Ground Motion Response Spectra Research Articles

Consecutive combined response spectrum

Appropriate estimates of earthquake response spectrum are essential for design of new structures, or seismic safety evaluation of existing structures. This paper presents an alternative procedure to construct design spectrum from a combined normalized response spectrum (NRSC) which is obtained from pseudo-velocity spectrum with the ordinate scaled by different peak ground amplitudes (PGA, PGV, PGD) in different period regions. And a consecutive function f(T) used to normalize the ordinates is defined. Based on a comprehensive study of 220 strong ground motions recorded during recent eleven large worldwide earthquakes, the features of the NRSC are discussed and compared with the traditional normalized acceleration, velocity and displacement response spectra (NRSA, NRSV, NRSD). And the relationships between ground amplitudes are evaluated by using a weighted mean method instead of the arithmetic mean. Then the NRSC is used to define the design spectrum with given peak ground amplitudes. At last, the smooth spectrum is compared with those derived by the former approaches, and the accuracy of the proposed spectrum is tested through an analysis of the dispersion of ground motion response spectra.

Variation of earthquake ground motions within a very small distance

At present, dense strong motion observation networks have been established in Japan. One of the important findings based on these networks is that strong ground motions are quite site-dependent. Characteristics of observed ground motions at nearby stations can exhibit a significant variation, even when the stations are within several hundreds of meters. These observations raise one important question; if characteristics of strong ground motions exhibit large variations even for smaller regions, we should be concerned about the application of observed or predicted ground motions for the assessment of structures. In particular, if ground-motion parameters such as PGA, PGV, Spectral Intensity, etc., exhibit large variations for smaller regions, their use for the seismic design and practice will be subject to restriction. In other words, the evaluation of variation of these parameters is an important issue. From such a point of view, the authors investigated the variation of observed ground motions within a very small distance in this study. First of all, fifteen couples of adjacent strong motion stations in Japan, where the distance is within 100m, were listed up based on our field reconnaissance. Then, microtremor measurements were carried out at each of the station pairs. Next, variation of recorded earthquake ground motions for the station pairs was examined based on various ground motion parameters and response spectra. Moreover, we investigated the key factor which is affecting the variation of observed ground motions.

NGA-West2 Models for Ground Motion Directionality

The NGA-West2 research program, coordinated by the Pacific Earthquake Engineering Research Center (PEER), is a major effort to produce refined models for predicting ground motion response spectra. This study presents new models for ground motion directionality developed as part of that project. Using a database of recorded ground motions, empirical models have been developed for a variety of quantities related to direction-dependent spectra. A model is proposed for the maximum spectral acceleration observed in any orientation of horizontal ground motion shaking ( Sa RotD100), which is formulated as a multiplicative factor to be coupled with the NGA-West2 models that predict the median spectral accelerations over all orientations ( Sa RotD50). Models are also proposed for the distribution of orientations of the Sa RotD100 value, relative to the fault and the relationship between Sa RotD100 orientations at differing periods. Discussion is provided regarding how these results can be applied to perform seismic hazard analysis and compute realistic target spectra conditioned on different parameters.

Ground motion record simulation for structural analysis by consideration of spectral acceleration autocorrelation pattern

A novel approach is introduced to generate simulated ground motion records by considering spectral acceleration correlations at multiple periods. Most of the current reliable Ground Motion Record (GMR) simulation procedures use a seismological model including source, path and site characteristics. However, the response spectrum of simulated GMR is somewhat different when compared with the response spectrum based on recorded GMRs. More specifically, the correlation between the spectral values at multiple periods is a characteristic of a record which is usually different between simulated and recorded GMRs. As this correlation has a significant influence on the structural response, it is needed to investigate the consistency of the simulated ground motions with actual records. This issue has been investigated in this study by incorporating an optimization algorithm within the Boore simulation technique. Eight seismological key parameters were optimized in order to achieve approximately the same correlation coefficients and spectral acceleration between two sets of real and simulated records. The results show that the acceleration response spectra of the synthetic ground motions also have good agreement with the real recorded response spectra by implementation of the proposed optimized values.

