DSpace Collection:
http://hdl.handle.net/2122/242
2014-04-17T18:26:11ZThe October 23, 2011, Van (Turkey) earthquake and its relationship with neighboring structures
http://hdl.handle.net/2122/8959
Title: The October 23, 2011, Van (Turkey) earthquake and its relationship with neighboring structures
Authors: Moro, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione CNT, Roma, Italia; Cannelli, V.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; Chini, M.; Public Research Centre "Gabriel Lippmann" Belvaux, Luxembourg; Bignami, C.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione CNT, Roma, Italia; Melini, D.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; Stramondo, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione CNT, Roma, Italia; Saroli, M.; Università degli Studi di Cassino e del Lazio Meridionale, DICeMDipartimento di Ingegneria Civile e Meccanica, Cassino; Kyriakopoulos, C.; 4School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, Georgia (USA).; Brunori, C. A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia
Abstract: The present work reports the analysis of a possible relationship due to stress transfer between the two earthquakes that hit the province of Van, Eastern Turkey, on October 23, 2011 (Mw 5 7.2) and on November 9, 2011 (Mw55.6). The surface displacement field of the mainshock has been obtained through a combined data set made up of differential interferograms from COSMO-SkyMed and ENVISAT satellites,integrated with continuous GPS recordings from the Turkish TUSAGA-AKTIF network. This allowed us to retrieve the geometry and the slip distribution of the seismic source and to compute the Coulomb Failure Function (CFF) variation on the aftershock plane, in order to assess a possible causal relationship between the two events. Our results show that the November 9 earthquake could have been triggered by the October 23 shock, with transferred stress values largely exceeding 1 bar.2014-01-31T23:00:00ZCalculation of the local rupture speed of dynamically propagating earthquakes
http://hdl.handle.net/2122/8898
Title: Calculation of the local rupture speed of dynamically propagating earthquakes
Authors: Bizzarri, A; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Bologna, Bologna, Italia
Abstract: The velocity at which a propagating earthquake advances on the fault
surface is of pivotal importance in the contest of the source dynamics and
in the modeling of the ground motions generation. The rupture speed (vr )
is one of the results provided by spontaneous dynamic models of ruptures,
in that it is a part of the solution and it is not imposed a priori, like in
non spontaneous models or in kinematic models. Since vr is numerically
retrieved from the spatial distribution of the rupture times (tr ), a well–
constrained value of vr in a given fault node is important. In this paper
we focus on the numerical determination of vr. By comparing different
numerical schemes to compute vr from tr we show that, in general, central
finite differences schemes are more accurate than forward or backward
schemes, regardless the order of accuracy. Overall, the most efficient and
accurate algorithm is the five–points stencil method at the second–order
of accuracy. These conclusions hold for homogeneous and heterogeneous
configurations and for different constitutive models, such as the slip–
weakening law and the rate– and state–friction governing equations. It is
also shown how the determination of tr can affect vr; numerical results indicate
that if the fault slip velocity threshold (vl ) used to define tr is too
high (vl ≥ 0.1 m/s) the details of the rupture are missed, for instance the
jump of the rupture front eventually occurring for 2–D supershear ruptures.
On the other hand, for vl ≤ 0.01 m/s the results appear to be stable
and independent on the choice of vl. Finally, it is confirmed that in
the special case of the linear slip–weakening friction law the computation
of vr from the threshold criterion on the fault slip velocity and from
the achievement of the maximum yield stress are equivalent.2013-11-30T23:00:00ZMonitoraggio sismico del territorio nazionale: stato dell'arte e sviluppo delle reti di monitoraggio sismico
http://hdl.handle.net/2122/8813
Title: Monitoraggio sismico del territorio nazionale: stato dell'arte e sviluppo delle reti di monitoraggio sismico
Authors: Sergio, Guardato; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia
Abstract: Il sistema CUMAS (Cabled Underwater Module
for Acquisition of Seismological data) è un
prodotto tecnologico-scientifico complesso nato
con il Progetto V4 [Iannaccone et al., 2008] allo
scopo di monitorare l’area vulcanica dei Campi
Flegrei (fenomeno del bradisismo).
Si tratta di un modulo sottomarino cablato e
connesso a una boa galleggiante (meda elastica). Il
sistema è in grado di acquisire e trasmettere alla
sala di monitoraggio dell’OV, in continuo e in
tempo reale, sia i segnali sismologici sia quelli di
interesse geofisico ed oceanografico (maree,
correnti marine, segnali acustici subacquei,
parametri funzionali di varia natura).
