Duration Of Strong Ground Motion Research Articles

Basin boundary seismic effects in Mexico City southern region

AbstractRapid changes in geotechnical and geological ground conditions lead to significant ground motion variability. This condition mainly occurs at the so-called basin edges, where there is an abrupt transition between soft highly compressible soils and stiffer materials. This problem becomes more relevant in areas where ground subsidence drastically changes the dynamic response of high plasticity clay deposits, such as those found in Mexico City, due to fundamental site period evolution with time. This paper presents site response analyses at an abrupt transition area in the southeast Mexico City region, along the edges of the Xochimilco-Chalco lakes. Considerable damage associated with three-dimensional wave propagation effects was observed in this zone during the September 2017 Puebla-Mexico earthquake. A series of three-dimensional finite difference numerical models of the basin edge were developed to evaluate ground motion variability, considering topographic effects and soil non-linearities. Good agreement between the computed response and the observed damage during the 2017 Puebla-Mexico earthquake reconnaissance was found. In addition, several normal and subduction events with a return period of 250 years were considered to evaluate the effect that frequency content, and strong ground motion duration have on the soil response variability. From the results gathered here, it was established the relevance of accounting for three-dimensional wave propagation fields to assess site effects at basin-edge zones properly and to be able to implement proper risk mitigation measurements at these zones.

An ameliorative duration of pulse-like ground motion records for nonlinear structural analysis

The near-field pulse-like ground motion contains obvious long-period and large pulse characteristic, which makes the nonlinear response of the structure exceed the general prediction of seismic response results. In order to reserve the obvious pulse component while selecting the strong ground motion duration part of the near-field pulse-like ground motion record without causing a large loss of spectral characteristics, the paper proposes an ameliorative truncated strong ground motion duration—useful duration. It is proposed based on the elastic acceleration response spectrum. Its principle is to make the acceleration response spectrum corresponding to useful duration and that corresponding to the original ground motion record as close and consistent as possible. The research results show that from the perspective of elastic response spectrum matching, the response spectrum matching error corresponding to useful duration is smaller than that of significant duration. In addition, the five types of periods corresponding to useful duration are closer to the period of original ground motion. Ulteriorly, from the displacement ratio spectrum of the elasto-plastic single-degree-of-freedom system, it is found that the average value of the elasto-plastic displacement ratio spectrum of useful duration and the original ground motion record is 0.98, which is very close to 1.00. It shows that the truncated ground motion can be used to replace the original ground motion to fully predict the nonlinear response of typical structures. Additionally, the effectiveness is further verified in the nonlinear response of three reinforced concrete frame structures, and the nonlinear response results of the structures are calculated using the time-history of useful duration, with less discreteness.

Evaluation of random-vibration procedures to estimate response spectral ordinates on soft soil sites from fourier amplitude spectra

This study evaluates Random-Vibration Procedures (RVP) to estimate 5% damped response spectra of ground motions recorded on soft soil sites from Fourier Amplitude Spectra (FAS). The study makes use of 136 ground motions recorded in the soft soil Mexico City region during two recent large magnitude earthquakes. Seven different RVP are considered in this investigation consisting of four peak factor models, three strong ground motion duration models, and four non-stationary empirical correction factors. Spectral ordinates computed through conventional time integration were compared to approximate spectral ordinates computed using the FAS of the recorded acceleration time series in combination with RVP. A statistical error analysis was then conducted to determine how effective the various RVP were at estimating the exact pseudo-acceleration response spectra computed with response history analyses. It is found that most RVP commonly used today produce significant systematic overestimations of spectral ordinates at the fundamental mode of the soil deposit. Modifications to durations are proposed to be used in conjunction with various peak factors to reduce overestimations at the site period.

