Equivalent Linear Site Response Analysis Research Articles

Impact of Randomized Soil Properties and Rock Motion Intensities on Ground Motion

Seismic site response is inevitably influenced by natural variability of soil properties and anticipated earthquake intensity. This study presents the influence of variability in shear wave velocity (Vs) and amplitude of input rock motion on seismic site response analysis. Monte Carlo simulations were employed to randomize the Vs profile for different scenarios. A series of 1-D equivalent linear (EQL) seismic site response analyses were conducted by combining the randomized Vs profile with different levels of rock motion intensities. The results of the analyses are presented in terms of surface spectral acceleration, amplification factors (AFs), and peak ground acceleration (PGA). The mean and standard deviation of these parameters are thoroughly discussed for a wide range of randomized Vs profile, number of Vs randomizations, and intensities of input rock motions. The results demonstrate that both the median PGA and its standard deviations across different number of Vs profile realization exhibit a slight variation. As few as twenty Vs profile realizations are sufficient to compute reliable response parameters. Both rock motion intensity and standard deviation of Vs variability cause significant variation in computed surface parameters. However, the variability in the number of records used to conduct site response has no significant impact on ground response if the records closely match the target spectrum. Incorporating the multiple sources of variabilities can reduce uncertainty when conducting ground response simulations.

City-scale buildings damage estimation based on broadband physics-based ground motion simulation of 2021 Ms 6.4 Yangbi, China, earthquake

This article proposed a computational workflow for city-scale building damage estimation based on broadband physics-based ground motion simulation. The dynamic stiffness matrix method in frequency-wavenumber domain is employed for broadband physics-based ground motion simulation of finite fault along with site response correction using equivalent-linear site response analysis approach. With simulated ground motion, seismic response of buildings, using multi-degree of freedom model, is simulated using nonlinear time history analysis, and building damage is evaluated based on a trilinear backbone curve of story’s nonlinear force-drift model. Main advantage of the framework lies in the employed dynamic stiffness matrix method for ground motion simulation, which can efficiently generate broadband ground motions in perfect parallel and naturally capture the physics of finite fault source, propagation path, and spatial variability characteristics of ground motion. To demonstrate the salient features of proposed workflow, the 2021 Ms 6.4 Yangbi earthquake is simulated with frequency resolution up to 20 Hz, and seismic damage of buildings in Yangbi county are estimated. Results show that most traditional wood-adobe structures suffer moderate to severe damage, and engineered seismic buildings (mostly RC frame) in Yangbi county suffer minor damage, which agrees with field investigation results.

Evaluation of Modified Frequency Dependent Equivalent Linear Method for Deconvolution Site Response Analysis

ABSTRACT Frequency-dependent equivalent linear (FD-EQL) site response analysis methods, developed as potential substitutes for the EQL procedure to better simulate the nonlinear soil response, have been reported to overpredict the high-frequency wave propagation. Modified procedures proposed to overcome this limitation have demonstrated to improve the fits with the nonlinear analysis results. The method has not yet been applied to perform a deconvolution analysis, where a conventional EQL analysis often fails to converge or provide reliable estimate. The conventional EQL procedure and one of the modified FD-EQL method, which uses an empirical factor f to interpolate the strain spectrum between the EQL and FD-EQL outputs, are used to perform a series of deconvolution analyses using an idealized 1000 m profile and twelve Kik-net downhole arrays. The residuals of recorded and deconvoluted motions are shown to increase with strain for the EQL method even when using the recommended frequency cut-off. For the FD-EQL method, the range of f recommended for convolution analyses is shown to provide unrealistic responses in performing deconvolution analyses. A new range that produces unbiased residuals for all strain amplitudes is proposed. Comparisons highlight that the modified FD-EQL yields reliable predictions of the within motion for all profiles and motion intensities, automatically suppressing the amplification of high-frequency noise typically accompanied in a deconvolution analysis.

