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.

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.

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.

Preliminary microzonation of the Memphis, Tennessee, area

1982 ◽  
Vol 72 (3) ◽  
pp. 1011-1024
Author(s):  
Sunil Sharma ◽  
William D. Kovacs
Keyword(s):  
United States ◽  
Soil Properties ◽  
Damping Ratio ◽  
Ground Surface ◽  
Strong Motion ◽  
Response Analysis ◽  
Borehole Data ◽  
Central United States ◽  
Hazardous Zone ◽  
High Level

abstract The city of Memphis, which is situated very close to the inferred epicenter of one of the three major 1811 to 1812 earthquakes, is in a potentially hazardous zone which will be susceptible to the usual seismic hazards. By recognizing the high level of seismicity in the New Madrid area, this study attempts to microzone the potential hazards by considering the following subjects: (i) the seismicity of the central United States; (ii) design earthquakes; and (iii) response analysis which allows construction of the necessary microzonation maps. The seismicity of the region is evaluated from state-of-the-art literature as there is no recorded strong-motion data available for the central United States. Synthetically generated accelerograms, simulating the design earthquakes, were used to represent the ground motions which were applied at a depth of 45 m, below ground surface, at numerous sites in Memphis. The soil stratigraphy was conceptualized from borehole data, made available by local sources, and dynamic soil properties estimated from available empirical correlations. The results of the response analysis were transformed into microzonation maps depicting: (i) zones showing qualitative estimates of ground response; (ii) zones showing the natural frequency of the soils; (iii) zones showing the peak spectral acceleration for 2 per cent damping ratio; and (iv) zones of liquefaction potential. These maps are useful for preliminary design and are not intended to be used on a quantitative basis. Further investigation is necessary in determining the stratigraphy and soil properties for a site-specific design and analysis.

Modeling of the Subsurface Structure from the Seismic Bedrock to the Ground Surface for a Broadband Strong Motion Evaluation in Kumamoto Plain

2018 ◽  
Vol 13 (5) ◽  
pp. 917-927 ◽  
Author(s):  
Shigeki Senna ◽  
Atsushi Wakai ◽  
Haruhiko Suzuki ◽  
Atsushi Yatagai ◽  
Hisanori Matsuyama ◽  
...  
Keyword(s):  
Soil Structure ◽  
Main Shock ◽  
Ground Surface ◽  
Strong Motion ◽  
Seismic Intensity ◽  
S Wave ◽  
The 2016 Kumamoto Earthquakes ◽  
Significant Damage ◽  
Geologic Model ◽  
2016 Kumamoto Earthquakes

During the 2016 Kumamoto earthquakes, two earthquakes of seismic intensity 7 were observed in Mashiki Town, the foreshock (MJMA6.5) of April 14 and the main shock (MJMA7.3) of April 16, resulting in significant damage to structures near the fault. The distribution of damage of houses and other buildings [1] showed a tendency in which damage was concentrated in areas near the surface earthquake fault where the main shock presumably occurred. However, there were locations with slight damage even though they were immediately above the fault and locations with a relatively significant damage even though they were far from the fault. These phenomena are highly likely to be a result of soil structure. First, we built an initial geologic model by collecting boring data in areas of the Kumamoto plain near the fault where damage was severe. Next, we observed microtremors, collected earthquake observational records, and adjusted the layer thickness and S-wave velocity of the initial geologic model. Finally, we built a shallow and deep integrated ground model, compared it to the building damage distribution, and discussed the implications.

Edgecombe earthquake

1987 ◽  
Vol 20 (3) ◽  
pp. 201-249 ◽  
Author(s):  
M. J. Pender ◽  
T. W. Robertson
Keyword(s):  
Structural Damage ◽  
Ground Surface ◽  
Strong Motion ◽  
Normal Fault ◽  
Lateral Spreading ◽  
Ground Acceleration ◽  
Paper Mills ◽  
North West ◽  
The North ◽  
The Town

On March 2 1987, at 01h 42m 34s UT an earthquake of magnitude (ML) 6.3 occurred near 37.91°S, 176.79°E close to the town of Edgecumbe in the North Island, New Zealand. The depth is provisionally estimated to be 12 ± 1 km. Seismic activity in the general area during the previous week culminated in a foreshock on March 2 of ML 5.2 at 01h 35m 37s. Four aftershocks with magnitudes in excess of 5.0 occurred on March 2 at 01h 51m 08s (ML 5.6), 02h 07m 23s (ML 5.1), 06h 56m 32s (ML 5.2) and 07h 55m 09s (ML 5.2). The earthquakes occurred at the end of summer after a long period of dry weather. Modified Mercalli Intensities of MM IX have been reported in and around Edgecumbe, with possible instances of MM X. Strong motion accelerographs recorded peak ground acceleration of up to 0.33 g within 15 km of the epicentre. The main shock produced a complex series of surface scarps, the longest being about 7 km long striking SW from Edgecumbe. About 1.3 m maximum extension occurred across the scarp with the area to the north-west being downthrown by about a maximum of 1.5 m which continued to subside slowly. Other smaller normal fault traces have also been detected as well as compressional rolls. There was extensive evidence of level ground liquefaction and lateral spreading near rivers. Both these phenomena produced eruption of sands at the ground surface. Some wells were observed to have increased flows or increased pressures whilst others were had decreased flows. General regional subsidence of the alluvial plains in the area up to 2m has been confirmed by levelling completed within three weeks of the earthquake. Structural damage was confined to the alluvial plains in which the town of Edgecumbe is centred. The depth of sediments on the plains is not less than 350 m. There was extensive minor damage to roads. Severe damage to many houses and other single storey structures. A dairy factory complex in Edgecumbe, two paper mills in Kawerau and a paperboard mill in Whakatane all sustained damage, in some cases considerable. At present information on the damage in the paper mills is not available.

