Evaluation Of Site Effects Research Articles

Soil and Sediments Microzonation for Evaluation of Site Effects on Earthquake Damages in Mobarakeh, Esfahan, Iran

As an important step in effectively reducing seismic risk and the vulnerability of the city of Mobarakeh to earthquakes, a site effect microzonation Study was conducted. Seismic hazard analysis for a return period of 475 years was carried out. Data from 10 borings was collected and analyzed, geophysical surveys were conducted and seismology and geoelectric measurements taken in more than 17 stations through out the city. The study area was divided into a grid of 500×500 m2 elements and the sub-surface ground conditions were classified into 5 representative geotechnical profiles. Electric resistivity was measured in close to 17 geotechnical boreholes and surface and sub-surface sediments were collected and analyzed. Site response analyses were carried out on each representative profile using 30 different base rock input motions. Distribution maps of site periods and peak ground acceleration and old and new texture buildings through out the city were developed, providing a useful basis for land-use planning in the city.

Evaluation of site effects in the Aterno river valley (Central Italy) from aftershocks of the 2009 L’Aquila earthquake

A temporary network of 33 seismic stations was deployed in the area struck by the 6th April 2009, Mw 6.1 (Scognamiglio et al. in Seism Res Lett 6/81, 2010), L’Aquila earthquake (central Italy), with the aim to investigate the site amplification within the Aterno river Valley. The seismograms of 18 earthquakes recorded by 14 of the 33 stations were used to evaluate the average horizontal to vertical spectral ratio (HVSR) for each site and the standard horizontal spectral ratio (SSR) between a site and a reference station. The obtained results have been compared to the geological and geophysical information in order to explain the resonance frequencies and the amplification levels with respect to surface geology of the valley. The results indicate that there is no uniform pattern of amplification, because of the complex geologic setting, as the thickness and degree of cementation of the deposits is highly variable.

The effect of intramuscular injection of dinoprost or gonadotropin-releasing hormone in dairy cows on beef quality1

Intramuscular injections of drugs and vaccines cause tissue damage and subsequent effects on tenderness and consumer acceptability of beef. In the 2007 National Market Cow and Bull Beef Quality Audit, 100% of plants reported fabricating subprimal cuts such as rib eyes and tenderloins from cow and bull carcasses. Dairy beef quality should therefore be a consideration when injections are given to dairy animals. The discussion about injection site reactions and tenderness has focused on vaccines and antimicrobial drugs with little concern for the effects of reproductive hormones. The objective of this study was to quantify antemortem the effects of semimembranosis/semitendinosis muscle injection of dinoprost and GnRH in lactating dairy cows by estimating the weight of tissue damaged and comparing that with a drug known to cause extensive tissue damage, flunixin meglumine. Tissue damage was estimated from previously reported equations for grams of muscle tissue damage based on area under the curve of serum concentrations of the muscle enzyme creatine kinase over time. Dinoprost and flunixin injection both caused a significantly increased estimate of muscle tissue damaged compared with needle only (P = 0.0351 and 0.0355, respectively). Dinoprost and flunixin caused a marginally significant increased muscle tissue damage compared with GnRH (P = 0.1394 and 0.1475, respectively). No statistically significant difference was found between the estimated weight of muscle tissue damaged by flunixin compared with dinoprost (P = 1.0000), or by saline compared with GnRH (P = 0.7736) or needle only (P = 0.4902). The assumption that reproductive hormones are less damaging than vaccines and antimicrobial drugs should be examined more closely, including postmortem evaluation of injection site lesions and effects on tenderness.

