92 research outputs found
A new MD-ML relationship for Mt. Etna earthquakes (Italy)
A homogenous database of magnitude observations is a basic requirement
for seismic hazard estimation and other seismic studies. Unfortunately,
the magnitude reported in the seismic catalogue of Mt. Etna is not
homogenous. Only the duration magnitude (MD) is available up to 2005,
while since then the more stable local magnitude (ML) has also been calculated.
To have a uniform dataset, earthquake data recorded at Mt. Etna
during the period 2005-2014 were used to derive a new relationship between
local and duration magnitude, by applying the General Orthogonal
Regression (GOR), which is an alternative to least squares when the
ratio between errors on the independent and the dependent variables can
be estimated. The relationship obtained is:
ML = 1.164 (Âą0.011) *MD â 0.337 (Âą0.020)
The new relationship allows to back-extend the local magnitude dataset
to cover a period of about 15 year
Seismological investigations in the Gioia Tauro Basin (southern Calabria, Italy)
This study provides new seismological information to characterize the seismically active area of the Gioia
Tauro basin (southern Calabria, Italy). Seismic activity recorded by a temporary network from 1985 to 1994 was
analyzed for focal mechanisms, stress tensor inversion, P-wave seismic attenuation and earthquake source parameters
estimation. Fault plane solutions of selected events showed a variety of different mechanisms, even if
a prevalence of normal dip-slip solutions with prevalent rupture orientations occurring along ca. NE-SW directions
was observed. Stress tensor inversion analysis disclosed a region governed mainly by a NW-SE extensional
stress regime with a nearly vertical Ď1. These results are consistent with the structure movements affecting
the studied area and with geodetic data.
Furthermore, evaluation of P-waves seismic attenuation and earthquake source parameters of a subset of events
highlighted a strong heterogeneity of the crust and the presence of fault segments and/or weakened zones where
great stress accumulation or long-rupture propagation are hindered
Intrinsic Qp at Mt. Etna from the inversion of rise times of 2002 microearthquake sequence
About three-hundred microearthquakes, preceeding and accompanying the 2002-2003 Mt. Etna flank eruption,
were considered in this study. On the high-quality velocity seismograms, measurements of the first half cycle of
the wave, the so-called rise time Ď, were carried out. By using the rise time method, these data were inverted to
infer an estimate of the intrinsic quality factor Qp of P waves and of the source rise time Ď0 of the events, which
represents an estimate of the duration of the rupture process. Two kind of inversions were carried out. In the first
inversion Ď0 was derived from the magnitude duration of the events, assuming a constant stress drop and Qp was
inferred from the inversion of reduced rise times ĎâĎ0. In the second inversion both Ď0 and Qp were inferred from
the inversion of rise times. To determine the model parameters that realize the compromise between model simplicity
and quality of the fit, the corrected Akaike information criterion was used. After this analysis we obtained
Qp=57Âą42. The correlation among the inferred Ď0 and Qp, which is caused by some events which concomitantly
have high Ď0 (>30 ms) and high Qp (>100) indicates that the technique used is able to model rise time versus
travel time trend only for source dimensions less than about 80 m
Fault plane orientations of microearthquakes at Mt. Etna from theinversion of P-wave rise times
A crucial point in the analysis of tectonic earthquakes occurring in a volcanic area is the inference of the
orientation of the structures along which the ruptures occur. These structures represent zones of weakness
which could favor the migration of melt toward the surface and the assessment of their geometry is a
fundamental step toward efficient evaluation of volcanic risk. We analyzed a high-quality dataset of 171 lowmagnitude,
tectonic earthquakes that occurred at Mt. Etna during the 2002â2003 eruption. We applied a
recently developed technique aimed at inferring the source parameters (source size, dip and strike fault) and
the intrinsic quality factor Qp of P waves from the inversion of rise times. The technique is based on
numerically calibrated relationships among the rise time of first P waves and the source parameters for a
circular crack rupturing at a constant velocity. For the most of the events the directivity source effect did not
allow us to constrain the fault plane orientation. For a subset of 45 events with well constrained focal
mechanisms we were able to constrain the âtrueâ fault plane orientation. The level of resolution of the fault
planes was assessed through a non linear analysis based on the random deviates technique. The significance
of the retrieved fault plane solutions and the fit of the assumed source model to data were assessed through
a Ď-square test. Most of the retrieved fault plane solutions agree with the geometrical trend of known
surface faults. The inferred source parameters and Qp are in agreement with the results of previous studie
Fault plane orientation of microearthquakes at Mt. etna from the inversion of P-wave rise times
