Characteristics Of Earthquake Ground Motions Research Articles

Temporal aN and aT in Earthquake Ground Motion at a Single Point

This paper describes a continued study on three-dimensional temporal characteristics of earthquake ground motions at a single point. Based on an instantaneous tangential and normal acceleration decomposition of ground acceleration trajectory, a ground motion can be partitioned into a finite sequence of staggered time intervals of acceleration and deceleration. A formulation is developed to estimate speed and angular changes over a partitioned interval in terms of rates of positive and negative tangential and normal acceleration. Based on these concepts, general ground motion properties, peak ground acceleration, peak ground velocity, and peak ground displacement are examined. Several Northridge earthquake records are studied in detail. It is found that the highest peak of ground acceleration in these records corresponds to a high peak of deceleration, and a velocity maximum often precedes the peak of acceleration.

3D Temporal Characteristics of Earthquake Ground Motion at Single Point

In this paper, we present the results of a study of the temporal 3D characteristics of earthquake ground motion at a single point, which are a completely different set from the frequently used spatial 3D characteristics. A ground motion trajectory from the 1995 Kobe earthquake is analyzed, based on the concept of temporal curvature and torsion. Kinematic turning and twisting of the ground motion are found to have occurred in the form of temporal curvature and torsion pulses. These pulses have typical durations of 100 or 20 ms, respectively. These two types of pulses offer some detailed characterization of the ground acceleration behaviors.

Aseismic designs based on artificial simulations

It is commonly believed that the time-varying frequency characteristics are important for the inelastic response of structures. Design code modification means structural cost changes; therefore any change must be based on solid evidence. Although the significance of time-varying frequency characteristics to ground motion has been recognized for a while, much more in-depth research is necessary before any meaningful engineering design conclusions can be reached. We apply joint time-frequency analysis techniques to a fully non-stationary ground motion model, with both intensity and frequency being non-stationary. The chirplet-based signal approximation is used to extract the time-varying frequencies from seismic ground-motion data samples. Based on that information, we compute the frequency-dependent modulating function in the stochastic model of the evolutionary random process. We generate and compare the artificial waves based on stochastic models of a uniform modulating random process and an evolutionary random process, separately. We also investigate the importance of the time-varying frequency characteristics of earthquake ground motion through an oscillator, with a single degree of freedom and elastic-plastic material behavior.

Probabilistic Representation and Transmission of Nonstationary Processes in Multi-Degree-of-Freedom Systems

A relatively simple and straightforward procedure is presented for representing non-stationary random process data in a compact probabilistic format which can be used as excitation input in multi-degree-of-freedom analytical random vibration studies. The method involves two main stages of compaction. The first stage is based on the spectral decomposition of the covariance matrix by the orthogonal Karhunen-Loeve expansion. The dominant eigenvectors are subsequently least-squares fitted with orthogonal polynomials to yield an analytical approximation. This compact analytical representation of the random process is then used to derive an exact closed-form solution for the nonstationary response of general linear multi-degree-of-freedom dynamic systems. The approach is illustrated by the use of an ensemble of free-field acceleration records from the 1994 Northridge earthquake to analytically determine the covariance kernels of the response of a two-degree-of-freedom system resembling a commonly encountered problem in the structural control field. Spectral plots of the extreme values of the rms response of representative multi-degree-of-freedom systems under the action of the subject earthquake are also presented. It is shown that the proposed random data-processing method is not only a useful data-archiving and earthquake feature-extraction tool, but also provides a probabilistic measure of the average statistical characteristics of earthquake ground motion corresponding to a spatially distributed region. Such a representation could be a valuable tool in risk management studies to quantify the average seismic risk over a spatially extended area.

