Engineering implications of ground motions from the Northridge earthquake

1996 ◽  
Vol 86 (1B) ◽  
pp. S270-S288 ◽  
Author(s):  
Susan W. Chang ◽  
Jonathan D. Bray ◽  
Raymond B. Seed
Keyword(s):  
Site Response ◽  
Ground Motions ◽  
Free Field ◽  
Strong Motion ◽  
Site Amplification ◽  
Northridge Earthquake ◽  
Horizontal Acceleration ◽  
Predictive Relationships ◽  
Stiff Soil ◽  
Maximum Horizontal Acceleration

Abstract The magnitude, duration, and frequency content of ground motions from the Northridge earthquake are analyzed and compared to predictive relationships typically used in engineering design and to the 1994 Uniform Building Code (UBC). A relationship between maximum horizontal acceleration on soil versus maximum horizontal acceleration on rock is presented based on strong-motion recordings at free-field sites. The effect of geologic conditions on localized damage patterns is shown to be important for this earthquake, although many of the sites within the affected region are stiff soil sites classified as S1 or S2 sites by the UBC. The results of preliminary seismic site response analyses performed at two deep alluvial sites indicate that much of the observed site amplification can be captured by one-dimensional wave propagation analyses.

scholarly journals What can we learn from the January 2012 northern Italy earthquakes?

2012 ◽  
Vol 55 (1) ◽  
Author(s):  
Marco Massa ◽  
Gabriele Ameri ◽  
Sara Lovati ◽  
Rodolfo Puglia ◽  
Gianlorenzo Franceschina ◽  
...  
Keyword(s):  
Strong Motion ◽  
Northern Italy ◽  
Hazard Map ◽  
Civil Protection ◽  
Po Plain ◽  
Motion Data ◽  
Horizontal Acceleration ◽  
Magnitude Range ◽  
Seismic Hazard Map ◽  
Maximum Horizontal Acceleration

<p>This note focuses on the ground motion recorded during the recent moderate earthquakes that occurred in the central part of northern Italy (Panel 1), a region that is characterized by low seismicity. For this area, the Italian seismic hazard map [Stucchi et al. 2011] assigns a maximum horizontal acceleration (rock site) of up to 0.2 g (10% probability of being exceeded in 50 yr). In the last 4 yr, this region has been struck by 9 earthquakes in the magnitude range 4 <span>≤</span>M<span>w </span><span>≤</span> 5.0, with the three largest located in the Northern Apennines (the M<span>w </span>4.9 and 5.0 Parma events, in December 2008 and January 2012) and on the Po Plain (the M<span>w </span>4.9 Reggio Emila event, in January 2012). We have analyzed the strong-motion data (distance &lt;300 km) from these events as recorded by stations belonging to the Istituto Nazionale di Geofisica e Vulcanologia (RAIS, http://rais.mi.ingv.it; RSNC, http://iside.rm.ingv.it) and the Department of Civil Protection (RAN, www.protezionecivile.it; http://itaca.mi.ingv.it). […]</p>

Repeatable Source, Path, and Site Effects from the 2019 M 7.1 Ridgecrest Earthquake Sequence

2020 ◽  
Vol 110 (4) ◽  
pp. 1530-1548 ◽  
Author(s):  
Grace A. Parker ◽  
Annemarie S. Baltay ◽  
John Rekoske ◽  
Eric M. Thompson
Keyword(s):  
Los Angeles ◽  
Ground Motion ◽  
Site Response ◽  
Ground Motions ◽  
Warning System ◽  
Site Amplification ◽  
Earthquake Sequence ◽  
Ground Acceleration ◽  
Small Magnitude ◽  
Earthquake Early Warning System

ABSTRACT We use a large instrumental dataset from the 2019 Ridgecrest earthquake sequence (Rekoske et al., 2019, 2020) to examine repeatable source-, path-, and site-specific ground motions. A mixed-effects analysis is used to partition total residuals relative to the Boore et al. (2014; hereafter, BSSA14) ground-motion model. We calculate the Arias intensity stress drop for the earthquakes and find strong correlation with our event terms, indicating that they are consistent with source processes. We look for physically meaningful trends in the partitioned residuals and test the ability of BSSA14 to capture the behavior we observe in the data. We find that BSSA14 is a good match to the median observations for M&gt;4. However, we find bias for individual events, especially those with small magnitude and hypocentral depth≥7  km, for which peak ground acceleration is underpredicted by a factor of 2.5. Although the site amplification term captures the median site response when all sites are considered together, it does not capture variations at individual stations across a range of site conditions. We find strong basin amplification in the Los Angeles, Ventura, and San Gabriel basins. We find weak amplification in the San Bernardino basin, which is contrary to simulation-based findings showing a channeling effect from an event with a north–south azimuth. This and an additional set of ground motions from earthquakes southwest of Los Angeles suggest that there is an azimuth-dependent southern California basin response related to the orientation of regional structures when ground motion from waves traveling south–north are compared with those in the east–west direction. These findings exhibit the power of large, spatially dense ground-motion datasets and make clear that nonergodic models are a way to reduce bias and uncertainty in ground-motion estimation for applications like the U.S. Geological Survey National Seismic Hazard Model and the ShakeAlert earthquake early warning System.

