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  • Seismological Society of America  (9)
  • 1
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    8 March 2010 Elazig-Kovancilar (Turkey) Earthquake: Observations on Ground Motions and Building Damage (2011)
    Seismological Society of America
    Details
    Publication Date: 2011-01-01
    Print ISSN: 0895-0695
    Electronic ISSN: 1938-2057
    Topics: Geosciences
    Published by Seismological Society of America
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  • 2
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    Full Waveform Inversion for Seismic Velocity and Anelastic Losses in Heterogeneous Structures (2007)
    Seismological Society of America
    Details
    Publication Date: 2007-12-01
    Description: We present a least-squares optimization method for solving the nonlinear full waveform inverse problem of determining the crustal velocity and intrinsic attenuation properties of sedimentary valleys in earthquake-prone regions. Given a known earthquake source and a set of seismograms generated by the source, the inverse problem is to reconstruct the anelastic properties of a heterogeneous medium with possibly discontinuous wave velocities. The inverse problem is formulated as a constrained optimization problem, where the constraints are the partial and ordinary differential equations governing the anelastic wave propagation from the source to the receivers in the time domain. This leads to a variational formulation in terms of the material model plus the state variables and their adjoints. We employ a wave propagation model in which the intrinsic energy-dissipating nature of the soil medium is modeled by a set of standard linear solids. The least-squares optimization approach to inverse wave propagation presents the well-known difficulties of ill posedness and multiple minima. To overcome ill posedness, we include a total variation regularization functional in the objective function, which annihilates highly oscillatory material property components while preserving discontinuities in the medium. To treat multiple minima, we use a multilevel algorithm that solves a sequence of subproblems on increasingly finer grids with increasingly higher frequency source components to remain within the basin of attraction of the global minimum. We illustrate the methodology with high-resolution inversions for two-dimensional sedimentary models of the San Fernando Valley, under SH-wave excitation. We perform inversions for both the seismic velocity and the intrinsic attenuation using synthetic waveforms at the observer locations as pseudoobserved data.
    Print ISSN: 0037-1106
    Electronic ISSN: 1943-3573
    Topics: Geosciences , Physics
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  • 3
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    Full Anelastic Waveform Tomography Including Model Uncertainty (2008)
    Seismological Society of America
    Details
    Publication Date: 2008-12-01
    Description: This article is concerned with the problem of seismic inversion in the presence of model uncertainty. In a recent article (Askan et al., 2007), we described an inverse adjoint anelastic wave propagation algorithm for determining the crustal velocity and attenuation properties of basins in earthquake-prone regions. We formulated the tomography problem as a constrained optimization problem where the constraints are the partial and the ordinary differential equations that govern the anelastic wave propagation from the source to the receivers. We employed a wave propagation model in which the intrinsic energy-dissipating nature of the soil medium was modeled by a set of standard linear solids. Assuming no information was initially available on the target shear-wave velocity distribution, we employed a homogeneous shear-wave velocity profile as the initial guess. In practice, some information is usually available. The purpose of the present article is to modify our nonlinear inversion method to start from an initial velocity model, and include a priori information regarding the initial model parameters in the misfit (objective) function. To represent model uncertainties, given an initial velocity model, in addition to the data misfit term in our objective function, we include an L (super 2) -normed weighting term, which quantifies the model estimation errors, independently of the measured data. We use total variation (TV) regularization to overcome ill posedness. We illustrate the methodology with pseudo-observed data from two-dimensional sedimentary models of the San Fernando Valley, using a source model with an antiplane slip function.
    Print ISSN: 0037-1106
    Electronic ISSN: 1943-3573
    Topics: Geosciences , Physics
    Published by Seismological Society of America
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  • 4
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    Strong-Ground-Motion Simulation of the 6 April 2009 L'Aquila, Italy, Earthquake (2012)
    Seismological Society of America
    Details
    Publication Date: 2012-08-01
    Description: On 6 April 2009, an earthquake of M (sub w) 6.13 (Herrmann et al., 2011) occurred in central Italy, close to the town of L'Aquila. Although the earthquake is considered to be a moderate-size event, it caused extensive damage to the surrounding area. The earthquake is identified with significant directivity effects: high-amplitude, short-duration motions are observed at the stations that are oriented along the rupture direction, whereas low-amplitude, long-duration motions are observed at the stations oriented in the direction opposite to the rupture. The complex nature of the earthquake combined with its damage potential brings the need for studies that assess the seismological characteristics of the 2009 L'Aquila mainshock. In this study, we present the strong-ground-motion simulation of this particular earthquake using a stochastic finite-fault model with a dynamic corner frequency approach. For modeling the resulting ground motions, we choose two finite-fault source models that take into account the source complexity of the L'Aquila mainshock. In order to test the sensitivity of ground-motion parameters to the seismic wave attenuation parameters, we use two different attenuation models obtained in the study region using weak-motion and strong-motion databases. Comparisons are made between the attenuation of synthetics and ground-motion prediction equations (GMPEs). Synthetic ground motions are further compared with the observed ones in terms of Fourier amplitude and response spectra at 21 strong-ground-motion stations that recorded the mainshock within an epicentral distance of 100 km. The spatial distribution of shaking intensity obtained from the "Did You Feel It?" project and site survey results are compared with the spatial distributions of simulated peak ground-motion intensity parameters. Our results show that despite the limitations of the method in simulating the directivity effects, the stochastic finite-fault model seems an effective and fast tool to simulate the high-frequency portion of ground motions.
