Site-Response Characteristics Evaluated from Strong Motion Records of the 2003 Boumerdes, Algeria, Earthquake

2010 ◽  
Vol 26 (3) ◽  
pp. 803-823 ◽  
Author(s):  
Abdelghani Meslem ◽  
Fumio Yamazaki ◽  
Yoshihisa Maruyama ◽  
Djillali Benouar ◽  
Nasser Laouami ◽  
...  
Keyword(s):  
Transfer Functions ◽  
Site Response ◽  
Strong Motion ◽  
Spectral Ratios ◽  
Quaternary Deposits ◽  
Ground Acceleration ◽  
Predominant Period ◽  
Response Characteristics ◽  
Seismic Motion ◽  
Boumerdes Earthquake

Site response characteristics at seismic stations were investigated using horizontal-to-vertical (H/V) spectral ratios calculated from a seismic-motion dataset of the 2003 Boumerdes earthquake, and transfer functions were evaluated from soil profile data. Although high peak ground acceleration (PGA) values were recorded at some sites, the nonlinear effect at these stations was not clear. The H/V spectral ratios calculated from weak and strong motion events did not show a clear difference in the predominant period and amplitudes, and the shapes of the H/V ratios were flat for some stations. These observations are characteristic of the presence of firm to hard layers under the stations; however, one station was located on Quaternary deposits showed a remarkable amplification at the predominant period and a high PGA value.

Apparent Wave Velocity and Site Amplification at the California Strong Motion Instrumentation Program Carquinez Bridge Geotechnical Arrays during the 2014 M6.0 South Napa Earthquake

2018 ◽  
Vol 34 (1) ◽  
pp. 327-347 ◽  
Author(s):  
Tadahiro Kishida ◽  
Hamid Haddadi ◽  
Robert B. Darragh ◽  
Robert E. Kayen ◽  
Walter J. Silva ◽  
...  
Keyword(s):  
Main Shock ◽  
Transfer Functions ◽  
Site Response ◽  
Damping Ratio ◽  
Soft Clay ◽  
Ground Surface ◽  
Strong Motion ◽  
Ground Acceleration ◽  
Clay Deposits ◽  
Resonance Frequencies

The Carquinez Bridge geotechnical arrays are operated by the California Strong Motion Instrumentation Program (CSMIP) and recorded a peak ground acceleration (PGA) of approximately 1.0g at ground surface during the 2014 South Napa earthquake. The recorded PGA was significantly larger than those at the nearby surface sites. This study considers surface and downhole recordings from the additional 28 earthquakes recorded at the same arrays to understand the effects of wave propagation and site response at these arrays. Several site response analyses are performed to understand soil nonlinearity using the observed ground accelerations during the 2014 South Napa sequence. Apparent shear wave velocities are calculated from downhole records, which show clear reduction as ground motion intensity increases. Empirical transfer functions (EFTs) are also calculated in which the resonance frequencies became lower during strong shaking during the 2014 South Napa main shock. The in-situ critical damping ratio appears to be frequency dependent in the soft clay deposits. Lower damping at frequencies greater than about 5 Hz may have contributed to the observed PGA at Array #1 during the main shock.

Seismic site response in the greater Vancouver, British Columbia, area: spectral ratios from moderate earthquakes

1999 ◽  
Vol 36 (2) ◽  
pp. 195-209 ◽  
Author(s):  
John F Cassidy ◽  
Garry C Rogers
Keyword(s):  
Site Response ◽  
Strong Motion ◽  
River Delta ◽  
Data Sets ◽  
Fraser River ◽  
Spectral Ratios ◽  
Data Set ◽  
Seismic Site Response ◽  
Fraser River Delta ◽  
S Period

Three-component, digital recordings of two recent moderate earthquakes provide valuable new insight into the response to seismic shaking in the greater Vancouver area, particularly on the Fraser River delta. The 1996 M = 5.1 Duvall, Washington, earthquake (180 km southeast of Vancouver) triggered strong-motion seismographs at seven sites and the 1997 M = 4.3 Georgia Strait earthquake (37 km west of Vancouver) triggered instruments at 13 sites in the greater Vancouver area. The latter data set is especially important because it contains the first three-component recordings made on bedrock in greater Vancouver. Both data sets represent weak ground motion, with peak horizontal accelerations of 0.5-1.5% gravity (g) for the Duvall earthquake, and 0.2-2.4% g for the Georgia Strait earthquake. Using the method of spectral ratios, we estimate the site response for each of the strong-motion instrument soil sites. On the Fraser River delta amplification is observed over a relatively narrow frequency range of 1.5-4 Hz (0.25-0.67 s period), with peak amplification of 4-10 (relative to competent bedrock) for the thick soil delta centre sites, and about 7-11 for the delta edge sites. Relative to firm soil, the peak amplification ranges from 2 to 5 for the thick soil delta centre sites, and 2 to 6 for the delta edge sites. At higher frequencies, little or no amplification, and in many cases slight attenuation, is observed.Key words: seismic site response, Fraser delta, earthquakes.

