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.

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>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.

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.

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.

Analysis of Site Amplification Phenomena: An Application in Ripabottoni for the 2002 Molise, Italy, Earthquake

2004 ◽  
Vol 20 (1_suppl) ◽  
pp. 107-118 ◽  
Author(s):  
Marco Massa ◽  
Gabriele Ferretti ◽  
Andrea Cevasco ◽  
Luana Isella ◽  
Claudio Eva
Keyword(s):  
Fundamental Frequency ◽  
Site Effects ◽  
Site Response ◽  
Site Amplification ◽  
Simulation Code ◽  
Dimensional Simulation ◽  
Molise Region ◽  
A Site ◽  
The University ◽  
The Village

The geophysical working group of the University of Genoa conducted a field experiment to analyze site amplification effects in Ripabottoni, a village in the Molise region of Italy. We used both noise and earthquake recordings, combined with detailed geologic and geotechnical surveys, to define site amplification phenomena. The site effects determination was obtained using the Nakamura technique and the H/V spectral analysis applied to earthquake recordings. The results were validated by applying a one-dimensional simulation code. The computed spectral ratios point out three different typologies of site effects: the southern sector of Ripabottoni is characterized by an absence of local amplification phenomena; the central sector of the village shows a local amplification phenomena with a fundamental frequency of 4–6 Hz; and the northeastern side of the village shows a site response at a fundamental frequency between 2–3 Hz.

Seismic site effects and the spatial interpolation of earthquake seismograms: Results using aftershocks of the 1986 North Palm Springs, California, earthquake

1990 ◽  
Vol 80 (6A) ◽  
pp. 1504-1532
Author(s):  
Paul Spudich ◽  
David P. Miller
Keyword(s):  
Transfer Function ◽  
Site Response ◽  
Incidence Angle ◽  
Ground Motions ◽  
Geologic Structure ◽  
S Wave ◽  
Linear System Of Equations ◽  
Seismic Site Effects ◽  
Palm Springs ◽  
A Site

Abstract We address the following two questions. Can a microearthquake's ground motions be modeled by incident P and S waves that excite a site transfer-function that is a smooth function of incidence angle? Given recorded ground motions from a set of earthquakes having known locations and mechanisms, can we derive such a site transfer-function and use it to obtain the ground motions that would result from an earthquake source occurring somewhere in the same volume but having a location and mechanism that are different from the recorded events? Although many factors will cause two distinct microearthquake sources to have different seismograms at a common station, in this paper we concentrate only upon the differences caused by source mechanisms, P- and S-wave travel-time variations and by variations in the site transfer-function. We specifically exclude the effects of waves scattered from heterogeneities in the geologic structure away from the seismic site. We express the site transfer-function as a sum of several terms having simple dependences upon incidence angle and azimuth. Each term is an independent function of time. Given a set of seismograms observed at the site, we solve a linear system of equations for the time dependences of each term. These time series may be used to calculate the seismograms that would have resulted from an earthquake having arbitrary mechanism and location. This step is an interpolation. We have applied this technique to seismograms after aftershocks of the 1986 North Palm Springs earthquake. Our interpolation technique works fairly well within the volume occupied by the recorded events, but the method is not very successful at providing accurate seismograms for sources located outside the aftershock volume. The primary causes of the inaccuracy are the inadequacy of our chosen angular functions to model the site response fully and the likely scattering of seismic waves by geological heterogeneities (in this case, the Banning and Mission Creek faults) near the seismic stations. Our methods could be used to determine the effects of single scattering from lateral heterogeneities in geologic structure.

An open-source site database of strong-motion stations in Japan: K-NET and KiK-net (v1.0.0)

2021 ◽  
pp. 875529302098802
Author(s):  
Chuanbin Zhu ◽  
Graeme Weatherill ◽  
Fabrice Cotton ◽  
Marco Pilz ◽  
Dong Youp Kwak ◽  
...  
Keyword(s):  
Open Source ◽  
Site Response ◽  
Strong Motion ◽  
Spectral Ratio ◽  
Peak Frequency ◽  
Site Amplification ◽  
Machine Learning Techniques ◽  
Regional Variability ◽  
Motion Models ◽  
Source Site

