New GMPEs for the Sagami Bay Region in Japan for Moderate Magnitude Events with Emphasis on Differences on Site Amplifications at the Seafloor and Land Seismic Stations of K-NET

2020 ◽  
Vol 110 (5) ◽  
pp. 2577-2597 ◽  
Author(s):  
Jinjun Hu ◽  
Jingyang Tan ◽  
John X. Zhao
Keyword(s):  
Water Layer ◽  
Soil Condition ◽  
Site Amplification ◽  
Site Conditions ◽  
Sagami Bay ◽  
Site Class ◽  
Offshore Area ◽  
Local Site ◽  
Individual Site ◽  
Kanto Basin

ABSTRACT Ground-motion prediction equations (GMPEs) for the horizontal and vertical spectral accelerations (SAs) from the offshore area off the Sagami Bay is presented in this article. To compare the ground motions on the seafloor with those at onshore sites, an onshore GMPE was derived for the onshore stations adjacent to the offshore sites and including those in the Kanto basin sites. The offshore dataset includes 738 three-component records, and the onshore dataset includes 3775 records; both datasets are derived from the same set of 233 earthquakes selected for this study. The local site conditions of the offshore sites are investigated by implementing the mean horizontal-to-vertical response spectral ratios because soil condition data are unavailable. Individual site correction terms are used for the offshore sites due to differences among the site conditions, whereas site-class terms are used for the onshore sites based on the travel-time-averaged shear-wave velocity to 30 m (VS30). A comparison between the offshore and onshore models shows that the horizontal SAs for the whole periods and vertical SAs for moderate and long periods of the offshore motions are considerably larger than those of the onshore motions due to the deep deposition layer comprising soft sediment blanketing the seafloor; the vertical SAs of the offshore motions are slightly smaller than those of the onshore motions at short spectral periods. The inconsistency of the vertical motions at short periods may be due to the combined effect of the deposition layer and water layer. However, the vertical site amplification for short periods is independent of the water depth, and the reason of high-frequency deficiency in vertical components need further investigation.

scholarly journals A study on sensitivity of seismic site amplification factors to site conditions for bridges

2018 ◽  
Vol 51 (4) ◽  
pp. 197-211
Author(s):  
Muhammad Tariq A. Chaudhary
Keyword(s):  
Seismic Design ◽  
Site Amplification ◽  
Site Conditions ◽  
Design Codes ◽  
Design Code ◽  
Bridge Design ◽  
Site Class ◽  
Vibration Period ◽  
Amplification Factors ◽  
Site Classes

Seismic site amplification factors and seismic design spectra for bridges are influenced by site conditions that include geotechnical properties of soil strata as well as the geological setting. All modern seismic design codes recognize this fact and assign design spectral shapes based on site conditions or specify a 2-parameter model with site amplification factors as a function of site class, seismic intensity and vibration period (short and long). Design codes made a number of assumptions related to the site conditions while specifying the values of short (Fa) and long period (Fv) site amplification factors. Making these assumptions was necessary due to vast variation in site properties and limited availability of actual strong motion records on all site conditions and seismic setting in a region. This paper conducted a sensitivity analysis for site amplification factors for site classes C and D in the AASHTO bridge design code by performing a 1-D site response analysis in which values of site parameters like strata depth, travel-time averaged shear wave velocity in the top 30 m strata (Vs30), plasticity index (PI), impedance contrast ratio (ICR) and intensity of seismic ground motion were varied. The results were analyzed to identify the site parameters that impacted Fa and Fv values for site classes C and D. The computed Fa and Fv values were compared with the corresponding values in the AASHTO bridge design code and it was found that the code-based Fa and Fv values were generally underestimated and overestimated respectively.

Correspondence between Site Amplification and Topographical, Geological Parameters: Collation of Data from Swiss and Japanese Stations, and Neural Networks-Based Prediction of Local Response

2021 ◽  
Author(s):  
Paolo Bergamo ◽  
Conny Hammer ◽  
Donat Fäh
Keyword(s):  
Frequency Response ◽  
Large Scale ◽  
Site Response ◽  
Low Frequency ◽  
Field Measurements ◽  
Site Amplification ◽  
Local Response ◽  
Regional Variability ◽  
Individual Site ◽  
Digital Elevation

