and in particular from the setting of Toeplitz operators and Generalized Locally Toeplitz matrix-sequences. Several numerical experiments are conducted, which confirm the correctness of the theoretical findings.Published10-43JCR Journa
Determination of the oxidation state of primary melts using two proxies
No full textAlthough many studies have demonstrated that arc magmas are more oxidized than mid-ocean ridge (MORB) and oceanic island basalts (OIB), the oxidation state of their mantle source is still debated. This ongoing debate is mainly due to contradictory fO2 values obtained from different proxies (e.g., Fe3+/ΣFe of olivine-hosted melt inclusions and glasses; Zn/ΣFe, V/Sc, V/Ga of lavas). On the one hand, some studies using V/Sc, V/Ga and Zn/ ΣFe of lavas tend to show that the oxidation state of the mantle beneath arcs cannot be distinguished from that of the MORB mantle. On the other, Fe3+/ΣFe of glasses and olivine-hosted melt inclusions suggest that the sub-arc mantle is more oxidized than the mantle beneath ridges. Here, we estimate the oxygen fugacity of high-Mg olivine-hosted melt inclusions from various mid-ocean ridges and arcs, from one hot spot (Reunion Island) and Mount Etna using two fO2 proxies: the Fe3+/ΣFe of melts and the partition coefficient of V between olivine and melt (Dv
Ol/Melt). After assessing the role of secondary processes such as volatile degassing and fractional
crystallization on the fO2 of melts and reconstructing primary melt compositions, we show that (1) fO2 values derived from Fe3+/ΣFe and Dv
Ol/Melt are comparable and (2) arc and Mount Etna primary melts are more oxidized
than mid-ocean ridge and Reunion Island primary melts. We then demonstrate, from Zr/Nb, that the observed variability in primary melt fO2 is not due to chemical variability of the mantle source. Finally, the correlations between incompatible trace element ratios such as Th/La, Ba/La, Ba/Th and La/Yb and the fO2 of primary melts reveal a link between the oxidized nature of arc and Mount Etna primary magmas to slab fluid and/or sediment melt influence. Our arc dataset displays a variety of subduction influences, from fluid-dominated (Aoba and Mount Meager) to sediment melt-dominated (La Sommata) influences. The origin of the oxidation of Mount Etna magmas is more complicated to identify and the nature of the oxidized metasomatic fluids that likely percolated through the mantle source before magma generation is yet to be determined.
1.Published121701OSV2: Complessità dei processi vulcanici: approcci multidisciplinari e multiparametriciJCR Journa
Investigating Spectral Estimates of Stress Drop for Small to Moderate Earthquakes With Heterogeneous Slip Distribution: Examples From the 2016–2017 Amatrice Earthquake Sequence
No full textThe 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.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.Publishede2022JB025022OST2 Deformazione e Hazard sismico e da maremotoJCR Journa
What we can say (or not) about the seismic sequence of the November 9th 2022, Mw 5.5, earthquake in the Marche offshore: an analysis of the Italian Seismic Bulletin on phase interpretation, velocity models and uncertainties of earthquake locations
No full textIntroduction
In November 2022 a seismic sequence occurred in the Marche offshore, about 29 km from the coast and the city of Fano. The sequence started on November 9 (06:07:25 UTC) with a ML=5.7 earthquake (Mw=5.5 from TDMD computation, Scognamiglio et al., 2006), immediately followed by a ML=5.2 earthquake (06:08:29 UTC) located about 8 km to the south. The two mainshocks activated a seismic sequence with about 400 aftershocks lasting the first week, 13 of them with ML>= 3.5 (Fig. 1).
Few hours after the occurrence of the mainshock, the BSI (“Bollettino Sismico Italiano”) working group started to manually analyze P and S phase arrival times and seismogram amplitudes of earthquakes with magnitude ML>= 3.5 recorded by the the Italian National Seismic Network (Rete Sismica Nazionale, hereafter RSN) in order to better constrain hypocenter locations previously provided by the seismic surveillance room of the INGV in Rome for rapid communication to the Italian Civil Protection (Dipartimento Protezione Civile, DPC). Later, the BSI working group analyzed the seismicity of the sequence of the first weeks of seismic activity by revising hypocentral parameters of more than 500 events.
