An Empirical Model for Significant Duration of the Ground Motions Containing Velocity Pulses

2021 ◽  
Vol 57 (6) ◽  
pp. 950-964
Author(s):  
Masoud Daryoushi ◽  
Hamid Saffari ◽  
Abbas Mahdavian
Keyword(s):  
Empirical Model ◽  
Ground Motions ◽  
Significant Duration

Physically Parameterized Prediction Equations for Significant Duration in Active Crustal Regions

2016 ◽  
Vol 32 (4) ◽  
pp. 2057-2081 ◽  
Author(s):  
Kioumars Afshari ◽  
Jonathan P. Stewart
Keyword(s):  
Standard Deviation ◽  
Ground Motions ◽  
Prediction Equations ◽  
Global Database ◽  
Significant Duration ◽  
Crustal Earthquakes ◽  
Aleatory Variability ◽  
Active Tectonic ◽  
Variability Model ◽  
Source Duration

We develop prediction equations for the median and standard deviation of the significant duration of earthquake ground motions from shallow crustal earthquakes in active tectonic regions. We consider significant duration parameters for 5–75%, 5–95%, and 20–80% of the normalized Arias intensity. The equations were derived from a global database with M 3.0–7.9 events. We find significant noise effects on duration parameters that compel us to exclude some records that had been used previously to develop models for amplitude parameters. Our equations include an M-dependent source duration term that also depends on focal mechanism. At small M, the data suggest approximately M-independent source durations that are close to 1 sec. The increase of source durations with M is slower over the range ∼5 to 7.2–7.4 than for larger magnitudes. We adopt an additive path term with breaks in distance scaling at 10 km and 50 km. We include site terms that increase duration for decreasing V S30 and increasing basin depth. Our aleatory variability model captures decreasing between- and within-event standard deviation terms with increasing M.

Evaluation of Earthquake Response Spectra Directionality Using Stochastic Simulations

2021 ◽  
Author(s):  
Alan Poulos ◽  
Eduardo Miranda ◽  
Jack W. Baker
Keyword(s):  
Stochastic Process ◽  
Ground Motion ◽  
Ground Motions ◽  
Gaussian White Noise ◽  
Response Spectra ◽  
Orientation Dependence ◽  
Stochastic Simulations ◽  
Earthquake Ground Motion ◽  
Significant Duration ◽  
Simulated Ground Motions

ABSTRACT For earthquake-resistant design purposes, ground-motion intensity is usually characterized using response spectra. The amplitude of response spectral ordinates of horizontal components varies significantly with changes in orientation. This change in intensity with orientation is commonly known as ground-motion directionality. Although this directionality has been attributed to several factors, such as topographic irregularities, near-fault effects, and local geologic heterogeneities, the mechanism behind this phenomenon is still not well understood. This work studies the directionality characteristics of earthquake ground-motion intensity using synthetic ground motions and compares their directionality to that of recorded ground motions. The two principal components of horizontal acceleration are sampled independently using a stochastic model based on finite-duration time-modulated filtered Gaussian white-noise processes. By using the same stochastic process to sample both horizontal components of motion, the variance of horizontal ground acceleration has negligible orientation dependence. However, these simulations’ response spectral ordinates present directionality levels comparable to those found in real ground motions. It is shown that the directionality of the simulated ground motions changes for each realization of the stochastic process and is a consequence of the duration being finite. Simulated ground motions also present similar directionality trends to recorded earthquake ground motions, such as the increase of average directionality with increasing period of vibration and decrease with increasing significant duration. These results suggest that most of the orientation dependence of horizontal response spectra is primarily explained by the finite significant duration of earthquake ground motion causing inherent randomness in response spectra, rather than by some physical mechanism causing polarization of shaking.

Comparison of the Recorded Significant Duration of the Lushan Earthquake with Empirical Model Predictions

2019 ◽  
Vol 109 (6) ◽  
pp. 2325-2339
Author(s):  
Yuzhu Bai
Keyword(s):  
Empirical Model ◽  
High Frequency ◽  
Goodness Of Fit ◽  
Free Field ◽  
Empirical Models ◽  
Lushan Earthquake ◽  
Arias Intensity ◽  
Significant Duration ◽  
Model Predictions ◽  
Frequency Components

Abstract Using 72 free‐field accelerograms with the closest site‐rupture distances (Rrup) less than 300 km, this study calculates the recorded significant duration of the 2013 Mw 6.7 Lushan earthquake and compares the calculated results with empirical model predictions. The significant duration parameters are for 5%–75% (D5–75) and 5%–95% (D5–95) of the normalized Arias intensity. For Rrup<150  km, the models of Du and Wang (2017; hereafter, DW17) are relatively less biased in predicting the Lushan significant duration. The goodness‐of‐fit results indicate that the models of DW17, Afshari and Stewart (2016; hereafter, AS16), and Kempton and Stewart (2006; hereafter, KS06) are the best models to predict D5–75 of the Lushan event. Meanwhile, most of the selected empirical models predict the Lushan event better for D5–75 than for D5–95. Moreover, the enrichment of high‐frequency components of ground motion causes the recorded D5–95 of the Lushan event to be larger than median predictions in high‐frequency bands. Among the five selected earthquakes (1994 Mw 6.7 Northridge, 2003 Mw 6.5 San Simeon, 2004 Mw 6.6 Niigata, 2008 Mw 7.9 Wenchuan, and 2013 Mw 6.7 Lushan earthquakes), the Lushan earthquake is predicted relatively better by all empirical models. The intraevent and interevent residuals of AS16 model from China earthquakes are within the scatter of those from the events in the Next Generation Attenuation‐West2 (NGA‐West2) database, indicating that the China earthquake significant duration is consistent with the model developed through the NGA‐West2 database. Furthermore, the regional dependences of significant duration are not observed for the Wenchuan or the Lushan earthquake.