This article describes an open-source site database for a total number of 1742 earthquake recording sites in the K-NET (Kyoshin network) and KiK-net (Kiban Kyoshin network) networks in Japan. This database contains site characterization parameters directly derived from available velocity profiles, including average wave velocities, bedrock depths, and velocity contrast. Meanwhile, it also consists of earthquake horizontal-to-vertical spectral ratio (HVSR) and peak parameters, for example, peak frequency, amplitude, width, and prominence. In addition, the site database also comprises topographic and geological proxies inferred from regional models or maps. Each parameter is derived in a consistent manner for all sites. This site database can benefit the application of machine learning techniques in studies on site amplification. Besides, it can facilitate, for instances, the search of the optimal site parameter(s) for the prediction of site amplification, the development and testing of ground-motion models or methodologies, as well as investigations on spatial or regional variability in site response. All resources (the site database, earthquake HVSR data at all sites, and the MATLAB script for peak identification) can be freely accessed via: https://doi.org/10.5880/GFZ.2.1.2020.006

Ground motion and site effect observations in the wellington region from the 2016 Mw7.8 Kaikōura, New Zealand earthquake

2017 ◽  
Vol 50 (2) ◽  
pp. 94-105 ◽  
Author(s):  
Brendon A. Bradley ◽  
Liam M. Wotherspoon ◽  
Anna E. Kaiser
Keyword(s):  
Ground Motion ◽  
Site Response ◽  
Ground Motions ◽  
Site Effect ◽  
Site Amplification ◽  
Design Standards ◽  
Site Class ◽  
Near Surface ◽  
Long Period ◽  
Basin Edge

This paper presents ground motion and site effect observations in the greater Wellington region from the 14 November 2016 Mw7.8 Kaikōura earthquake. The region was the principal urban area to be affected by the earthquake-induced ground motions from this event. Despite being approximately 60km from the northern extent of the causative earthquake rupture, the ground motions in Wellington exhibited long period (specifically T = 1 - 3s) ground motion amplitudes that were similar to, and in some locations exceeded, the current 500 year return period design ground motion levels. Several ground motion observations on rock provide significant constraint to understand the role of surficial site effects in the recorded ground motions. The largest long period ground motions were observed in the Thorndon and Te Aro basins in Wellington City, inferred as a result of 1D impedance contrasts and also basin-edge-generated waves. Observed site amplifications, based on response spectral ratios with reference rock sites, are seen to significantly exceed the site class factors in NZS1170.5:2004 for site class C, D, and E sites at approximately T=0.3-3.0s. The 5-95% Significant Duration, Ds595, of ground motions was on the order of 30 seconds, consistent with empirical models for this earthquake magnitude and source-to-site distance. Such durations are slightly longer than the corresponding Ds595 = 10s and 25s in central Christchurch during the 22 February 2011 Mw6.2 and 4 September 2010 Mw7.1 earthquakes, but significantly shorter than what might be expected for large subduction zone earthquakes that pose a hazard to the region. In summary, the observations highlight the need to better understand and quantify basin and near-surface site response effects through more comprehensive models, and better account for such effects through site amplification factors in design standards.

scholarly journals Reduction of Bias and Uncertainty in Regional Seismic Site Amplification Factors for Seismic Hazard and Risk Analysis

GeoHazards ◽  
2021 ◽  
Vol 2 (3) ◽  
pp. 277-301
Author(s):  
Mohammad Kamruzzaman Talukder ◽  
Philippe Rosset ◽  
Luc Chouinard
Keyword(s):  
North America ◽  
Seismic Hazard ◽  
Shear Wave ◽  
Site Response ◽  
Ground Motions ◽  
Site Amplification ◽  
Soil Profiles ◽  
Site Class ◽  
Amplification Factors ◽  
Wave Velocities

