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  • 11
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    Source parameters scaling of the 2004 Kobarid (Western Slovenia) seismic sequence. (2013)
    Elsevier Science Limited
    Details
    Publication Date: 2021-06-08
    Description: 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.
    Description: Published
    Description: 58-75
    Description: 3.3. Geodinamica e struttura dell'interno della Terra
    Description: JCR Journal
    Description: restricted
    Keywords: Earthquakes ; Source parameters ; Scaling law ; Seismic sequences ; Northeastern Italy ; Western Slovenia ; 04. Solid Earth::04.06. Seismology::04.06.03. Earthquake source and dynamics
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 12
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    Source parameters and scaling relationships in the Friuli-Venezia Giulia (Northeastern Italy) region (2007)
    Elsevier
    Details
    Publication Date: 2017-04-04
    Description: We estimated the source parameters of 53 local earthquakes (2.0 〈ML 〈 5.7) of the Friuli-Venezia Giulia (Northeastern Italy) area, recorded by the short-period local seismic network of the Istituto Nazionale di Oceanografia e Geofisica Sperimentale (OGS), in the period 1995–2003. Data were selected on the basis of high quality locations and focal mechanisms. Standard H/V spectral ratios (HVRS) of the three-component stations of the network were performed in order to assess local amplifications, and only stations showing HVRS not exceeding two were considered for the source parameters estimation. Both velocity and acceleration data were used to compute the SH-wave spectra. Observed spectra were corrected for attenuation effects using an independent regional estimate of the quality factor Q and a station dependent estimate of the spectral decay parameter k. Only earthquakes withML 〉 3.0 recorded with a sampling rate of 125 cps were used to compute k, thus allowing to visualize a linear trend of the high frequency acceleration spectrum up to 40–50 Hz. SH-wave spectra, corrected for attenuation, showed an ω−2 shape allowing a good fit with the Brune model. Seismic moments and Brune radii ranged between 1.5 × 1012 and 1.1 × 1017 Nm and between 0.1 and 2.7 km respectively.We obtainedMo = 1.1 × 1017 Nm for the seismic moment of the Kobarid (SLO) main shock, in good agreement with the Harvard CMT solution (Mo = 3.5 × 1017 Nm). Brune stress drops were confined to the range from 0.07 to 5.31MPa, with an average value of 0.73MPa and seem to be approximately constant over five orders of magnitude of seismic moment. Radiated seismic energy computed from two nearby stations scales with seismic moment according to logEs = 1.30 logMo − 9.06, and apparent stress values are between 0.02 and 4.26MPa. The observed scatter of Brune stress drop data allowed to hypothesize a scaling relation Mo ∝ f −3.43 c between seismic moment and corner frequency in order to accommodate both Brune stress drop and apparent stress scalings. No systematic differences are evidenced between stress parameters of earthquakes with different focal mechanisms. As a consequence, a relation of the seismic stress release with the strength of rocks can be hypothesized. A high correlation (r 〉 0.9) of Brune stress drop is found with both apparent stress and RMS stress drop, according to σB = 2.0 σa and σrms = 2.26 σB respectively.
    Description: Published
    Description: 148-167
    Description: JCR Journal
    Description: reserved
    Keywords: Earthquakes ; Attenuation ; Seismic spectra ; Seismic moment ; Seismic stress ; 04. Solid Earth::04.06. Seismology::04.06.03. Earthquake source and dynamics
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 13
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    Source parameters and stress release of seismic sequences occurred in the Friuli - Venezia Giulia region (Northeastern Italy) and in Western Slovenia (2007)
    Details
    Publication Date: 2017-04-04
    Description: The source parameters of the major events of a swarm and of two seismic sequences, occurred in the Friuli area (North-eastern Italy) and in Western Slovenia, were estimated. The Claut swarm (C96) occurred since the end of January to June 1996, with a MD 4.3 major shock and it appears composed of 3 sub-sequences. The two sequences are the Kobarid sequence (K98) started on April, 12, 1998 with a MD 5.6 mainshock and the M.te Sernio (S02) sequence caused by the February, 14, 2002 earthquake (MD =4.9). Acceleration and velocity data recorded by the local seismic network of the Istituto Nazionale di Oceanografia e di Geofisica Sperimenale (OGS) and corrected for attenuation, were employed to estimate seismic moments and radiated energies. Source dimensions were inferred from the computed corner frequencies and the stress release was estimated from the Brune stress drop, the apparent stress and the RMS stress drop. On the whole, seismic moments range from 1.7 x 1012 to 1.1 x 1017 Nm, and radiated energies are in the range 106 – 1013 J. Brune stress drops are scattered and do not show any evidence of a self-similarity breakdown for sources down to 130 m radius. The radiated seismic energy scales as a function of seismic moment, with a slope of the scaling relation that decreases for increasing seismic moments. The mechanism of stress release was analyzed by computing the ε parameter of Zuniga (1993). The K98 and S02 sequences are characterized by a wide range of the ε parameter with stress drop mechanism varying from partial locking to overshoot cases. The ε values of the C96 swarm are more homogeneous and close to the Orowan’s condition. The radiated seismic energy and the ratio of stress drop between mainshock and aftershocks appear different among the analyzed cases. We therefore investigated the relationship between the stress parameters of the main shock and the energy radiated by the aftershock sequences. For this purpose, we also estimated the source parameters of two other sequences occurred in the area, with mainshocks of MD 4.1 and MD 5.1, respectively. We found a positive correlation between the Brune stress drop of the mainshock and the ratio between the radiated energy of the mainshock and the summation of the energies radiated by the aftershocks.