Recorded ground motion and site effects evaluation for the April 6, 2009 L’Aquila earthquake

On April 6, 2009 a ML = 5.8 earthquake hit the city of L’Aquila on the Apennine chain in central Italy. Notwithstanding the moderate-size event the L’Aquila city and several small villages along the Aterno river valley suffered severe damage, because of the unusual strong motions, mainly due to proximity to the fault (estimated hypocentral depth of about 10 km). In this paper the main features of the recorded motion are discussed. Four accelerometric stations were located within the surface projection of the fault and recorded peak values ranging from 0.4 to 0.6 g. The recorded motions were characterised by short durations and high peak accelerations both in the horizontal and vertical directions. The strong portions of vertical and horizontal motions occurred almost simultaneously due to the short travel paths of P and S waves from the fault to the ground surface near the fault area. Hence site response analyses were performed for the sites where recording stations were located. The geotechnical subsoil model was derived by boreholes, in situ dynamic tests (D-H and SDMT) and by laboratory tests (RCT). One-dimensional numerical analyses were carried out employing the well known computer code EERA. The numerical model was calibrated, in the linear equivalent range, by comparing numerical results with the horizontal acceleration recorded components.

Evaluation of Peak Ground Acceleration and Response Spectra Considering the Local Site Effects

The local site effects play an important role in the evaluation of seismic hazard. The proper evaluation of the local site effects will help in evaluating the amplification factors for different locations. This article deals with the evaluation of peak ground acceleration and response spectra based on the local site effects for the study area. The seismic hazard analysis was done based on a probabilistic logic tree approach and the peak horizontal acceleration (PHA) values at the bed rock level were evaluated. Different methods of site classification have been reviewed in the present work. The surface level peak ground acceleration (PGA) values were evaluated for the entire study area for four different site classes based on NEHRP site classification. The uniform hazard response spectrum (UHRS) has been developed for the city of Bangalore and the details are presented in this work.

Heavier Damages without Site Effects and Site Effects with Lighter Damages: Boumerdes City (Algeria) after the May 2003 Earthquake

The ambient vibration H/V method (Nakamura 1989) is now widely used to determine the fundamental soil frequency and has proven to be a good tool for site effect evaluation ( e.g. , Bonnefoy-Claudet, Cornou et al. 2006). More particularly, it has been used for the zoning of a number of cities around the world, such as Basel, Switzerland (Fah et al. 1997); Quito, Ecuador (Gueguen et al. 2000); Barcelona, Spain (Alfaro et al. 2001); Caracas, Venezuela (Duval et al. 2001); Almeria, Spain (Navarro et al. 2001); and Thessaloniki, Greece (Panou et al. 2005). This method has also been used to find a correlation between damages from an earthquake and the frequency of ambient vibration H/V peaks ( e.g. Gueguen et al. 1998; Panou et al. 2005; Teves Costa et al. 2007; Cara et al. 2008). Other studies show that this correlation is not always clear or even does not exist (Fallahi 2003; Gonzales et al. 2004; Chatelain, Guillier, and Parvez 2008; Theodulis et al. 2008). The 21 May 2003 Algerian ( Mw = 6.8) earthquake produced severe damages in the city of Boumerdes, among others (see Figure 1 for locations). These damages were not uniformly distributed throughout the city, with a destruction level varying from 0 up to 5%, except in two neighborhoods where it reached 30% (Hamane et al. 2007). These observations led us to try to link the destruction pattern to variations of local seismic wave amplification. One of the most widely used methods for studying this type of site effect is based on recording ambient vibrations (noise) in both the vertical and horizontal directions and computing their spectral ratio (a comprehensive review of ambient vibration studies may be found in Bonnefoy-Claudet, Bard, and Cotton 2006). The physical meanings of the ambient …

The seismic microzonation of the city of Catania (Italy) for the maximum expected scenario earthquake of January 11, 1693

Safety against earthquake hazards presents two aspects: structural safety against potentially destructive dynamic forces and site safety related to geotechnical phenomena, such as amplification, landsliding and soil liquefaction. The correct evaluation of seismic hazard is, therefore, highly affected by risk factors due to geological nature and geotechnical properties of soils. In response to these new developments, several attempts have been made to identify and appraise geotechnical hazards and to represent them in the form of zoning maps, in which locations or zones with different levels of hazard potential are identified. The geotechnical zonation of the subsoil of the city of Catania (Italy) suggests a high vulnerability of the physical environment added to site amplification of the ground motion phenomena. The ground response analysis at the surface, in terms of time history and response spectra, has been obtained by some 1D equivalent linear models and by a 2D linear model, using a design scenario earthquake as input at the conventional bedrock. In particular, the study has regarded the evaluation of site effects in correspondence of the database of about 1200 boreholes and water-wells available in the data-bank of the Catania area. According to the response spectra obtained through the application of the 1D and 2D models, the city of Catania has been divided into some zones with different peak ground acceleration at the surface, to which corresponds a different value of the Seismic Geotechnical Hazard. A seismic microzoning map of the urban area of the city of Catania has been obtained. The map represents an important tool for the seismic improvement of the buildings, indispensable for the mitigation of the seismic risk.