crucial point in the analysis of tectonic earthquakes occurring in a volcanic area is the inference of the orientation of the structures along which the ruptures occur. These structures represent zones of weakness which could favor the migration of melt toward the surface and the assessment of their geometry is a fundamental step toward efficient evaluation of volcanic risk. We analyzed a high-quality dataset of 171 low-magnitude, tectonic earthquakes occurred at Mt. Etna during the 2002-2003 eruption. We applied a recently developed technique aimed at inferring the source parameters (source size, dip and strike fault) and the intrinsic quality factor Qp of P waves from the inversion of rise times. The technique is based on numerically calibrated relationships among the rise time of first P waves and the source parameters for a circular crack rupturing at a constant velocity. For the most of the events the directivity source effect did not allow us to constrain the fault plane orientation. For a subset of 45 events with well constrained focal mechanisms we were able to constrain the âtrueâ fault plane orientation. The level of resolution of the fault planes was assessed through a non linear analysis based on the random deviates technique. The significance of the retrieved fault plane solutions and the fit of the assumed source model to data was assessed through a Ď-square test. Most of the retrieved fault plane solutions agree with the geometrical trend of known surface faults. The inferred source parameters and Qp are in agreement with the results of previous studies
The XMM Cluster Survey: the interplay between the brightest cluster galaxy and the intracluster medium via AGN feedback
Using a sample of 123 Xâray clusters and groups drawn from the XMM Cluster Survey first data release, we investigate the interplay between the brightest cluster galaxy (BCG), its black hole and the intracluster/group medium (ICM). It appears that for groups and clusters with a BCG likely to host significant active galactic nuclei (AGN) feedback, gas cooling dominates in those with T X > 2âkeV while AGN feedback dominates below. This may be understood through the subunity exponent found in the scaling relation we derive between the BCG mass and cluster mass over the halo mass range 10 13 < M 500 < 10 15 âM â and the lack of correlation between radio luminosity and cluster mass, such that BCG AGN in groups can have relatively more energetic influence on the ICM. The L X â T X relation for systems with the most massive BCGs, or those with BCGs coâlocated with the peak of the ICM emission, is steeper than that for those with the least massive and most offset, which instead follows selfâsimilarity. This is evidence that a combination of central gas cooling and powerful, well fuelled AGN causes the departure of the ICM from pure gravitational heating, with the steepened relation crossing selfâsimilarity at T X = 2âkeV. Importantly, regardless of their black hole mass, BCGs are more likely to host radioâloud AGN if they are in a massive cluster ( T X âł 2âkeV) and again coâlocated with an effective fuel supply of dense, cooling gas. This demonstrates that the most massive black holes appear to know more about their host cluster than they do about their host galaxy. The results lead us to propose a physically motivated, empirical definition of âclusterâ and âgroupâ, delineated at 2âkeV.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/91324/1/j.1365-2966.2012.20764.x.pd
Un anno di Comitato Unico di Garanzia: riflessioni all'INGV
LâIstituto Nazionale di Geofisica e Vulcanologia - INGV ha istituito il Comitato Unico di Garanzia per le pari opportunitĂ , la valorizzazione del benessere di chi lavora e contro le discriminazioni â CUG nel luglio 2011, ai sensi della L.183/2010.
Il CUG ha assunto, estendendoli, i compiti del precedente Comitato Pari OpportunitĂ , ossia, come da delibera CD n.4.3.2.11 del 28/6/2011:
⢠focalizzare i problemi relativi alle pari opportunità ;
⢠contribuire a migliorare la qualità della vita negli ambienti di lavoro e a valorizzare le risorse umane;
⢠verificare gli equilibri tra i sessi nelle posizioni funzionali a parità di requisiti professionali;
⢠formulare proposte per: la gestione flessibile delle risorse umane e le attività di formazione professionale;
è inoltre chiamato a perseguire gli obiettivi della direttiva dei dipartimenti della Funzione Pubblica e per le Pari Opportunità del 4 marzo 2011, per esercitare compiti propositivi, consultivi e di verifica.
I compiti affidati dallâAmministrazione da un lato e le sollecitazioni ricevute dal personale dallâaltro hanno portato ad una serie di azioni, tra le principali:
⢠la redazione di un Codice per la tutela della dignitĂ delle persone e per la prevenzione delle molestie sessuali e morali dellâINGV, lâindividuazione della Consigliera di Fiducia e lâavvio di un ciclo di seminari sullâargomento, nellâambito della prevenzione delle discriminazioni;
⢠una lettura di genere delle bozze dei nuovi regolamenti dellâente, con proposte di modifiche ispirate alla Carta Europea dei Ricercatori â CdR (e.g. principi di Non discriminazione, Equilibrio di genere) e alla normativa in tema di pari opportunitĂ e tutela della maternitĂ , parte delle quali recepite nel Regolamento del Personale e nel Disciplinare in materia di orario di servizio; unâazione, questa, legata allâadesione in via sperimentale alla Human Resources Strategy for Researchers, iniziativa della ComunitĂ Europea per lâeffettiva implementazione della CdR;
⢠nellâambito del processo di valutazione della ricerca dellâANVUR, lâevidenziazione di alcune criticitĂ presenti nel bando, in relazione alla valutazione della maternitĂ , risultate in una interrogazione parlamentare e in una lettera aperta, grazie al contributo dellâAssociazione Donne e Scienza e dei CUG dellâINFN e del CNR.