    Description: Submitted
    Description: open
    Keywords: earthquakes ; seismic sequences ; source parameters ; scaling law ; stress drop ; 04. Solid Earth::04.06. Seismology::04.06.03. Earthquake source and dynamics
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: manuscript
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  • 14
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    Source parameters and stress release of seismic sequences occurred in the Friuli Venezia Giulia region (Northeastern Italy) and in Western Slovenia (2007)
    elsevier
    Details
    Publication Date: 2017-04-04
    Description: The source parameters of the major events of a swarm and of two seismic sequences, occurred in the Friuli area (Northeastern Italy) and in Western Slovenia, were estimated. The Claut swarm (C96) occurred since the end of January to June 1996, with a MD 4.3 major shock and it appears composed of three sub-sequences. The two sequences are the Kobarid sequence (K98) started on April 12, 1998 with a MD 5.6 mainshock and the M.te Sernio (S02) sequence caused by the February 14, 2002 earthquake (MD = 4.9). Acceleration and velocity data recorded by the local seismic network of the Istituto Nazionale di Oceanografia e di Geofisica Sperimenale (OGS) and corrected for attenuation, were employed to estimate seismic moments and radiated energies. Source dimensions were inferred from the computed corner frequencies and the stress release was estimated from the Brune stress drop, the apparent stress and the RMS stress drop. On the whole, seismic moments range from 1.7×1012 to 1.1×1017 Nm, and radiated energies are in the range 106–1013 J. Brune stress drops are scattered and do not show any evidence of a self-similarity breakdown for sources down to 130m radius. The radiated seismic energy scales as a function of seismic moment, with a slope of the scaling relation that decreases for increasing seismic moments. The mechanism of stress release was analyzed by computing the ε parameter of Zuniga [Zuniga, R., 1993. Frictional overshoot and partial stress drop. Which one? Bull. Seismol. Soc. Am. 83, 939–944]. The K98 and S02 sequences are characterized by a wide range of the ε parameter with stress drop mechanism varying from partial locking to overshoot cases. The ε values of the C96 swarm are more homogeneous and close to the Orowan’s condition. The radiated seismic energy and the ratio of stress drop between mainshock and aftershocks appear different among the analyzed cases.We therefore investigated the relationship between the stress parameters of the main shock and the energy radiated by the aftershock sequences. For this purpose, we also estimated the source parameters of two other sequences occurred in the area, with mainshocks of MD 4.1 and 5.1, respectively. We found a positive correlation between the Brune stress drop of the mainshock and the ratio between the radiated energy of the mainshock and the summation of the energies radiated by the aftershocks.