Nonlinear Site Effects from the 30 November 2018 Anchorage, Alaska, Earthquake

2021 ◽  
Author(s):  
John D. Thornley ◽  
Utpal Dutta ◽  
John Douglas ◽  
Zhaohui (Joey) Yang
Keyword(s):  
Site Response ◽  
Strong Motion ◽  
North American Plate ◽  
Peak Ground Velocity ◽  
Reference Station ◽  
Earthquake Hazards ◽  
Ground Acceleration ◽  
Nonlinear Site Response ◽  
Generalized Inversion Technique ◽  
Versus Peak

ABSTRACT Anchorage, Alaska, is a natural laboratory for recording strong ground motions from a variety of earthquake sources. The city is situated in a tectonic region that includes the interface and intraslab earthquakes related to the subducting Pacific plate and crustal earthquakes from the upper North American plate. The generalized inversion technique was used with a local rock reference station to develop site response at >20 strong-motion stations in Anchorage. A database of 94 events recorded at these sites from 2005 to 2019 was also compiled and processed to compare their site response with those in the 2018 Mw 7.1 event (main event). The database is divided into three datasets, including 75 events prior to the main event, the main event, and 19 aftershocks. The stations were subdivided into the site classes defined in the National Earthquake Hazards Reduction Program based on estimated average shear-wave velocity in of the upper 30 m (VS30), and site-response results from the datasets were compared. Nonlinear site response was observed at class D and DE sites (VS30 of 215–300 and 150–215  m/s, respectively) but not at class CD and C sites (VS30 of 300–440 and 440–640  m/s, respectively). The relationship of peak ground acceleration versus peak ground velocity divided by VS30 (shear-strain proxy) was shown to further support the observation that sites with lower VS30 experienced nonlinear site response.

The accuracy of soil response estimates using soil-to-rock spectral ratios

1996 ◽  
Vol 86 (2) ◽  
pp. 519-523
Author(s):  
Igor A. Beresnev ◽  
Kuo-Liang Wen
Keyword(s):  
Site Response ◽  
Soft Soil ◽  
Strong Motion ◽  
Finite Depth ◽  
Spectral Ratios ◽  
Site Specific ◽  
Soil Response ◽  
Strong Motion Records ◽  
The Real ◽  
Specific Amplification

Abstract Spectral ratios between soft soil and reference rock sites are often used to predict the sedimentary site response to earthquakes. However, their relationship with the genuine site-specific amplification function is often unclear. We compare the soil-to-rock spectral ratios between the stations that are 3.3 km apart with the “genuine” response given by the ratios between the surface and 17 and 47 m downhole. Data from the SMART1 array in Taiwan are used. The “weak” and “strong” motion records are addressed separately to allow for nonlinear soil response. The soil-to-rock spectral ratios are nearly identical to the “true” amplification at the frequencies from 1 to 10 Hz, if the finite depth of the borehole is taken into account. They correctly capture the strong-motion deamplification effect. However, the soil-to-rock spectral ratios are roughly 1.4 times more uncertain than surface-to-47-m ratios. In summary, the soil-to-rock spectral ratios can be considered as the reliable estimates of the real site response.

Site Response Studies for Purpose of Revising NEHRP Seismic Provisions

1996 ◽  
Vol 12 (3) ◽  
pp. 407-439 ◽  
Author(s):  
C. B. Crouse ◽  
J. W. McGuire
Keyword(s):  
Earthquake Engineering ◽  
Site Response ◽  
Soft Soil ◽  
Strong Motion ◽  
Earthquake Hazard ◽  
Ground Acceleration ◽  
Amplification Factors ◽  
Soil Class ◽  
Engineering Research ◽  
Stiff Soil