The 2022 Marche offshore sequence took place along the Adriatic outer front of the northern Apennines in central Italy. Offshore seismic reflection profiles image a shallow thrust-and-fold system striking WNW–ESE to NNW–SSE. Along the coastal Adriatic area, active blind thrusts deform Plio-Quaternary siliciclastic turbidites that are few hundreds of meters to more than 2 km thick in correspondence of ramp anticlines and synclines, respectively. In a recent work, through the analysis of high-quality background seismicity data, De Nardis et al. (2022) identified two lithospheric-scale active thrusts deepening westward under the Adriatic outer front from upper- to lower-crustal depths. These new data support previous thick-skinned interpretations of seismic commercial profiles and CROP03 deep reflection data (Lavecchia et al., 2003). Focal mechanisms of weak to moderate (ML < 4.8) local earthquakes occurred between 2009-2017 at upper- to deep-crustal depths show prevailing reverse and reverse/oblique solutions (De Nardis et al., 2022) and subordinate strike-slip faulting (Mazzoli et al., 2014).
The analysis of the 2022 Marche offshore sequence opens again the discussion on the uncertainties related to the hypocenter locations of earthquakes that occur in the Adriatic offshore domain (e.g., Di Stefano et al., 2022) and the limits of our present capability to provide an accurate seismotectonic interpretation of the instrumental seismicity in this region. Actually, the 2022 sequence area is only covered on land by RSN, with the closest seismic station located at about 28 km from the epicentral location of the mainshock. The particular geometry of the network along the Italian coast makes it difficult to correctly constrain hypocenter locations compared with other regions of Italy. Taking into account this configuration, although the INGV is able to obtain coherent earthquake information for Civil Protection purposes into the limits of the communication threshold, we note that data provided by the seismic surveillance room in terms of both seismic phase readings of arrival times for hypocenter location and waveform amplitudes for magnitude computation need to a more accurate analysis if the main goal is the correct reconstruction of the active structures involved in the sequence. This analysis should include a) a careful revision of the arrival time pickings to reduce the errors due to seismic phase misinterpretations, b) an accurate study to constrain earthquake locations with appropriate velocity models, and c) the hypocenter solution assessment through adequate tests that define which information can be inferred from earthquake location results.
Data analysis and phases interpretation
Through the interpretation of the seismic records, the BSI analysts have identified refracted first arrivals of P and S phases at epicentral distances of about 60 km, smaller than those expected for Pn/Sn refracted phases at the Moho discontinuity (e.g., Di Stefano and Ciaccio, 2014) whose arrivals should be observed at distances of about 90-100 km in this area. Since possible systematic misinterpretation of P and S arrivals can strongly affect the correct hypocenter locations, we have carefully revised the phase pickings provided by the INGV surveillance room by discriminating direct from refracted phases at stations located at distances greater than 60 km. This is mainly important for interpretation of weak S refracted phases that are often hidden into the arrivals after the P phase. We have taken into account these characteristics in the earthquake location process by only using clear direct/refracted S phases in our inversion procedure. The comparison of the ML>= 3.5 hypocenter locations performed by the BSI and the INGV surveillance room (Figs. 1 and 2) shows how an accurate analysis of the pickings is necessary to obtain robust earthquake locations for seismotectonic interpretation: even using the same hypocenter location code and velocity model, we observe that the mislocation of the hypocenters in this area can range from few to about 10 kilometers (Fig. 1) while the formal errors are strongly reduced after the BSI picking revision (Fig. 2)
The velocity model issue
Events location in the Adriatic Sea suffers from the lack of a specific velocity model for the seismic sequence area. The use of inadequate velocity parameters during the location process can introduce systematic errors, which may result in incorrect seismotectonic interpretations. We therefore built and tested different velocity models from both available geophysical data and our inversion of the velocity structure using the arrival time readings revised by the BSI working group.
In order to define deterministic 1D models suitable for earthquake location (Vp and Vp/Vs), we integrated sonic logs from local deep wells (ViDEPI Project, 2005) with literature data that include: seismic commercial profiles, deep seismic refraction surveys, the CROP03 crustal profile, Receiver Function and regional seismic tomography models, Vp/Vs reference values for mid- and lower-crustal crystalline rocks (Coward et al., 1999; Ponziani et al., 1995; Lavecchia et al., 2003; Spada et al., 2013; Di Stefano et al., 2009, Christiansen and Mooney, 1993).