Generation and Evaluation of CPT Data Using Kriging Interpolation Technique

The cone penetration test (CPT) has been the de facto field exploration method in geotechnical engineering for decades. Variations of CPT can measure parameters for seismic, environmental, and hydrological applications. Analyzing response often requires properties in areas that have little or no data. Therefore, given the limited CPT data, it is critical to understand how to accurately estimate the soil properties at unsampled locations. In this paper, we generated soil shear wave velocity profiles using the kriging interpolation technique and assessed their performance using site response analysis. Four kriging interpolation-based shear wave velocity profiles and four additional CPT-based shear wave velocity profiles defined site conditions for response analysis. We performed a series of 1-D equivalent linear site response analyses using STRATA software. The site response analysis results are presented as amplification factors (AF), peak ground acceleration (PGA) profiles, surface spectral acceleration, and surface acceleration time histories. Compared to CPT-based profiles, the results of kriging interpolation-based profiles were evaluated and discussed. The results confirmed the reliability of the kriging interpolation technique in predicting soil parameters at unsampled locations.

Probabilistic Liquefaction Analysis Using Standard Penetration Test

Abstract The Youd etal liquefaction resistance curves developed in 2001 to characterize the cyclic resistance of soil based on SPT test are the most used in the context of the Seed and Idriss simplified procedure as a deterministic model. These curves were developed from a modified database of Seed etal. in 1985 with the assumption that the actual peak shear stress (τd) induced at depth h is always less than that predicted by the simplified procedure (τr) of Seed and Idriss (rd= τd/τr<1). By using a suite of equivalent linear site response analyses to adjust the dynamic and the simplified shear stress at depth h, Filali and Sbartai showed in 2017 that the dynamic peak shear stress for some earthquakes is greater than the simplified peak shear stress (rd>1). As in this case, the assumption of the simplified procedure is not verified, Filali and Sbartai have proposed a corrector factor (RC) in the range where rd >1 to adjust the deformable and rigid body. In this paper, we will present a probabilistic study for the evaluation of the liquefaction potential using a database based on SPT measurement compiled after the Chi-Chi Taiwan earthquake, in which the cyclic stress ratio is evaluated using the proposed corrector factor. The objective of this study is to present a probabilistic shape of the cyclic resistance ratio (CRR) curves based on the original simplified method of Seed and Idriss and the corrected version and a new formulation for computing the probability of liquefaction.

Site-Specific Ground Response Analysis using the Geotechnical Dataset in Moderate Seismicity Region

An understanding of the soil response to dynamic waves from the earthquakes is an important aspect of engineering safety measures against tremors. This research presents the equivalent linear site response analysis of the Miri district by using a geotechnical dataset. The main objective of this paper is to study the amplification factor for the district of Miri. Analysis of site response is critical in determining the earthquake risk and harm allocation during earthquakes. The standard penetration test ‘N’ value (SPT-N) has been used in this study. A specific soil-type relationship has been used between shear wave velocity and SPT-N value to produce profiles of shear wave velocity in each borehole site in the Miri district. For all SPT-N borehole sites, site response parameters were interpolated to produce site response maps and shear wave velocity maps in the geographical information system (GIS) environment. The research showed that the Malaysian national annex to Eurocode 8 (MNA-EC8) site class C, D and E are dominant in the Miri district. Due to the inadequacy of records of input ground motions of low-to-moderate seismicity regions, this research used an earthquake record from other locations well-matched from a target response spectrum with similar characteristics obtained from the Pacific Earthquake Engineering Research Center (PEER) online database (PEER NGA). The equivalent linear method (EQL) using DEEPSOIL is an extensively researched numeric technique that is used for assessment of site response. From the results, it has been found that the amplification ratio varies from 2.1 to 4.79 and it suggests that it is vital to study the site effect in the seismic hazard assessment of the Miri district. The work also emphasizes the relationship between seismic microzonation and site response analysis in order to reduce the adverse effects of earthquakes in Miri city by planning a proper land use.

Semi-empirical estimation of the Zagreb ML 5.5 earthquake (2020) ground motion amplification by 1D equivalent linear site response analysis

The 22 March 2020 Zagreb ML 5.5 earthquake ground shaking resulted in damage to buildings and infrastructure. The most affected buildings were older and cultural heritage buildings (built before 1963) in the old city centre with significant damage extent in the epicentral zone (southeastern foothills of Medvednica Mt.). This study presents site response analysis on the realistic site profiles from the epicentre towards the accelerometric stations QUHS and QARH and comparison with strong motion data recorded during the Zagreb 2020 earthquake. Semi-empirical estimation of the ground motion amplification (i.e., peak ground acceleration at surface) showed that modelled and recorded values are comparable. Moreover, we present 2D model of peak ground acceleration at surface (PGAsurf ) variation for the superimposed site profile from the epicentre towards two accelerometric stations. Ground motion amplification for the Zagreb ML 5.5 earthquake scenario showed that PGAsurf is larger by a factor of 2 than the bedrock value (approx. 0.35 g in the epicentre and 0.20 g on the 12 km distant accelerometric station). This study is a contribution to better understanding of the Zagreb ML 5.5 earthquake effects and significance of local site effects in the damage extent, something that combined with older and heritage buildings resulted in high economic consequences. Therefore, it is important that site-specific ground motion simulation and seismic microzonation of the Zagreb continues with installation of an accelerometric array. This is very important for earthquake retrofitting and resilience of the low, mid- and high-rise buildings with particular care of cultural and historical buildings as well for the further urban planning.

