Evaluation of the effect of depth to bedrock on seismic amplification phenomena

When an earthquake occurs, the propagation of the seismic waves is conditioned by local conditions, e.g., depth to seismic bedrock and impedance ratio between soft soil and seismic bedrock. Bearing in mind that the maximum depth of site prospections generally does not extend up to seismic bedrock depth, a parametric study was carried out with reference to ideal case studies in order to investigate the effect on local seismic amplification of the depth to bedrock.The results are presented in terms of charts of amplification factors (i.e., ratio of integral quantities referred to free-field and reference response spectra) and minimum depth to investigate vs building type. These charts will allow defining the thickness of the cover deposit that should be characterised in terms of geophysical and geotechnical parameters in order to perform seismic site response analysis according to a precautionary approach, in areas where depth to seismic bedrock is higher than conventional maximum depth of site surveys.

Download Full-text

Spectral displacement (SD) of banda aceh’s soft soil for seismic vulnerability assessment

MATEC Web of Conferences ◽

10.1051/matecconf/201819710001 ◽

2018 ◽

Vol 197 ◽

pp. 10001 ◽

Cited By ~ 2

Author(s):

Taufiq Saidi ◽

Teuku Budi Aulia ◽

Bambang Setiawan ◽

Nora Abdullah ◽

Muttaqin Hasan

Keyword(s):

Vulnerability Assessment ◽

Seismic Vulnerability ◽

Site Response ◽

Response Spectrum ◽

Soft Soil ◽

Response Spectra ◽

Response Analysis ◽

Seismic Vulnerability Assessment ◽

Wide Range ◽

Banda Aceh

Reliable spectral displacement (SD) in a wide range of response periods is crucial in seismic vulnerability assessment for Banda Aceh-Indonesia as the city is founded on a thick-soft soil. This SD is excellent for estimating building drift ratio from which the vulnerability of building is assessed. SD can be obtained from conversion of the acceleration spectra (converted SD) and site response analysis (analyzed SD). In this paper, both converted- and analysed-SDs are developed for Banda Aceh’s soft soil case using three historical seismic events of the 2012 Simeulue II, the 2013 Mane-Geumpang, and the 2013 Bener Meriah earthquakes and three soil models from which acceleration-displacement response spectrum (ADRS) of Banda Aceh’s soft soil is proposed. This proposed ADRS is compared to the generic response spectra of Centre of Research and Development of Housing and Settlement (PUSKIM) Indonesia. It can be concluded that the Proposed ADRSs can be used as another source in determining the performance of a building beside the PUSKIM ADRSs. Furthermore, the developed SDs were used to calculate the drift of 2-, 3-, and 4-storey typical shop-house buildings at Banda Aceh-Indonesia.

Download Full-text

Simplified Criteria to Select Ground Response Analysis Methods for Seismic Building Design: Equivalent Linear versus Nonlinear Approaches

Bulletin of the Seismological Society of America ◽

10.1785/0120200319 ◽

2021 ◽

Author(s):

Mauro Aimar ◽

Sebastiano Foti

Keyword(s):

Seismic Waves ◽

Site Response ◽

Building Design ◽

Soil Conditions ◽

Response Analysis ◽

Depth Range ◽

Ground Response Analysis ◽

Equivalent Linear ◽

Acceleration Time Histories ◽

Soil Deposits

ABSTRACT The possible amplification of seismic waves in soil deposits is crucial for the seismic design of buildings and geotechnical systems. The most common approaches for the numerical simulation of seismic site response are the equivalent linear (EQL) and the nonlinear (NL). Even though their advantages and limitations have been investigated in several studies, the relative field of applicability is still under debate. This study tested both methods over a wide population of soil models, which were subjected to a set of acceleration time histories recorded from strong earthquakes. A thorough comparison of the results of the EQL and the NL approaches was carried out, to identify the conditions in which the relative differences are significant. This assessment allowed for the definition of simplified criteria to predict when the two schemes are or are not compatible for large expected shaking levels. The proposed criteria are based on simple and intuitive parameters describing the soil deposit and the ground-motion parameters, which can be predicted straightforwardly. Therefore, this study provides a scheme for the choice between the EQL and the NL approaches that can be used even at the preliminary design stages. It appears that the EQL approach provides reliable amplification estimates in soil deposits with thickness up to 30 m, except for very deformable soils, but this depth range may be extended at long vibration periods. This result reveals a good level of reliability of the EQL approach for various soil conditions encountered in common applications, even for high-intensity shaking.

