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  • 1
    Publication Date: 2018-06-29
    Type: Conference or Workshop Item , NonPeerReviewed
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  • 2
    Publication Date: 2013-10-25
    Print ISSN: 0895-0695
    Electronic ISSN: 1938-2057
    Topics: Geosciences
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  • 3
    Publication Date: 2013-05-03
    Description: Near-field ground-motion data are available in semi-real time either from modern strong-motion or continuous Global Positioning System (GPS) networks, allowing robust solutions for earthquake source parameters, which are useful for rapid disaster assessment and early warning. These wide applications require the ground-motion data to cover a very broad frequency band that, however, is usually not available. This paper presents a case study on the 2011 M w  9.0 Tohoku earthquake, showing how the ground-motion information from geodetic and seismic instrumentations is complementary, and suggesting the joint use of both types of data, particularly when the network coverage is sparse. First the strong-motion records from the two Japanese networks, K-NET and KiK-Net, are analyzed using an automatic empirical baseline correction tool. The static coseismic displacement data are obtained by double integration and then used to derive the permanent slip distribution on the earthquake fault. Comparisons with the corresponding GPS-based solutions yield a quantitative estimation of uncertainties of the empirical baseline correction. Furthermore, a dozen nearby GPS and strong-motion station pairs are selected to demonstrate that the information in their time series agrees with each other. Finally, methods for combining both types of ground-motion observation systems are discussed, and the wide applicability of this approach is highlighted.
    Print ISSN: 0037-1106
    Electronic ISSN: 1943-3573
    Topics: Geosciences , Physics
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  • 4
    Publication Date: 2013-01-11
    Description: In this study, we estimate the location and magnitude of Central Asian earthquake from macroseismic intensity data. A set of 2373 intensity observations from 15 earthquakes is analysed to calibrate non-parametric models for the source and attenuation with distance, the distance being computed from the instrumental epicentres located according to the International Seismological Centre (ISC) catalogue. In a second step, the non-parametric source model is regressed against different magnitude values (e.g. M LH , m b , M S , M w ) as listed in various instrumental catalogues. The reliability of the calibrated model is then assessed by applying the methodology to macroseismic intensity data from 29 validation earthquakes for which both M LH and m b are available from the Central Asian Seismic Risk Initiative (CASRI) project and the ISC catalogue. An overall agreement is found for both the location and magnitude of these events, with the distribution of the differences between instrumental and intensity-based magnitudes having almost a zero mean, and standard deviations equal to 0.30 and 0.44 for m b and M LH , respectively. The largest discrepancies are observed for the location of the 1985, M LH  = 7.0 southern Xinjiang earthquake, whose location is outside the area covered by the intensity assignments, and for the magnitude of the 1974, m b  = 6.2 Markansu earthquake, which shows a difference in magnitude greater than one unit in terms of M LH . Finally, the relationships calibrated for the non-parametric source model are applied to assign different magnitude-scale values to earthquakes that lack instrumental information. In particular, an intensity-based moment magnitude is assigned to all of the validation earthquakes.
    Print ISSN: 0956-540X
    Electronic ISSN: 1365-246X
    Topics: Geosciences
    Published by Oxford University Press on behalf of The Deutsche Geophysikalische Gesellschaft (DGG) and the Royal Astronomical Society (RAS).
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  • 5
    Publication Date: 2014-08-13
    Description: Seismic noise is generally considered as a reproducible and temporarily stationary natural source of energy. We present a study on the statistical features of the soil motion due to the seismic noise wavefield and the dependencies on the near-surface geology. We have investigated the variations of the 3-D average squared soil displacement over different timescales. The results clearly indicate ballistic behaviour for short timescales being indicative for the properties of the shallow material. Differences in the structural heterogeneity of the subsoil produce different scattering properties, changing the character of motion from nearly ballistic to diffusive on frequency-dependent timescales for all materials. Although in a strict sense the seismic noise wavefield is not completely isotropic, an ultimate pre-condition for a diffusive wavefield, the deviations compared to a uniform distribution are rather small. This means that the emergence of the Green's function is effective for all network sites after a sufficient self-averaging process that is provided by the scattering and the random spatial-temporal noise source distribution.