A novel strong ground motion duration to reduce computation time of structural time history analysis

As a widely used dynamic computation method for seismic response analysis of structures, time history analysis (THA) can be a time-consuming procedure in some situations. In order to reduce the calculation time, this study proposed a novel strong ground motion duration which can truncate the head and tail weak signals of records before THA. The initial point of proposed duration refers to the concept of bracketed duration, while the termination point is determined by the maximum displacement responses of equivalent single-degree-of-freedom (SDOF) systems of the structure. The relationship between the fundamental period and period-lengthening level of structure is counted from previous research and fitted with a formula which is used to compute the period range of equivalent SDOF systems. After comparing the structural responses and time-saved percentage of truncated records by proposed duration with those by other definition of durations, results prove that the proposed duration has significant time-saving procedure and reliable computation results on THA.

Tunnel-soil-bridge seismic interaction on soft clay

Seismic tunnel-soil-bridge interaction in high plasticity soft clays can lead to significant ground motion variability, affecting on-ground structures located next to or above underground facilities. This technical note presents a numerical study aiming at establishing tunnel-bridge seismic interaction effects on soft clays. Initially, we revised this interaction considering the impact that frequency content, intensity, and strong ground motion duration have on the interplay between incoming seismic waves reflected in the tunnel and the energy feeding back from the bridge swinging back and forth during a large earthquake. Series of three-dimensional finite difference models were developed. Seismic analyses considered both normal and subduction events with a return period of 250 years. From the results gathered in these analyses, the ground motion modification in the surrounding soil occurs in both the transverse and longitudinal components due to tunnel-bridge interaction. The tunnel underneath the bridge establishes detrimental soil-structure interaction effects for normal and subduction events.

Combining Discrete Wavelet Transform and Strong Ground Motion Duration to Reduce Computational Costs in Dynamic Analysis of Structures

The dynamic time history analysis is the most accurate method for calculating the structure response relative to the vibrating load. The use of this method is time-consuming due to the long-duration earthquakes and is generally less commonly used. Wavelet trans-forms are one of the new methods for filtering waves. The duration of a strong ground motion is actually a concept that can be used to turn an earthquake with a long time into an earthquake with a shorter time. In this paper, two concepts of filtration using wavelet transform and the use of a duration of strong ground motion are used for the time history analysis of structures. For this purpose, the acceleration of the earthquake in 5 states was filtered by wavelet transform. In each stage, the high and low frequencies are separated, and the number of earthquake acceleration points is half-past. Then the beginning and the end of the main earthquake and the approximate waves obtained from the wavelet transform are removed using the concept of the duration of the strong ground motion. Finally, two two-dimensional and three-dimensional structures are analyzed using the main earthquake and the waves obtained by combining the two concepts of wavelet transform and the duration of strong ground motion. The results show that by reducing the number of acceleration points of the main earthquake record to more than 95%, the dynamic response error is less than 8%.

Use of Artificial Neural Networks to predict strong ground motion duration of interplate and inslab mexican Earthquakes for soft and firm soils

Artificial neural network models are developed to predict strong ground motion duration of sub- duction events for soft and firm soils. To train the artificial neural network a database with a total of 3153 seismic records with two horizontal components for interplate and inslab earthquakes is employed. The principal component method is used to carry out a dimensionality reduction of the input parameters to develop the artificial neural network models. The predicted values of the strong ground motion duration trained by the artificial neural network models are compared with those estimated with empirical expressions. In general, the strong ground motion duration predicted with the artificial neural networks follows the same tendency of that calculated with the empirical equa- tions, although in some cases, the strong ground motion duration predicted by using the artificial neural network models presents sudden changes in its behavior. For this reason, it is recommended to carry out several verifications of the trained artificial neural network models before using them for further engineering applications, for example the simulation of synthetic records or the evaluation of seismic damage indices.

