Characteristics Of Seismic Ground Motion Research Articles

Influence of frequency characteristics of seismic ground motion on the fragility of an RC frame structure

Ground-motion frequency characteristics have a significant impact on structural damage. A quantitative description of the impact of ground-motion spectral features on structures is an urgent topic that requires solutions. In this study, the ratio of peak displacement to peak acceleration (R d2a ) is used as a representative index of the ground-motion spectral characteristics. The seismic records collected from the Kik-net strong-motion array in Japan are grouped according to their R d2a values. By adopting the incremental dynamic analysis method, the seismic fragility curves of a six-story RC frame structure loaded by inputting seismic records with different R d2a values are calculated using the OpenSees platform. The influence of R d2a values on the structural fragility is analyzed. Ground-motion records of liquefied sites are collected, and the peak ratios of seismic records at the liquefied sites are analyzed to reveal the differences in the fragility of the six-story RC structures at liquefied and non-liquefied sites. The results of this study are expected to serve as a reference for the evaluation of structural fragility and to understand the effect of ground-motion frequency characteristics on the fragility of RC frame structures.

Nonlinear seismic response of seabed with terrain variation and seawater-seabed coupling

Understanding the seismic characteristics of submarine sites and conducting seismic response analysis for such locations are crucial for the safety of marine engineering. However, due to a shortage of strong motion records, the ground motion of offshore earthquakes has not yet been fully characterized. The actual seabed conditions are highly intricate, necessitating consideration of factors such as the dynamic coupling effect between seawater and seabed, the strong nonlinearity of seafloor soft sediments, and the diverse nature of natural submarine terrain. In this study, the modified Davidenkov dynamic constitutive model is used to simulate the nonlinear behavior of the soil. The Coupled Acoustic-Structure method is utilized to simulate the interaction between seawater and seabed. Three typical and simplified terrains, namely flat terrain, valley terrain, and hilly terrain, are individually modeled. The measured seafloor ground motions with different frequency components are used as bidirectional seismic excitations input from the bedrock. The amplification factor in terms of CAV is introduced to evaluate the amplification of seismic ground motion characteristics at seabed surface with respect to those at the bedrock surface. The acceleration response spectra in both horizontal and vertical directions, as well as the corresponding vertical-to-horizontal response spectral ratios, at the representative points are obtained, respectively. Several key findings are consistent with the features of the observed offshore and onshore earthquake ground motions. Numerical examples are presented to illustrate the different influence rules of terrain condition, overlying water depth, and seismic intensity on the nonlinear seismic response characteristics.

Ground motion characteristics of the 2015 central Nepal (Gorkha-Dolakha) Earthquake and 2023 SE Turkey Earthquake doublets

The Alpine-Himalayan orogenic belt, the well-identified seismically active region in the world, has been evidenced by the occurrence of recent two devastating earthquake doublets in 2015 in central Nepal (MW 7.8 and MW 7.3) and in 2023 in southeastern Turkey(MW 7.8 and MW 7.5). In this study, seismic ground motion characteristics of two damaging earthquakes namely the 2015 central Nepal earthquake doublet that occurred in the central Himalaya and the 2023 southeastern Turkey earthquake doublet that occurred in the eastern Mediterranean has been investigated. The observed strong-motion recordings indicate that the peak ground acceleration (PGA) values are about 152.61–154.96 cm/s2 of the 2015 central Nepal earthquake doublet at KATNP station and about 451.834–842.924 cm/s2 of the 2023 southeastern Turkey earthquake doublet at station 3137. The seismic ground motion of both the 2015 central Nepal and the 2023 SE Turkey earthquakes doublet shows that the 2015 central Nepal doublet produced much lower peak ground acceleration than the 2023 southeastern Turkey earthquake doublet.