ウェーブレット変換による地震動の時間-周波数解析

Behaviors of structures during an earthquake are dominated by the accumulation and rate of input energy in frequency domain as well as in time domain. However, such energy parameters have not been related to time-frequency characteristics of earthquake ground motions. This paper proposes a wavelet analysis as a tool to clarify the relationships between time-frequency characteristics of earthquake motions and behaviors of structures. First, the relationships between wavelet coefficients deduced from wavelet transform and time history of energy input are derived. Then, the proposed time-frequency analysis is applied to the motions recorded during the 1995 Hyogoken-nanbu Earthquake, which reveals the relationships between epicentral distance and input energy both in frequency and time domains.

Earthquake ground motion characteristics and seismic energy dissipation : H. Sucuoglu & A. Nurtug, Earthquake Engineering & Structural Dynamics, 24(9), 1995, pp 1195–1213

Earthquake ground motion characteristics and seismic energy dissipation : H. Sucuoglu & A. Nurtug, Earthquake Engineering & Structural Dynamics, 24(9), 1995, pp 1195–1213

Earthquake ground motion characteristics and seismic energy dissipation

AbstractThe sensitivity of seismic energy dissipation to ground motion and system characteristics is assessed. It is found that peak ground acceleration, peak ground velocity to acceleration (V/A), dominant period of ground excitation and effective response duration are closely correlated with the energy dissipated by a SDOF system. Ductility ratio and damping ratio have no significant influence on the energy dissipation. An energy dissipation index is proposed for measuring the damage potential of earthquake ground motion records which includes the effects of basic excitation and response characteristics contributing to the seismic energy dissipation. The proposed index is compared with several intensity measures for the set of 94 ground motion records considered in the study.

建築構造物を対象とした設計用入力地震動の強さ

The recent philosophies and methods in seismic design of buildings are discussed. In these two or three decades, several kinds of new type buildings have been constructed in Japan, that is, high rise buildings, nuclear power plant structures, base isolated buildings, structures on soft soil ground in so called “Water front” areas, and so on. These social demands of constructions have needed new philosophy and method for seismic design. On the other hand, the recent earthquake events occurred in the world, for instance, the 1968 Tokachi-oki earthquake, the 1979 Imperial Valley earthquake, the 1985 Michoacan earthquake and others, showed us important information. The actual situations of building damage and the observed data by strong motion seismographs have showed clearly that the characteristics of earthquake ground motion are greatly effected due to earthquake source processes, seismic wave propagation from source to site, deep subsurface structure in the concerned district and local site conditions. The lessons learned from these recent earthquakes have promoted the developments in the methods of evaluation of intensity of earthquake ground motion to apply the seismic design of buildings. The many kinds of attenuation formulae have been proposed on the basis of the data set of many strong motion accelerograms in the recent destructive earthquakes, and the methods of ground motion simulations have been studied on the theories of physical state on seismic fault, rupture process of seismic source, and wave propagation. Then, the current trends and ideas of evaluation of seismic load, design spectrum or ground motion time histories for response analyses, and new representation of intensity of earthquake ground motion to buildings by “energy spectrum” are discussed in this paper.

Orientation error estimation of buried seismographs in array observation

AbstractArray observation is an efficient tool to investigate various characteristics of earthquake ground motion. However, seismographs used in arrays may involve unexpected errors in their orientations. Methods of orientation error estimation were developed in three‐dimensional space by comparing recorded ground motions at a reference point with those at a checking point. A maximum cross‐correlation method and a maximum coherence method were proposed and their accuracy was demonstrated. The earthquake ground motions recorded in the Chiba array and in two other arrays were used in numerical examples. Non‐trivial orientation errors were detected for all these arrays. The cross‐correlation coefficients and the coherence values between two points increased significantly by correcting the estimated orientation errors.

Engineering implication of ground motion A/V ratio

An earthquake data set consisting of 45 strong motion records was analyzed to investigate the significance of the peak ground acceleration-to-velocity (A/V) ratio as a parameter to indicate the dynamic characteristics of earthquake ground motions. It was found that the A/V ratio of ground motions is a viable indicator of the M (magnitude)-R (epicentral distance) relationships associated with the motions. Due to its tacit correlation with the M-R relationship, the A/V ratio provides useful information regarding the relative frequency content and duration of strong shaking for ground motions resulting from different seismic environments. In light of these observations, the implications of seismic ground motions having different A/V ratios on engineering design were discussed, and an example to incorporate this ratio into the specification of seismic design forces for building structures was illustrated.