A Nonlinear Site Amplification Model for the Horizontal Component Developed for Ground-Motion Prediction Equations in Japan Using Site Period as the Site-Response Parameter

ABSTRACT This article presents a nonlinear site amplification model for ground-motion prediction equations (GMPEs), using site period as site-effect proxy based on the measured shear-wave velocity profiles of selected KiK-net and K-NET sites in Japan. This model was derived using 1D equivalent-linear site-response analysis for a total of 516 measured soil-site shear-wave velocity profiles subjected to a total of 912 components of rock-site records. The modulus reduction and damping curves for each soil layer were assigned based on the soil-type description for a particular layer. The site period and site impedance ratio affect both the linear and nonlinear parts of this study, and were used as the site parameters in the 1D amplification model. A large impedance ratio enhances the amplification ratios when the site responds elastically and enhances the nonlinear response when the site develops a significant nonlinear response. The effects of moment magnitude and source distance on the linear part of the 1D amplification model were also incorporated in the model. To implement the 1D amplification model into GMPEs, a model adjustment is required to match the GMPE amplification ratio at weak motion and to retain the nonlinear amplification ratio at the strong motion of the 1D model. The two-step adjustment method by Zhao, Hu, et al. (2015) was adopted in this study with significant modifications. It is not possible to obtain a credible second-step adjustment parameter using the GMPEs dataset only. We proposed three methods for calculating the scale factors. Method 1 is a constant angle in a 30°–60° range for all spectral periods; method 2 was based on the GMPE dataset and 1-D model parameters; and method 3 was based on the strong-motion records used for the 1D site modeling. A simple second-step adjustment factor leads to smoothing amplification ratios and soil-site spectrum.

Seismic Performance Evaluation of Two-story and Three-span Subway Station in Different Engineering Sites

ABSTRACT This study firstly investigates the seismic intensity measures (IMs) from the existing scalar ones that are suitable for the prediction of seismic response of shallowly buried rectangular underground structures. The peak acceleration and peak velocity at the ground surface are identified as the optimal IMs based on their efficiency, practicality, and proficiency. A series of seismic fragility curves are then developed for a two-story and three-span underground subway station embedded in three different typical engineering sites using nonlinear incremental dynamic analyses. In this study, the input ground motions at the level of engineering bedrock for the underground structure–soil interaction system are obtained through one-dimensional equivalent linear site response analysis according to the one-dimensional wave propagation theory. Comparison of the numerical results in this paper with the previous empirical and numerical fragility curves shows that the fragility analysis method in this paper is feasible, which can quantitatively give the failure probability of structures at different performance levels, and can provide reference for seismic design of underground structures. The numerical results indicate that both the characteristics of ground motions and the site profile have significant influence on the seismic fragility curves of underground structures. Underground subway stations are generally more vulnerable to seismic damage when embedded in engineering sites with lower average shear velocity. Moreover, seismic damage margin ratios are proposed for the underground structure in different site classes to show the confidence levels of its seismic performance when subjected to different levels of earthquake events, and can be used as a preliminary index for the earthquake risk assessment of subway station.

Evaluation of Uncertainties in Site Response Analysis of Deep Soil Profiles in South Carolina Coastal Plain

