NGA-West2 Equations for Predicting Vertical-Component PGA, PGV, and 5%-Damped PSA from Shallow Crustal Earthquakes

2016 ◽  
Vol 32 (2) ◽  
pp. 1005-1031 ◽  
Author(s):  
Jonathan P. Stewart ◽  
David M. Boore ◽  
Emel Seyhan ◽  
Gail M. Atkinson
Keyword(s):  
Site Response ◽  
Vertical Component ◽  
Site Amplification ◽  
Intensity Measures ◽  
Global Database ◽  
Crustal Earthquakes ◽  
Anelastic Attenuation ◽  
Nonlinear Site Response ◽  
Active Tectonic ◽  
Geometric Spreading

We present ground motion prediction equations (GMPEs) for computing natural log means and standard deviations of vertical-component intensity measures (IMs) for shallow crustal earthquakes in active tectonic regions. The equations were derived from a global database with M 3.0–7.9 events. The functions are similar to those for our horizontal GMPEs. We derive equations for the primary M- and distance-dependence of peak acceleration, peak velocity, and 5%-damped pseudo-spectral accelerations at oscillator periods between 0.01–10 s. We observe pronounced M-dependent geometric spreading and region-dependent anelastic attenuation for high-frequency IMs. We do not observe significant region-dependence in site amplification. Aleatory uncertainty is found to decrease with increasing magnitude; within-event variability is independent of distance. Compared to our horizontal-component GMPEs, attenuation rates are broadly comparable (somewhat slower geometric spreading, faster apparent anelastic attenuation), VS30-scaling is reduced, nonlinear site response is much weaker, within-event variability is comparable, and between-event variability is greater.

Comparisons of the NGA Ground-Motion Relations

2008 ◽  
Vol 24 (1) ◽  
pp. 45-66 ◽  
Author(s):  
Norman Abrahamson ◽  
Gail Atkinson ◽  
David Boore ◽  
Yousef Bozorgnia ◽  
Kenneth Campbell ◽  
...  
Keyword(s):  
Site Response ◽  
Strike Slip ◽  
Data Sets ◽  
Sediment Depth ◽  
Long Period ◽  
Crustal Earthquakes ◽  
Nonlinear Site Response ◽  
Soil Sediment ◽  
Active Tectonic ◽  
Standard Deviations

The data sets, model parameterizations, and results from the five NGA models for shallow crustal earthquakes in active tectonic regions are compared. A key difference in the data sets is the inclusion or exclusion of aftershocks. A comparison of the median spectral values for strike-slip earthquakes shows that they are within a factor of 1.5 for magnitudes between 6.0 and 7.0 for distances less than 100 km. The differences increase to a factor of 2 for M5 and M8 earthquakes, for buried ruptures, and for distances greater than 100 km. For soil sites, the differences in the modeling of soil/sediment depth effects increase the range in the median long-period spectral values for M7 strike-slip earthquakes to a factor of 3. The five models have similar standard deviations for M6.5-M7.5 earthquakes for rock sites and for soil sites at distances greater than 50 km. Differences in the standard deviations of up to 0.2 natural log units for moderate magnitudes at all distances and for large magnitudes at short distances result from the treatment of the magnitude dependence and the effects of nonlinear site response on the standard deviation.

NGA-West2 Equations for Predicting PGA, PGV, and 5% Damped PSA for Shallow Crustal Earthquakes

2014 ◽  
Vol 30 (3) ◽  
pp. 1057-1085 ◽  
Author(s):  
David M. Boore ◽  
Jonathan P. Stewart ◽  
Emel Seyhan ◽  
Gail M. Atkinson
Keyword(s):  
Intensity Measures ◽  
Global Database ◽  
Crustal Earthquakes ◽  
Aleatory Variability ◽  
Distance Dependence ◽  
Active Tectonic ◽  
Class 1 ◽  
Site Term ◽  
Residuals Analysis ◽  
Variability Model

We provide ground motion prediction equations for computing medians and standard deviations of average horizontal component intensity measures (IMs) for shallow crustal earthquakes in active tectonic regions. The equations were derived from a global database with M 3.0–7.9 events. We derived equations for the primary M- and distance-dependence of the IMs after fixing the V S30-based nonlinear site term from a parallel NGA-West2 study. We then evaluated additional effects using mixed effects residuals analysis, which revealed no trends with source depth over the M range of interest, indistinct Class 1 and 2 event IMs, and basin depth effects that increase and decrease long-period IMs for depths larger and smaller, respectively, than means from regional V S30-depth relations. Our aleatory variability model captures decreasing between-event variability with M, as well as within-event variability that increases or decreases with M depending on period, increases with distance, and decreases for soft sites.