Seismic soil-structure interaction with consideration of spatial incoherence of seismic ground motions: A case study

This paper presents a case study of seismic soil-structure interaction (SSI) analysis with consideration of spatial incoherence of seismic input ground motions. The SSI analyses were performed using the SASSI computer program for the Auxiliary Control Building (ACB) structure of an existing nuclear power plant on a hard rock site located in the Center and Eastern United States (CEUS) region. The incoherent seismic input motions for the hard rock site used for the analyses were generated using the computer program INCOH that works together with SASSI. The objective of the analyses was to generate maximum seismic response parameters for assessment of potential impact of newly developed site-specific (ground motion) response spectra (SSRS) on the seismic design of the ACB and potential benefits that could be gained by considering spatial incoherence of seismic input motions.Maximum seismic response values for selected response parameters of interest were generated with both SSRS-compatible coherent and incoherent seismic input motions. Comparisons were made of the corresponding maximum response parameter values and in-structure (acceleration) response spectra (ISRS) generated for both the coherent and incoherent motion inputs. These comparisons indicate that, by incorporating incoherence of ground motions in the seismic input, the maximum response values reduces and the ISRS peak amplitudes in the high frequency range (>10Hz) also reduce from the corresponding response values resulting from the coherent motion input. The amount of ISRS-amplitude reduction increases as the spectral frequency increases, as expected. Such reductions can be as much as 20–50%. This case study demonstrates that, for a CEUS hard rock site where relatively high high-frequency in the seismic input response spectra exist, consideration of spatial incoherence of input motions would result in substantial benefits in reducing the high-frequency seismic responses. Such benefits are especially significant when a standard plant design is to be constructed at a CEUS hard rock site where the site-specific ground motion response spectra (GMRS) contain high high-frequency spectral contents.

Stochastic Finite-Fault Simulations of the 2011 Tohoku, Japan, Earthquake

We performed stochastic finite‐fault simulations for the moment magnitude ( M ) 9.0 11 March 2011 Tohoku earthquake at KiK‐net sites using the EXSIM algorithm (Motazedian and Atkinson, 2005; Atkinson et al. , 2009; Boore, 2009). The average response spectra of the simulated ground motions were calculated and compared with observed ground motions to determine whether stochastic finite‐fault modeling can reproduce key features of the recorded motions. To account for variations in source characteristics, we examined three rupture‐process models: a single‐event model with random slip distribution, a single‐event model with prescribed slip distribution (Yagi, 2011; see [Data and Resources][1]), and a multiple‐event model with five strong‐motion generation areas (Kurahashi and Irikura, 2011). The analysis results indicate that the single‐event models can model the high‐frequency response spectra values well but result in significant model bias in the low‐frequency range. By contrast, the multiple‐event model produces ground motions that are in good agreement with the observations in both high‐ and low‐frequency ranges. Furthermore, the multiple‐event model can capture temporal characteristics of observed ground motions, including multiphase arrivals of major seismic‐wave groups. Importantly, the calibrated EXSIM model for the 2011 Tohoku earthquake can be used to produce predicted ground motions in other regions, such as the Cascadia subduction region of North America, by suitable modifications of regional attenuation and site parameters. The suitability of the simple stochastic simulation method to prediction of motions for future events, the details of which are poorly known, makes its calibration to Tohoku a useful exercise. [1]: #sec-14

地震規模・震源位置が同じ2地震による同一地点の観測記録に基づく応答スペクトル振幅のばらつき

The variations of the ground motion response spectra are examined by comparing pairs of ground motion records observed at the same site from two earthquakes with the same magnitude and hypocenter location. In the analysis, it is assumed that the variations of the spectral amplitude is composed of the between-events variations and the within-event variations (also called the intra-event variations and the inter-event variations), and evaluate the standard deviations of each variation. The evaluation result of the logarithmic standard deviation of the total variations (σ) is about 0.35-0.45. And, the standard deviation of the between-events variations (σB) is about 0.2, and the standard deviation of the within-event variations (σW) is about 0.3-0.4. The σW decreases with increasing the distance. This distance dependence can be caused by the effects of scattering of seismic waves in the path.