Soil amplification based on seismometer array and microtremor observations in Chiba, Japan

AbstractSoil amplification characteristics of earthquake ground motion were investigated in terms of peak ground acceleration and transfer function based on the Chiba array observation records. The amplification of peak ground acceleration occurred mostly at the top soft layer and was similar for the three components. The effects of non‐linear response of soil deposits on the transfer function were examined. Transfer functions calculated by ensemble average were close for the two horizontal components while those obtained from a smoothing operation were generally different. Both the transfer functions from the ensemble average and the smoothing operation underestimated the gain factor around the natural frequencies. A two‐step smoothing procedure was proposed and a rotary spectrum was used to improve the estimation of the transfer function. Microtremors were observed at the locations of the boreholes where seismometers are buried. The power spectrum and spatial coherency of the microtremors were compared with those of the earthquake ground motion. Emphasis was placed on the wavetypes which dominated the peaks in the power spectra.

On the Relationship between Azimuth Dependency of Earthquake Ground Motion and Deep Basin Structure beneath the Osaka Plain.

The typical characteristics of earthquake ground motion in the Osaka Plain are the later arrivals with large amplitudes that are considered to be generated at the edges of the basin structure. We found that the amplitudes of later arrivals have the azimuth dependency according to the location of the epicenters; the amplitudes of the later arrivals generated by the southern earthquakes are larger than those generated by the northern earthquakes. It is, found that the azimuth dependency is not caused by the source effects but by the effects of the basement structure. The basin structure of the Osaka Plain in the N-S direction was obtained through refraction seismic surveys. The survey lines were extended in both north and south directions from the explosion point at a northern area of the Osaka Port; each line had a length of 20-30 km.The modified Aki and Lamer (A-L) method was applied to study the azimuth dependency of the amplitudes of the later arrivals using the surveyed N-S section. From the calculation, the later arrival had a group velocity of 600 m/s which corresponded well to the observed velocities. The azimuth dependency, however, was not well simulated. It is supposed that the incongruity was caused by insufficient information on the edge structure of the sedimentary basin and the structure of shallow sediments.

Reply to Kenneth W. Campbell's “comment on ‘an investigation into earthquake ground motion characteristics in Eastern North America’”

Reply| December 01, 1988 Reply to Kenneth W. Campbell's “comment on ‘an investigation into earthquake ground motion characteristics in Eastern North America’” G. R. Toro; G. R. Toro Risk Engineering, Inc.5255 Pine Ridge Road Golden, Colorado 80403 Search for other works by this author on: GSW Google Scholar R. K. McGuire R. K. McGuire Risk Engineering, Inc.5255 Pine Ridge Road Golden, Colorado 80403 Search for other works by this author on: GSW Google Scholar Author and Article Information G. R. Toro Risk Engineering, Inc.5255 Pine Ridge Road Golden, Colorado 80403 R. K. McGuire Risk Engineering, Inc.5255 Pine Ridge Road Golden, Colorado 80403 Publisher: Seismological Society of America Received: 11 Jul 1988 First Online: 03 Mar 2017 Online Issn: 1943-3573 Print Issn: 0037-1106 Copyright © 1988, by the Seismological Society of America Bulletin of the Seismological Society of America (1988) 78 (6): 2102–2104. https://doi.org/10.1785/BSSA0780062102 Article history Received: 11 Jul 1988 First Online: 03 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation G. R. Toro, R. K. McGuire; Reply to Kenneth W. Campbell's “comment on ‘an investigation into earthquake ground motion characteristics in Eastern North America’”. Bulletin of the Seismological Society of America 1988;; 78 (6): 2102–2104. doi: https://doi.org/10.1785/BSSA0780062102 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyBulletin of the Seismological Society of America Search Advanced Search This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Comment on “an investigation into earthquake ground motion characteristics in Eastern North America” by G. R. Toro and R. K. McGuire