Spatial and Temporal Distribution of Lobate Scarps in the Lunar South Polar Region: Evidence for Latitudinal Variation of Scarp Geometry, Kinematics and Formation Ages, Neo‐Tectonic Activity and Sources of Potential Seismic Risks at the Artemis Candidate Landing Regions

AbstractLobate scarps (thrust faults) in the lunar south polar region (90°–60°S) provide important insights into tectonic history, seismicity, and seismic hazard potential of landing sites. In this study, we discovered 75 new lobate scarps and >500 segments, exhibiting latitudinal variation of geometry and movement directions. Formation ages of 141 prominent scarp segments show fault growth rates and directions, decreasing ages from south pole to mid‐latitude, continuous tectonic activity in the last 100 million years with a peak around 10 Ma, seismic resetting of ages, and timings of global contraction. The scarps are capable of producing small‐medium size moonquakes within 5–10 km depths. The deterministic seismic hazard analysis, considering occurrence of MW 1–4 shallow moonquakes along the scarps in the next few decades, and their seismic ground motion characteristics, suggests variable levels of potential seismic risk at the Artemis candidate landing regions and further probabilistic seismic hazard analysis is necessary.

Simulation of response spectrum-compatible ground motions using wavelet-based multi-resolution analysis

This study proposed a simple and effective response spectrum-compatible ground motions simulation method to mitigate the scarcity of ground motions on seismic hazard analysis base on wavelet-based multi-resolution analysis. The feasibility of the proposed method is illustrated with two recorded ground motions in El Mayor-Cucapah earthquake. The results show that the proposed method enriches the ground motions exponentially. The simulated ground motions agree well with the attenuation characteristics of seismic ground motion without modulating process. Moreover, the pseudo-acceleration response spectrum error between the recorded ground motion and the average of the simulated ground motions is 5.2%, which fulfills the requirement prescribed in Eurocode 8 for artificially simulated ground motions. Besides, the cumulative power spectra between the simulated and recorded ground motions agree well on both high- and low-frequency regions. Therefore, the proposed method offers a feasible alternative in enriching response spectrum-compatible ground motions, especially on the regions with insufficient ground motions.

Evaluation of Seismic Ground Motion Characteristics at Holocene Valley in the Southern Part of Kanto Region

Evaluation of Seismic Ground Motion Characteristics at Holocene Valley in the Southern Part of Kanto Region

Temporal and spectral characteristics of seismic ground motions: Offshore versus onshore

To distinguish offshore and onshore seismic ground motions, conventional analyses in terms of peak ground acceleration (PGA) and earthquake response spectrum (ERS) have been carried out in a recent work by authors and other papers in literature. In the present study, distinct temporal and spectral characteristics between onshore and offshore earthquake ground motions are further investigated in time-domain and frequency-domain. The data used is 69 pairs of concurrent onshore and offshore ground motions collected from the Kyoshin Network (K-NET). Each pair of data are of approximately identical epicenter distances. Comparisons are made on zero-up-crossing period (Tz), peak-to-trough acceleration range (Apt) and period (Tpt), duration of ground motion (Td), predominant frequency (fp) and the spectral bandwidth parameter (ε). The results indicate that for offshore horizontal and vertical seismic signals, statistics of Tz, Tpt, Td and predominant period Tp tend to be larger than the onshore counterparts. Meanwhile, ε of the offshore vertical ground motions is also greater. Through the proposed energy ratio (ER) analysis, the spectral energy of offshore ground motion is found to shift to moderate and low frequency bands. The time-frequency analysis conducted by Hilbert-Huang transform (HHT) shows that the Hilbert spectra of offshore accelerations contain larger spectral energy than the onshore counterpart but the corresponding instantaneous frequencies at peak energy are smaller, especially for horizontal recordings. Therefore, larger dynamic response of offshore structures is prone to be induced by the offshore ground excitation. This is further validated through the dynamic analysis of a marine pipeline in case study.

The effect of local topography on the seismic response of a coupled train-bridge system

The local topography has a significant effect on the characteristics of seismic ground motion. This paper investigates the influence of topographic effects on the seismic response of a train-bridge system. A 3-D finite element model with local absorbing boundary conditions is established for the local site. The time histories of seismic ground motion are converted into equivalent loads on the artificial boundary, to obtain the seismic input at the bridge supports. The analysis of the train-bridge system subjected to multi-support seismic excitations is performed, by applying the displacement time histories of the seismic ground motion to the bridge supports. In a case study considering a bridge with a span of 466 m crossing a valley, the seismic response of the train-bridge system is analyzed. The results show that the local topography and the incident angle of seismic waves have a significant effect on the seismic response of the train-bridge system. Leaving these effects out of consideration may lead to unsafe analysis results.

