Semi-Empirical Nonlinear Site Amplification from NGA-West2 Data and Simulations

2014 ◽  
Vol 30 (3) ◽  
pp. 1241-1256 ◽  
Author(s):  
Emel Seyhan ◽  
Jonathan P. Stewart
Keyword(s):  
Ground Motions ◽  
Nonlinear Effects ◽  
Site Amplification ◽  
Site Factors ◽  
Reference Velocity ◽  
Regional Trends ◽  
Motion Scaling ◽  
Ground Motion Scaling ◽  
A Site ◽  
Semi Empirical

We analyze NGA-West2 data and simulations to develop a site amplification model that captures ground motion scaling with V S30 and soil nonlinear effects. We parameterize nonlinearity as the gradient of site amplification with respect to peak acceleration for reference (firm) sites. Both data analyses and simulations indicate nonlinearity for sites with V S30 < 500 m/s and spectral periods T < ∼3 s. Following approximate removal of nonlinear effects from the data, we evaluate V S30-scaling of ground motions, which is most pronounced for T ≥ ∼0.2 s and saturates for hard rock sites. Regional trends in V S30-scaling and nonlinearity were not found to be sufficiently robust to justify inclusion in our model. We apply the site amplification model to derive site factors now approved for building code applications. Principal causes of changes relative to previous values are reduction of the reference velocity (at which amplification is unity) to 760 m/s and reduced nonlinearity.

Implications of the Mw9.0 Tohoku-Oki Earthquake for Ground Motion Scaling with Source, Path, and Site Parameters

2013 ◽  
Vol 29 (1_suppl) ◽  
pp. 1-21 ◽  
Author(s):  
Jonathan P. Stewart ◽  
Saburoh Midorikawa ◽  
Robert W. Graves ◽  
Khatareh Khodaverdi ◽  
Tadahiro Kishida ◽  
...  
Keyword(s):  
Ground Motion ◽  
Ground Motions ◽  
Site Amplification ◽  
Low Frequencies ◽  
High Frequencies ◽  
Wave Velocities ◽  
Shear Wave Velocities ◽  
Active Tectonic ◽  
Motion Scaling ◽  
Ground Motion Scaling

The Mw9.0 Tohoku-oki Japan earthquake produced approximately 2,000 ground motion recordings. We consider 1,238 three-component accelerograms corrected with component-specific low-cut filters. The recordings have rupture distances between 44 km and 1,000 km, time-averaged shear wave velocities of VS30 = 90 m/s to 1,900 m/s, and usable response spectral periods of 0.01 sec to >10 sec. The data support the notion that the increase of ground motions with magnitude saturates at large magnitudes. High-frequency ground motions demonstrate faster attenuation with distance in backarc than in forearc regions, which is only captured by one of the four considered ground motion prediction equations for subduction earthquakes. Recordings within 100 km of the fault are used to estimate event terms, which are generally positive (indicating model underprediction) at short periods and zero or negative (overprediction) at long periods. We find site amplification to scale minimally with VS30 at high frequencies, in contrast with other active tectonic regions, but to scale strongly with VS30 at low frequencies.

A model for estimating amplification effects on seismic hazards and scenario ground motions in southern Ontario

2017 ◽  
Vol 44 (6) ◽  
pp. 441-451 ◽  
Author(s):  
Sebastian Braganza ◽  
Gail M. Atkinson
Keyword(s):  
Site Response ◽  
Ground Motions ◽  
Peak Frequency ◽  
Site Amplification ◽  
Seismic Hazards ◽  
Damage Potential ◽  
Southern Ontario ◽  
Response Variable ◽  
Study Support ◽  
A Site

Site amplification effects in southern Ontario are highly variable and strongly influence felt effects and damage potential. Site parameters such as shear-wave velocity in the top 30 metres of soil (VS30), traditionally used to estimate site amplification, are not well known in this region. Thus, regional maps of shaking potential and seismic hazard are often overgeneralized. In this study, a site amplification model based on peak frequency (fpeak) is compared to one based on VS30, as given by the 2015 National Building Code of Canada (NBCC). Earthquakes and scenario events are used to estimate ground motions and shaking intensities. It is shown that both models generally predict similar felt intensities but show significant differences in their predicted amplification of ground motions as a function of frequency. The results of this study support the use of fpeak as a site response variable for estimating amplification effects in southern Ontario.