統計的グリーン関数法による平均的応答スペクトルの直接評価

Considerable differences are sometimes observed among the response spectra of ground motions synthesized by fault model under the same fault parameters. The causes of variation of response spectra are classified into two factors. The one is the random nature of fault rupture process, and the other is problem issued from synthesis method itself. The variation caused by latter factor is undesirable in practical use. This paper presents the method for the direct evaluation of average response spectrum by stochastic Green's function method. In the proposed method, the element earthquake motion is not transformed into time domain using random phase, and the average response spectrum of target large fault is directly evaluated in frequency domain. The average response spectrum can be evaluated without variation because the present method does not include any random factor. The verification tests are carried out using homogeneous fault and the fault consisting of asperity and background region. The average response spectra evaluated by the proposed method agree well with the median of the response spectra of earthquake ground motions synthesized by the ordinal waveform synthesis method.

Comparative Analysis of the Influence of Slope Terrain on Characteristics of Horizontal and Vertical Ground Motion Response Spectrum

All previous earthquake damage show earthquake damage of the buildings on the slope is serious than the buildings on flat ground, so it is important to analyze of the influence of slope terrain on characteristics of horizontal and vertical ground motion response spectrum. The horizontal and vertical seismic elastic responses of 28 viscoelastic rocky slopes by white noises excited, with height of 10m to70m and slope of 15°to 60°, are calculated by numerical finite element analysis method. The influence laws of height and degree of slope on horizontal and vertical ground motion response spectrum and response spectral ratio are analyzed. The distribution laws of the corresponding period of the maximum of response spectral ratios are contrasted. The maximum of amplification factor of design horizontal and vertical ground motion for structures on rock slopes are given to be the references to code for seismic design of building structures.

Comparative Analysis of the Influence of Slope Terrain on Characteristics of Horizontal and Vertical Ground Motion Response Spectrum

All previous earthquake damage show earthquake damage of the buildings on the slope is serious than the buildings on flat ground, so it is important to analyze of the influence of slope terrain on characteristics of horizontal and vertical ground motion response spectrum. The horizontal and vertical seismic elastic responses of 28 viscoelastic rocky slopes by white noises excited, with height of 10m to70m and slope of 15°to 60°, are calculated by numerical finite element analysis method. The influence laws of height and degree of slope on horizontal and vertical ground motion response spectrum and response spectral ratio are analyzed. The distribution laws of the corresponding period of the maximum of response spectral ratios are contrasted. The maximum of amplification factor of design horizontal and vertical ground motion for structures on rock slopes are given to be the references to code for seismic design of building structures.

Near-source Strong Ground Motions Observed in the 22 February 2011 Christchurch Earthquake

On 22 February 2011 at 12:51 p.m. local time, a moment magnitude Mw 6.3 earthquake occurred beneath the city of Christchurch, New Zealand, causing an level of damage and human casualties unparalleled in the country's history. Compared to the preceding 4 September 2010 Mw 7.1 Darfield earthquake, which occurred approximately 30 km to the west of Christchurch, the close proximity of the 22 February event led to ground motions of significantly higher amplitude in the densely populated regions of Christchurch. As a result of these significantly larger ground motions, structures in general, and commercial structures in the central business district in particular, were subjected to severe seismic demands and, combined with the event timing, structural collapses accounted for the majority of the 181 casualties (New Zealand Police 2011). This manuscript provides a preliminary assessment of the near-source ground motions recorded in the Christchurch region. Particular attention is given to the observed spatial distribution of ground motions, which is interpreted based on source, path, and site effects. Comparison is also made of the observed ground motion response spectra with those of the 4 September 2010 Darfield earthquake and those used in seismic design in order to emphasize the amplitude of the ground shaking and also elucidate the importance of local geotechnical and deep geologic structure on surface ground motions. New Zealand resides on the boundary of the Pacific and Australian plates (Figure 1) and its active tectonics are dominated by: 1) oblique subduction of the Pacific plate beneath the Australian plate along the Hikurangi trough in the North Island; 2) oblique subduction of the Australian plate beneath the Pacific plate along the Puysegur trench in the southwest of the South Island; and 3) oblique, right-lateral slip along numerous crustal faults in the axial tectonic belt, of which the …