Empirical Site Amplification Modelling for Horizontal and Vertical Ground Motions in Taiwan

2020 ◽  
Author(s):  
Chun-Hsiang Kuo ◽  
Shu-Hsien Chao ◽  
Che-Min Lin ◽  
Jyun-Yan Huang ◽  
Kuo-Liang Wen
Keyword(s):  
Ground Motion ◽  
Amplification Factor ◽  
Ground Motions ◽  
Free Field ◽  
Site Amplification ◽  
Amplification Factors ◽  
Taipei Basin ◽  
Vertical Ground Motions ◽  
Vertical Ground ◽  
Site Amplification Factor

&lt;p&gt;Site amplification behavior are important in ground motion prediction. Seismic waves were amplified and caused significant building damages in the Taipei Basin by the 1986 Hualien offshore (subduction interface) and the 1999 Chi-Chi earthquakes (crustal), for which both of the epicentral distances were nearly 100 km. To understand local site amplifications in Taiwan, empirical site amplification factors for both horizontal and vertical ground motions are studied using recently constructed strong motion and site databases for the free-field TSMIP stations. Records of large magnitude earthquakes of M&lt;sub&gt;W&lt;/sub&gt; larger than 5.5 from 1991 to 2016 were selected for this study. Site amplification factors at site conditions with Vs30 between 120 m/s to 1600 m/s and bedrock accelerations up to 0.8 g were evaluated using ratios of spectral accelerations at different periods. The reference site condition, i.e. the engineering bedrock, is assumed as Vs30 of 760 m/s (B/C boundary) in this study. Our empirical site amplification form are borrowed from the site response function of ASK14 and CY14 ground motion models in NGA-West2 project with slight modification. Therefore our site amplification model includes a linear amplification term and a nonlinear deamplification term. The coefficients of the empirical models were obtained by a nonlinear regression analysis using the selected Taiwan data. Site amplification factor is a function of Vs30 and spectral intensity in the model. Similar linear site amplification factor to the NGA models is derived in our model; however, more significant soil nonlinearity behavior than the NGA models is likely captured from the empirical data. The amplification factor in vertical component is smaller than that in horizontal.&lt;/p&gt;

scholarly journals Variation of Earthquake Ground Motions with Focus on Site Amplification Factors: A Case Study

2019 ◽  
Vol 9 (4) ◽  
pp. 4355-4360 ◽  
Author(s):  
Y. Fukushima ◽  
T. Nagao
Keyword(s):  
Hazard Analysis ◽  
Probability Distributions ◽  
Ground Motions ◽  
Strong Motion ◽  
Site Amplification ◽  
Group Delay Time ◽  
Amplification Factors ◽  
Earthquake Ground Motions ◽  
Design Earthquake

In this paper, an evaluation of the variation of earthquake ground motions with a focus on site amplification factors based on spectral analysis is presented. By using strong motion record obtained at six sites in Japan, probability distributions of site amplification factors were shown. The relations between standard deviations of site amplification factors and distances between the sites were studied. The variations of representative values of earthquake ground motions based on the variations of site amplification factors were discussed by using probabilistic seismic hazard analysis with focus on Fourier amplitude and group delay time. The distributions of peak ground accelerations and peak ground velocities were shown. It is suggested that design earthquake ground motions considering the average site amplification factors may lead the engineering design on the dangerous side.