Quantification of the Influence of Deep Basin Effects on Structural Collapse Using SCEC CyberShake Earthquake Ground Motion Simulations

2019 ◽  
Vol 35 (4) ◽  
pp. 1845-1864 ◽  
Author(s):  
Nenad Bijelić ◽  
Ting Lin ◽  
Gregory G. Deierlein
Keyword(s):  
Los Angeles ◽  
Ground Motion ◽  
Ground Motions ◽  
Sedimentary Basins ◽  
Earthquake Ground Motion ◽  
Structural Collapse ◽  
Deep Basin ◽  
Intensity Measures ◽  
Significant Duration ◽  
Basin Effects

This paper examines the effects of earthquake ground motions in deep sedimentary basins on structural collapse risk using physics-based earthquake simulations of the Los Angeles basin developed through the Southern California Earthquake Center's CyberShake project. Distinctive waveform characteristics of deep basin seismograms are used to classify the ground motions into several archetype groups, and the damaging influence of the basin effects are evaluated by comparing nonlinear structural responses under spectrum and significant duration equivalent basin and nonbasin ground motions. The deep basin ground motions are observed to have longer period-dependent durations and larger sustained spectral intensities than nonbasin motions for vibration periods longer than about 1.5 s, which can increase structural collapse risk by up to 20% in ground motions with otherwise comparable peak spectral accelerations and significant durations. Two new metrics are proposed to quantify period-dependent duration effects that are not otherwise captured by conventional ground motion intensity measures. The proposed sustained amplitude response spectra and significant duration spectra show promise for characterizing the damaging effects of long duration features of basin ground motions on buildings and other structures.

Effects of the hanging wall and footwall on ground motions recorded during the Northridge earthquake

1996 ◽  
Vol 86 (1B) ◽  
pp. S93-S99
Author(s):  
N. A. Abrahamson ◽  
P. G. Somerville
Keyword(s):  
Ground Motion ◽  
Empirical Model ◽  
Empirical Data ◽  
Ground Motions ◽  
Hanging Wall ◽  
Systematic Difference ◽  
Wall Effect ◽  
Northridge Earthquake ◽  
Distance Range ◽  
Hanging Wall Effect

Abstract Systematic differences in ground motion on the hanging wall and footwall during the Northridge earthquake are evaluated using empirical data. An empirical model for the hanging-wall effect is developed for the Northridge earthquake. This empirical model results in up to a 50% increase in peak horizontal accelerations on the hanging wall over the distance range of 10 to 20 km relative to the median attenuation for the Northridge earthquake. In contrast, the peak accelerations on the footwall are not significantly different from the median attenuation over this distance range. Recordings from other reverse events show a similar trend of an increase in the peak accelerations on the hanging wall, indicating that this systematic difference in hanging-wall peak accelerations is likely to be observed in future reverse events.

scholarly journals Modification of Random Vibration Theory for the Near-fault Region

2021 ◽  
Author(s):  
Van-Bang Phung ◽  
Norm Abrahamson
Keyword(s):  
Earthquake Engineering ◽  
Empirical Model ◽  
Random Vibration ◽  
Ground Motions ◽  
Data Set ◽  
Conditional Model ◽  
Near Fault ◽  
Vibration Theory ◽  
Input Parameters ◽  
Random Vibration Theory

Abstract Standard random vibration theory (RVT) methods for estimating the horizontal spectral acceleration (PSA) amplitudes given the Fourier spectral amplitude (FAS) and ground-motion duration underestimate the PSA values for near-fault ground motions from large magnitudes. An empirical model that is unbiased for near-fault ground motions is developed using the statistical moments of the FAS and the duration as model input parameters, similar to standard RVT, but with a modification to also include magnitude and distance as input parameters. The data set used for the regression includes strong-motion recordings from active crustal regions in the NGA-West2 Pacific Earthquake Engineering Research (PEER) database from California earthquakes (M3.0-7.25) and global earthquakes (M5.0 – 7.9). The zeroth, first, and second spectral moments of the FAS of the 5%-damped oscillator response are used in the empirical model. The scaling with the moments of the FAS replaces the peak factor terms used in RVT. A parametric model for the 5-80% duration that depends on magnitude and distance is also developed to simplify the application of the model. Compared to the standard RVT approach, the conditional model significantly improves the estimation of near-fault PSA values estimated from the FAS. The conditional model is appropriate for use in converting non-ergodic FAS GMMs to non-ergodic PSA GMMs.

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