In order to obtain the velocity structure from our revised dataset, we first determined the Vp/Vs ratio by using the arrival time pickings of selected P and S phases. The mean velocity ratio Vp/Vs was computed through the cumulative Wadati diagram. Then, by collecting all the a priori available information regarding the structure of Adriatic Sea (velocities, layer thicknesses and Moho depth), we applied the VELEST software (Kissling, 1995) to compute a new 1D velocity model for earthquake location.
Conclusions
In this work we present our first analyses of the sequence and the accurate study of the velocity models that we obtained from both a revision of available data and the inversion of arrival time pickings analyzed by the BSI analists. Moreover, we will discuss our preliminary earthquake locations with a particular attention to resolution analysis and hypocenter location assessment.PublishedBologna, Italy4T. Sismicità dell'Itali
Aerosol absorption using in situ filter-based photometers and ground-based sun photometry in the Po Valley urban atmosphere
No full textLight-absorbing aerosols (LAAs) are short-lived climate forcers with a significant impact on Earth's radiative balance. LAAs include dust aerosols, black carbon (BC) and organic light-absorbing carbonaceous aerosol (collectively termed brown carbon, BrC), which have also been proven to be highly toxic. In this study, aerosol absorption at five wavelengths (ranging from ultraviolet to infrared) was monitored continuously using filter-based photometers during two winter seasons in 2020 and 2021 in the city of Modena (southern central Po Valley, northern Italy), at two regulatory air quality monitoring sites, along with other pollutants (coarse particulate matter, PM10; fine particulate matter, PM2.5; O3; NO; NO2; and C6H6) and the vehicular traffic rate. The aerosol optical depth (AOD) and other column aerosol optical properties were concurrently monitored at four wavelengths by an AErosol RObotic NETwork (AERONET) sun photometer under urban background conditions within Modena. In situ absorption levels were apportioned to both sources (fossil fuel and biomass burning) and species (BC and BrC), while columnar absorption was apportioned to BC, BrC and mineral dust. The combined analysis of the atmospheric aerosol and gas measurements and of the meteorological conditions (in situ and from the ERA5 reanalysis) identified the location of potential urban sources of BC and BrC, most likely related to traffic and biomass burning. In situ data show different diurnal/weekly patterns for BrC from biomass burning and BC from traffic, with minor differences between the background and the urban traffic conditions. AERONET version 3 absorption aerosol optical depth (AAOD) retrievals at four wavelengths allowed the estimation of the absorptive direct radiative effect due to LAAs over the same period under the reasonable assumption that the AOD signal is concentrated within the mixing layer. AERONET retrievals showed a modest correlation of columnar absorption with planetary boundary layer (PBL)-scaled in situ observations, although the correlation improved significantly during a desert dust transport event that affected both in situ aerosol and columnar absorption, particularly in the blue spectrum range. A low correlation occurred between the contribution of BrC to aerosol absorption for the in situ and the columnar observations, with the BrC contribution being generally larger for in situ observations. Finally, evidence of a highly layered atmosphere during the study period, featuring significant spatial mixing and modest vertical mixing, was shown by ERA5-based atmospheric temperature profiles and by the large correlation of concurrent AERONET AOD retrievals in Modena and in Ispra (on the northwestern side of the Po Valley, ca. 225 km from Modena).Published14841–14869OSA2: Evoluzione climatica: effetti e loro mitigazioneJCR Journa
Geoethics for Redefining Human-Earth System Nexus
No full textThe globalized society is held together by an intricate system of human relationships. This system constitutes a planetary architecture characterized by (a) a complex technological structure, (b) the homogenization of cultural forms and economic systems, (c) growing social, political and economic inequalities. Faced with planetary systemic perturbations (such as pandemics and wars), the globalized society shows criticalities, but also strengths, despite it is still too vulnerable to anthropogenic environmental changes. These changes modify the physical–chemical-biological characteristics of the Earth system and therefore represent a great threat to human communities, more serious than the pandemic threat from SARS-CoV-2, perhaps equal to the threat of a nuclear war, since it is the habitability of the planet by humanity and many other living species to be in danger. In order to promptly