κ0 for soil sites: Observations from KiK-net sites and their use in constraining small-strain damping profiles for site response analysis

2019 ◽  
Vol 36 (1) ◽  
pp. 111-137 ◽  
Author(s):  
Boqin Xu ◽  
Ellen M Rathje ◽  
Youssef Hashash ◽  
Jonathan Stewart ◽  
Kenneth Campbell ◽  
...  
Keyword(s):  
Shear Wave ◽  
Wave Velocity ◽  
Shear Wave Velocity ◽  
Site Response ◽  
Strong Motion ◽  
Small Strain ◽  
Site Amplification ◽  
Site Response Analysis ◽  
Response Analysis ◽  
One Dimensional

Small-strain damping profiles developed from geotechnical laboratory testing have been observed to be smaller than the damping inferred from the observed site amplification from downhole array recordings. This study investigates the high-frequency spectral decay parameter ( κ0) of earthquake motions from soil sites and evaluates the use of κ0 to constrain the small-strain damping profile for one-dimensional site response analysis. Using data from 51 sites from the Kiban-Kyoshin strong motion network (KiK-net) array in Japan and six sites from California, a relationship was developed between κ0 at the surface and both the 30-m time-averaged shear wave velocity ( V s30) and the depth to the 2.5 km/s shear wave velocity horizon ( Z2.5). This relationship demonstrates that κ0 increases with decreasing V s30 and increasing Z2.5. An approach is developed that uses this relationship to establish a target κ0 from which to constrain the small-strain damping profile used in one-dimensional site response analysis. This approach to develop κ0-consistent damping profiles for site response analysis is demonstrated through a recent site amplification study of Central and Eastern North America for the NGA-East project.

Overview of strong-motion data from the Darfield earthquake

2010 ◽  
Vol 43 (4) ◽  
pp. 222-227 ◽  
Author(s):  
Jim Cousins ◽  
Graeme H. McVerry
Keyword(s):  
Main Shock ◽  
Ground Motions ◽  
Strong Motion ◽  
Vertical Acceleration ◽  
Strong Motion Data ◽  
Motion Data ◽  
Near Fault ◽  
Long Period ◽  
Fault Record ◽  
Stiff Soil

The Darfield earthquake of 3rd September 2010 UT and its aftershocks have yielded New Zealand’s richest set of strong-motion data since recording began in the early 1960s. Main-shock accelerograms were returned by 130 sites, ten of which had peak horizontal accelerations in the range 0.3 to 0.82g. One near-fault record, from Greendale, had a peak vertical acceleration of 1.26g. Eighteen records showed peak ground velocities exceeding 0.5 m/s, with three of them exceeding 1 m/s. The records included some with strong long-period directivity pulses, some with other long-period components that were related to a mixture of source and site effects, and some that exhibited the effects of liquefaction at their sites. There were marked differences between records on the deep alluvium of Christchurch City and the Canterbury Plains, and those on shallow stiff soil sites. The strong-motion records provide the opportunity to assess the effects of the earthquake in terms of the ground motions and their relationship to design motions. They also provide an invaluable set of near-source motions for seismological studies. Our report presents an overview of the records and some preliminary findings derived from them.

Influence of site amplification of seismic ground motions on forces in building structures

1991 ◽  
Vol 18 (6) ◽  
pp. 964-973
Author(s):  
A. C. Heidebrecht ◽  
P. Henderson ◽  
N. Naumoski ◽  
J. W. Pappin
Keyword(s):  
Site Response ◽  
Ground Motions ◽  
Site Amplification ◽  
Building Structures ◽  
Base Shear ◽  
Design Code ◽  
Seismic Design Code ◽  
Soil Site ◽  
Response Amplification ◽  
Different Characteristics

The results for nine sites with different characteristics subjected to earthquakes of varying intensity and frequency content are presented in the form of base shear coefficients, base shear coefficient ratios (surface to rock), and foundation factors. They indicate that large amplifications can be expected at structural periods close to the site periods, especially for low intensity excitation. Comparisons are made with the provisions of the National Building Code of Canada (NBCC) 1990. They show that, depending on the site and the nature and level of the excitation, the expected base shear can be well in excess of the values specified by the NBCC. Key words: seismic, design, code, soil, site, response, amplification, base, shear.