Strong Motion Models for Duration and Arias Intensity for Strong Motion Records in Chile

Chile presents a high seismicity and very particular characteristics due to its subductive environment and high convergence rate of the interacting plates. In this paper, ground motion models (GMM) for Arias Intensity and strong ground motion duration are developed based on recently compiled Chilean earthquakes records. The Chilean derived GMM are later compared with global and subduction models. For the duration case, two definitions are considered: significant duration and bracketed duration. Care is taken to consider newly define rupture areas for the major earthquake in the catalog, which allows to redefine the distances to be used in the analysis. The strong motion records are processed using robust techniques and standardized procedures. The model parameters are selected using a Bayesian updating method. This allows to estimate the parameters as well as their corresponding uncertainties recognizing the variability of the coefficients and of the selected model. The derived ground motion predictive model associated is validated through a residual analysis and probability distributions, obtained from the adjustment method. Additionally, for the bracketed duration analysis, a classification method based on Support Vector Machine (SVM) is used, with the aim to incorporate the records with duration of zero seconds. The comparison of the resultant model with the existing ones allows to confirm the differences that the tectonic Chilean environment produces, characterized mainly by a high relative convergence rate between plates and interplate thrust earthquakes with high magnitudes.

Effect of intensity measures on the response of a 3D-structure under different ground motion duration

In seismic performance assessment of structures, the features of ground motion (GM) duration on the response of building structures remain vague and have inconclusive results. Also, intensity measures (IMs) link the ground motion hazard with the structural response; hence, using a suitable IM plays a significant role in the prediction of structural response. In this research, the effect of strong ground motion duration and the correlation coefficient of different intensity measures on the residual inter-story drift (RIDR) of a three-dimensional steel structure were investigated. Using nonlinear dynamic analyses and a total number of 34 earthquake records, the relationship between short- and long-duration seismic parameters including amplitude, energy, and frequency content parameters were investigated. The correlation between the 14 selected scalar intensity measures and the RIDR of the structure was also investigated. The results showed the highest correlation between the seismic parameters, such as Peak ground acceleration (PGA), Housner Intensity (HI), and Velocity spectrum intensity (VSI), with other seismic parameters in both short- and long-duration strong ground motions. Based on the maximum residual inter-story drift index, Mehanny and Cordova index (IMC), Bojórquez and Iervolino index (INP), and the geometric mean of Sa (Saave) intensity measures represented the least dispersion versus long-duration records. On the other hand, INP, Spectra acceleration at the period of T1 Sa(T1), and Saave intensity measures showed the least dispersion versus short-duration records.

Foundation enhancement for reducing tunnel-building seismic interaction on soft clay

Seismic tunnel-soil-building interaction in high plasticity soft clays can led to important ground motion variability that affect medium to low rise buildings located adjacent to the underground structure. This paper presents a numerical study aiming at establishing the performance of an enhanced foundation system to be used as a mean to reduce detrimental interaction and enhanced the seismic performance of mid to low buildings located nearby tunnels. Initially, interaction effects are revised considering the effect that frequency content, intensity, and strong ground motion duration have on the interplay between incoming seismic waves reflected in the tunnel, and the energy feeding back from the building swinging back and forth during a large earthquake. Series of three-dimensional finite difference models were developed. Seismic analyses considered both normal and subduction events with a return period of 250 years were carried out. Finally, the seismic performance of the enhanced foundation system was established. From the results gathered in here, it was clearly established the effectiveness of the proposed system to reduce both foundation ground motions and building seismic demand.

Wavelet-based Decomposition of Ground Acceleration for Efficient Calculation of Seismic Response in Elastoplastic Structures

The nonlinear dynamic analysis provides a more accurate simulation of the structural behavior against earthquakes. On the other hand, this analysis method is time-consuming since the time-step integration schemes are used to calculate the responses of the structure. Wavelet transform is also considered as one of the strong computing tools in studying the properties of the waves. The continuous wavelet transform is a time-frequency study and examines the frequency content of the waves while, the discrete wavelet transform is used to reduce sampling data and also to eliminate the noise of the waves. In this paper, the discrete and continuous wavelet transforms are used to reduce the wave sampling and therefore to reduce the required time for analysis. In this regard, eight near- and far- field earthquakes are studied. The frequency content of the earthquake is investigated by the Fourier spectrum and the continuous wavelet transform. The results show that the first five frequencies for the main earthquakes are similar to those values of earthquakes obtained by wavelet transform. Besides, it is shown that using wavelet transform for the main and decomposed earthquakes indicates that the duration of strong ground motion and the time of dominant frequency occur approximately in the same domain. Finally, it is concluded that the required calculation time reduces to about 80 % with an error less than 6 % when the main earthquake is decomposed by wavelet transform and the approximation waves are used in the nonlinear dynamic analysis.