ABSTRACTThe South Carolina Coastal Plain consists of deep soil sediments over basement bedrock. The depth of basement bedrock varies from being present at the surface to a depth of more than 1200 m at the southern tip of the state. A large variation exists in the thickness of the sediment, which impacts the seismic site response analyses of the Coastal Plain, particularly in areas where the availability of deep shear-wave velocity profiles is limited. This study evaluates the impact of variations in the shear-wave velocity profiles for two sites in the South Carolina Coastal Plain. The shear-wave velocity profiles were measured using different geophysical methods, including a combined multichannel analysis of surface waves and microtremor array measurement (MASW-MAM) method and P–S suspension logging. The equivalent-linear site response analyses were conducted by applying a synthetic earthquake motion at the depth of the B–C boundary (a depth of competent rock in which the shear-wave velocity is 760 m/s). The results are presented in terms of the amplification factor and its standard deviation. Results show that the average shear-wave velocity at the first 30 m (VS30), the shear-wave velocity contrast at the interface of the base layer and the B–C boundary, and the depth to the B–C boundary have a significant impact on the amplification factor and its variability, particularly for the amplification factor at periods higher than 0.1 s. The MASW-MAM method provided significantly lower VS30 values than the P–S suspension logging method at one of the two sites. Consequently, an additional peak in the amplification factor was observed for the site that had a low VS30, and the corresponding period was close to the resonant period of the loose, surface deposit.

Nonlinear and Equivalent Linear Site Response Analysis of Istanbul Soils

The effect of local soil characteristics on the propagation of earthquake waves has been commonly studied by researchers. However, the validity of the results obtained by these studies is limited only to the relevant soil conditions. The main purpose of this study is to examine the effect of soil conditions on the propagation of seismic waves in Istanbul. In this regard, soil information belonging to different districts of Istanbul has been compiled. The site response analysis was simulated using a time-domain nonlinear response analysis based on the effective stress method and frequency-domain equivalent linear analysis based on the total stress method. A widely used one-dimensional response analysis program DEEPSOIL was used to estimate the soil response of the sites. Modeled soil profiles were subjected to 1999 Kocaeli earthquake motion and the results of the analysis are presented as spectral acceleration, PGA, and lateral displacements. The results obtained from both of the analyses were evaluated comparatively in terms of the effect of soil properties on the propagation of the seismic waves. The effect of the analysis method based on different approaches on the results is examined. The highlighting results obtained on how the propagation of earthquake waves will be affected by soil conditions. The liquefaction potential of soil profiles was also evaluated using the data of the soil properties of the investigation area.

Response spectra for moderate seismic area - application to Miri district of Sarawak, Malaysia

The aim of this paper is to estimate the response spectra for moderate seismic area in Sarawak, Malaysia. In the present study, the response spectra for Miri district, in Sarawak, has been obtained by using 1-D equivalent linear site response analysis at 114 borehole locations. All the borehole sites are classified based on average shear wave velocity (Vs30) as per Malaysia National Annex to Eurocode 8 (MNA-EC8) site classifications using the geotechnical relationship. In this study, the input motion was selected from Pacific Earthquake Engineering Research (PEER-NGA) online database compatible with target response spectra of Sarawak at engineering bedrock by considering the seismic hazard map for 2475 years as return period and by following the 475 years return period as shown in (MNA-EC8). From the results of this study, it was found that the maximum response spectral acceleration (response spectra with 5% damping) is 2.25 g, 3.25 g and 1.7 g at the ground surface for MNA-EC8 site classes C, D and E respectively. It was also found that the results are under the provisions of seismic design code of Malaysia. The suggested results in this study can be used as a reference in Malaysia to support the MNA-EC8.

Adjustment of site factors for basin effects from site response analysis and deep downhole array measurements in Taipei

Local site effects can amplify seismic shaking and damage caused by earthquakes. Site factors (SF) are used in seismic design to account for these effects to modify ground motions from a reference rock site. Average shear wave velocity in the top 30 m of soil (V s,30 ) is typically used to predict SF. However, recent studies have shown that using V s,30 alone may be insufficient in quantifying SF under the presence of deep soil deposits and proposed SFs that account for the bedrock depth (e.g. Z 1.0 , depth with V s of 1 km/s). This study evaluates these depth-dependent SFs using 1D nonlinear and equivalent-linear site response analyses. The predicted SFs are also compared with observations of downhole arrays installed within Taipei Basin. Based on numerical and observational results, depth correction factors are recommended in conjunction with SFs of seismic design code to reflect the effect of different sediment thicknesses in the design process. • We characterize the amplification behavior associated with bedrock depth and V s,30 . • Review recently proposed site factors (SF) that account for the bedrock depth • Assess SFs versus bedrock depth (Z 1.0 ) via 1D site response analyses • Empirical assessment of SFs using seven downhole arrays in Taipei Basin • Basin-depth correction factors in conjunction with code-based SFs for seismic design