Download Full-text

Sensitivity analysis of geotechnical site conditions effect on the seismic response of a saturated inhomogeneous poroviscoelastic soil profile

World Journal of Engineering ◽

10.1108/wje-12-2017-0388 ◽

2018 ◽

Vol 15 (6) ◽

pp. 661-677 ◽

Cited By ~ 1

Author(s):

Toufiq Ouzandja ◽

Mohamed Hadid

Keyword(s):

Soil Properties ◽

Seismic Response ◽

Pore Water ◽

Soil Profile ◽

Water Saturation ◽

Free Field ◽

Response Spectra ◽

Response Analysis ◽

Content Type ◽

Linear And Nonlinear

Purpose This paper aims to present the investigation of the linear and nonlinear seismic site response of a saturated inhomogeneous poroviscoelastic soil profile for different soil properties, such as pore-water saturation, non-cohesive fines content FC, permeability k, porosity n and coefficient of uniformity Cu. Design/methodology/approach The inhomogeneous soil profile is idealized as a multi-layered saturated poroviscoelastic medium and is characterized by the Biot’s theory, with a shear modulus varying continuously with depth according to the Wichtmann’s model. Seismic response analysis has been evaluated through a computational model, which is based on the exact stiffness matrix method formulated in the frequency domain assuming that the incoming seismic waves consist of inclined P-SV waves. Findings Unlike the horizontal seismic response, the results indicate that the vertical one is strongly affected by the pore water saturation. Moreover, in the case of fully saturated soil profile, the same vertical response spectra are found for the two cases of soil behavior, linear and nonlinear. Originality/value This research is a detailed study of the geotechnical soil properties effect on the bi-directional seismic response of saturated inhomogeneous poroviscoelastic soil profile, which has not been treated before; the results are presented in terms of the peak acceleration ratio, as well as the free-field response spectra and the spectral ratio (V/H).

Download Full-text

Design Earthquake Response Spectrum Affected by Shallow Soil Deposit

Advances in Civil Engineering ◽

10.1155/2019/4079217 ◽

2019 ◽

Vol 2019 ◽

pp. 1-18 ◽

Cited By ~ 1

Author(s):

Dong-Kwan Kim ◽

Hong-Gun Park ◽

Chang-Guk Sun

Keyword(s):

Soil Depth ◽

Site Response ◽

Response Spectrum ◽

Soft Soil ◽

Response Spectra ◽

Earthquake Response ◽

Ground Acceleration ◽

Site Class ◽

Shallow Soil ◽

Short Period

Site response analyses were performed to investigate the earthquake response of structures with shallow soil depth conditions in Korea. The analysis parameters included the properties of soft soil deposits at 487 sites, input earthquake accelerations, and peak ground-acceleration levels. The response spectra resulting from numerical analyses were compared with the design response spectra (DRS) specified in the 2015 International Building Code. The results showed that the earthquake motion of shallow soft soil was significantly different from that of deep soft soil, which was the basis of the IBC DRS. The responses of the structures were amplified when their dynamic periods were close to those of the site. In the case of sites with dynamic periods less than 0.4 s, the spectral accelerations of short-period structures were greater than those of the DRS corresponding to the site class specified in IBC 2015. On the basis of these results, a new form of DRS and soil factors are proposed.