Il sistema è in grado di ricevere comandi da remoto
per variare diversi parametri di acquisizione e di
monitorare un cospicuo numero di variabili di
funzionamento.
Il sistema si avvale del supporto di una boa
galleggiante attrezzata. La boa è installata a largo
del golfo di Pozzuoli (Napoli) a circa 3 km dalla
costa. Il modulo sottomarino, collegato via cavo
alla parte fuori acqua della boa, è installato sul
fondale marino a una profondità di circa 100 metri.2010-12-31T23:00:00ZEnergy flux of propagating ruptures with cohesive force
http://hdl.handle.net/2122/8777
Title: Energy flux of propagating ruptures with cohesive force
Authors: Bizzarri, A; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Bologna, Bologna, Italia
Abstract: The energy flux F at the rupture tip has been previously computed only
for 2D steady-state singular cracks. In this paper, I compute F for fully dynamic 3D
ruptures, propagating both with constant and variable rupture speed (v_r) over finite
faults directed by a governing law with a cohesive zone (and thus nonsingular ruptures).
The results presented here indicate that F is positive and increasing over the
whole range of v_r from zero up to P-wave speed. This is in contrast with 2D steady-state
singular cracks, which predict the existence of a forbidden zone in the range of
rupture speeds because in that interval F would be negative. Moreover, I found that in
3D ruptures with cohesive force, F is proportional to v_r, again in contrast to 2D
steady-state singular cracks, in which F is not a unique function of v_r and also exhibits
an inverse dependence on v_r. More specifically, it emerges that fast earthquakes tend
to have a higher energy flux at the crack tip compared with slow ruptures. Finally, I
show that the magnitude of F is basically due to its component aligned in the direction
of the initial shear stress.2013-09-30T22:00:00ZSource parameters scaling of the 2004 Kobarid (Western Slovenia) seismic sequence.
http://hdl.handle.net/2122/8754
Title: Source parameters scaling of the 2004 Kobarid (Western Slovenia) seismic sequence.
Authors: Franceschina, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Milano-Pavia, Milano, Italia; Gentili, S.; Istituto Nazionale di Oceanografia e Geofisica Sperimentale, Centro Ricerche Sismologiche, Cussignacco, Udine, Italia.; Bressan, G.; Istituto Nazionale di Oceanografia e Geofisica Sperimentale, Centro Ricerche Sismologiche, Cussignacco, Udine, Italia.
Abstract: Source parameters of the mainshock (ML=5.3) and of 165 aftershocks (0.8 < ML < 3.5) of the 2004 Kobarid (Western Slovenia) seismic sequence are investigated in order to determine the corresponding source scaling relations. Data recorded from July to December 2004 by the Friuli and Veneto seismic network (FV), managed by the Istituto Nazionale di Oceanografia e di Geofisica Sperimentale (OGS) and installed in Northeastern Italy, are employed to obtain the SH-wave amplitude Fourier spectra of the selected earthquakes. For source spectra computation, we consider only records with significant values of the signal-to-noise ratio and, to account for local amplifications, we compute standard H/V spectral ratios (HVSR) for all the stations of the network. After correction for attenuation effects, source spectra obtained at stations with negligible site effects show a good fit with a ω-square model. We adopt different approaches to compute the source parameters and final results are chosen based on the obtained misfits between observed and theoretical source spectra. For 21 earthquakes of the sequence the obtained results are confirmed by the Empirical Green Function (EGF) technique, applied by estimating the spectral ratios of couples of events with hypocentral distance differences smaller than 500 m and magnitude differences greater than 1. The mainshock of the sequence is characterized by a seismic moment of 3.5x10^16 Nm and a corner frequency