Site-dependent attenuation relations of seismic motion parameters at depth using borehole data

1995 ◽  
Vol 85 (6) ◽  
pp. 1790-1804
Author(s):  
Yoshimitsu Fukushima ◽  
Jean-Christophe Gariel ◽  
Ryozo Tanaka
Keyword(s):  
Transfer Functions ◽  
Ground Surface ◽  
Response Spectra ◽  
Borehole Data ◽  
Ground Acceleration ◽  
Attenuation Relations ◽  
Attenuation Relationships ◽  
Geological Conditions ◽  
Velocity Response ◽  
Different Depths

Abstract Using more than 500 accelerometric records from three vertical arrays located in Japan, we performed a regression analysis in order to derive attenuation relationships at underground sites with depths ranging from 100 to 950 m. Analyses were conducted on both peak ground acceleration and pseudo-velocity response spectra. Because of a positive correlation between magnitude and distance, a two-step regression technique was employed. Results show that, compared with surface ground motion, peak accelerations at underground sites are lower by a factor ranging from 1.5 to 4 according to the depth. In the case of response spectra, differences between ground surface and underground spectra are dependent on geological conditions. For the three sites considered in the study, underground pseudo-velocity response spectra show amplitudes lower by a factor ranging from 1.5 to 10 according to the depth or the period considered. Ratios between the receiver responses obtained at different depths provided average transfer functions. Those were compared with transfer functions calculated by averaging ratios of observed response spectra between different depths. A good agreement between the two techniques was found. Finally, theoretical transfer functions were estimated using both one-dimensional SH and complete wave modeling. It was shown that the characteristics of the incident wave field can play an important role in the estimation of theoretical transfer functions.

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.

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 <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.

scholarly journals A decade of progress in seismology since the Edgecumbe earthquake

1997 ◽  
Vol 30 (2) ◽  
pp. 163-166
Author(s):  
Euan G. C. Smith
Keyword(s):  
New Zealand ◽  
Site Response ◽  
Active Faults ◽  
Strong Motion ◽  
Historical Seismicity ◽  
Ground Acceleration ◽  
Earthquake Catalogues ◽  
Motion Data ◽  
Moderate Earthquake ◽  
Large Earthquakes

During the decade, the contemporaneous increase in data from moderately large earthquakes in New Zealand (and overseas) and the re-equipping of the New Zealand seismograph and accelerograph networks has seen good progress on several fronts. Earthquakes are now more accurately located and their spatial distribution is better defined. There have been improvements in the various databases used for seismic hazard assessments: active faults, earthquake catalogues, historical seismicity, and strong ground motions. The increase in strong-motion data has enabled the development of better models for Peak Ground Acceleration, and the effect of site conditions on site response, particularly for weak-to-moderate earthquake motions, has been studied in detail.

THE EMPIRICAL GREEN’S FUNCTION TECHNIQUE MODIFICATION FOR ACCELEROGRAM SYNTHESIS IN LOWSEISMICITY REGIONS

2018 ◽  
Vol 12 (5-6) ◽  
pp. 72-80
Author(s):  
A. A. Krylov
Keyword(s):  
Green’S Function ◽  
Green's Function ◽  
Main Shock ◽  
Amplitude Spectrum ◽  
Strong Motion ◽  
Function Technique ◽  
Focal Region ◽  
Empirical Green’S Function ◽  
Epicentral Zone ◽  
Empirical Green's Function

In the absence of strong motion records at the future construction sites, different theoretical and semi-empirical approaches are used to estimate the initial seismic vibrations of the soil. If there are records of weak earthquakes on the site and the parameters of the fault that generates the calculated earthquake are known, then the empirical Green’s function can be used. Initially, the empirical Green’s function method in the formulation of Irikura was applied for main shock record modelling using its aftershocks under the following conditions: the magnitude of the weak event is only 1–2 units smaller than the magnitude of the main shock; the focus of the weak event is localized in the focal region of a strong event, hearth, and it should be the same for both events. However, short-termed local instrumental seismological investigation, especially on seafloor, results usually with weak microearthquakes recordings. The magnitude of the observed micro-earthquakes is much lower than of the modeling event (more than 2). To test whether the method of the empirical Green’s function can be applied under these conditions, the accelerograms of the main shock of the earthquake in L'Aquila (6.04.09) with a magnitude Mw = 6.3 were modelled. The microearthquake with ML = 3,3 (21.05.2011) and unknown origin mechanism located in mainshock’s epicentral zone was used as the empirical Green’s function. It was concluded that the empirical Green’s function is to be preprocessed. The complex Fourier spectrum smoothing by moving average was suggested. After the smoothing the inverses Fourier transform results with new Green’s function. Thus, not only the amplitude spectrum is smoothed out, but also the phase spectrum. After such preliminary processing, the spectra of the calculated accelerograms and recorded correspond to each other much better. The modelling demonstrate good results within frequency range 0,1–10 Hz, considered usually for engineering seismological studies.

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