The site response of two rock and soil station pairs to strong and weak ground motion

1991 ◽  
Vol 81 (5) ◽  
pp. 1885-1899
Author(s):  
Robert B. Darragh ◽  
Anthony F. Shakal
Keyword(s):  
Ground Motion ◽  
Site Response ◽  
Soft Soil ◽  
Ground Acceleration ◽  
Ground Shaking ◽  
Soil Site ◽  
Rock Site ◽  
Loma Prieta ◽  
Strong Ground ◽  
Stiff Soil

Abstract The site response to strong and weak ground motion depends largely on the subsurface conditions at the soil site for the two rock-soil station pairs studied. The first station pair consists of a soft-soil site (Treasure Island) and a sandstone and shale site (Yerba Buena Island). These stations recorded strong ground shaking from the Loma Prieta mainshock and weak ground motion from four aftershocks. The range of peak ground acceleration is from approximately 0.00006 to 0.07 g at the rock site. Compared to the rock site, the strong ground motion at the soft-soil site is amplified by a factor of about 3 over a frequency range from 0.5 to 2.0 Hz. The amplification is much higher for weak motion and suggests a dependence on signal amplitude. For example, near 1 Hz, the site response shows an increasing amplification as magnitude (and the peak velocity at the rock site) decreases. For events of local magnitude 7.0, 4.3, 4.1, 3.5, and 3.3, the maximum soil-site amplifications are 4, 12, 17, 19, and 25, respectively. A second station pair consisting of a stiff-soil site (Gilroy #2) and a sandstone site (Gilroy #1) was also studied with contrasting results. These two stations recorded strong ground shaking from the 1979 Coyote Lake, 1984 Morgan Hill, and 1989 Loma Prieta mainshocks. Weak ground motion was recorded at these stations after the Loma Prieta mainshock. The range of peak ground acceleration is from 0.006 to 0.43 g at the rock site. Unlike the results for the soft-soil study above, the estimated stiff-soil site responses are not significantly different for strong and weak motion from 0.5 to 2.0 Hz. Near 0.7 Hz, the stiff-soil site responses range from 2.5 to 4.5 for strong ground shaking from three mainshocks and from 1.5 to 4.0 for weak ground shaking from thirteen aftershocks.

scholarly journals Prediction and evaluation of nonlinear site response with potentially liquefiable layers in the area of Nafplion (Peloponnesus, Greece) for a repeat of historical earthquakes

2010 ◽  
Vol 10 (11) ◽  
pp. 2281-2304 ◽  
Author(s):  
V. K. Karastathis ◽  
G. A. Papadopoulos ◽  
T. Novikova ◽  
Z. Roumelioti ◽  
P. Karmis ◽  
...  
Keyword(s):  
Ground Motion ◽  
Strong Ground Motion ◽  
Site Response ◽  
Soft Soil ◽  
Soil Layer ◽  
Ground Acceleration ◽  
Nonlinear Site Response ◽  
Strong Ground Motion Simulation ◽  
Scenario Earthquakes ◽  
Strong Ground

Abstract. We examine the possible non-linear behaviour of potentially liquefiable layers at selected sites located within the expansion area of the town of Nafplion, East Peloponnese, Greece. Input motion is computed for three scenario earthquakes, selected on the basis of historical seismicity data, using a stochastic strong ground motion simulation technique, which takes into account the finite dimensions of the earthquake sources. Site-specific ground acceleration synthetics and soil profiles are then used to evaluate the liquefaction potential at the sites of interest. The activation scenario of the Iria fault, which is the closest one to Nafplion (M=6.4), is found to be the most hazardous in terms of liquefaction initiation. In this scenario almost all the examined sites exhibit liquefaction features at depths of 6–12 m. For scenario earthquakes at two more distant seismic sources (Epidaurus fault – M6.3; Xylokastro fault – M6.7) strong ground motion amplification phenomena by the shallow soft soil layer are expected to be observed.

scholarly journals Earthquakes on the surface: earthquake location and area based on more than 14 500 ShakeMaps

2018 ◽  
Vol 18 (6) ◽  
pp. 1665-1679
Author(s):  
Stephanie Lackner
Keyword(s):  
Ground Motion ◽  
Strong Ground Motion ◽  
Earthquake Location ◽  
Primary Concern ◽  
Ground Acceleration ◽  
Ground Shaking ◽  
Geographic Context ◽  
The Social ◽  
Strong Ground

Abstract. Earthquake impact is an inherently interdisciplinary topic that receives attention from many disciplines. The natural hazard of strong ground motion is the reason why earthquakes are of interest to more than just seismologists. However, earthquake shaking data often receive too little attention by the general public and impact research in the social sciences. The vocabulary used to discuss earthquakes has mostly evolved within and for the discipline of seismology. Discussions on earthquakes outside of seismology thus often use suboptimal concepts that are not of primary concern. This study provides new theoretic concepts as well as novel quantitative data analysis based on shaking data. A dataset of relevant global earthquake ground shaking from 1960 to 2016 based on USGS ShakeMap data has been constructed and applied to the determination of past ground shaking worldwide. Two new definitions of earthquake location (the shaking center and the shaking centroid) based on ground motion parameters are introduced and compared to the epicenter. These definitions are intended to facilitate a translation of the concept of earthquake location from a seismology context to a geographic context. Furthermore, the first global quantitative analysis on the size of the area that is on average exposed to strong ground motion – measured by peak ground acceleration (PGA) – is provided.