ABSTRACT We address the relation between seismic local amplification and topographical and geological indicators describing the site morphology. We focus on parameters that can be derived from layers of diffuse information (e.g., digital elevation models, geological maps) and do not require in situ surveys; we term these parameters as “indirect” proxies, as opposed to “direct” indicators (e.g., f0, VS30) derived from field measurements. We first compiled an extensive database of indirect parameters covering 142 and 637 instrumented sites in Switzerland and Japan, respectively; we collected topographical indicators at various spatial extents and focused on shared features in the geological descriptions of the two countries. We paired this proxy database with a companion dataset of site amplification factors at 10 frequencies within 0.5–20 Hz, empirically measured at the same Swiss and Japanese stations. We then assessed the robustness of the correlation between individual site-condition indicators and local response by means of statistical analyses; we also compared the proxy-site amplification relations at Swiss versus Japanese sites. Finally, we tested the prediction of site amplification by feeding ensembles of indirect parameters to a neural network (NN) structure. The main results are: (1) indirect indicators show higher correlation with site amplification in the low-frequency range (0.5–3.33 Hz); (2) topographical parameters primarily relate to local response not because of topographical amplification effects but because topographical features correspond to the properties of the subsurface, hence to stratigraphic amplification; (3) large-scale topographical indicators relate to low-frequency response, smaller-scale to higher-frequency response; (4) site amplification versus indirect proxy relations show a more marked regional variability when compared with direct indicators; and (5) the NN-based prediction of site response is the best achieved in the 1.67–5 Hz band, with both geological and topographical proxies provided as input; topographical indicators alone perform better than geological parameters.

30 Ooctober 2020 Samos-Sigacik Earthquake: On Strong Ground Motion and Local Site Amplification

2021 ◽  
Author(s):  
Eser Çakti ◽  
Karin Sesetyan ◽  
Ufuk Hancilar ◽  
Merve Caglar ◽  
Emrullah Dar ◽  
...  
Keyword(s):  
Ground Motion ◽  
Structural Damage ◽  
Strong Ground Motion ◽  
Epicentral Distance ◽  
Strong Motion ◽  
Aegean Sea ◽  
Site Amplification ◽  
Local Site ◽  
Basin Effects ◽  
Strong Ground

<p>The Mw 6.9 earthquake that took place offshore between the Greek island of Samos and Turkey’s İzmir province on 30 October 2020 came hardly as a surprise. Due to the extensional tectonic regime of the Aegean and high deformation rates, earthquakes of similar size frequently occur in the Aegean Sea on fault segments close to the shores of Turkey, affecting the settlements on mainland Turkey and on the Greek Islands. Samos-Sigacik earthquake had a normal faulting mechanism. It was recorded by the strong motion networks in Turkey and Greece. Although expected, the earthquake was an  outstanding event in the sense of  highly localized, significant levels of building damage as a result of amplified ground motion levels. This presentation is an overview of strong ground motion characteristics of this important event both regionally and locally. Mainshock records suggest that local site effects, enhanced by basin effects could be responsible for structural damage in central Izmir, the third largest city of Turkey located at 60-70 km epicentral distance. We installed a seven-station network in Bayraklı and Karşıyaka districts of İzmir within three days of the mainshock in search of site and basin effects.  Through analysis of recorded aftershocks we explore the amplification characeristics of soils in the two aforementioned districts  and try to understand the role basin effects might have played in the resulting ground motion levels and consequently damage. </p>

Investigation of Seismic Site Amplification for Non-NEHRP Site Conditions: Site Response Study of Columbia, SC

2014 ◽  
Author(s):  
C. Guney Olgun ◽  
Morgan Eddy ◽  
Elizabeth A. Godfrey ◽  
Martin C. Chapman ◽  
Mark Tilashalski ◽  
...  
Keyword(s):  
Site Response ◽  
Site Amplification ◽  
Site Conditions

Mapping NEHRP VS30 Site Classes

2005 ◽  
Vol 21 (2) ◽  
pp. 353-370 ◽  
Author(s):  
Thomas L. Holzer ◽  
Amy C. Padovani ◽  
Michael J. Bennett ◽  
Thomas E. Noce ◽  
John C. Tinsley
Keyword(s):  
San Francisco ◽  
Site Amplification ◽  
Cone Penetration ◽  
Site Class ◽  
Mean Values ◽  
Shear Wave Velocities ◽  
Class D ◽  
Geologic Maps ◽  
Definition Of ◽  
Site Classes

Site-amplification potential in a 140-km2 area on the eastern shore of San Francisco Bay, California, was mapped with data from 210 seismic cone penetration test (SCPT) soundings. NEHRP VS30 values were computed on a 50-m grid by both taking into account the thickness and using mean values of locally measured shear-wave velocities of shallow geologic units. The resulting map of NEHRP VS30 site classes differs from other published maps that (1) do not include unit thickness and (2) are based on regional compilations of velocity. Although much of the area in the new map is now classified as NEHRP Site Class D, the velocities of the geologic deposits within this area are either near the upper or lower VS30 boundary of Class D. If maps of NEHRP site classes are to be based on geologic maps, velocity distributions of geologic units may need to be considered in the definition of VS30 boundaries of NEHRP site classes.

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