address the dangers of the anthropogenic changes underway, a closer and more structured international cooperation between states is needed. There are no alternatives. But this goal today appears increasingly difficult and distant due to the international geopolitical instability triggered by the war in Ukraine. In fact, only, human communities that share ethical principles and values on which to base new forms of relationship between human beings and the Earth system are able to face the planetary ecological crisis and build a possible future on Earth. In this perspective, geoethics is proposed as global ethics of a complex world, founded on the principles of dignity, freedom and responsibility and aimed at the renewal of the human-Earth System nexus and the realization of an ecological humanism.Published5-231TM. Formazion
A Two-stage Signal Decomposition into Jump, Oscillation and Trend using ADMM
No full textWe present a thorough implementation of the two-stage framework proposed in [A.Cicone, M.Huska, S.H.Kangand, S.Morigi, JOT:a Variational Signal Decomposition into Jump, Oscillation and Trend, IEEE Transactions on Signal Processing, 2022]. The method assumes as input a 1D signal represented by a finite-dimensional vector in RN. In the first stage the signal is decomposed into Jump (piece-wise constant), Oscillation, and Trend (smooth) components, and in the second stage the results are refined using residuals of other components. We propose an efficient numerical solution for the first stage based on alternating direction method of multipliers, and a solid algorithm for the solution of the second stage.Published153–166OSA3: Climatologia e meteorologia spazialeJCR Journa
RecSec a web application for the Record Sections of Euro-Mediterranean earthquakes
No full textIn this short note, we introduce a web application where the Record Sections, automatically created
after a revised earthquake location, can be accessed. The Record Sections are graphical representations
of the waveforms of seismic events in Distance-Time diagrams. They are created for each event occurring
in the Euro-Mediterranean area with a magnitude greater than 2.8 and for which a definitive location
is computed by the INGV surveillance service. The analysed stations belong to many European seismic
networks whose waveforms are distributed through EIDA [European Integrated Data Archive,
http://www.orfeus-eu.org/data/eida/]. The IT tool we have realized, described in this note, is a useful
multipurpose instrument: it can be fruitfully employed both for research purposes, for a rapid quality
control of seismic stations and also for educationINGVPublished1-20OST4 Descrizione in tempo reale del terremoto, del maremoto, loro predicibilità e impattoN/A or not JC
Assessing flank instability of Stromboli volcano (Italy) by reappraising the 30 December 2002 tsunamigenic landslides
No full textBearing in mind the destructive potential of tsunamis
induced by volcanic landslides, the tsunamigenic event occurring
at Stromboli volcano in Italy on 30 December 2002 has been reexamined
here, by means of visible images and slope stability analysis.
This was one of the few examples in the world of a flank collapse
occurring at a volcano that was directly observed. We present
the results of stability analyses, together with a sequence of photos
collected from a helicopter a few minutes before the collapse. The
result of this study is that the sequence of landslides triggering the
2002 Stromboli tsunami can be defined as the final stage of a lateral
magma intrusion that exerted a high thrust at high altitude, destabilizing
the entire slope. This study allows a more complete understanding
of the event that took place on Stromboli on 30 December
2002. Furthermore, the approach used here, if appropriately modified,
can be used in other contexts, contributing to the understanding
of the condition that leads to tsunamigenic landslidesOpen access funding provided by Istituto Nazionale di Geofisica e
Vulcanologia within the CRUI-CARE Agreement. This research was
funded by the “Presidenza del Consiglio dei Ministri–Dipartimento
della Protezione Civile”, through the UniFi-DPC 2019–2021 agreement
(Scientific Responsibility: N.C.). The contents of this paper
represent the authors’ ideas and do not necessarily correspond to
the official opinion and policies of the “Presidenza del Consiglio dei
Ministri–Dipartimento della Protezione Civile”. This research was
also funded by the Project FIRST-ForecastIng eRuptive activity at
Stromboli volcano: Timing, eruptive style, size, intensity, and duration,
INGV-Progetto Strategico Dipartimento Vulcani 2019 (Delibera
n. 144/2020; Scientific Responsibility: S.C.). The SSAP software
research and development was funded by CONACYT (Mexico):
Proyectos Ciencia Basica: CB-2016/286764.Published1363–13805V. Processi eruttivi e post-eruttiviJCR Journa