    Print ISSN: 0037-1106
    Electronic ISSN: 1943-3573
    Topics: Geosciences , Physics
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  • 5
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    Fault Process and Broadband Ground-Motion Simulations of the 23 October 2011 Van (Eastern Turkey) Earthquake (2013)
    Seismological Society of America
    Details
    Publication Date: 2013-10-22
    Print ISSN: 0037-1106
    Electronic ISSN: 1943-3573
    Topics: Geosciences , Physics
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  • 6
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    Relationships between Felt Intensity and Recorded Ground-Motion Parameters for Turkey (2014)
    Seismological Society of America
    Details
    Publication Date: 2014-01-21
    Description: In this paper, empirical relationships between modified Mercalli intensity (MMI) and recorded peak ground-motion parameters are developed for Turkey. Strong ground motion data from moderate-to-large earthquakes are employed along with the corresponding MMI information inferred from isoseismal maps and earthquake damage reports. Linear least-squares regression technique is used to derive the following simple relationships between MMI and peak ground acceleration (PGA), peak ground velocity (PGV), and pseudospectral acceleration (PSA): MMI=0.132+3.884Xlog(PGA), MMI=2.673+4.340Xlog(PGV), MMI=-0.247+3.404Xlog[PSA(0.3 s)], MMI=-0.934+4.119Xlog[PSA(1.0 s)], and MMI=-0.313+4.453Xlog[PSA(2.0 s)]. Despite weak dependencies of the residuals on magnitude or distance terms, we also developed refined predictive relationships that include M (sub w) and epicentral distance as independent variables. The simple predictive equations are then compared with similar relationships developed with data from other regions in the world. These comparisons confirm that such relationships should be derived from regional datasets because both the ground-motion content and damage types exhibit local properties. Alternatively, refined relationships, which do not show any regional dependencies, can be employed. Finally, an application is presented in terms of a comparison between the estimated (computed) and observed intensity map of the 17 August 1999 Kocaeli (M (sub w) 7.4) earthquake. The estimated maps from both MMI-PGA and MMI-PGV relationships are found to be in close agreement with the observed intensity map.
    Print ISSN: 0037-1106
    Electronic ISSN: 1943-3573
    Topics: Geosciences , Physics
    Published by Seismological Society of America
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  • 7
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    A Methodology for Seismic Loss Estimation in Urban Regions Based on Ground-Motion Simulations (2011)
    Seismological Society of America
    Details
    Publication Date: 2011-03-22
    Description: Seismic vulnerability assessment of residential buildings in regions of high seismicity is an interdisciplinary problem requiring major inputs from fields of seismology and earthquake engineering. The basic two components of loss estimation methods are information on regional seismicity and building stock. This study presents a realistic loss estimation methodology where the first component, input ground motions, is obtained from regional ground-motion simulations using the stochastic finite-fault technique. The second component, building vulnerability information, on the other hand, is taken into account using fragility analyses. Introducing the ground-motion intensity parameters obtained from simulations to the fragility curves, we obtain seismic loss distribution in a region. In this study, we demonstrate the loss estimation methodology with an application to three northwestern cities in Turkey (Duzce, Bolu, and Kaynasli) that experienced two major earthquakes (M (sub w) 7.4 and M (sub w) 7.1) in less than three months in 1999. We initially verify the methodology with comparisons of observed and estimated damage ratios for the 12 November 1999 (M (sub w) 7.1) Duzce earthquake. Later, we present the estimated damage ratios under scenario earthquakes in the region for a magnitude range of M (sub w) 5.5-7.5. M (sub w) 6.5 is predicted to be the threshold magnitude for the cities of Duzce and Kaynasli where more than 60% of the building stock experience moderate and heavy damage. Because Bolu is at a farther distance from the fault plane, less damage is estimated for M (sub w) 5.5-7.0 than those in the other centers. For M (sub w) 7.5, all three cities are predicted to experience substantial rates of heavy damage and collapse.