Le esperienze fatte confermano lâopportunitĂ di dare voce a tutte le donne dellâIstituto e di fare rete tra i Comitati degli enti di ricerca.UnpublishedCertosa di Pontignano (Siena), Italyope
La sequenza sismica nel versante nord-occidentale dell'Etna del 19-27 Dicembre 2009 : evidenze di ricarica magmatica profonda?
Eâ stata analizzata la sequenza sismica che ha interessato il versante nord-occidentale dellâEtna nel periodo 19-27 dicembre 2009 (Fig. 1). Essa è stata caratterizzata da oltre 400 scosse di magnitudo compresa tra 1.0 e 4.8, localizzate ad una profonditĂ tra 20 e 30 km, con un rilevante rilascio energetico, come si osserva dalla distribuzione temporale del numero delle scosse e dellâenergia ad esse associata nel tempo (Fig. 2). Ă interessante notare come lâenergia rilasciata durante la sequenza risulti essere quasi il triplo dellâenergia del periodo sineruttivo 2008, pur essendo pressochĂŠ uguale il numero di scosse registrate.
In questo settore dellâarea etnea, caratterizzato da sismicitĂ profonda, poco frequente e di modesta energia, la modalitĂ di rilascio sismico della sequenza in oggetto costituisce un elemento di novitĂ . Infatti, piĂš del 50% delle scosse si sono verificate nel corso delle prime 24 ore, come tipicamente osservato nel corso di sciami vulcanici sineruttivi.
Eâ importante evidenziare che nellâarea etnea eventi sismici con profonditĂ focali comprese tra i 10 e i 30 km vengono considerati dei veri e propri âmarkersâ di attivitĂ vulcanica (e.g. Puglisi et al., 2001), in quanto si verificano abbastanza regolarmente durante i periodi intra-eruttivi e possono essere messi in relazione con i meccanismi di ricarica magmatica (e.g. Bonaccorso, 2001). Essi sono principalmente localizzati nei settori occidentale e meridionale del vulcano lungo strutture orientate NO-SE e NNO-SSE e, occasionalmente, lungo strutture orientate NE-SO (Patanè et al., 2004). Pertanto è ragionevole ipotizzare che il fenomeno oggetto del presente studio possa essere ricondotto ad una fase di ricarica profonda del sistema magmatico etneo
Instrumental seismic catalogue of Mt. Etna earthquakes (Sicily, Italy): ten years (2000-2010) of instrumental recordings
Instrumental seismic catalogues are an essential tool for the zonation of
the territory and the production of seismic hazard maps. They are also a
valuable instrument for detailed seismological studies regarding active
volcanoes and, above all, for interpreting the magma dynamics and the
evolution of eruptive phenomena. In this paper, we show the first instrumental
earthquake catalogue of Mt. Etna, for the period 2000-2010, with
the purpose of producing a homogeneous dataset of 10 years of seismological
observations. During this period, 16,845 earthquakes have been
recorded by the seismic network run by the Istituto Nazionale di Geofisica
and Vulcanologia, Osservatorio Etneo, in Catania. A total of 6,330 events,
corresponding to approximately 40% of all earthquakes recorded, were located
by using a one-dimensional VP velocity model. The magnitude completeness
of the catalogue is equal to about 1.5 for the whole period, except
for some short periods in 2001 and 2002-2003 and at the end of 2009. The
reliability of the data collected is supported by the good values of the main
hypocentral parameters through the time. The spatial distribution of seismicity
allowed the highlighting of several seismogenetic areas characterized
by different seismic rates and focal depths. This seismic catalogue
represents a fundamental tool for several research aiming to a better understanding
of the behavior of an active volcano such as Mt. Etna
Seismological constraints for the dyke emplacement of the July-August 2001 lateral eruption at Mt. Etna volcano, Italy
In this paper we report seismological evidence regarding the emplacement of the dike that fed the July 18 - August
9, 2001 lateral eruption at Mt. Etna volcano. The shallow intrusion and the opening of the eruptive fracture
system, which mostly occurred during July 12, and July 18, were accompanied by one of the most intense seismic
swarms of the last 20 years. A total of 2694 earthquakes (1 ÂŁ Md ÂŁ 3.9) were recorded from the beginning of the
swarm (July 12) to the end of the eruption (August 9). Seismicity shows the upward migration of the dike from
the basement to the relatively thin volcanic pile. A clear hypocentral migration was observed, well constraining
the upwards propagation of a near-vertical dike, oriented roughly N-S, and located a few kilometers south of the
summit region. Earthquake distribution and orientation of the P-axes from focal mechanisms indicate that the
swarm was caused by the local stress source related to the dike intrusion
- âŚ