Simulation-Based Hanging Wall Effects

2014 ◽  
Vol 30 (3) ◽  
pp. 1269-1284 ◽  
Author(s):  
Jennifer L. Donahue ◽  
Norman A. Abrahamson
Keyword(s):  
Ground Motion ◽  
Ground Motions ◽  
Hanging Wall ◽  
Finite Fault ◽  
Simulation Based ◽  
Geometrical Effect ◽  
Motion Scaling ◽  
Ground Motion Scaling ◽  
Rupture Distance ◽  
Source Site

The hanging wall (HW) effect is defined as the increase in ground motion at short distances for sites on the hanging wall side of a rupture when compared to sites on the footwall (FW) side at the same closest distance. In general, it is a geometrical effect due to the use of a closest distance metric, such as rupture distance, that does not capture the main features of the ground motion scaling for sites near dipping faults. To constrain the HW scaling on magnitude, distance, dip, and depth to top of rupture, finite-fault simulations were used to generate ground motions from 34 source geometries with 30 realizations of the slip distribution and hypocenter locations. The scaling of resulting response spectral accelerations at over 130,000 source/site combinations were parameterized to model the dependence of the HW effects. This HW scaling was utilized to constrain some of the NGA-West2 ground motion prediction equations.

Testing non-linear amplification factors used in ground motion models

2021 ◽  
Author(s):  
Karina Loviknes ◽  
Danijel Schorlemmer ◽  
Fabrice Cotton ◽  
Sreeram Reddy Kotha
Keyword(s):  
Ground Motion ◽  
Site Effects ◽  
Ground Motions ◽  
Site Amplification ◽  
Building Codes ◽  
Linear Amplification ◽  
Motion Models ◽  
Earthquake Predictability ◽  
Non Linear ◽  
Ground Motion Models

&lt;p&gt;Non-linear site effects are mainly expected for strong ground motions and sites with soft soils and more recent ground-motion models (GMM) have started to include such effects. Observations in this range are, however, sparse, and most non-linear site amplification models are therefore partly or fully based on numerical simulations. We develop a framework for testing of non-linear site amplification models using data from the comprehensive Kiban-Kyoshin network in Japan. The test is reproducible, following the vision of the Collaboratory for the Study of Earthquake Predictability (CSEP), and takes advantage of new large datasets to evaluate &lt;span&gt;whether or not&lt;/span&gt; non-linear site effects predicted by site-amplification models are supported by empirical data. The site amplification models are tested using residuals between the observations and predictions from a GMM based only on magnitude and distance. When the GMM is derived without any site term, the site-specific variability extracted from the residuals is expected to capture the site response of a site. The non-linear site amplification models are tested against a linear amplification model on individual well-record&lt;span&gt;ing&lt;/span&gt; stations. Finally, the result is compared to building codes where non-linearity is included. The test shows that for most of the sites selected as having sufficient records, the non-linear site-amplification models do not score better than the linear amplification model. This suggests that including non-linear site amplification in GMMs and building codes may not yet be justified, at least not in the range of ground motions considered in the test (peak ground acceleration &lt; 0.2 g).&lt;/p&gt;

scholarly journals A Site Amplification Model for Crustal Earthquakes

Geosciences ◽  
2018 ◽  
Vol 8 (7) ◽  
pp. 264 ◽  
Author(s):  
M. Sandıkkaya ◽  
L. Dinsever
Keyword(s):  
Soft Soil ◽  
Correlation Coefficients ◽  
Nonlinear Effects ◽  
Site Amplification ◽  
Sigmoid Function ◽  
Deep Soil ◽  
Soil Stiffness ◽  
Site Model ◽  
Soil Nonlinearity ◽  
Crustal Earthquakes

A global dataset which is composed of more than 20,000 records is used to develop an empirical nonlinear soil amplification model for crustal earthquakes. The model also includes the deep soil effect. The soil nonlinearity is formulated in terms of input rock motion and soil stiffness. The input rock motion is defined by the pseudo-spectral acceleration at rock site condition (PSArock) which is also modified with between-event residual. Application of PSArock simplifies the usage of the site model by diminishing the need of using the period-dependent correlation coefficients in hazard studies. The soil stiffness is expressed by a Gompertz sigmoid function which restricts the nonlinear effects at both of the very soft soil sites and very stiff soil sites. In order to surpass the effect of low magnitude and long-distant recordings on soil nonlinearity, the nonlinear site coefficients are constrained by using a limited dataset. The coefficients of linear site scaling and deep soil effect are obtained with the full database. The period average of site-variability is found to be 0.43. The sigma decreases with decreasing the soil stiffness or increasing input rock motion. After employing residual analysis, the region-dependent correction coefficients for linear site scaling are also obtained.

scholarly journals Evaluation of the Ground Motion Scaling Procedures for Concrete Gravity Dams

2017 ◽  
Vol 199 ◽  
pp. 844-849
Author(s):  
Berat Feyza Soysal ◽  
Bekir Özer Ay ◽  
Yalin Arici
Keyword(s):  
Ground Motion ◽  
Gravity Dams ◽  
Concrete Gravity Dams ◽  
Motion Scaling ◽  
Ground Motion Scaling
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