Download Full-text

Site Response Analysis Using Downhole Array Recordings during the March 2011 Tohoku-Oki Earthquake and the Effect of Long-Duration Ground Motions

Earthquake Spectra ◽

10.1193/1.4000114 ◽

2013 ◽

Vol 29 (1_suppl) ◽

pp. 37-54 ◽

Cited By ~ 27

Author(s):

Byungmin Kim ◽

Youssef M.A. Hashash

Keyword(s):

Subduction Zone ◽

Site Response ◽

Soft Rock ◽

Response Spectra ◽

Response Analysis ◽

Soil Behavior ◽

Long Duration ◽

Downhole Array ◽

Downhole Arrays ◽

Array Recordings

Downhole arrays provide enhanced understanding of dynamic soil behavior and site response. Historically, downhole array recordings have been available only for earthquakes with relatively limited durations. New recordings from a number of KiK-net downhole arrays during the 11 March 2011, Mw 9.0, subduction zone earthquake near the east coast of Honshu, Japan, allow us to investigate dynamic soil characteristics and site response due to long-duration subduction zone earthquakes. Using these recordings, we perform one-dimensional site response analyses to evaluate the applicability of commonly used analysis approaches under long-duration earthquakes. We find that site response analyses capture key features of measured surface response spectra particularly at soft rock/stiff soil sites subject to long-duration motion. However, at softer soil sites, it appears that the modulus reduction is overestimated and site-specific characterization is needed.

Download Full-text

Improved Approach for Modeling Nonlinear Site Response of Highly Strained Soils: Case Study of the Service Hall Array in Japan

Earthquake Spectra ◽

10.1193/121714eqs212m ◽

2016 ◽

Vol 32 (2) ◽

pp. 1055-1074 ◽

Cited By ~ 8

Author(s):

Ramin Motamed ◽

Kevin Stanton ◽

Ibrahim Almufti ◽

Kirk Ellison ◽

Michael Willford

Keyword(s):

Nuclear Power ◽

Site Response ◽

Free Field ◽

Peak Strength ◽

Response Analysis ◽

Soil Behavior ◽

Backbone Curve ◽

Ground Response Analysis ◽

Nonlinear Site Response ◽

Highly Strained

A nonlinear ground response analysis is conducted for the Niigata-ken Chuetsu-oki earthquake recorded at a free-field vertical array near the Kashiwazaki-Kariwa Nuclear Power Plant in Japan. A bidirectional site response analysis is carried out using LS-DYNA which allows user defined stress-strain relationships to dictate soil behavior subjected to dynamic loading. Dynamic soil behavior is characterized using a two-stage hyperbolic backbone curve implemented with modifications to consider the peak strength of soil layers as well as the strain at which the peak strength is fully mobilized. The effects of bidirectional input motions, strain rate, and the shape of the shear modulus degradation curves are investigated, and it is demonstrated that each factor can have a significant influence on the results.

Download Full-text

Study on the influence of seafloor soft soil layer on seismic ground motion

10.5194/nhess-2020-177 ◽

2020 ◽

Author(s):

Jingyan Lan ◽

Juan Liu ◽

Xing Song

Keyword(s):

Seismic Response ◽

Ground Motion ◽

Sea Water ◽

Response Spectrum ◽

Soft Soil ◽

Free Field ◽

Soil Layer ◽

Response Analysis ◽

Peak Acceleration ◽

Seismic Response Analysis

Abstract. In the complex medium system of sea area, the overlying sea water and the surface soft soil have a significant impact on the seafloor ground motion, which brings great seismic risk to the safety of offshore engineering structures. In this paper, four sets of typical free field models are constructed and established, which are land model, land model with surface soft soil, sea model and sea model with surface soft soil. The dynamic finite difference method is used to carry out two-dimensional seismic response analysis of typical free field based on the input forms about P and SV wave. By comparing the seismic response analysis results of four groups of calculation models, the effects of overlying seawater and soft soil on peak acceleration and acceleration response spectrum are studied. The results show that when SV wave is input, the peak acceleration and response spectrum of the surface of soft soil on the surface and the seabed surface can be amplified, while the overlying sea water can significantly reduce the ground motion. When P wave is used, the effect of overlying seawater and soft soil on peak acceleration and response spectrum of surface and seabed can be ignored. The peak acceleration decreases first and then increases from the bottom to the surface, and the difference of peak acceleration calculated by four free field models is not obvious. The results show that the overlying sea water and the surface soft soil layer have little effect on the peak acceleration of ground motion below the surface.