Site effect evaluation in the basin of Santiago de Chile using ambient noise measurements

SUMMARY We performed extensive ambient vibration measurements in the basin of Santiago de Chile (Chile), and we look for testing the reliability of the horizontal-to-vertical amplitude spectra ratio method (H/V ) as a tool to provide qualitative and quantitative information of site effects in complex geological media. The interpretation of the H/V data was carried out conformably to the SESAME project consensus criteria and outlines three major patterns: (1) clear peaked H/V curves related to sharp underground velocity contrast; (2) H/V peak of low amplitude and flat curve related to weak contrast and (3) broad H/V peak indicating the presence of strong lateral variations of underground structure. H/V measurements, however, reveal a discrepancy between the computed soil resonance frequencies and the expected building resonance, therefore not leading to a straight interpretation of the intensity distribution derived from observed damage to one storey houses in Santiago after the 1985 Valparaiso earthquake. Indeed, the H/V technique mostly maps the first fundamental frequency; however, it fails to show higher resonance modes. In the case of the city of Santiago, this method works well for assessing the seismic hazard for high-rise buildings, but is questionable for smaller structures as is the case of a great percentage of constructions in the city.

Evaluation of site effects using numerical analyses in Celano (Italy) finalized to seismic risk assessment

In this paper the results of the numerical analyses, related to a site of the Abruzzo Region (Celano-AQ), finalized to the evaluations of site effects, are shown. The aim of the work was to give a methodology and results that can be used in seismic risk analysis, at the level of urban planning. Therefore, a series of geologic, geomorphologic, geotechnical and geophysical analyses have been carried out to characterize the lithological units and to identify the areas affected by site effects. The expected seismic inputs are individuated and two-dimensional numerical analyses have been done. The results are presented in terms of elastic pseudo-acceleration spectra and amplification factors, computed as the ratio between spectral intensity of output and input, in the period ranges 0.1–0.5 and 0.1–2.5 s.

Deterministic Ground-Motion Scenarios for Engineering Applications: The Case of Thessaloniki, Greece

Abstract In this article we present a deterministic study to estimate seismic ground motions expected in urban areas located near active faults. The purpose was to generate bedrock synthetic time series to be used as seismic input into site effects evaluation analysis and loss estimates for the urban area and infrastructures of Thessaloniki (Northern Greece). Two simulation techniques (a full wave method to generate low-frequency seismograms, ∼1 Hz) were used to compute time series associated with four different reference earthquakes having magnitudes from 5.9 to 6.5 and located within 30 km of Thessaloniki. The propagation medium and different source parameters were tested through the modeling of the 1978 Thessaloniki earthquake ( M 6.5). Moreover two different nucleation points were considered for each fault in order to introduce additional variability in the ground-motion estimates. Between the two cases, the quasi-unilateral rupture propagation toward the city produces both higher median peak ground acceleration (PGA) and peak ground velocity (PGV) values and higher variability than bilateral ones. Conversely, the low-frequency ground motion, that is, peak ground displacement (PGD), is slightly influenced by the position of the nucleation point, and its variability is related to the final slip distribution on the faults of the reference earthquakes and to the location of the sites with respect to the nodal planes of the radiation pattern. To validate our deterministic shaking scenarios, we verified that the synthetic peak ground motions (PGA and PGV) and spectral ordinates are within one standard deviation of several ground-motion prediction equations valid for the region. At specific sites we combined the low- and high-frequency synthetics to obtain broadband time series that cover the entire frequency band of engineering interest (0–25 Hz). The use of synthetic seismograms instead of empirical equations in the hazard estimates provides a complete evaluation of the expected ground motions both in frequency and time domains, including predictions at short distances from the fault (0–10 km) and at periods larger than 2–3 sec.