Effects of site geometry on short-distance spatial coherency in Argostoli, Greece

The spatial variation of the earthquake ground motion over short distances can significantly affect the dynamic response of large and extended engineered structures, especially on sites with inhomogeneity in surface geology and geometry. In current practices, such variation is taken into account in terms of coherency, a function of frequency and distance, established on an essentially empirical basis and difficult to extrapolate at different sites. Hence, a better understanding of its physical significance and its relationship with the underlying ground structure is indispensable. A two-dimensional dense array, deployed at the small and shallow Koutavos-Argostoli valley in Cephalonia, Greece, provided an abundance of data to study the stochastic characteristics of seismic ground motions over very short distances. A set of 46 magnitude 2–5 events at epicentral distances 0–200 km has been selected for the analysis. The lagged coherency of the S-wave dominating seismogram was computed for each station-pair within the array and was averaged over various distance intervals for the whole data set. The results indicate a lack of a clear dependence of the average coherency on the magnitude, back azimuth or site-to-source distance of the event. The most striking result concerns the influence of the site geometry: the coherency is systematically lower for the pairs aligned perpendicular to the axis of the valley (2D) compared to those aligned in the parallel direction. This finding is consistent with the dominance of valley-edge generated surface waves propagating from one edge to the other. The averaged coherency estimates are only weakly represented by the existing parametric models, indicating its strong site dependent nature.

Site response analyses using downhole arrays at various seismic hazard levels of Singapore

Local site conditions can significantly influence the characteristics of seismic ground motions. In this study, site response analyses using one-dimensional linear elastic (LE), equivalent-linear (EQL) and nonlinear (NL) approaches are performed at different seismic hazard levels of Singapore. Two seismic stations, namely, the KAP and BES stations located at soft soil sites, are selected from the national network of Singapore. Firstly, site response estimates using the LE, EQL (SHAKE04) and NL (DEEPSOIL) approaches are compared with the borehole recordings. Results show favorable matches between the predictions and the observations at the KAP site, while under-predictions are observed for all the three site effect approaches at the BES site. Secondly, the applicability of the LE, EQL and NL models is examined at different hazard levels of Singapore. It is found that for the hazard level at a return period of 475 years, the computed maximum strain (γmax) is 0.06% and then the EQL model can provide accurate site response predictions. However, for the hazard level at a return period of 2475 years, the calculated γmax is larger than 2%, resulting in notable differences in the predictions of different site response models. This study highlights the importance of site effects in seismic hazard analysis of Singapore.

Dynamic Characterization and Site Response Studies for an Offshore Site Based on Detailed Geotechnical Tests

The uniqueness of this paper is large amount of field test data and in addition laboratory test results on undisturbed soil samples, has been analyzed to capture the effect of local site condition and material properties of overlying soil on seismic ground motion characteristics. This study involves the seismic site characterization and ground response analysis of an offshore site in Western Yemen. From the results of field and laboratory tests, dynamic properties such as shear modulus and damping ratio for a very low to high strain levels was determined and site characterization was also carried out. Using seismic cone penetration test (SCPT) data a new correlation has been developed to predict the shear wave velocity. Synthetic ground motion was generated using Boore's stochastic modeling technique for ground response analysis and peak ground acceleration (PGA) was evaluated and presented in the paper. This paper also presents a site specific design response spectrum based on Eurocode, corresponding to 475 and 2500 year return period.

EFFECTS OF FOLD STRUCTURE IN THE KASHIWAZAKI-KARIWA NUCLEAR POWER STATION ON THE GROUND MOTION CHARACTERISTICS OF NIIGATAKEN CHUETSU-OKI EARTHQUAKE

In the Kashiwazaki-Kariwa Nuclear Power Station, the seismic ground motion in the south side of the site, was significantly larger than that in the north side of the site, in the 2007 Niigataken Chuetsu-oki earthquake. In order to analyze the effects of geological structure below the site on the seismic ground motion characteristics in the site, we made 2-D soil model and simulated the seismic ground motion with the model using the finite difference method. The soil model was estimated by the result of the geological investigations and described the folding structure just below the Kashiwazaki-Kariwa Nuclear Power Station. For input motion, we defined point source or plane wave, and we considered many directions as the incidence angle. From the result of analysis, we concluded that seismic wave concentrated in the local area of the site with the influence of the complex ground structure, and the ground motion in the south side became larger than that in the north side.