Simulation-based site amplification model for shallow bedrock sites in Korea

2021 ◽  
pp. 875529302098198
Author(s):  
Muhammad Aaqib ◽  
Duhee Park ◽  
Muhammad Bilal Adeel ◽  
Youssef M A Hashash ◽  
Okan Ilhan
Keyword(s):  
Linear Models ◽  
Site Response ◽  
Site Amplification ◽  
One Dimensional ◽  
Nonlinear Component ◽  
Nonlinear Site Response ◽  
Simulation Based ◽  
Linear And Nonlinear ◽  
Input Motion ◽  
Nonlinear Components

A new simulation-based site amplification model for shallow sites with thickness less than 30 m in Korea is developed. The site amplification model consists of linear and nonlinear components that are developed from one-dimensional linear and nonlinear site response analyses. A suite of measured shear wave velocity profiles is used to develop corresponding randomized profiles. A VS30 scaled linear amplification model and a model dependent on both VS30 and site period are developed. The proposed linear models compare well with the amplification equations developed for the western United States (WUS) at short periods but show a distinct curved bump between 0.1 and 0.5 s that corresponds to the range of site natural periods of shallow sites. The response at periods longer than 0.5 s is demonstrated to be lower than those of the WUS models. The functional form widely used in both WUS and central and eastern North America (CENA), for the nonlinear component of the site amplification model, is employed in this study. The slope of the proposed nonlinear component with respect to the input motion intensity is demonstrated to be higher than those of both the WUS and CENA models, particularly for soft sites with VS30 < 300 m/s and at periods shorter than 0.2 s. The nonlinear component deviates from the models for generic sites even at low ground motion intensities. The comparisons highlight the uniqueness of the amplification characteristics of shallow sites that a generic site amplification model is unable to capture.

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.

Pitfalls of Deterministic Application of Nonlinear Site Factors in Probabilistic Assessment of Ground Motions

2009 ◽  
Vol 25 (3) ◽  
pp. 541-555 ◽  
Author(s):  
Christine A. Goulet ◽  
Jonathan P. Stewart
Keyword(s):  
Site Effects ◽  
Site Response ◽  
Ground Motions ◽  
Site Conditions ◽  
Return Periods ◽  
Site Factors ◽  
Intensity Measures ◽  
Site Specific ◽  
Nonlinear Site Response ◽  
Rock And Soil

It is common for ground motions to be estimated using a combination of probabilistic and deterministic procedures. Probabilistic seismic hazard analyses (PSHA) are performed to estimate intensity measures ( IMs) for reference site conditions (usually rock). This is followed by a deterministic modification of the rock IMs to account for site effects, typically using site factors from the literature or seismic codes. We demonstrate for two California sites and three site conditions that the deterministic application of nonlinear site factors underestimates ground motions evaluated probabilistically for return periods of engineering interest. Reasons for this misfit include different standard deviation terms for rock and soil sites, different controlling earthquakes, and overestimation of the nonlinear component of the site response in the deterministic procedure. This problem is solved using site-specific PSHA with appropriate consideration of nonlinear site response, within the hazard integral.