scholarly journals Earthquake ground shaking hazard assessment for the Lower Hutt and Porirua areas, New Zealand

1992 ◽  
Vol 25 (4) ◽  
pp. 286-302 ◽  
Author(s):  
R. J. Van Dissen ◽  
J. J. Taber ◽  
W. R. Stephenson ◽  
S. Sritheran ◽  
S. A. L. Read ◽  
...  
Keyword(s):  
Ground Motion ◽  
Strong Motion ◽  
Spectral Ratio ◽  
Fine Sand ◽  
Geographic Variations ◽  
Ground Acceleration ◽  
Ground Shaking ◽  
Earthquake Scenarios ◽  
Shear Wave Velocities ◽  
Strong Ground

Geographic variations in strong ground shaking expected during damaging earthquakes impacting on the Lower Hutt and Porirua areas are identified and quantified. Four ground shaking hazard zones have been mapped in the Lower Hutt area, and three in Porirua, based on geological, weak motion, and strong motion inputs. These hazard zones are graded from 1 to 5. In general, Zone 5 areas are subject to the greatest hazard, and Zone 1 areas the least. In Lower Hutt, zones 3 and 4 are not differentiated and are referred to as Zone 3-4. The five-fold classification is used to indicate the range of relative response. Zone 1 areas are underlain by bedrock. Zone 2 areas are typically underlain by compact alluvial and fan gravel. Zone 3-4 is underlain, to a depth of 20 m, by interfingered layers of flexible (soft) sediment (fine sand, silt, clay, peat), and compact gravel and sand. Zone 5 is directly underlain by more than 10 m of flexible sediment with shear wave velocities in the order of 200 m/s or less. The response of each zone is assessed for two earthquake scenarios. Scenario 1 is for a moderate to large, shallow, distant earthquake that results in regional Modified Mercalli intensity V-VI shaking on bedrock. Scenario 2 is for a large, local, but rarer, Wellington fault earthquake. The response characterisation for each zone comprises: expected Modified Mercalli intensity; peak horizontal ground acceleration; duration of strong shaking; and amplification of ground motion with respect to bedrock, expressed as a Fourier spectral ratio, including the frequency range over which the most pronounced amplification occurs. In brief, high to very high ground motion amplifications are expected in Zone 5, relative to Zone 1, during a scenario 1 earthquake. Peak Fourier spectral ratios of 10-20 are expected in Zone 5, relative to Zone 1, and a difference of up to three, possibly four, MM intensity units is expected between the two zones. During a scenario 2 event, it is anticipated that the level of shaking throughout the Lower Hutt and Porirua region will increase markedly, relative to scenario 1, and the average difference in shaking between each zone will decrease.

Ground-motion models for Vrancea intermediate-depth earthquakes

2021 ◽  
pp. 875529302110329
Author(s):  
Elena Florinela Manea ◽  
Carmen Ortanza Cioflan ◽  
Laurentiu Danciu
Keyword(s):  
Ground Motion ◽  
Site Response ◽  
Seismic Station ◽  
Moment Magnitude ◽  
Peak Ground Velocity ◽  
Ground Acceleration ◽  
Ground Shaking ◽  
Intermediate Depth ◽  
Motion Models ◽  
Ground Motion Models

A newly compiled high-quality ground-shaking dataset of 207 intermediate-depth earthquakes recorded in the Vrancea region of the south-eastern Carpathian mountains in Romania was used to develop region-specific empirical predictive equations for various intensity measures: peak ground acceleration, peak ground velocity, and 5%-damped pseudo-spectral acceleration up to 10 s. Besides common predictor variables (e.g. moment magnitude, depth, hypocentral distance, and site conditions), additional distance scaling parameters were added to describe the specific attenuation pattern observed at the stations located not only on the back and fore but also along the Carpathian arc. In this model, we introduce a proxy measure for the site as the fundamental frequency of resonance to characterize the site response at each recording seismic station beside the soil classes. To additionally reduce the site-to-site variability, a non-ergodic methodology was considered, resulting in a lower standard deviation of about 25%. Statistical evaluation of the newly proposed ground-motion models indicates robust performance compared to regional observations. The model shows significant improvements in describing the spatial variability (at different spectral ordinates), particularly for the fore-arc area of the Carpathians where a deep sedimentary basin is located. Furthermore, the model presented herein improves estimates of ground shaking at longer spectral ordinates (>1 s) in agreement with the observations. The proposed ground-motion models are valid for hypocentral distances less than 500 km, depths over 70 km and within the moment magnitude range of 4.0–7.4.

scholarly journals A comparative study of strong ground motion records from the 30 August 2013 south Tibet earthquake on the rock and soil sites of the Kathmandu valley