Site amplification factors in National Building Codes are typically specified as a function of the average shear wave velocity over the first 30 m (Vs30) or site class (A, B, C, D and E) for defined ranges of Vs30 and/or ranges of depth to bedrock. However, a single set of amplification factors may not be representative of site conditions across the country, introducing a bias in seismic hazard and seismic risk analyses. This is exemplified by significant differences in geological settings between East and West coast locations in North America. Western sites are typically characterized by lower impedance contrasts between recent surface deposits and bedrock in comparison to Eastern sites. In North America, site amplification factors have been derived from a combination of field data on ground motions recorded during West Coast earthquakes and numerical models of site responses that are meant to be representative of a wide variety of soil profiles and ground motions. The bias on amplifications and their impact on seismic hazards is investigated for the Montreal area, which ranks second for seismic risks in Canada in terms of population and hazard (PGA of 0.25 g for a 2475 years return period). Representative soil profiles at several locations in Montreal are analyzed with 1-D site response models for natural and synthetic ground motions scaled between 0.1 to 0.5 g. Since bedrock depths are typically shallow (<30 m) across the island, bedrock shear wave velocities have a significant influence on the impedance contrast and amplifications. Bedrock shear wave velocity is usually very variable due to the differences in rock formations, level of weathering and fracturing. The level of this uncertainty is shown to be greatly decreased when rock quality designation (RQD) data, common information when bore hole data are logged, is available since it is highly correlated with both shear and compression wave velocities. The results are used to derive region-specific site amplification factors as a function of both Vs30 and site fundamental frequency and compared to those of the National Building Code of Canada (2015). The results of the study indicate that there are large uncertainties associated with these parameters due to variability in soil profiles, soil properties and input seismic ground motions. Average and confidence intervals for the mean and for predictions of amplification factors are calculated for each site class to quantify this uncertainty. Amplifications normalized relative to class C are obtained by accounting for the correlation between site class amplifications for given ground motions. Non-linearity in the analysis of equivalent linear 1-D site response is taken into account by introducing the non-linear G/Gmax and damping ratios curves. In this method, it is assumed that the shear strain compatible shear modulus and damping ratio values remains constant throughout the duration of the seismic excitation. This assumption is not fully applicable to a case when loose saturated soil profile undergo heavy shaking (PGA > 0.3 g). In this study, all simulations with input motion PGA >0.3 g have been performed by using the EL method instead of the NL method considering that cohesive soils (clay and silt) at Montreal sites are stiff and cohesionless soils (sand and gravel) are considerably dense. In addition, the field and laboratory data required to perform NL analyses are not currently available and may be investigated in future works.

scholarly journals Evaluation of Seismic Site Amplification Using 1D Site Response Analyses at Ba Dinh Square Area, Vietnam

2021 ◽  
Vol 2021 ◽  
pp. 1-11
Author(s):  
Ngoc-Long Tran ◽  
Muhammad Aaqib ◽  
Ba-Phu Nguyen ◽  
Duy-Duan Nguyen ◽  
Viet-Linh Tran ◽  
...  
Keyword(s):  
Site Response ◽  
Ground Motions ◽  
Site Amplification ◽  
Response Analysis ◽  
Ground Response ◽  
Ground Response Analysis ◽  
Ground Acceleration ◽  
Site Specific ◽  
Design Spectrum ◽  
Equivalent Linear

This study presents a case study on ground response analysis of one of the important cultural heritages in Hanoi, Vietnam. One-dimensional nonlinear and equivalent linear site response analyses which are commonly applied to solve the problem of seismic stress wave propagation are performed at the Ba Dinh square area. A measured in-situ shear wave velocity profile and corresponding geotechnical site investigation and laboratory test data are utilized to develop the site model for site-specific ground response analysis. A suite of earthquake records compatible with Vietnamese Design Code TCVN 9386: 2012 rock design spectrum is used as input ground motions at the bedrock. A few concerns associated with site-specific ground response evaluation are analyzed for both nonlinear and equivalent linear procedures, including shear strains, mobilized shear strength, and peak ground acceleration along with the depth. The results show that the mean maximum shear strains at any soil layer are less than 0.2% in the study area. A deamplification portion within the soil profile is observed at the layer interface with shear wave velocity reversal. The maximum peak ground acceleration (PGA) at the surface is about 0.2 g for equivalent linear analysis and 0.16 g for nonlinear analysis. The ground motions are amplified near the site natural period 0.72 s. The soil factors calculated in this study are 1.95 and 2.07 for nonlinear and equivalent linear analyses, respectively. These values are much different from the current value of 1.15 for site class C in TCVN 9386: 2012. A comparison of calculated response spectra and amplification factors with the local standard code of practice revealed significant discrepancies. It is demonstrated that the TCVN 9386: 2012 soil design spectrum is unable to capture the calculated site amplification in the study area.

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.

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