The effect of soil nonlinearity on high-frequency spectral decay and implications for site response analysis

This study uses recorded ground motions at soil sites over a range of shaking intensities to investigate the effects of soil nonlinearity on the high-frequency spectral decay, as quantified by the parameter [Formula: see text]. Equivalent-linear site response analyses indicate that [Formula: see text] should increase significantly with increasing shear strain and ground motion intensity due to increases in soil damping. However, using more than 2500 motions from 32 sites, this study shows that [Formula: see text] does not vary systematically with the induced shear strain but instead remains at its small-strain value. This observation indicates that high-frequency components of motion are consistent with small-strain damping, rather than the strain-compatible damping used in site response analysis. It is demonstrated that equivalent-linear site response analyses for large strains can be modified to generate surface motions with more realistic high-frequency content by scaling the predicted surface motion to fit the small-strain [Formula: see text] or by employing frequency-dependent soil properties that account for the frequency dependence of the induced strains.

Evaluation of Seismic Site Amplification Using 1D Site Response Analyses at Ba Dinh Square Area, Vietnam

This study presents a case study on ground response analysis of one of the important cultural heritages in Hanoi, Vietnam. One‐dimensional nonlinear and equivalent linear site response analyses which are commonly applied to solve the problem of seismic stress wave propagation are performed at the Ba Dinh square area. A measured in‐situ shear wave velocity profile and corresponding geotechnical site investigation and laboratory test data are utilized to develop the site model for site‐specific ground response analysis. A suite of earthquake records compatible with Vietnamese Design Code TCVN 9386: 2012 rock design spectrum is used as input ground motions at the bedrock. A few concerns associated with site‐specific ground response evaluation are analyzed for both nonlinear and equivalent linear procedures, including shear strains, mobilized shear strength, and peak ground acceleration along with the depth. The results show that the mean maximum shear strains at any soil layer are less than 0.2% in the study area. A deamplification portion within the soil profile is observed at the layer interface with shear wave velocity reversal. The maximum peak ground acceleration (PGA) at the surface is about 0.2 g for equivalent linear analysis and 0.16 g for nonlinear analysis. The ground motions are amplified near the site natural period 0.72 s. The soil factors calculated in this study are 1.95 and 2.07 for nonlinear and equivalent linear analyses, respectively. These values are much different from the current value of 1.15 for site class C in TCVN 9386: 2012. A comparison of calculated response spectra and amplification factors with the local standard code of practice revealed significant discrepancies. It is demonstrated that the TCVN 9386: 2012 soil design spectrum is unable to capture the calculated site amplification in the study area.

Yield acceleration of reinforced soil slopes using the modified pseudo-dynamic method

This study presents the yield acceleration of reinforced soil slopes using the horizontal slice approach. Yield acceleration plays a key role in calculating the permanent seismic displacement of slopes. The modified pseudo-dynamic method, in conjunction with the equivalent linear site response analysis, is used. Unlike the pseudo-static analysis, the pseudo-dynamic method takes into account the effects of time and phase difference of waves propagation. The developed computer code is used to compute the yield acceleration. Using the planar and log-spiral slip surfaces, this code considers the distribution of reinforcement layers as uniform and variable spacing. The effect of surcharge pressure is also considered. According to the results, the modified pseudo-dynamic method using the equivalent linear ground response analysis led to more critical results than other methods.

Determination of seismic hazard and soil response of a critical region in Turkey considering far-field and near-field earthquake effect

Evaluation of earthquake impacts in settlements with a high risk of earthquake occurrence is important for the determination of site-specific dynamic soil parameters and earthquake-resistant structural planning. In this study, dynamic soil properties of Karliova (Bingol) city center, located near to the intersection point of the North Anatolian Fault Zone and the East Anatolian Fault Zone and therefore having a high earthquake risk, were investigated by one-dimensional equivalent linear site response analysis. From ground response analyses, peak ground acceleration, predominant site period, 0.2-sec and 1-sec spectral accelerations and soil amplification maps of the study area were obtained for both near-field and far-field earthquake effects. The average acceleration spectrum obtained from analysis, for a near-field earthquake scenario, was found to exceed the design spectra of the Turkish Earthquake Code and Eurocode 8. Yet, the average acceleration spectrum was found to remain below the respective design spectra of the two codes for the far-field earthquake scenario. According to both near- and far-field earthquake scenarios in the study area, the low-rise buildings with low modal vibration durations are expected to be exposed to high spectral acceleration values and high-rise buildings with high modal vibration durations will be exposed to lower spectral accelerations. While high amplification ratios are observed in the north of the study area for the near-distance earthquake scenario, high amplification ratios are observed in the south of the study area for the long-distance earthquake scenario.