of 0.8 Hz, corresponding, in the Brune’s model (1970), to a fault radius of 1465 m and a stress drop of 4.9 MPa. Aftershocks have seismic moments in the range [3.3x10^11, 1.8x10^14] Nm, corner frequencies between 1.9 and 12.4 Hz (Brune radii between 95 and 638 m) and stress drops in the range [0.03, 1.55] MPa. The observed scaling of seismic moment (M0) with the local magnitude (ML) is consistent with the trend: Log M0 = 1.06 ML + 10.56. The Brune radius (rB) increases with the seismic moment according to: Log rB = 0.22 Log M0 - 0.40. Moreover, in spite of the high dispersion that characterizes the estimates of the Brune stress drop (ΔσB), we observe also an increase of ΔσB with M0. The mainshock is characterized by 2.4 x10^12 J radiated energy (ES) and 1.9 MPa apparent stress (σa). Aftershocks have energies between 2.0 x10^5 and 7.4 x10^8 J and apparent stress values increasing with the seismic moment in the range [0.01, 0.48] MPa. Radiated energies increase with seismic moments according to the empirical relationship: Log ES = 1.53 Log M0 - 12.47. The scaling of both ΔσB and σa with M0 in the range of magnitude between 0.8 to 5.3, evidences the non-self-similarity characteristics of the 2004 Kobarid seismic sequence. Similar results have been obtained by previous studies concerning the source parameter scaling of the background seismicity and of other seismic sequences of the area.2013-07-21T22:00:00ZApproaching the seismogenic source of the Calabria 8 September 1905 earthquake: New geophysical, geological and biochemical data from the S. Eufemia Gulf (S Italy)
http://hdl.handle.net/2122/8726
Title: Approaching the seismogenic source of the Calabria 8 September 1905 earthquake: New geophysical, geological and biochemical data from the S. Eufemia Gulf (S Italy)
Authors: Loreto, M. F.; Istituto di Scienze Marine – Consiglio Nazionale delle Ricerche, U.O.S. Bologna, Via Gobetti 101, 40129 Bologna; Fracassi, U.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; Franzo, A.; Istituto Nazionale di Oceanografia e di Geofisica Sperimentale, Borgo Grotta Gigante 42/C, 34010 Sgonico (TS); Del Negro, P.; Istituto Nazionale di Oceanografia e di Geofisica Sperimentale, Borgo Grotta Gigante 42/C, 34010 Sgonico (TS); Zgur, F.; Istituto Nazionale di Oceanografia e di Geofisica Sperimentale, Borgo Grotta Gigante 42/C, 34010 Sgonico (TS); Facchin, L.; Istituto Nazionale di Oceanografia e di Geofisica Sperimentale, Borgo Grotta Gigante 42/C, 34010 Sgonico (TS)
Abstract: Recognizing the seismogenic source of major historical earthquakes, particularly when these have occurred offshore, is a long-standing issue across the Mediterranean Sea and elsewhere. The destructive earthquake (M ~7) that struck western Calabria (southern Italy) on the night of 8 September 1905 is one such case. having various authors proposed a seismogenic source, with apparently diverse hypotheses and without achieving a unique solution. To gain novel insight into the crustal volume where the 1905 earthquake took place and to seek a more robust solution for the seismogenic source associated with this destructive event, we carried out a well-targeted multidisciplinary survey within the Gulf of S. Eufemia (SE Tyrrhenian Sea), collecting geophysical data, oceanographic measurements, and biological, chemical and sedimentary samples.
We identified three main tectonic features affecting the sedimentary basin in the Gulf of S. Eufemia: 1) a NE-SW striking, ca. 13-km-long, normal fault, here named S. Eufemia Fault; 2) a WNW-striking polyphased fault system; and 3) a likely E-W trending lineament. Among these, the normal fault shows evidence of activity witnessed by the deformed recent sediments and by its seabed rupture along which, locally, fluid leakage occurs. Features in agreement with the anomalous distribution of prokaryotic abundance and biopolymeric C content, resulted from the shallow sediments analyses.
