Beyond SaGMRotI: Conversion to SaArb, SaSN, and SaMaxRot

Watson-Lamprey, Jennie; Boore, David M.

doi:10.1785/0120070007

Cited by 84 publications

(58 citation statements)

References 11 publications

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“…We find that a ratio close to unity is obtained up to 5 km both for PGA and PGV. Our results agree with the study of Watson-Lamprey and Boore (2007), which clearly shows that the maximum amplitude is observed on the SN direction only at very short distances from the fault and that at larger distances the SN component of ground motion seldom corresponds to the largest value.…”

Section: Ground-motion Componentssupporting

confidence: 92%

Italian strong motion records in ITACA: overview and record processing

Pacor

Paolucci

Ameri

et al. 2011

Bull Earthquake Eng

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The published version 1.0 of the new Italian strong-motion database ITACA (Italian ACcelerometric Archive,http://itaca.mi.ingv.it) includes to date (December 2010) about 4,000 three-component waveforms up to M 6.9,from more than 1,800 earthquakes up to 6.9,recorded by about 400 stations in the period 1972–2009. The uncorrected and corrected strong motion data are archived and can be retrieved with their metadata,concerning events,stations and waveforms. The aim of this paper is to present the procedures for processing the records included in ITACA,accounting for the heterogeneity of this data set,both in terms of quality and amplitude of records as well as illustrating the main features of the ITACA strong-motion dataset. Later,we focus on the “exceptional” ground-motion records,that we,conventionally,denote as those having peak acceleration and peak velocity larger than 300 cm/s2 and 15 cm/s,respectively. These records are less than 2% of the whole ITACA dataset but they are the most relevant for the seismic hazard and engineering implications. Such large peak values,recorded at distances up to 30 km,are related not only to the strongest Italian earthquakes,but also to events with magnitude down to 4. Furthermore,we investigate the dependence of the largest peak values on horizontal and vertical directions and on source-to-site distance

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Section: Ground-motion Componentssupporting

confidence: 92%

Italian strong motion records in ITACA: overview and record processing

Pacor

Paolucci

Ameri

et al. 2011

Bull Earthquake Eng

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“…The orientation of this critical azimuth varies with oscillator period. The medians of maximum-direction ground motions are systematically higher than those for the geometric mean by factors ranging from 1.2 to 1.35 depending on oscillator period (Beyer and Bommer 2006;Watson-Lamprey and Boore 2007;Bozorgnia 2007, 2008). Using different procedures, modification factors of 1.1 to 1.5 were found by Huang et al (2008).…”

Section: Bidirectional Ground Motion Definitionsmentioning

confidence: 88%

“…Hazard analyses performed with relatively high r ln values for a reference rock site and then modified by deterministic site factors overestimate ground motions (Goulet and Stewart 2009). In summary, while the GMRotI50 r ln is arguably too low relative to r ln for the arbitrary component (difference in variance of 0.03-0.05 for PGA to 1.0 sec S a ; Bozorgnia 2007, Watson-Lamprey andBoore 2007), it is also too high for common site conditions (e.g., for a change of V s30 from the common reference value of 760 m=s to a typical soil site condition of 270 m=s, the difference in variance is $0.1 to 0.03 for PGA to 1.0 sec S a for M>7 earthquakes at distances < $15 km; Abrahamson et al 2008). While this trade-off of compensating errors is hardly ideal, the use of the existing USGS probabilistic ground motion maps combined with NEHRP site and risk factors represents the most reasonable (probabilistically most consistent) basis currently available for evaluating design ground motions along the principal axes of structures.…”

Section: Rationale For the Bias Concernmentioning

confidence: 89%

“…By definition, S a-arb will be smaller than the GMRotI50 spectral ordinate for 50% of the possible orientations. Beyer and Bommer (2006), Bozorgnia (2007, 2008), and Watson-Lamprey and Boore (2007) found that GMPEs derived from arbitrary-component motions have similar medians but larger standard deviations relative to GMPEs derived from the geometric mean. The second additional measure is the maximum-direction ground motion defined in the Introduction and illustrated in Figure 1.…”

Section: Bidirectional Ground Motion Definitionsmentioning

confidence: 96%

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Representation of Bidirectional Ground Motions for Design Spectra in Building Codes

et al. 2011

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The 2009 NEHRP Provisions modified the definition of horizontal ground motion from the geometric mean of spectral accelerations for two components to the peak response of a single lumped mass oscillator regardless of direction. These maximum-direction (MD) ground motions operate under the assumption that the dynamic properties of the structure (e.g., stiffness, strength) are identical in all directions. This assumption may be true for some in-plan symmetric structures, however, the response of most structures is dominated by modes of vibration along specific axes (e.g., longitudinal and transverse axes in a building), and often the dynamic properties (especially stiffness) along those axes are distinct. In order to achieve structural designs consistent with the collapse risk level given in the NEHRP documents, we argue that design spectra should be compatible with expected levels of ground motion along those principal response axes. The use of MD ground motions effectively assumes that the azimuth of maximum ground motion coincides with the directions of principal structural response. Because this is unlikely, design ground motions have lower probability of occurrence than intended, with significant societal costs. We recommend adjustments to make design ground motions compatible with target risk levels.

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“…The record can be used to assess the principal directions of ground motions based on the Arias intensity tensor or the axis along the maximum response, which are unknown a priori (Arias, 1970(Arias, , 1996Hong and Goda, 2007;Watson-Lamprey and Boore, 2007). By defi nition, the major, intermediate, and minor principal directions or axes are associated with the maximum, intermediate, and minimum values of the Arias intensity measure, respectively (Arias, 1970(Arias, , 1996Penzien and Watabe, 1975;Kubo and Penzien, 1979).…”

Section: Introductionmentioning

confidence: 99%

Characteristics of horizontal ground motion measures along principal directions

Hong

Goda²

2010

Earthq. Engin. Engin. Vib.

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Ground motion records are often used to develop ground motion prediction equations (GMPEs) for a randomly oriented horizontal component, and to assess the principal directions of ground motions based on the Arias intensity tensor or the orientation of the major response axis. The former is needed for seismic hazard assessment, whereas the latter can be important for assessing structural responses under multi-directional excitations. However, a comprehensive investigation of the pseudo-spectral acceleration (PSA) and of GMPEs conditioned on different axes is currently lacking. This study investigates the principal directions of strong ground motions and their relation to the orientation of the major response axis, statistics of the PSA along the principal directions on the horizontal plane, and correlation of the PSA along the principal directions on the horizontal plane. For these, three sets of strong ground motion records, including intraplate California earthquakes, inslab Mexican earthquakes, and interface Mexican earthquakes, are used. The results indicate that one of the principal directions could be considered as quasi-vertical. By focusing on seismic excitations on the horizontal plane, the statistics of the angles between the major response axis and the major principal axis are obtained; GMPEs along the principal axes are provided and compared with those obtained for a randomly oriented horizontal component; and statistical analysis of residuals associated with GMPEs along the principal directions is carried out.

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Beyond SaGMRotI: Conversion to SaArb, SaSN, and SaMaxRot

Cited by 84 publications

References 11 publications

Italian strong motion records in ITACA: overview and record processing

Italian strong motion records in ITACA: overview and record processing

Representation of Bidirectional Ground Motions for Design Spectra in Building Codes

Characteristics of horizontal ground motion measures along principal directions

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