The effect of duration of strong ground motion on the ductility demand of SDOF structure

As one of the basic parameters of strong ground motion, the duration of strong ground motion has not been considered in the seismic design codes over the world. To study the ground motion duration on the effects of the SDOF structure ductility demand, the Ds5-75 is chosen as the duration index, and the ductility demand ratio spectrum under long and short ground motion is calculated, then the effect of duration on structural ductility demand under different strength reduction factor is analyzed. The results show that the ductility demand of the structure under long duration ground motion is significantly greater than that under the short duration ground motion. For most periods, the ductility demand of long-duration ground motion is 1.3 times that of short-duration ground motion, and the maximum is 2.5 times. It is suggested that the effect of duration should be considered when the time history analysis of structure is carried out.

Effect of strong ground motion duration on the expected peak values of floor response spectra in elastic buildings

Effect of strong ground motion duration on the expected peak values of floor response spectra in elastic buildings

Sufficiency of the spectral shape in predicting peak and cumulative structural earthquake responses

In recent years, selection of strong ground motion records by means of intensity measures representing the spectral shape of the earthquake excitation has been studied by many researchers. These studies indicate the adequacy of this record selection approach in reduction of the scattering of seismic responses. In present study, this method has been studied more in depth to reveal the sufficiency of the spectral shape in predicting structural seismic responses such as the plastic deformation and the dissipated hysteresis energy which are associated with cumulative properties of the selected records. For this purpose, after selecting the records based on the spectral shape, the correlation of some seismic responses and strong ground motion duration of earthquake records are explored. Findings indicate strong correlation of some structural responses with the significant duration of the records. This fact implies that the spectral shape could not reflect all characteristics of the strong ground motion and emphasizes the importance of additional criteria along with the spectral shape in the record selection.

Basin Resonance and Seismic Hazard in Jakarta, Indonesia

We use earthquake ground motion modelling via Ground Motion Prediction Equations (GMPEs) and numerical simulation of seismic waves to consider the effects of site amplification and basin resonance in Jakarta, the capital city of Indonesia. While spectral accelerations at short periods are sensitive to near-surface conditions (i.e., V S 30 , average shear-wave velocity at topmost 30 m of soil), our results suggest that, for basins as deep as Jakarta’s, available GMPEs cannot be relied on to accurately estimate the effect of basin depth on ground motions at long periods (>3 s). Amplitudes at such long periods are influenced by trapping of seismic waves in the basin, resulting in longer duration of strong ground motion, and interference between incoming and reflected waves as well as focusing at basin edges may amplify seismic waves. In order to simulate such phenomena in detail, a basin model derived from a previous study is used as a computational domain for deterministic earthquake scenario modeling in a 2-dimensional cross-section. A M w 9.0 megathrust, a M w 6.5 crustal thrust and a M w 7.0 intraslab earthquake are chosen as scenario events that pose credible threats to Jakarta, and the interactions with the basin of seismic waves generated by these events were simulated. The highest long-period PGVs amplifications are recorded at sites near the middle of the basin and near its southern edge, with maximum amplifications of PGV in the horizontal component of 726% for the crustal, 1500% for the megathrust and 1125% for the deep intraslab earthquake scenario, respectively. We find that the levels of response spectral acceleration fall below those of the 2012 Indonesian building Codes’s design response spectra for short periods (<1 s), but closely approach or may even exceed these levels for longer periods.