    Description: Published
    Description: 192-214
    Description: 3.3. Geodinamica e struttura dell'interno della Terra
    Description: JCR Journal
    Description: partially_open
    Keywords: seismic sequence ; 04. Solid Earth::04.06. Seismology::04.06.03. Earthquake source and dynamics
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 15
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    Sequential integrated inversion of tomographic images and gravity data: an application to the Friuli area (Northeastern Italy) (2012)
    Istituto Nazionale di Oceanografia e di Geofisica Sperimentale-OGS
    Details
    Publication Date: 2017-04-04
    Description: The three-dimensional pattern of elastic moduli (bulk modulus, Young modulus, shear modulus) of the upper crust (0-10 km depth) has been determined in the Friuli area (north-eastern Italy) from the 3D Vp, Vp/Vs and density structures. Firstly, 3D Pwave velocity and P to S velocity ratio were modeled by joint inversion for hypocentres and velocity structure. Then, we apply the tomographic inversion method of Sequential Integrated Inversion (SII) to recover the three dimensional density structure. The pattern of the elastic moduli is characterized by marked lateral and depth variations that reflect the geologic-structural heterogeneity of the area, produced by the superposition of several tectonic phases with different orientations of the principal axes of stress. The bulk (K), Young (E) and shear (G) moduli image a high rigidity body with an irregular shape, at 4-8 km depth. The body is characterized by G ≥ 3.2·1010 N·m-2, K ≥ 6.8·1010 N·m-2 and E ≥ 8.4·1010 N·m-2 and is associated to platform limestones and dolomitic rocks. The seismicity is mainly located along the sharp variations of the moduli pattern, in or adjacent to high rigidity zones. The most severe earthquakes (ML between 4.5 and 6.4), occurred in the study area from 1976 to the present day, are located in a transition zone from high to low rigidity patterns. Our interpretation is that the elastic moduli variations, closely related to variability in rock mechanical properties, influence the occurrence of earthquakes by processes of stress concentrations. The values of the elastic moduli recently obtained from laboratory measurements on the main lithologic units fall in the middlehigh range of the values obtained with the present investigation. Keywords: Seismic tomography, gravity anomalies, seismicity, elastic moduli, Friuli, NE Italy
    Description: Published
    Description: 191-212
    Description: 3.3. Geodinamica e struttura dell'interno della Terra
    Description: JCR Journal
    Description: restricted
    Keywords: Seismic tomography ; gravity anomalies ; seismicity ; elastic moduli ; Friuli ; NE Italy ; 04. Solid Earth::04.01. Earth Interior::04.01.04. Mineral physics and properties of rocks ; 04. Solid Earth::04.02. Exploration geophysics::04.02.02. Gravity methods ; 04. Solid Earth::04.02. Exploration geophysics::04.02.06. Seismic methods ; 04. Solid Earth::04.06. Seismology::04.06.07. Tomography and anisotropy
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 16
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    Mapping Wnt/ -catenin signaling during mouse development and in colorectal tumors (2003)
    National Academy of Sciences
    Details
    Publication Date: 2003-03-07
    Print ISSN: 0027-8424
    Electronic ISSN: 1091-6490
    Topics: Biology , Medicine , Natural Sciences in General
    Published by National Academy of Sciences
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  • 17
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    Neuroprotective effect of osmotin against ethanol-induced apoptotic neurodegeneration in the developing rat brain (2014)
    Springer Nature
    Details
    Publication Date: 2014-03-28
    Description: Neuroprotective effect of osmotin against ethanol-induced apoptotic neurodegeneration in the developing rat brain Cell Death and Disease 5, e1150 (March 2014). doi:10.1038/cddis.2014.53 Authors: M I Naseer, I Ullah, M L Narasimhan, H Y Lee, R A Bressan, G H Yoon, D J Yun & M O Kim
    Keywords: osmotinadiponectinethanolneuroprotectionFAS
    Electronic ISSN: 2041-4889
    Topics: Biology , Medicine
    Published by Springer Nature
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  • 18
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    Ultrastructural localization of concanavalid a binding sites on elastic fibers (1983)
    Elsevier
    Details
    Publication Date: 1983-01-01
    Print ISSN: 0304-3991
    Electronic ISSN: 1879-2723
    Topics: Electrical Engineering, Measurement and Control Technology , Natural Sciences in General , Physics
    Published by Elsevier
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  • 19
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    Observations en culture sur les phases initiales de d�veloppement de Peyssonnelia squamaria (1977)
    Springer
    Details
    Publication Date: 1977-01-01
    Print ISSN: 0025-3162
    Electronic ISSN: 1432-1793
    Topics: Biology
    Published by Springer
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  • 20
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    Early reproductive stages in the crustose coralline alga Phymatolithon lenormandii are strongly affected by mild ocean acidification (2013)
    Springer
    Details
    Publication Date: 2013-05-29
    Print ISSN: 0025-3162
    Electronic ISSN: 1432-1793
    Topics: Biology
    Published by Springer
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