Evaluation of earthquake-induced structural damages by wavelet transform

The dynamic behavior of inelastic structures during an earthquake is a complicated non-stationary process that is affected by the random characteristics of seismic ground motions. The conventional Fourier analysis describes the feature of a dynamic process by decomposing the signal into infinitely long sine and cosine series, which loses all time-located information. However, both time and frequency localizations are necessary for the analysis of an evolutionary spectrum of non-stationary processes. In this paper, an analytical approach for seismic ground motions is developed by applying the wavelet transform, which focuses on the energy input to the structure. The procedure of identification of the instantaneous modal parameters based on the continuous wavelet transform (CWT) is given in detail. And then, a novel method using the auto-regressive moving average (ARMA), called “prediction extension”, is presented to remedy the edge effect during the numerical computation of the CWT. The effectiveness of the method is verified by the use of the benchmark model developed by the American Society of Civil Engineers (ASCE). Finally, a scale model with three-storey reinforced concrete frame-share wall structure is made and tested on a shaking table to investigate the relation between the dynamic properties of structures and energy accumulation and its change rates during the earthquake. The results have shown that the wavelet transform is able to provide a deep insight into the identity of transient signals through time-frequency maps of the time variant spectral decomposition.

Estimation of seismic observation records in the vicinity of large earthquakes and its impact on geological disposal program

AbstractJapan is located at the converging plate boundaries and is one of the most earthquake-prone zones in the world. In order to ensure the safety of a geological repository against earthquakes, a site with a high possibility of direct destruction by active faults should be excluded, and the relationship between the characteristics of seismic ground motion, subsurface structures, geological disposal system and the propagation characteristics of seismic ground motion should be fully investigated. Earthquake-resistant design based on the latest technology is also very important for ensuring the safety of a geological repository.Following rapid improvement of seismic observation networks after the Hyogoken Nanbu earthquake in 1995, numerous seismic observation records have been obtained in the vicinity of large earthquakes. According to these seismic observations, some phenomena that might affect the safety of a geological disposal system have occurred. Some earthquakes occurred in the areas where active faults had not been identified, while some records showed that seismic motion in the deep underground environment was greater than that at the surface. We have identified the implications from the latest information concerning large earthquakes for the geological disposal program. This study made it clear that detailed investigation incorporating state-of-the-art technologies could reduce the likelihood of missing active faults to an extremely low level and a more practical analysis of seismic ground motion could be achieved by taking the latest information into account.

Seismic ground motion analysis of Shanghai Pudong Airport site considering the effects of spatial correlation and irregular topography

The terminal No. II of Shanghai Pudong International Airport is located at Pudong District of Shanghai City near shore of East China Sea, and the area of the long-span terminal is 400 m × 200 m. The construction site of the terminal locates on the irregular topography, and its alluvium achieves about 300 m in thickness. The spatial correlation of seismic ground motion, as well as the amplification of soft alluvium and the effect of irregular topography, should be considered. This paper uses a simplified method to obtain the response spectrum of the engineering bedrock under the irregular topography. The spectrum is used to generate the sets of spatially correlative horizontal and vertical seismic motions. The surface ground motion was calculated under incidence of the spatially correlative seismic motion by 2D finite element method (FEM) model considering nonlinear properties of the soil by means of the equivalent linear method. In order to compare the effect of 2D irregular topography, the seismic response analysis of 1D model is carried out by using the equivalent linear method. For indicating the effect of the spatial correlation of input motions, the horizontal uniform inputs, as well as the horizontal and vertical uniform input are carried out for the seismic response analysis of the site. Finally, some characteristics of seismic ground motion calculated for previously mentioned cases are compared.