Assessment of the Seismic Site Amplification in the City of Ivanec (NW Part of Croatia) Using the Microtremor HVSR Method and Equivalent-Linear Site Response Analysis

The city of Ivanec is located between valley of the Bednja River and Mt. Ivanščica and this area can be prone to significant seismic site amplification due to local site characteristics. This study presents the first assessment of seismic site amplification for the city of Ivanec by the microtremor horizontal-to-vertical-spectral-ratio (HVSR) method and the equivalent-linear (EQL) site response analysis. Based on microtremor measurements and HVSR analysis, fundamental soil frequency and HVSR peak amplitude maps indicate potentially seismic danger zones. The 1-D EQL site response analysis was performed using multiple suites of earthquake ground motions scaled to the 95- and 475-year return periods of peak ground accelerations. Site amplification maps at the predominant peak frequency and ground surface indicate two microzones, one with high amplification in the central part of the city due to soft soil characteristics, and the other with small amplification in the transitional zone from alluvial basin towards the foothills of Mt. Ivanščica. HVSR peak amplitudes and site response peak amplifications showed similar spatial distributions with similar predominant peak frequencies but with different amplitude levels. Site amplification maps provided significant information about potential resonance effects for structures of certain heights that can be correlated with the local ground shaking characteristics.

Seismic behaviour of rocking bridge pier supported by elastomeric pads on pile foundation

Life line structures such as elevated flyovers and rail over bridges should remain functional after an earthquake event to avoid possible traffic delays and risk to general public. Generally, restraining the structure by reducing the degrees of freedom often cause serious damages that occurs during a seismic event through yielding of the structural components. By allowing the structure to rock through uplift using suitable arrangements can be a plausible seismic resilient technique. In this context, this article proposes a novel seismic resilient pile supported bridge pier foundation, which uses elastomeric pads installed at top of pile cap. The effect of pile soil interaction along with ground response analysis is also incorporated in the full bridge model adopted for the study. One dimensional equivalent linear site response analyses were performed to arrive at the amplified/attenuated ground motions along the depth of soil.The seismic performance of the proposed bridge with new rocking isolation concept is compared with existing bridge located in medium seismic zone of India. With the help of non-linear dynamic time history analysis and nonlinear static pushover analysis, the bridge modelled using the proposed novel rocking isolation technique shows good re-centering capability during earthquakes with negligible residual drifts and uniform distribution of ductility demand along the piers of the bridge considered in this study.

An investigation on the evaluation of dynamic soil characteristics of the Elazig City through the 1-D equivalent linear site-response analysis

Consideration of the effects of the site response in the design of civil structures systems is of important to mitigate the damages to a certain extent on structures and the environment. Hence, it is relatively crucial to reliably attain the dynamic soil parameters of an earthquake-prone city/state. In the current study, a comprehensive investigation on the dynamic soil properties of the city of Elazig with very close proximity to the East Anatolian Fault Zone (EAFZ) having a high potential of producing destructive earthquakes is carried out. Performing probabilistic seismic hazard analysis (PSHA), the moment magnitude of the city is determined as Mw = 7.7 according to 10% probability of exceedance in 50 years. Bedrock-level acceleration spectra is developed utilizing different attenuation relationships for the city, and 1-D equivalent linear site response analysis is conducted on an example soil profile of the city through the SHAKE2000 software considering 16 earthquake motions recorded at the bedrock level. Local surface acceleration spectra obtained from the analysis are then compared to the design spectra of the Turkish Seismic Code for Buildings (TSCB) and Eurocode-8 (EC8) in an attempt to identify the difference between the code spectra and local surface spectra. In addition, in situ geotechnical tests of standard penetration and seismic refraction are conducted at different locations of the study area. Incorporating the results from the field tests into the site response analysis, the soil amplification factor, predominant soil period, peak ground acceleration and spectral maps for the period of T = 0.2 and T = 1.0 s are obtained for the study area. The outcomes from the analysis reveals that structures with higher vibration period than T = 1.0 s are subjected to lower spectral acceleration (Sa), whereas higher Sa values can be used for those with a vibration period lower than T = 0.2 s.