Summary of the Abrahamson & Silva NGA Ground-Motion Relations

2008 ◽  
Vol 24 (1) ◽  
pp. 67-97 ◽  
Author(s):  
Norman Abrahamson ◽  
Walter Silva
Keyword(s):  
Standard Deviation ◽  
Ground Motion ◽  
Site Response ◽  
Hanging Wall ◽  
Site Location ◽  
Crustal Earthquakes ◽  
Nonlinear Site Response ◽  
Short Period ◽  
Standard Deviations ◽  
Improved Model

Empirical ground-motion models for the rotation-independent average horizontal component from shallow crustal earthquakes are derived using the PEER NGA database. The model is applicable to magnitudes 5–8.5, distances 0–200 km, and spectral periods of 0–10 sec. In place of generic site categories (soil and rock), the site is parameterized by average shear-wave velocity in the top 30 m ( VS30) and the depth to engineering rock (depth to VS=1000 m/s). In addition to magnitude and style-of-faulting, the source term is also dependent on the depth to top-of-rupture: for the same magnitude and rupture distance, buried ruptures lead to larger short-period ground motions than surface ruptures. The hanging-wall effect is included with an improved model that varies smoothly as a function of the source properties (M, dip, depth), and the site location. The standard deviation is magnitude dependent with smaller magnitudes leading to larger standard deviations. The short-period standard deviation model for soil sites is also distant-dependent due to nonlinear site response, with smaller standard deviations at short distances.

An NGA-West2 Empirical Model for Estimating the Horizontal Spectral Values Generated by Shallow Crustal Earthquakes

2014 ◽  
Vol 30 (3) ◽  
pp. 1155-1177 ◽  
Author(s):  
I. M. Idriss
Keyword(s):  
Empirical Model ◽  
Site Response ◽  
Earthquake Ground Motion ◽  
Model Parameters ◽  
Motion Data ◽  
Crustal Earthquakes ◽  
Nonlinear Site Response ◽  
Average Shear ◽  
Recorded Data ◽  
A Site

An empirical model for estimating the horizontal pseudo-absolute spectral accelerations (PSA) generated by shallow crustal earthquakes was published in 2008 using the recorded earthquake ground motion data collected and documented as part of the original Next Generation Attenuation (NGA) project. A significant number of additional recordings were collected over the past three years, and the 2008 model has been revised using the new data and is presented in this paper. The model was again selected to be simple, and the model parameters were estimated using the expanded database. The revised model incorporates V S30 as an independent variable because, with the expanded database, it was found that V S30 was required to be included as an independent parameter to allow for a reasonably unbiased fit to the recorded data. It is noted that V S30 is not being used to account for nonlinear site response, but strictly to allow for a better fit to the data. These parameters are presented for sites with an average shear wave velocity in the upper 30 m, V S30, for sites with V S30 ≥ 450 m/s. Parameters for sites with V S30 < 450 m/s are not included in this paper. For a site with V S30 = 450 m/s, there is an overall increase in PGA averaging about 50% over a distance of about 100 km using the 2013 model in comparison to the 2008 model. On the other hand, for a site with V S30 = 900 m/s, there is an overall decrease of about 10% using the 2013 model in comparison to the 2008 model.

Ground Motion Prediction Equations for the Vertical Ground Motion Component Based on the NGA-W2 Database

2017 ◽  
Vol 33 (2) ◽  
pp. 499-528 ◽  
Author(s):  
Zeynep Gülerce ◽  
Ronnie Kamai ◽  
Norman A. Abrahamson ◽  
Walter J. Silva
Keyword(s):  
Ground Motion ◽  
Site Response ◽  
Vertical Component ◽  
Weighted Average ◽  
Motion Models ◽  
Nonlinear Site Response ◽  
Vertical Ground Motion ◽  
Vertical Ground ◽  
Standard Deviations ◽  
Ground Motion Models

Empirical ground motion models for the vertical component from shallow crustal earthquakes in active tectonic regions are derived using the PEER NGA-West2 database. The model is applicable to magnitudes 3.0–8.0, distances of 0–300 km, and spectral periods of 0–10 s. The model input parameters are the same as used by Abrahamson et al. (2014) except that the nonlinear site response and depth to bedrock effects are evaluated but found to be insignificant. Regional differences in large distance attenuation and site amplification scaling between California, Japan, China, Taiwan, Italy, and the Middle East are included. Scaling for the hanging-wall effect is incorporated using the constraints from numerical simulations by Donahue and Abrahamson (2014) . The standard deviation is magnitude dependent with smaller magnitudes leading to larger standard deviations at short periods but smaller standard deviations at long periods. The vertical ground motion model developed in this study can be paired with the horizontal component model proposed by Abrahamson et al. (2014) to produce a V/H ratio. For applications where the horizontal spectrum is derived from the weighted average of several horizontal ground motion models, a V/H model derived directly from the V/H data (such as Gülerce and Abrahamson 2011 ) should be preferred.