The numerous seismogenic sources proposed in the literature during the past 15 years make up a composite framework of this sector of western Calabria, that we tested against a) the geological evidence from the newly acquired dataset, and b) the regional seismotectonic models. Such assessment allows us to propose the NE-SW striking normal fault as the most probable candidate for the seismogenic source of the 1905 earthquake. Re-appraising a major historical earthquake as the 1905 one enhances the seismotectonic picture of western Calabria. Further understanding of the region and better constraining the location of the seismogenic source may be attained through integrated interpretation of our data together with a) on-land field evidence, and b) seismological modeling.2012-12-31T23:00:00ZMagnitude scale for LP events: a quantification scheme for volcanic quakes
http://hdl.handle.net/2122/8682
Title: Magnitude scale for LP events: a quantification scheme for volcanic quakes
Authors: Del Pezzo, E.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia; Bianco, F.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia; Borgna, I.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia
Abstract: The peculiar source characteristics of long-period seismic events (time persistency of the source, low-frequency peaks in the source spectrum, absence of high-frequency radiation) prevent the formation of a definite high-frequency coda in the seismograms. In contrast, this is well formed in volcano–tectonic quakes. For this reason, the widely used duration magnitude scale that is based on the proportionality between the energy and the coda duration cannot be used for long-period estimation. In observatory practice, the long-period magnitude is sometimes estimated using the same duration magnitude scale, leading to confusing results. In this report, we show a new method to estimate the magnitude of long-period events that generally occur for volcanoes, with some application examples from data for Mt Etna (Italy), Colima Volcano (Mexico) and Campi Flegrei (Italy).2013-04-28T22:00:00ZPossible model of electromagnetic signals before earthquakes
http://hdl.handle.net/2122/8671
Title: Possible model of electromagnetic signals before earthquakes
Authors: Dudkin, F.; Lviv Centre of Institute for Space Research, Ukraine; Korepanov, V.; Lviv Centre of Institute for Space Research, Ukraine; Hayakawa, M.; University of Electro-Communications, Japan; De Santis, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia
Abstract: Few days before many earthquakes a general change in the ratio of vertical to horizontal magnetic field components in the ULF band, often called “polarization”,
has been observed that can be considered as a magnetic precursor of the subsequent earthquake. To explain such a specific behavior, we propose a simple model based on a linear current approximation depending on some assumption on the signal to noise ratio. This model is confirmed through a comparison that has been carried out between the experimental magnetic field data at Matsushiro (Japan, 1998.06.30, M=4.7) and Simeiz (Crimea, Ukraine, 1998.10.16, M=4.3 and 1998.10.18, M=4.3) earthquakes. About 1 – 2 days before these events we had recorded
the anomalous decrease of the ratio of vertical to horizontal magnetic field
components in Pc4 – Pc3 band. The NE-SW direction of the corresponding current
linear model well agrees with the main tectonic feature of both seismogenic events.
Additionally we also estimate the signal to noise ratio limits for the detection of
ULF magnetic field components in Corralitos and Stanford campus for Loma Prieta (MS 7.1, 1989) earthquake.2012-12-31T23:00:00ZA few earthquake conundrums resolved
http://hdl.handle.net/2122/8670
Title: A few earthquake conundrums resolved
Authors: Crampin, S.; British Geological Survey, Edinburgh, Scotland, UK; Gao, Y.; Institute of Earthquake Science, China Earthquake Administration, Beijing, China; De Santis, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia
Abstract: Several fundamental questions (conundrums) about earthquakes and rocks are inexplicable in terms of conventional sub-critical geophysics. These questions have become so familiar that they are now generally
accepted as the way earthquakes and rocks behave and are not recognised as presenting conceptual difficulties. These conundrums are resolved by a new understanding of fluid-rock deformation, where
fluid-saturated microcracks in almost all rocks are so closely-spaced they verge on failure and hence are highly-compliant critical-systems which impose a range of new properties on conventional sub-critical
geophysics. This new understanding of fluid-rock deformation, this New Geophysics, allows earthquakes to be stress-forecast, and has implications and applications to many solid Earth developments.2013-01-29T23:00:00ZThe Volcano-Seismic Clock of the South American Pacific Margin - A Possible First Link Between Natural Disasters Prevention and Expanding Earth
http://hdl.handle.net/2122/8662
Title: The Volcano-Seismic Clock of the South American Pacific Margin - A Possible First Link Between Natural Disasters Prevention and Expanding Earth
Authors: Scalera, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia
Editors: Scalera, Giancarlo; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia
Abstract: A volcano-seismic correlation was for a long time suspected to occur on the
Pacific margin of South America. Scalera (2008) using the data available in 2006 in the
Smithsonian Institution Catalogue of the volcanic eruptions, has revealed evidence that
earthquakes happened into the South-American Wadati-Benio zone – with magnitude
greater than 8.4 –are associated to an enhanced rate of volcanic eruptions, but has been
impossible to determine the causal chain between the two phenomena. After 2006, the effort
of the Smithsonian Institution to improve our knowledge of this region has resulted in
a greatly increased completeness of the catalogue, adding the new eruptions for the 2000-
2010 interval, but also an additional 50% of new entries in the list of the Andean volcanoes.
The occurrence of the Chilean earthquake of Maule – 27 February 2010 (M=8.8); occurred
at five decades from the 1960 quake – has been the occasion to rework all the data searching
for additional clues able to indicate a preferred causal direction eruptions-earthquakes
or earthquakes-eruptions – or from a third more general cause (e.g. a mantle movements) to
both eruptions and earthquakes. This short note discusses the three above-said hypotheses
and tries to establish if these results could be useful to the aims of the Civil Protection in
the programs of prevention and/or forecasting of natural disasters.2012-11-30T23:00:00Z