Download Full-text

A Site-Specific Response Analysis: A Case Study in Hanoi, Vietnam

Applied Sciences ◽

10.3390/app10113972 ◽

2020 ◽

Vol 10 (11) ◽

pp. 3972 ◽

Cited By ~ 1

Author(s):

Van-Quang Nguyen ◽

Muhammad Aaqib ◽

Duy-Duan Nguyen ◽

Nguyen-Vu Luat ◽

Duhee Park

Keyword(s):

Site Response ◽

Response Spectra ◽

Response Analysis ◽

Specific Response ◽

Site Class ◽

Soil Stiffness ◽

Design Spectrum ◽

Class D ◽

The Difference ◽

A Site

A series of one-dimensional (1-D) site response analyses were performed using the nonlinear (NL) and equivalent linear (EQL) approaches to assess the applicability of the Vietnamese earthquake-resistance design code TCVN 9386: 2012. Six soil profiles were selected from three districts in Hanoi (Vietnam). A number of ground motions compatible with the rock design spectrum were used as input for carrying out analyses. The results highlight that the calculated response is higher than the design spectrum for site class C and lower for site class D. The normalized response spectra of the EQL approach results are higher than those of the NL approach. Moreover, the peak ground accelerations at the surface from EQL analyses are greater than those of the NL method because the latter generates a higher amount of nonlinearity. The results from the NL approach also illustrate that the deamplification phenomenon occurs in the soft soils of the Hanoi region (e.g., soil profile P3 and P5 of site class D). Additionally, the shear strains calculated from the NL method are closely matched with those from the EQL method, the difference between them increasing with a decrease in soil stiffness.

Download Full-text

Evaluation of stratigraphic effects on seismic site response over large areas: the case study of Italy

10.5194/egusphere-egu21-2014 ◽

2021 ◽

Author(s):

Gaetano Falcone ◽

Gianluca Acunzo ◽

Amerigo Mendicelli ◽

Federico Mori ◽

Giuseppe Naso ◽

...

Keyword(s):

Ground Motion ◽

Site Effects ◽

Risk Mitigation ◽

Site Response ◽

Free Field ◽

Response Spectra ◽

Seismic Intensity ◽

Site Condition ◽

Ground Shaking ◽

Seismic Site Response

Estimation of site effects over large areas is a key-issue for land management and emergency system planning in a risk mitigation perspective. In general, site-conditions are retrieved from available global datasets and the ground-shaking estimation is based on ground motion prediction equations.An advanced procedure to estimate site effects over large areas is here proposed with reference to the Italian territory. Site-condition were defined for homogenous morpho-geological areas in accordance to the borehole logs and the geophysical data archived in the Italian database for seismic microzonation (https://www.webms.it/). Ground motion modifications were determined by means of about 30 milion of one-dimensional numerical simulations of local seismic site response. Correlations between amplification factors (i.e. the ratio between free-field and outcrop response spectra), AF, and site-condition (i.e. harmonic mean of the shear wave velocity in the upper 30&#160;m of the deposit, VS30) were determined for each morpho-geological homogeneous area depending on the reference seismic intensity (i.e. referred to the outcropping stiff rock characterised by VS30&#160;&#8805;&#160;800&#160;m/s). The AF-VS30 correlations were proved to satisfactory forecast the site effects when compared with the results of site specific estimation of local seismic site response.

Download Full-text