    Print ISSN: 0037-1106
    Electronic ISSN: 1943-3573
    Topics: Geosciences , Physics
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  • 8
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    Stochastic Strong Ground Motion Simulation of the 12 November 1999 Duzce (Turkey) Earthquake Using a Dynamic Corner Frequency Approach (2010)
    Seismological Society of America
    Details
    Publication Date: 2010-07-27
    Description: On 12 November 1999, only three months after the 17 August 1999 Kocaeli earthquake (M (sub w) 7.4), an earthquake of M (sub w) 7.1 occurred immediately to the east of the Kocaeli rupture in northwestern Turkey resulting in extensive structural damage in the city of Duzce and its surrounding area. It was reported to be a right-lateral strike slip event on the previously unbroken segment of the North Anatolian fault zone with a north-dipping fault plane. This paper presents stochastic finite-fault simulation of near-field ground motions from this earthquake at selected near-fault stations based on a dynamic corner frequency approach using the computer program EXSIM (Motazedian and Atkinson, 2005). The method requires region-specific source, path, and site characterizations as input model parameters. The source mechanism of the 1999 Duzce event and regional path effects are well constrained from previous studies of the earthquake. The local site effects at the selected stations are studied as a combination of the kappa operator and frequency-dependent soil amplification. The model parameters are validated against recordings and a stress-drop value of 100 bars is estimated for the 1999 Duzce earthquake. The validated model is then used to compute synthetic records around the fault. Distribution of peak ground-motion parameters is observed to be consistent with the building damage distribution in the near-fault region most affected by the seismic shaking. The attenuation of synthetic ground-motion parameters is compared with recent ground-motion prediction equations proposed for the region by Gulkan and Kalkan (2002), Ulusay et al. (2004), and Akkar and Bommer (2007), as well as two next generation attenuation models by Boore and Atkinson (2007) and Campbell and Bozorgnia (2007). Despite discrepancies at several stations, stochastic finite-fault modeling based on a dynamic corner frequency approach confirms to be a practical tool to reproduce the ground motions of large earthquakes.
    Print ISSN: 0037-1106
    Electronic ISSN: 1943-3573
    Topics: Geosciences , Physics
    Published by Seismological Society of America
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  • 9
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    Strong-Ground-Motion Simulation of the 6 April 2009 L’Aquila, Italy, Earthquake (2012)
    Seismological Society of America
    Details
    Publication Date: 2017-04-04
    Description: On 6 April 2009, an earthquake of Mw 6:13 (Herrmann et al., 2011) occurred in central Italy, close to the town of L’Aquila. Although the earthquake is considered to be a moderate-size event, it caused extensive damage to the surrounding area. The earthquake is identified with significant directivity effects: highamplitude, short-duration motions are observed at the stations that are oriented along the rupture direction, whereas low-amplitude, long-duration motions are observed at the stations oriented in the direction opposite to the rupture. The complex nature of the earthquake combined with its damage potential brings the need for studies that assess the seismological characteristics of the 2009 L’Aquila mainshock. In this study, we present the strong-ground-motion simulation of this particular earthquake using a stochastic finite-fault model with a dynamic corner frequency approach. For modeling the resulting ground motions, we choose two finite-fault source models that take into account the source complexity of the L’Aquila mainshock. In order to test the sensitivity of ground-motion parameters to the seismic wave attenuation parameters, we use two different attenuation models obtained in the study region using weak-motion and strong-motion databases. Comparisons are made between the attenuation of synthetics and ground-motion prediction equations (GMPEs). Synthetic ground motions are further compared with the observed ones in terms of Fourier amplitude and response spectra at 21 strong-ground-motion stations that recorded the mainshock within an epicentral distance of 100 km. The spatial distribution of shaking intensity obtained from the “Did You Feel It?” project and site survey results are compared with the spatial distributions of simulated peak ground-motion intensity parameters. Our results show that despite the limitations of the method in simulating the directivity effects, the stochastic finite-fault model seems an effective and fast tool to simulate the high-frequency portion of ground motion.
    Description: Published
    Description: 1429-1445
    Description: 4.1. Metodologie sismologiche per l'ingegneria sismica
    Description: JCR Journal
    Description: restricted
    Keywords: 2009 L'Aquila sequence ; strong ground motion simulations ; 04. Solid Earth::04.06. Seismology::04.06.04. Ground motion
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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