A strong motion database was compiled for California earthquakes of surfacewave magnitudes, Ms ≥ 6, occurring from 1933 through 1992. The database consisted of horizontal peak ground acceleration and 5 percent damped response spectra of accelerograms recorded on four different local geologies: rock (class A), soft rock or stiff soil (class B), medium stiff soil (class C), and soft soil (class D). The results of analyses of the database within each of these site classes were used to derive a set of site-dependent spectral amplification factors for oscillator periods between 0.1 and 4.0 sec and ground acceleration levels between 0.1 and 0.4 g. The amplification factors at 0.3 and 1.0 sec periods (designated as Fa and Fv, respectively) are generally within 20 percent of those recommended during the 1992 Site Response Workshop conducted by the National Center for Earthquake Engineering Research (NCEER). The Fa and Fv values recommended from our study and those from the NCEER workshop are intended for use by code committees making future revisions to the National Earthquake Hazard Reduction Program (NEHRP) seismic provisions and the Uniform Building Code.

Comparison of earthquake and microtremor ground motions in El Centro, California

1973 ◽  
Vol 63 (4) ◽  
pp. 1227-1253 ◽  
Author(s):  
F. E. Udwadia ◽  
M. D. Trifunac
Keyword(s):  
Site Response ◽  
Ground Motions ◽  
Strong Motion ◽  
Site Conditions ◽  
Ground Shaking ◽  
Response Characteristics ◽  
Local Site ◽  
Simple Features ◽  
Low Amplitude ◽  
Local Site Conditions

abstract Strong earthquake ground shaking has been investigated by the study of 15 events recorded in El Centro, California. The strong-motion records analyzed show that no simple features (e.g., local site conditions) govern the details of local ground shaking. Any effects of local subsoil conditions at this site appear to be overshadowed by the source mechanism and the transmission path, there being no distinctly identifiable site periodicities. Microtremor measurements have been taken in the area surrounding the strong-motion site. The objective was an investigation of possible correlations with strong ground motions and the analysis of site-response characteristics. Basic difficulties in ascertaining local site conditions through such low-amplitude ground motions are illustrated. It has been found that in this area microtremor and earthquake processes are widely different in character, there being little to no correlation between the ground's response to earthquakes and to microtremor excitations. Microtremors have been found to be nonstationary over periods of about a day or so, introducing further uncertainties into inferences from such measurements.

scholarly journals Ground response of the Kathmandu Sedimentary Basin with reference to 30 August 2013 South-Tibet Earthquake

2014 ◽  
Vol 47 (1) ◽  
pp. 23-34 ◽  
Author(s):  
S. Rajaure ◽  
B. Koirala ◽  
R. Pandey ◽  
C. Timsina ◽  
M Jha ◽  
...  
Keyword(s):  
Site Response ◽  
Low Frequency ◽  
Frequency Range ◽  
Spectral Ratios ◽  
Ground Acceleration ◽  
Soil Layers ◽  
Nonlinear Site Response ◽  
Basin Effects ◽  
Acceleration Record ◽  
South Tibet

Ground acceleration of the 30 August 2013 (M4.9), South Tibet Earthquake has been recorded by five accelerometers deployed in the Kathmandu Valley. Analysis of the ground acceleration record reveals that that the EW component was dominant across the valley, and with the exception of one, all stations on sediments recorded PGA much higher than the station on rock. The site response functions, evaluated as the Fourier spectral ratios of the horizontal components on soil relative to the corresponding component on rock, are remarkably similar in the low frequency range (<0.8 Hz) and reveal strong amplification that likely corresponds to basin effects. By contrast, the high frequency site response shows strong variability across the soil sites, likely attributed to the underlying stratigraphy of the shallow soil layers of the valley. The most pronounced differences manifest in the frequency range >2Hz, which is consistent with the variability in PGA across the valley. Because of the small intensity of this event, the empirical site response recorded can be, approximately, considered linear. As such, this study establishes a reference for future studies on nonlinear site response, which is likely to be triggered during future stronger earthquakes.

Numerical evaluation of the effect of cross-coupling of different components of ground motion in site response analyses

1999 ◽  
Vol 89 (4) ◽  
pp. 877-887
Author(s):  
Roberto Paolucci
Keyword(s):  
Transfer Function ◽  
Ground Motion ◽  
Site Response ◽  
Strong Motion ◽  
Cross Coupling ◽  
Response Functions ◽  
Spectral Ratios ◽  
Acceleration Time Histories ◽  
Time Histories ◽  
Input Motion