    Keywords: Seismology
    Print ISSN: 0956-540X
    Electronic ISSN: 1365-246X
    Topics: Geosciences
    Published by Oxford University Press on behalf of The Deutsche Geophysikalische Gesellschaft (DGG) and the Royal Astronomical Society (RAS).
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  • 6
    Publication Date: 2014-07-01
    Description: The assessment of the shear wave velocity ( V s) and quality factor ( Q s) profiles below a site is necessary to characterize its site response. Recently, methods based on the analysis of seismic noise have proved to be very efficient for providing a sufficiently accurate estimation of the V s versus depth at reasonable costs for engineering seismology purposes. In this study, it is investigated if the same methods can also provide, with just a few additional and successive calculation steps, realistic Q s versus depth estimations. A data set of seismic noise collected at the Tito test site in southern Italy by a microarray of seismological stations was used, and the obtained Q s results are compared with those estimated by independent geophysical investigations. It is shown that the values are consistent and that the seismic noise analysis has the potential to also provide a more comprehensive ( V s and Q s) description of the geological structure below a site. ©2014 Springer Science+Business Media Dordrecht
    Print ISSN: 1383-4649
    Electronic ISSN: 1573-157X
    Topics: Geosciences , Physics
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  • 7
    Publication Date: 2013-04-01
    Description: Earthquake early warning systems (EEWS) are considered to be an effective, pragmatic, and viable tool for seismic risk reduction in cities. While standard EEWS approaches focus on the real-time estimation of an earthquake’s location and magnitude, innovative developments in EEWS include the capacity for the rapid assessment of damage. Clearly, for all public authorities that are engaged in coordinating emergency activities during and soon after earthquakes, real-time information about the potential damage distribution within a city is invaluable. In this work, we present a first attempt to design an early warning and rapid response procedure for real-time risk assessment. In particular, the procedure uses typical real-time information (i.e., P-wave arrival times and early waveforms) derived from a regional seismic network for locating and evaluating the size of an earthquake, information which in turn is exploited for extracting a risk map representing the potential distribution of damage from a dataset of predicted scenarios compiled for the target city. A feasibility study of the procedure is presented for the city of Bishkek, the capital of Kyrgyzstan, which is surrounded by the Kyrgyz seismic network by mimicking the ground motion associated with two historical events that occurred close to Bishkek, namely the 1911 Kemin ( M  = 8.2; ±0.2) and the 1885 Belovodsk ( M  = 6.9; ±0.5) earthquakes. Various methodologies from previous studies were considered when planning the implementation of the early warning and rapid response procedure for real-time risk assessment: the Satriano et al. (Bull Seismol Soc Am 98(3):1482–1494, 2008 ) approach to real-time earthquake location; the Caprio et al. (Geophys Res Lett 38:L02301, 2011 ) approach for estimating moment magnitude in real time; the EXSIM method for ground motion simulation (Motazedian and Atkinson, Bull Seismol Soc Am 95:995–1010, 2005 ); the Sokolov (Earthquake Spectra 161: 679–694, 2002 ) approach for estimating intensity from Fourier amplitude spectra; and the Tyagunov et al. (Nat Hazard Earth Syst Sci 6:573–586, 2006 ) approach for risk computation. Innovatively, all these methods are jointly applied to assess in real time the seismic risk of a particular target site, namely the city of Bishkek. Finally, the site amplification and vulnerability datasets considered in the proposed methodology are taken from previous studies, i.e., Parolai et al. (Bull Seismol Soc Am, 2010 ) and Bindi et al. (Soil Dyn Earthq Eng, 2011 ), respectively. ©2012 Springer Science+Business Media B.V.