Mapping of Average Shear Wave Velocity for Bangalore Region: A Case Study

Mapping the shear wave velocity profile is an important part in seismic hazard and microzonation studies. The shear wave velocity of soil in the city of Bangalore was mapped using the Multichannel Analysis of Surface Wave (MASW) technique. An empirical relationship was found between the Standard Penetration Test (SPT) corrected N value [Formula: see text] and measured shear wave velocity [Formula: see text]. The survey points were selected in such a way that the results represent the entire Bangalore region, covering an area of [Formula: see text]. Fifty-eight 1-D and 20 2-D MASW surveys were performed and their velocity profiles determined. The average shear wave velocity of Bangalore soils was evaluated for depths of [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text] and [Formula: see text]. The sub-soil classification was made for seismic local site effect evaluation based on average shear wave velocity of [Formula: see text] depth [Formula: see text] of sites using the National Earthquake Hazards Reduction Program (NEHRP) and International Building Code (IBC) classification. Mapping clearly indicates that the depth of soil obtained from MASW closely matches with the soil layers identified in SPT bore holes. Estimation of local site effects for an earthquake requires knowledge of the dynamic properties of soil, which is usually expressed in terms of shear wave velocity. Hence, to make use of abundant SPT data available on many geotechnical projects in Bangalore, an attempt was made to develop a relationship between Vs (m∕s) and [Formula: see text]. The measured shear wave velocity at 38 locations close to SPT boreholes was used to generate the correlation between the corrected N values and shear wave velocity. A power fit model correlation was developed with a regression coefficient [Formula: see text] of 0.84. This relationship between shear wave velocity and corrected SPT N values correlates well with the Japan Road Association equations.

Broadband (0.05 to 20 s) prediction of displacement response spectra based on worldwide digital records

A new set of empirical equations for prediction of displacement response spectral ordinates from 20 Hz to T = 20 s is illustrated. The coefficients of the equations were obtained by regressing a dataset based on 1,155 tri-axial digital and 9 analog accelerometer records from 60 earthquakes worldwide. Long period disturbances in the accelerograms were evaluated and removed using a very recent method, aimed at preserving the long-period spectral content of the records. Analysis of variance has disclosed only little evidence for regional dependence of ground motions, while a carefully conducted evaluation of site effects resulted in clearly differentiated spectral amplification bands associated to the main ground types B, C, and D of Eurocode 8. Spectral ordinates for vibration periods >5 s were found to scale with magnitude quite consistently with theoretical scaling from Brune’s model. On the other hand, comparison of results with those yielded by recent prediction models in Europe and the United States (NGA), indicated that the latter may not be uniformly reliable at long periods. The proposed empirical equations are easily implemented in computer programs for seismic hazard assessment, being characterized by a simple functional form and a restricted number of predictor variables.

Evaluation of Site Effects in Hong Kong

This paper describes an investigation into the potential seismic site response effects for the ground conditions in Hong Kong. A site classification map for the Hong Kong region has been produced using current IBC site classes. Published geological maps and detailed ground investigation information have been used for the classification. One-dimensional site response analyses have been carried out to determine how various representative types of site profiles of Hong Kong will potentially respond to earthquake ground motion. The response of soil profiles was investigated using three input earthquake ground-motion levels corresponding to bedrock motion with 50%, 10% and 2% probability of being exceeded in 50 years. The results are presented in terms of spectral ratios for the different Site Classes. A simplified manual procedure for rapid assessment of site response effects has been developed by the University of Hong Kong to produce displacement- based design response spectra. There are extensive areas of reclamation in Hong Kong and the potential for liquefaction in these areas, and other areas underlain by non-cohesive, saturated soils, was considered sufficiently high to warrant investigation. The methodology and results of a liquefaction assessment are presented in the final part of this paper