Probabilistic study of the influence of ground motion variables on response spectra

(Received October 2, 2010, Accepted June 24, 2011)Abstract. Response spectra of earthquake ground motions are important in the earthquake-resistantdesign and reliability analysis of structures. The formulation of the response spectrum in the frequencydomain efficiently computes and evaluates the stochastic response spectrum. The frequency information ofthe excitation can be described using different functional forms. The shapes of the calculated responsespectra of the excitation show strong magnitude and site dependency, but weak distance dependency. Inthis paper, to compare the effect of the earthquake ground motion variables, the contribution of thesesources of variability to the response spectrum’s uncertainty is calculated by using a stochastic analysis.The analytical results show that earthquake source factors and soil condition variables are the mainsources of uncertainty in the response spectra, while path variables, such as distance, anelastic attenuationand upper crust attenuation, have relatively little effect. The presented formulation of dynamic structuralresponse in frequency domain based only on the frequency information of the excitation can provide animportant basis for the structural analysis in some location that lacks strong motion records.Keywords: probabilistic; Fourier amplitude; response spectra; design earthquake

A Short Note on Ground-motion Recordings from the M 7.9 Wenchuan, China, Earthquake and Ground-motion Prediction Equations in the Central and Eastern United States

Ground-motion prediction equations (GMPEs) are one of the key input parameters for seismic hazard assessment ( e.g. , Petersen et al. 2008) and for the site-specific ground-motion response spectrum (GMRS) for nuclear power plants (U.S. Nuclear Regulatory Commission 2007). Examples of GMPEs developed for the central and eastern United States include Somerville et al. (2001), Silva et al. (2002), Campbell (2003), and Atkinson and Boore (2006). Led by Pacific Earthquake Engineering Research, a significant effort is under way to systematically develop GMPEs for the central and eastern United States, next-generation attenuation for the eastern North America, or so-called NGA-East. The development of GMPEs in the central and eastern United States is hindered by the lack of ground-motion observations, particularly from large earthquakes (M 7 or larger). It is desirable to compare any GMPE developed for the central and eastern United States with the ground-motion observations from similar earthquakes in other stable continental regions (SCR) of the world. For example, Cramer and Kumar (2003) compared ground motions recorded by structural response recorders ( i.e. , engineering seismoscopes) within 300 km fault-distance from the 2001 Bhuj, India, earthquake (M 7.6) to several published GMPEs for the central and eastern United States. On 12 May 2008, a large intra-plate earthquake (M 7.9) occurred in Wenchuan, China, along …

Deterministic approach to the seismic hazard of dam sites in Kızılırmak basin, Turkey

Dams constructed on the seismically active regions have a high-risk potential for downstream life and property. Strong ground motion can result in instability of the dam and strength loss of foundation. Active faults within the foundation of dam have the potential to cause damaging displacement of the structures. Appropriate design measures should be considered to obtain rational solution to the problem of catastrophic release of water from the reservoir, and especially to resist earthquake loads. Safety concerns for dams under the earthquake loads involve the seismic hazard evaluation of dam site for the overall stability of structure. Various types of analyses can be used, ranging from a simplified analysis to more complex procedures based on ground motion parameters and response spectra. This paper briefly evaluates seismic hazard analyses for dam structures, and introduces the analyses for thirty-six dams with height ranging from 15 to 195 m in Kizilirmak basin, Turkey. The seismic hazard analyses have indicated that peak ground acceleration varies within a wide range (0.09–0.45 g) for the dam sites of the basin.

중·저준위 방사성 폐기물 처분장의 지진위험도 평가를 위한 지반운동스펙트럼 산정

In this study, a ground motion response spectrum for the seismic risk assessment of low and intermediate level radioactive waste repositories was developed. For the development of the ground motion response spectrum, a probabilistic seismic hazard analysis (PSHA) was performed. Through the performance of a PSHA, a seismic hazard curve which was based on a seismic bed rock was developed. A uniform hazard spectrum was determined by using a developed seismic hazard curve. Artificial seismic motions were developed based on the uniform hazard spectrum. A seismic response analysis was performed on the developed artificial seismic motion. Finally, an evaluation response spectrum for the seismic risk assessment analysis of low and intermediate level radioactive waste repositories was developed.