    Print ISSN: 1383-4649
    Electronic ISSN: 1573-157X
    Topics: Geosciences , Physics
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  • 8
    Publication Date: 2014-01-01
    Description: We apply the Bakun and Wentworth ( Bull Seism Soc Am 87:1502–1521, 1997 ) method to determine the location and magnitude of earthquakes occurred in Central Asia using MSK-64 intensity assignments. The attenuation model previously derived and validated by Bindi et al. ( Geophys J Int , 2013 ) is used to analyse 21 earthquakes that occurred over the period 1885–1964, and the estimated locations and magnitudes are compared to values available in literature. Bootstrap analyses are performed to estimate the confidence intervals of the intensity magnitudes, as well as to quantify the location uncertainty. The analyses of seven significant earthquakes for the hazard assessment are presented in detail, including three large historical earthquakes that struck the northern Tien-Shan between the end of the nineteenth and the beginning of the twentieth centuries: the 1887, M 7.3 Verny, the 1889, M 8.3 Chilik and the 1911, M 8.2 Kemin earthquakes. Regarding the 1911, Kemin earthquake the magnitude values estimated from intensity data are lower (i.e. MILH = 7.8 and MIW = 7.6 considering surface wave and moment magnitude, respectively) than the value M  = 8.2 listed in the considered catalog. These values are more in agreement with the value M S = 7.8 revised by Abe and Noguchi ( Phys Earth Planet In , 33:1–11, 1983b ) for the surface wave magnitude. For the Kemin earthquake, the distribution of the bootstrap solutions for the intensity centre reveal two minima, indicating that the distribution of intensity assignments do not constrain a unique solution. This is in agreement with the complex source rupture history of the Kemin earthquake, which involved several fault segments with different strike orientations, dipping angles and focal mechanisms (e.g. Delvaux et al. in Russ Geol Geophys 42:1167–1177, 2001 ; Arrowsmith et al. in Eos Trans Am Geophys Union 86(52), 2005 ). Two possible locations for the intensity centre are obtained. The first is located on the easternmost sub-faults (i.e. the Aksu and Chon-Aksu segments), where most of the seismic moment was released (Arrowsmith et al. in Eos Trans Am Geophys Union 86(52), 2005 ). The second location is located on the westernmost sub-faults (i.e. the Dzhil'-Aryk segment), close to the intensity centre location obtained for the 1938, M 6.9 Chu-Kemin earthquake (MILH = 6.9 and MIW = 6.8). ©2013 Springer Science+Business Media Dordrecht
    Print ISSN: 1383-4649
    Electronic ISSN: 1573-157X
    Topics: Geosciences , Physics
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  • 9
    Publication Date: 2013-04-01
    Description: We present results from a vertical array of accelerometers that was recently installed in Bishkek (Kyrgyzstan) with the long-term aim of recording strong motion data. Taking advantage of recordings of a Mb 4.7 earthquake that occurred 40 km from the array site during the installation phase, we provide results of some preliminary data analysis. First, estimates of the S-wave velocity and Q s structure are deduced by the inversion of the deconvolved wavefield between the sensors in the borehole. Furthermore, the application of the nonstationary ray decomposition Kinoshita (Earth Planets Space 61:1297-1312, 2009 ) allowed at least three reflectors in the shallow velocity structure below the array to be identified. The complex nature of the wavefield (with up-going, down-going waves, and converted phases) due to the coarse, unconsolidated subsoil structure is highlighted by means of numerical simulations of ground motion. ©2012 Springer Science+Business Media Dordrecht
    Print ISSN: 1383-4649
    Electronic ISSN: 1573-157X
    Topics: Geosciences , Physics
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  • 10
    Publication Date: 2003-10-01
    Description: In order to evaluate thefrequency dependence of site effects, thejoint analysis of the standard spectralratio technique with a sonogram approach isproposed (Joint Analysis of Sonogram andStandard Spectral Ratio). Two tools aresuggested: the enhanced sonograms andthe differential sonograms . Inparticular, the local geology effects areinvestigated by considering both theamplification of the seismic signals andtheir prolongation. Tests carried out onsynthetic signals show the capability ofthe sonogram approach to evaluate thefrequency-dependent lengthening of theseismic signal. The JASSSR is applied todata recorded by a dense local networkdeployed during the Umbria-Marche seismicsequence of 1997 and to data recorded inthe Volvi Test site (Euroseistest, Greece).The results show that using the JASSSR gives amore complete overview of the effects oflocal geology on seismic ground motion than maybe obtained by using the StandardSpectral Ratio alone. In particular, theeffect of secondary arrivals, both on theamplitude and on the lengthening of theseismic ground motion, can be pointed out.In addition, the characteristic frequencyof these arrivals can be evaluated. ©2003 Kluwer Academic Publishers
    Print ISSN: 1383-4649
    Electronic ISSN: 1573-157X
    Topics: Geosciences , Physics
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