Effects of Love Waves on Microtremor H/V Ratio

Abstract The horizontal-to-vertical (H/V) method has the potential to significantly contribute to site effects evaluation, in particular in urban areas. Within the European project, site effects assessment using ambient excitations (SESAME), we investigated the nature of ambient seismic noise in order to assess the reliability of this method. Through 1D seismic noise modeling, we simulated ambient noise for a set of various horizontally stratified structures by computing efficiently the displacement and stress of dynamic Green’s functions for a viscoelastic-layered half-space. We performed array analysis using the conventional semblance-based frequence-wavenumber method and the three-component modified spatial autocorrelation method on both vertical and horizontal components and estimated the contribution of different seismic waves (body/surface waves, Rayleigh/Love waves) at the H/V peak frequency. We show that the very common assumption that almost all the ambient noise energy would be carried by fundamental-mode Rayleigh waves is not justified. The relative proportion of different wave types depends on site conditions, and especially on the impedance contrast. For the 1D horizontally layered structures presented here, the H/V peak frequency always provides a good estimate of the fundamental resonance frequency whatever the H/V peak origin (Rayleigh wave ellipticity, Airy phase of Love waves, S -wave resonance). We also infer that the relative proportion of Love waves in ambient noise controls the amplitude of the H/V peak.

Shallow shear-wave reflection seismics in the tsunami struck Krueng Aceh River Basin, Sumatra

Abstract. As part of the project "Management of Georisk" (MANGEONAD) of the Federal Institute for Geosciences and Natural Resources (BGR), Hanover, high resolution shallow shear-wave reflection seismics was applied in the Indonesian province Nanggroe Aceh Darussalam, North Sumatra in cooperation with the Government of Indonesia, local counterparts, and the Leibniz Institute for Applied Geosciences, Hanover. The investigations were expected to support classification of earthquake site effects for the reconstruction of buildings and infrastructure as well as for groundwater exploration. The study focussed on the city of Banda Aceh and the surroundings of Aceh Besar. The shear-wave seismic surveys were done parallel to standard geoengineering investigations like cone penetrometer tests to support subsequent site specific statistical calibration. They were also partly supplemented by shallow p-wave seismics for the identification of (a) elastic subsurface parameters and (b) zones with abundance of groundwater. Evaluation of seismic site effects based on shallow reflection seismics has in fact been found to be a highly useful method in Aceh province. In particular, use of a vibratory seismic source was essential for successful application of shear-wave seismics in the city of Banda Aceh and in areas with compacted ground like on farm tracks in the surroundings, presenting mostly agricultural land use areas. We thus were able to explore the mechanical stiffness of the subsurface down to 100 m depth, occasionally even deeper, with remarkably high resolution. The results were transferred into geotechnical site classification in terms of the International Building Code (IBC, 2003). The seismic images give also insights into the history of the basin sedimentation processes of the Krueng Aceh River delta, which is relevant for the exploration of new areas for construction of safe foundations of buildings and for identification of fresh water aquifers in the tsunami flooded region.

Seismic site effects by an optimized 2D BE/FE method I. Theory, numerical optimization and application to topographical irregularities

This paper deals with the evaluation of seismic site effects due to the local topographical and geotechnical characteristics. The amplification of surface motions is calculated by a numerical method combining finite elements in the near field and boundary elements in the far field (FEM/BEM). The numerical technique is improved by time truncation. In the first part of this article, the accuracy and the relevance of this optimized method are presented. Moreover, parametric studies are done on slopes, ridges and canyons to characterize topographical site effects. The second part deals with sedimentary valleys. The complexity of the combination of geometrical and sedimentary effects is underlined. Extensive parametrical studies are done to discriminate the topographical and geotechnical effects on seismic ground movement amplifications in two-dimensional irregular configurations. Characteristic coefficients are defined to predict the amplifications of horizontal displacements. The accuracy of this quantitative evaluation technique is tested and discussed.