A Nonlinear Site Amplification Model for the Horizontal Component Developed for Ground-Motion Prediction Equations in Japan Using Site Period as the Site-Response Parameter

2021 ◽  
Author(s):  
Ruibin Hou ◽  
John X. Zhao
Keyword(s):  
Nonlinear Response ◽  
Site Response ◽  
Strong Motion ◽  
Site Amplification ◽  
Second Step ◽  
Ground Motion Prediction Equations ◽  
Ground Motion Prediction ◽  
Amplification Ratio ◽  
Soil Site ◽  
Site Period

ABSTRACT This article presents a nonlinear site amplification model for ground-motion prediction equations (GMPEs), using site period as site-effect proxy based on the measured shear-wave velocity profiles of selected KiK-net and K-NET sites in Japan. This model was derived using 1D equivalent-linear site-response analysis for a total of 516 measured soil-site shear-wave velocity profiles subjected to a total of 912 components of rock-site records. The modulus reduction and damping curves for each soil layer were assigned based on the soil-type description for a particular layer. The site period and site impedance ratio affect both the linear and nonlinear parts of this study, and were used as the site parameters in the 1D amplification model. A large impedance ratio enhances the amplification ratios when the site responds elastically and enhances the nonlinear response when the site develops a significant nonlinear response. The effects of moment magnitude and source distance on the linear part of the 1D amplification model were also incorporated in the model. To implement the 1D amplification model into GMPEs, a model adjustment is required to match the GMPE amplification ratio at weak motion and to retain the nonlinear amplification ratio at the strong motion of the 1D model. The two-step adjustment method by Zhao, Hu, et al. (2015) was adopted in this study with significant modifications. It is not possible to obtain a credible second-step adjustment parameter using the GMPEs dataset only. We proposed three methods for calculating the scale factors. Method 1 is a constant angle in a 30°–60° range for all spectral periods; method 2 was based on the GMPE dataset and 1-D model parameters; and method 3 was based on the strong-motion records used for the 1D site modeling. A simple second-step adjustment factor leads to smoothing amplification ratios and soil-site spectrum.

Seismic Response of a Hill in Wenxian, Gansu, Observed from Aftershocks of 2008 Wenchuan Earthquake

2011 ◽  
Vol 243-249 ◽  
pp. 3952-3957 ◽  
Author(s):  
Yu Xia Lu ◽  
Kun Liu ◽  
Yu Cheng Shi ◽  
Qian Li
Keyword(s):  
Site Response ◽  
Ground Motions ◽  
Strong Motion ◽  
Spectral Ratio ◽  
Gansu Province ◽  
Spectra Analysis ◽  
2008 Wenchuan Earthquake ◽  
Motion Data ◽  
Source Effects ◽  
The Hill

To help understand the ground motions of the topographic site, the workers of Seismic Bureau of Gansu province deployed a temporary array of seismometers around the Wenxian hill and recorded ground motions from Wenchuan aftershocks. Only 11 aftershocks were recorded on all stations across the hill, these data were collected to facilitate studies of site response, wave propagation effect, and correlations of mainshock damage with local site conditions. In this paper, we analyze the weak motion data as well as the strong-motion data, and conduct comparisons of peak ground accelerations, seismic spectra analysis, and spectral ratio analysis. A more complete description of the site’s amplification, its relationship to topography, and its relationship to earthquake source effects are provided. The result shows that the ground motion was consistently amplified at station at or near the top of the hill compared with stations at the base of the hill and the amplifications frequency dependent and has its maximum at the resonant frequency of the site.

Evaluation of Generalized Site Response Functions for Typical Soil Classes (B, C, and D) in Taiwan

2004 ◽  
Vol 20 (4) ◽  
pp. 1279-1316 ◽  
Author(s):  
Vladimir Yu Sokolov ◽  
C-H. Loh ◽  
K-L. Wen
Keyword(s):  
Site Response ◽  
Soft Rock ◽  
Site Amplification ◽  
Soil Class ◽  
Class D ◽  
Spectral Models ◽  
Amplitude Spectra ◽  
Class B ◽  
Large Earthquakes ◽  
Stiff Soil

Empirical amplification functions for site classes B, C, and D in Taiwan were evaluated as the ratio between Fourier amplitude spectra of recorded accelerograms and spectra modeled for a hypothetical very hard rock (VHR) site. The approach allowed testing applicability of various spectral models in the studied region. More than 1,000 acceleration records obtained during 21 intermediate-sized and large earthquakes (ML>5.5), including the ML 7.3 (MW 7.6) Chi-Chi earthquake (21 September 1999) and the large aftershocks (ML 6.8), were used. The evaluated amplification functions were compared with independent data, which were obtained recently for Taiwan, the western United States, and Greece. The prominent influence of geologic and geomorphologic factors on site amplification functions for the considered cases of rock (Class B), soft rock or very dense soil (Class C), and stiff soil (Class D) sites has been observed for the Taiwan region.

Sign in / Sign up

Export Citation Format

Share Document