Comment on “an investigation into earthquake ground motion characteristics in Eastern North America” by G. R. Toro and R. K. McGuire

狭帯域位相特性を考慮した建築設計用模擬地震動作成手法

Many works have been carried out in order to examine the phase characteristics of earthquake ground motions for the improvement of earthquake resistant design of building structures. Especially the phase difference distribution has lately attracted considerable attentions as it approximately determines the envelope of time history. This paper examines phase characteristics of recorded motions and their effects on the response spectra by use of the phase difference concept, and discusses the role of phase characteristics which should be considered in simulating motions. The standard deviation of phase differences, σ_<ΔΦ>, for components in a narrow frequency band was found to be considerably less than that for all components. It was also revealed that only the representation of σ_<ΔΦ> is not sufficient to express the phase characteristics of motions in terms of the peak acceleration, Amax, the envelope shape and response characteristics. Then, the narrow band phase difference tendency is cons- idered to be applied in simulating motions. A method of generating artificial ground motions with consideration for phase characteristics in narrow frequency ranges is proposed in this paper. Fourier phases are derived from phase differences generated with consideration for phase characteristics in narrow frequency ranges. The standard deviation of phase differences in a narrow frequency band is set to be about 0.75 times of that for all components which is supposed to be equal to σ_<ΔΦ> of recorded motions. Simulated motions according to the proposed method were confirmed to posess Amax, σ_<ΔΦ> and response spectra satisfactorily close to those of recorded motions.

Observation of 1- to 5-second microtremors and their application to earthquake engineering. Part III. A two-dimensional study of site effects in the San Fernando Valley

AbstractA two-dimensional study of the influence of deep sediment on seismic ground motions was conducted by recording and analyzing long-period microtremors in the San Fernando Valley, California. The recordings were made at 50 regularly distributed sites in the valley. Three reference sites were employed at the baserock outcrop around the valley so as to observe the time-dependent characteristics of the microtremors.Amplitudes in a period range of several seconds correlate with the thicknesses of the sedimentary layers. A site amplification effect, which was evaluated in terms of sediment-to-rock spectral ratios, is qualitatively consistent with available geological and strong motion data. The practical field observation procedure designed for this study, the two-dimensional approach, can be easily used in other surveys for estimating the spatial characteristics of earthquake ground motions in the period range of several seconds.

設計用模擬地震動に関する研究 : その 2 模擬地震動の作成に必要な地震動特性についての解析

設計用模擬地震動に関する研究 : その 2 模擬地震動の作成に必要な地震動特性についての解析

Relationships of maximum acceleration, maximum velocity, distance from source, and local site conditions for moderately strong earthquakes

The paper presents the results of a study to determine the influence of local geological conditions on the attenuation of peak accelerations and peak velocities, with increasing distance from the source of energy release, for earthquakes with a magnitude of about 6.5 occurring in the western part of the United States. While the results can only be considered to be strictly applicable to these conditions, it is hoped that they can also serve as a guide to possible relationships between peak accelerations and peak velocities which may be expected for earthquakes of higher magnitudes occurring in different locations and thereby serve a useful purpose in the difficult task of predicting the likely characteristics of earthquake ground motions in different geological settings.

Engineering characteristics of earthquake ground motions

This paper describes those engineering characteristics of earthquake ground motions pertinent to the development of vibratory motion criteria at nuclear plant sites. It includes a discussion and evaluation of current techniques used to characterize earthquake events and strong motion records, and the geologic factors that influence the ground shaking at a site. In addition, the paper provides an assessment of the data base on which the engineer must draw when formulating criteria; this data base includes the current library of strong motion measurements, artificial earthquake records, empirical scaling curves derived from strong motion records, and soils and geologic data presently available at accelerograph stations.