Liquefaction Occurrence Ratio Estimation Considering Strong Ground Motion Duration and Regional Characteristics

Liquefaction Occurrence Ratio Estimation Considering Strong Ground Motion Duration and Regional Characteristics

PRELIMINARY EVALUATION OF LOCAL SITE CONDITON IN YOGYAKARTA BASIN

The Yogyakarta Basin can be defined as NE – SW elongated depression zone of 20 km in width and 45 km in length, trending from Yogyakarta City in north to the Indian Ocean in south. The local geologic and soil conditions have a great influence on the intensity of ground motion and earthquake damage. Local site effects play an important role in earthquake-resistant design and must be accounted for on a case by case basis. Local site conditions can profoundly influence all of the important characteristics such as amplitude (peak acceleration, velocity and displacement), frequency content and duration of strong ground motion. The extent of their influence depends on the geometry and material properties of subsurface materials. Therefore, subsurface investigation was carried out through nine boreholes throughout the basin. Based on drill-logs, collected samples and laboratory test results, the subsurface soil profiles of nine areas in the basin are simplified for future strong ground motion simulation. Five subsurface layers in Tampuran, Krajan areas and six subsurface soil layers in Watu, Jl. Parangtritis, Wijirejo areas and seven layers in Jl. Parangtritis, Karang Semut, Bambang Lipuro areas and eight layers in Pranti area, have been simplified and the geotechnical properties of each layer have been evaluated as well. 
 
 Keywords: Basin, Yogyakarta, depression, ground motion, earthquake.

English

This study quantifies the influence of strong ground motion duration (SGMD) of aftershocks on the cumulative damage caused to a RC frame structure. Understanding the effect of ground motion duration on cumulative damage and failure mechanisms will bring us one step closer to preventing future earthquake-induced collapses and can also aid in improving Building code. In order to study the effects of Duration, the other time-frequency characteristics i.e. amplitude and frequency content are kept similar. A realistic nonlinear numerical structure is modelled in SAP2000 in order to incorporate cyclic deterioration of strength and stiffness. Two sets of data are considered i.e. longer duration (>40sec) and shorter duration (<25 sec) and for each set of data cumulative damage are calculated using modified Park and Ang Damage Index. It is seen that in general longer duration data sequence causes more damage than shorter duration sequences because of longer cycles of loading

Neural estimation of strong ground motion duration

This paper presents and discusses the use of neural networks to determine strong ground motion duration. Accelerometric data recorded in the Mexican cities of Puebla and Oaxaca are used to develop a neural model that predicts this duration in terms of the magnitude, epicenter distance, focal depth, soil characterization and azimuth. According to the above the neural model considers the effect of the seismogenic zone and the contribution of soil type to the duration of strong ground motion. The final scheme permits a direct estimation of the duration since it requires easy-to-obtain variables and does not have restrictive hypothesis. The results presented in this paper indicate that the soft computing alternative, via the neural model, is a reliable recording-based approach to explore and to quantify the effect of seismic and site conditions on duration estimation. An essential and significant aspect of this new model is that, while being extremely simple, it also provides estimates of strong ground motions duration with remarkable accuracy. Additional but important side benefits arising from the model’s simplicity are the natural separation of source, path, and site effects and the accompanying computational efficiency.

Rotation-invariant mean duration of strong ground motion

Strong-motion duration is usually computed separately for three components of recorded ground-motion time series. This results in different values of duration for the three components. Furthermore, the computed duration values are dependent on the sensor orientation. Physically, such dependence is not desirable. In this work, computing duration based on resultant recorded motion instead of individual components is proposed. Such a measure of duration is shown to be rotation-invariant and hence independent of the sensor axes. Furthermore, it is demonstrated that the duration of resultant motion represents the mean duration for all possible arbitrary sensor orientations in three-dimensional space. The results indicate that the apparent difference between duration of horizontal and vertical motion reported in the literature is not universal to all definitions of duration. A set of 462 three-component accelerograms from Europe and the Middle East is used to demonstrate and support the presented findings and arguments.