2016 ◽  
Vol 50 (1) ◽  
pp. 25-30
Author(s):  
Subeg Man Bijukchhen ◽  
Nobuo Takai ◽  
Michiko Shigefuji ◽  
Masayoshi Ichiyanagi ◽  
Tsutomu Sasatani ◽  
...  
Keyword(s):  
Ground Motion ◽  
Strong Ground Motion ◽  
Site Response ◽  
Underground Structure ◽  
Maximum Velocity ◽  
Kathmandu Valley ◽  
Rock Site ◽  
The Difference ◽  
Ground Motion Records ◽  
Strong Ground

The present site response study is based upon strong ground motion records from 4 seismic stations established by the Hokkaido University in the Kathmandu valley at Kirtipur, Tribhuvan University, Patan, and Thimi: one right above the bedrock and others over the lake sediments. We considered the rock-site station in Kirtipur as a reference site to quantify the amplification at sediment sites by analysing the Mb=4.9 Southern Tibet Earthquake of 30 August 2013. The horizontal maximum velocity of 0.84 cm/s is recorded in Thimi in contrast to 0.23 cm/s in Kirtipur. The highest spectral amplitude at sediment sites matches with results from microtremor study. Significant amplification is seen at 0.3-1 Hz band at sediment sites for whole waveform whereas analysis of the S-wave part indicates amplification in the 1-2 Hz band. Surface waves in the records of sediment sites continue for quite a long time compared to that of the rock-site and records of all sites contain Rayleigh waves. Though the difference in azimuth and epicentral distance of the sites are not significant, it is observed that the initial motion at the Kirtipur site is about 0.25 sec earlier than expected. This implies the difference in the underground body wave velocity structure of the sites. But the lack of accurate underground structure of the valley necessitates further study. For future research we will try to discuss the basin underground structure with strong ground motion data including Mb=4.4 Gorkha Earthquake of 25 November 2014 and Mb=5.0 Solukhumbu Earthquake of 18 December 2014.

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.

scholarly journals Earthquakes on the surface: earthquake location and area based on more than 14500 ShakeMaps

2018 ◽  
Author(s):  
Stephanie Lackner
Keyword(s):  
Ground Motion ◽  
Strong Ground Motion ◽  
Natural Hazard ◽  
Earthquake Location ◽  
Primary Concern ◽  
Ground Acceleration ◽  
Ground Shaking ◽  
The Social ◽  
Quantitative Data Analysis ◽  
Strong Ground

Abstract. Earthquake impacts are an inherently interdisciplinary topic that receives attention from many disciplines. The natural hazard of strong ground motion is the reason why earthquakes are of interest to others than seismologists. However, earthquake shaking data often receives too little attention by the general public and impact research in the social sciences. The vocabulary used to discuss earthquakes has mostly evolved within and for the discipline of seismology. Earthquake communication outside of seismology thus often uses suboptimal concepts that are not of primary concern. This study provides new theoretic concepts as well as novel quantitative data analysis based on shaking data. A dataset of relevant global earthquake ground shaking from 1960 to 2016 based on USGS ShakeMap data has been constructed and applied. Two new definitions of earthquake location (the shaking center and the shaking centroid) based on ground motion parameters are introduced and compared to the epicenter. Furthermore, the first global quantitative analysis on the size of the area that is on average exposed to strong ground motion – measured by peak ground acceleration (PGA) – is provided.

scholarly journals Investigating the influence of topographic irregularities and two-dimensional effects on surface ground motion intensity with one- and two-dimensional analyses

2014 ◽  
Vol 14 (7) ◽  
pp. 1773-1788 ◽  
Author(s):  
G. Ç. İnce ◽  
L. Yılmazoğlu
Keyword(s):  
Ground Motion ◽  
Site Response ◽  
Soil Conditions ◽  
Response Analysis ◽  
Two Dimensional ◽  
Ground Acceleration ◽  
Equivalent Linear ◽  
Local Soil ◽  
Different Depths ◽  
Earthquake Response Analysis

Abstract. In this work, the surface ground motion that occurs during an earthquake in ground sections having different topographic forms has been examined with one and two dynamic site response analyses. One-dimensional analyses were undertaken using the Equivalent-Linear Earthquake Response Analysis (EERA) program based on the equivalent linear analysis principle and the Deepsoil program which is able to make both equivalent linear and nonlinear analyses and two-dimensional analyses using the Plaxis 8.2 software. The viscous damping parameters used in the dynamic site response analyses undertaken with the Plaxis 8.2 software were obtained using the DeepSoil program. In the dynamic site response analyses, the synthetic acceleration over a 475-year return period representing the earthquakes in Istanbul was used as the basis of the bedrock ground motion. The peak ground acceleration obtained different depths of soils and acceleration spectrum values have been compared. The surface topography and layer boundaries in the 5-5' cross section which cuts across the study area west to east were selected in order to examine the effect of the land topography and layer boundaries on the analysis results, and were flattened and compared with the actual status. The analysis results showed that the characteristics of the surface ground motion change in relation to the varying local soil conditions and land topography.

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