Spectral Ground Motion Intensity Based on Capacity and Period Elongation

Ground motion intensity parameters are used to express the relationship between expected structural damage and the seismic forces imposed. The graphical representation of damage probability as a function of ground motion intensity leads to fragility curves that are generally used in loss estimation studies. The most typical parameters used to represent the ground motion intensity are peak ground acceleration, peak ground velocity, spectral acceleration, and spectral displacement. Other parameters obtained from the ground motion trace and response spectra have been recommended in literature, but no consensus on which intensity parameter to use exists because of the various drawbacks of these ground motion intensities. A new spectrum ground motion intensity parameter that relies on the expected elongated period of the structure under seismic forces has been developed. This intensity measure takes into account the approximate yield capacity of the structure and the area between the fundamental and elongated ...

Discussion on “Damping coefficients for near-fault ground motion response spectra”

This discussion is based on the paper by Hubbard and Mavroeidis [1]. In this paper, the authors have presented an interesting study on the effect of near-fault ground motions on the damping coefficients examining single degree of freedom (SDOF) systems. This discussion presents some comments on the results and the conclusions of that paper, which imply that some aspects need further clarification and/or improvement.

Damping coefficients for near-fault ground motion response spectra

Damping coefficients are frequently used in earthquake engineering as a simple way to adjust the pseudo-acceleration or displacement response spectra associated with a viscous damping ratio of 5% to the higher values of viscous damping needed for design of structures equipped with base isolation and/or supplemental energy dissipation devices. In this study, damping coefficients for the single-degree-of-freedom system subjected to near-fault ground motions are calculated for a large range of periods and damping levels. The results indicate that damping coefficients proposed in design codes and previous studies, based primarily on far-field ground motion records, tend to not be conservative for near-fault seismic excitations. A new approach is recommended for the derivation of damping coefficients appropriate for engineering analysis and design in the immediate vicinity of the earthquake fault. This includes the normalization of the period axis with respect to the duration of the ground velocity pulses recorded in the near-fault region. The pulse duration is controlled by the rise time on the fault plane and scales directly with earthquake magnitude.

Study on elastic response of structures to near-fault ground motions through record decomposition

Accelerograms recorded near active faults have some important characteristics that make them different from those recorded in far-fault regions. High-frequency components in acceleration records and long-period velocity pulses are among notable specifications of such ground motions. In this paper, a moving average filtering with appropriate cut-off frequency has been used to decompose the near-fault ground motions into two components having different frequency contents: first, Pulse-Type Record (PTR) that possesses long-period pulses; second, the relatively high-frequency BackGround Record (BGR), which does not include large velocity pulses. Comparing the results with those extracted through wavelet analysis shows that moving average filter is an appropriate and efficient tool for near-fault records decomposition. The method is applied to decompose a suite of 91 selected near-fault records and the elastic response of structures is examined through their response to the decomposed parts. The results emphasizes that in contrast with ordinary far-fault earthquake records, response spectra of near-fault ground motions typically have two distinct local peaks, which are representatives of the high- and low-frequency components, i.e., BGR and PTR, respectively. Moreover, a threshold period is identified below which the response of structures is dominated by BGR while PTR controls the response of structures with periods longer than this period.

Time-frequency response spectrum of rotational ground motion and its application

The rotational seismic motions are estimated from one station records of the 1999 Jiji (Chi-Chi), Taiwan, earthquake based on the theory of elastic plane wave propagation. The time-frequency response spectrum (TFRS) of the rotational motions is calculated and its characteristics are analyzed, then the TFRS is applied to analyze the damage mechanism of one twelve-storey frame concrete structure. The results show that one of the ground motion components can not reflect the characteristics of the seismic motions completely; the characteristics of each component, especially rotational motions, need to be studied. The damage line of the structure and TFRS of ground motion are important for seismic design, only the TFRS of input seismic wave is suitable, the structure design is reliable.