Seismic site effects by an optimized 2D BE/FE method II. Quantification of site effects in two-dimensional sedimentary valleys

This paper deals with the evaluation of seismic site effects due to the local topographical and geotechnical characteristics. The amplification of surface motions is calculated by a numerical method combining finite elements in the near field and boundary elements in the far field (FEM/BEM). The numerical technique is improved by time truncation. In the first part of this article, the accuracy and the relevance of this optimized method are presented. Moreover, parametric studies are done on slopes, ridges and canyons to characterize topographical site effects. The second part deals with sedimentary valleys. The complexity of the combination of geometrical and sedimentary effects is underlined. Extensive parametrical studies are done to discriminate the topographical and geotechnical effects on seismic ground movement amplifications in two-dimensional irregular configurations. Characteristic coefficients are defined to predict the amplifications of horizontal displacements. The accuracy of this quantitative evaluation technique is tested and discussed.

Evaluation of local site effects on earthquake damages of Fatih Mosque

Fatih Mosque and its Kulliye (complex) are one of the most important historical monuments in Istanbul. Since it has been built between 1463 and 1470, Fatih Mosque had been subjected to nine strong earthquakes and suffered various degrees of structural damage at every case, including the latest August 17, 1999 Kocaeli Earthquake ( M w = 7.4, epicentral distance approximately 100 km). Recently, a project has been initiated first to study the possible causes of earthquake damage and then develop retrofitting and strengthening techniques to protect this invaluable monument from further damages in the future earthquakes. As part of this investigation, local site soil conditions had been determined and site behavior during earthquakes had been studied in detail. In this paper, the results of 1-D site response analysis, which included convolution and deconvolution analyses utilizing the strong ground motions recorded during the August 17, 1999 Kocaeli Earthquake are presented. The results of the analyses had demonstrated the considerable degree of site amplification, compatible with the recorded motions and the damage suffered. The expected site behavior during a probable future earthquake is also studied using a site specific simulated bedrock motion, and earthquake parameters to be used in dynamic structural analysis are estimated.

A Hybrid Inversion Technique for the Evaluation of Source, Path, and Site Effects Employing S-Wave Spectra for Subduction and Upper-Crustal Earthquakes in El Salvador

We propose a hybrid inversion analysis (hia) technique aimed at incorporating earthquakes from different seismogenic sources in one single inversion scheme. The application of this technique provides estimations of the source, path, and site effects at 23 strong-motion stations in El Salvador, Central America. The strong-motion dataset comprises 404 triaxial accelerograms corresponding to 63 subduction and upper-crustal earthquakes with M S magnitudes between 3.0 and 7.8. Application of the hia technique reveals: (1) good matching of the estimated source spectra with those derived from the ω 2 point source model; (2) rapid and low attenuation patterns characterizing the upper-crustal volcanic belt and subduction zone, respectively; and (3) soil transfer functions characterized by amplification ratios larger than those derived from spectral ratio techniques by a factor of two. Reference- site-dependent techniques yield similar soil transfer functions at all stations, whereas the horizontal-to-vertical spectral ratio technique yields similar results at sites characterized by clearly predominant peaks.

Application of horizontal-to-vertical (H/V) Fourier spectral ratio for analysis of site effect on rock (NEHRP-class B) sites in Taiwan

The frequency-dependent amplification for rock (NEHRP-class B) sites was studied using earthquake ground-motion database collected in Taiwan during implementation of the Taiwan Strong Motion Instrumentation Program. The database used includes several hundred records from earthquakes of M L 4.0–7.3 occurred between 1993 and 2004. The characteristics of amplification were evaluated using the well-known technique of horizontal-to-vertical Fourier spectral ratio (H/V) of the S-wave phase [Lermo J, Chavez-Garcia FJ. Site effect evaluation using spectral ratios with only one station. Bull Seism Soc Am 1993;83:1574–94]. The study allows us to analyze peculiarities of rock sites amplification in Northern and Eastern Taiwan. It was suggested to divide the NEHRP-class B site amplification into four types based on frequency of maximum amplification and the shape of amplification function. The applicability of the technique was also checked for a few stiff and soft soil sites (NEHRP-classes D and E).