Abstract The effect of cross-coupling between the three components of ground motion in the evaluation of site-response functions, such as standard spectral ratios (SSRs) and horizontal-to-vertical spectral ratios (HVSRs), is analyzed in this article. Numerical analyses of the seismic response of fully 3D geological structures, namely, a real topographic irregularity and an ideal stratigraphic inclusion, have been carried out to obtain a 3D transfer function in the form of a 3 × 3 matrix. Each element of this matrix contains the frequency response in the ith direction due to an input motion in the jth direction. A synthetic set of acceleration time histories at the surface of the geological irregularity has been created by convolution with the 3D transfer function, using as input motion different real multicomponent strong-motion accelerograms recorded at stiff-soil or rock sites. The SSRs and HVSRs are calculated and compared with the theoretical 3D transfer function in order to highlight the effect of cross-coupling terms. These are found to generate a rather large dispersion in the site-response functions, as well as response peaks that could be misleading in the interpretation of both numerical and observed spectral ratios.

Topographical and geological amplifications determined from strong-motion and aftershock records of the 3 March 1985 Chile earthquake

1987 ◽  
Vol 77 (4) ◽  
pp. 1147-1167
Author(s):  
M. Çelebi
Keyword(s):  
Site Response ◽  
Strong Motion ◽  
Spectral Ratios ◽  
Data Set ◽  
Frequency Dependent ◽  
Central Chile ◽  
Strong Motion Records ◽  
Chile Earthquake ◽  
Populated Region ◽  
Geological Formations

Abstract Site-response experiments were performed 5 months after the MS = 7.8 central Chile earthquake of 3 March 1985 to identify amplification due to topography and geology. Topographical amplification at Canal Beagle, a subdivision of Viña del Mar, was hypothesized immediately after the main event, when extensive damage was observed on the ridges of Canal Beagle. Using frequency-dependent spectral ratios of aftershock data obtained from a temporarily established dense array, it is shown that there is substantial amplification of motions at the ridges of Canal Beagle. The data set constitutes the first such set depicting topographical amplification at a heavily populated region and correlates well with the damage distribution observed during the main event. Dense arrays established in Viña del Mar also yielded extensive data which are quantified to show that, in the range of frequencies of engineering interest, there was substantial amplification at different sites of different geological formations. To substantiate this, spectral ratios developed from the strong-motion records of the main event are used to show the extensive degree of amplification at an alluvial site as compared to a rock site. Similarly, spectral ratios developed from aftershocks recorded at comparable stations qualitatively confirm that the frequency ranges for which the amplification of motions occur are quite similar to those from strong-motion records. In case of weak motions, the denser arrays established temporarily as described herein can be used to identify the frequency ranges for which amplification occurs, to quantify the degree of frequency-dependent amplification and used in microzonation of closely spaced localities.

Testing Nonlinear Amplification Factors of Ground-Motion Models

2021 ◽  
Author(s):  
Karina Loviknes ◽  
Sreeram Reddy Kotha ◽  
Fabrice Cotton ◽  
Danijel Schorlemmer
Keyword(s):  
Ground Motion ◽  
Nonlinear Models ◽  
Site Response ◽  
Strong Motion ◽  
Site Amplification ◽  
Building Codes ◽  
Linear Amplification ◽  
Ground Acceleration ◽  
Nonlinear Site Response ◽  
The Impact

ABSTRACT We explore nonlinear site effects in the new Japanese ground-motion dataset compiled by Bahrampouri et al. (2020). Following the approach of Seyhan and Stewart (2014), we evaluate the decrease of soil amplification according to the increasing and corresponding ground motion on surface rock (VS30=760  m/s). To better predict the rock ground motion associated with each record, we take into account the between-event variability of the ground motion, and to better evaluate the impact of nonlinearity, we correct observed ground motion on soil by the site-specific linear amplification. Instead of grouping the stations by site-response proxy, we focus on individual stations with several strong-motion records. We develop a framework to test recently published nonlinear site amplification models against a linear site amplification model and compare the results with recent building codes that include nonlinearity. The results show that the site response varies greatly from site to site, indicating that conventional site proxies, such as VS30, are not sufficient to characterize nonlinear site response. Out of all of the Kiban–Kyoshin network stations, 20 stations are selected as having recorded sufficient data to be used in the test. Out of these 20 stations, five stations show signs of nonlinearity, that is, the nonlinear models performed better than the linear-amplification model for all periods T. For most sites, however, the linear site amplification models get the best score. This suggest that, for the range of predicted rock motion considered in this study (peak ground acceleration &lt;0.2g), nonlinearity may not have a sufficiently large impact on soil ground motion to justify the use of nonlinear site terms in ground-motion functional forms and seismic building codes for such moderate-level shaking.

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