Damping Scaling Factors for Vertical Elastic Response Spectra for Shallow Crustal Earthquakes in Active Tectonic Regions

2014 ◽  
Vol 30 (3) ◽  
pp. 1335-1358 ◽  
Author(s):  
Sanaz Rezaeian ◽  
Yousef Bozorgnia ◽  
I. M. Idriss ◽  
Norman A. Abrahamson ◽  
Kenneth W. Campbell ◽  
...  
Keyword(s):  
Standard Deviation ◽  
Damping Ratio ◽  
Vertical Component ◽  
Vertical Motion ◽  
Horizontal Component ◽  
Elastic Response ◽  
Earthquake Ground Motion ◽  
Crustal Earthquakes ◽  
Elastic Response Spectra ◽  
Active Tectonic

This paper develops a new model for a damping scaling factor (DSF) that can be used to adjust elastic response spectral ordinates for the vertical component of earthquake ground motion at a 5% viscous damping ratio to ordinates at damping ratios between 0.5% and 30%. Using the extensive NGA-West2 database of recorded ground motions from worldwide shallow crustal earthquakes in active tectonic regions, a functional form for the median DSF is proposed that depends on the damping ratio, spectral period, earthquake magnitude, and distance. Standard deviation is a function of the damping ratio and spectral period. The proposed model is compared to the DSF for the “average” horizontal component. In general, the peak in DSF is shifted toward shorter periods and is farther from unity for the vertical component. Also, the standard deviation of DSF for vertical motion is slightly higher than that observed for the “average” horizontal component.

Attenuation and source parameters of earthquakes in the Cascadia region

1995 ◽  
Vol 85 (5) ◽  
pp. 1327-1342 ◽  
Author(s):  
Gail M. Atkinson
Keyword(s):  
Stress Drop ◽  
Source Parameters ◽  
Vertical Component ◽  
Attenuation Curve ◽  
Motion Data ◽  
Anelastic Attenuation ◽  
Geometric Spreading ◽  
Random Process Theory ◽  
Source Spectra ◽  
Subducting Slab

Abstract Digital ground-motion data recorded by the Western Canada Telemetered Network (WCTN) are used to examine the attenuation and source parameters of earthquakes in the Cascadia region of southwestern British Columbia and northwestern Washington. The data base is comprised of over 1000 vertical-component Fourier spectra, from earthquakes of magnitude 3 to 7 at distances from 10 to 500 km. Regression analyses determine the shape and coefficients of the regional attenuation curve and source spectra for 68 earthquakes. Seismic moment and stress drop are inferred from the amplitudes of the source spectra. Shallow (h &lt; 10 km) earthquakes have an attenuation curve with a complex shape, exhibiting significant flattening (no apparent geometric spreading) in the distance range from 75 to 230 km; this shape is probably a result of strong reflected phases from mid-crustal discontinuities and the subducting slab. Events within the subducting slab and the lower crust exhibit a simple R−1 attenuation curve. The anelastic attenuation coefficient for the region as a whole is given by Q = 380f0.39. The duration of motion for each WCTN record is determined as the value that yields the observed relationship between time-domain and spectral-domain amplitudes, according to random process theory. These durations are approximately constant within 50 km of the source, then increase with distance as 0.07R. The high-frequency ground motions from Cascadia earthquakes are relatively weak. Cascadia source spectra are characterized by an average Brune stress drop of about 30 bars. This is significantly lower than the average California stress drop of 70 to 100 bars, and dramatically lower than the average eastern stress drop of 150 to 200 bars. It is concluded that there are significant regional variations in source parameters. Hazard estimates for the Cascadia region based on California groundmotion relations may be overly conservative.

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