Physically compliant, conditionally simulated spatially variable seismic ground motions for performance-based design

The performance-based design of lifeline systems requires spatially variable seismic excitations at the structures' supports that are consistent with prescribed seismic ground motion characteristics and an appropriate spatial variability model—such motions can be obtained through conditional simulation. This work revisits the concept of conditional simulation and critically examines the conformity of the generated motions with the characteristics of the target random field and observations from data recorded at dense instrument arrays. Baseline adjustment processing techniques for recorded earthquake accelerograms are extended to fit the requirements of simulated and conditionally simulated spatially variable ground motions. Emphasis is placed on the use of causal vs acausal filtering in the data processing. Acceleration, velocity and displacement time histories are evaluated in two example applications of the approach. The first application deals with a prescribed synthetic time history that incorporates nonstationarity in the amplitude and frequency content of the motions and depends on earthquake magnitude, source–site distance and local soil conditions; this example results in zero residual displacements. The second application considers as prescribed time history a recording in the vicinity of a fault and yields nonzero residual displacements. It is shown that the conditionally simulated time histories preserve the characteristics of the prescribed ones and are consistent with the target random field. The results of this analysis suggest that the presented methodology provides a useful tool for the generation of spatially variable ground motions to be used in the performance-based design of lifeline systems. Copyright © 2006 John Wiley & Sons, Ltd.

Seismic ground motion relationship in southern China based on stochastic finite-fault model

The characteristics of seismic ground motions in southern China are difficult to determine statistically due to a lack of strong ground motion data. In this study, a stochastic finites-fault ground motion model was adopted to simulate the seismic ground motions at bedrock for southern China, based on parameters derived from small and medium earthquakes that have occurred in the region. From these, the response spectra was estimated. A set of ground motion attenuation relationships was then developed based on simulated peak ground motions and response spectral parameters through regression, which would be applicable for use in engineering practice. Through comparison, it was demonstrated that the proposed ground motion relationships are generally consistent with those obtained from other reported ground motion attenuation models for southern China.

統計的グリーン関数法による強震動予測法の検証と仮想福岡地震への適用

In our previous work we extracted statistical characteristics of seismic ground motions from K-net records of 25 earthquakes observed at 142 stations in the Kyushu region in order to establish the synthesis method of statistical Green's functions. In this paper we study the strong motion prediction method using these statistical Green's functions. First, we apply this method to the Kagoshima-ken Hokuseibu earthquake of March 26, 1997 and compare the synthetics with the observed. Second, we simulate strong motions at the bedrock level during the Hyogo-ken Nanbu earthquake of 1995. Synthetic waveforms based on this method match quite well with the observed. Thus it is proved that we can predict the bedrock motions using our statistical Green's function if we properly express the source model. Finally we applied this method to predict strong motions in Fukuoka City for a hypothesized Fukuoka earthquake. First strong motions at the bedrock level are predicted and then the strong motions at the ground surface are obtained by the 1-D wave propagation theory. The peak ground velocity thus estimated reaches 100 cm/s, which is less than Kobe.

Characteristics of Seismic Ground Motion Based on the Observation of Aftershocks and Microtremors at the Range of Influence of the 1997 Kagoshima-ken Hokuseibu Earthquakes

Characteristics of Seismic Ground Motion Based on the Observation of Aftershocks and Microtremors at the Range of Influence of the 1997 Kagoshima-ken Hokuseibu Earthquakes

Dynamic characteristics of ground motions due to blasting

abstract There is considerable evidence that more rational damage criteria need to be generated with regard to low-rise structures subjected to seismic ground motions. There is not sufficient basis for specifying a maximum ground particle velocity criterion, such as 2 in/sec. A peak ground velocity guideline does not currently take into account a number of important parameters, including the predominant frequencies of the ground motion excitation and the structure being excited. Although a number of states have adopted peak-velocity criteria, such criteria have been ruled inadequate in certain legal decisions affecting blasting operations. The development of more rational damage criteria is thus of significant importance. Such criteria must necessarily consider the dynamic characteristics of seismic ground motions, i.e., pertinent and dominant frequency characteristics, response and Fourier spectra, etc. Very little analysis has been done with regard to determining the dynamic characteristics of blasting ground motions, however. This paper describes a research effort concerned with the determination of these characteristics for a sizeable number of actual blasting records using appropriate theoretical and computer analyses. Peak ground motion versus charge and distance relationships were derived, as well as pertinent response spectra. Statistical representations of the latter were also obtained using some 200 ground motions.