Soil Amplification Research Articles

The Importance of Assessing the Geological Site Effects of Ancient Earthquakes from the Archaeoseismological Point of View

Earthquakes have and continue to, occur worldwide, though some places are affected more than others by earthquake-induced ground shaking and the same earthquake can cause more damage in one area than in nearby locations due to site-specific geological site conditions, also known as local site effects. Depending on the chronology of the earthquakes, various disciplines of seismology include instrumental and historical seismology, archaeoseismology, palaeoseismology and neotectonics, each focusing on using specific sources of information to evaluate recent or ancient earthquakes. Past earthquakes are investigated to expand the pre-instrumental and instrumental earthquake catalog and better evaluate a region’s seismic hazard. Archaeoseismology offers a way to achieve these goals because it links how ancient civilizations and their environment might have interacted and responded to past earthquake-induced ground motion and soil amplification. Hence, archaeoseismology explores pre-instrumental (past) earthquakes that might have affected sites of human occupation and their nearby settings, which have left their co-seismic marks in ancient manufactured constructions exhumed by archaeological excavations. However, archaeoseismological observations are often made on a limited epicentral area, poorly constrained dated earthquakes and occasionally on unclear evidence of earthquake damage. Archaeological excavations or field investigations often underestimate the critical role that an archaeological site’s ancient geological site conditions might have played in causing co-seismic structural damage to ancient anthropogenic structures. Nevertheless, the archaeological community might document and inaccurately diagnose structural damage by ancient earthquake shaking to structures and even estimate the size of past earthquakes giving little or no consideration to the role of geological site effects in addressing the causative earthquake. This mixture of factors frequently leads to imprecise estimates of the size of ancient earthquakes and unlikely earthquake environmental impacts, leaving unexplained the location and the moment magnitude of the causative earthquake. Hence, it is essential not to rely solely on earthquake intensities based on archaeologically documented co-seismic damage without assessing the nature of the observed structural damage and the contribution of the geological site effects. This paper explains the geological site effects concept to archaeologists unfamiliar with the notion. It clarifies its role in assessing ground shaking, soil amplification and earthquake intensity by past earthquakes and how and why the geological site effects can be estimated when a site is thought to have been struck by an earthquake. Hence, the geological site effects must be considered when archaeological excavations describe and interpret destruction layers. Conversely, engineers and seismologists dealing with seismic hazard risk assessment must pay close attention to archaeological investigations assessing earthquake intensities and locations based on field evidence of damage to structures attributed to past earthquakes, because the geological site effects might have been factored in inaccurately or not at all.

An Investigation on Soil Amplification through Site Factors Used in Seismic Design Codes

This article aims to investigate the site amplification through site coefficients given in the seismic codes. A set of 84 ground motion records in a base rock form and targeted to have different frequency contents was formed. The surface forms of these records altered by 100 different soil conditions were determined. Using this set of 8400 ground motion records, site amplification phenomenon is examined. After a PGA of 0.3 g, ground motions have similar behaviour in terms of short period amplification. Numerical figures as average and with a safety level of 84% for the SS and S1 site coefficients were given and compared with the code which are observed to be unconservative for stiff soils and too conservative for soft soils. Linking SS with a V S value of 600 m/s and S1 with a V S value of 120 m/s seems to be useful to understand some amplification behaviours. The variability of ZB and ZC site classes for short period site coefficient and ZE and ZD site classes for midperiod site coefficient seems to be greater when compared to others.

Regional-scale site characterization mapping in high impedance environments using soil fundamental resonance (f0): New England, USA

In this work, we develop regional-scale site characterization maps of New England, a glaciated region in the Eastern United States, using site fundamental frequency (f0). Due to the strong impedance contrast that creates strongly resonant site response behavior in New England, f0 is the preferred site response proxy for the region and best characterizes spatial variability in soil amplification. We first develop a database of 1577 f0 values collected from the literature (1313) and picked from HVSR curves collected during an additional field campaign (487). Using the surficial geologic units from the conterminous US surficial geology map, we compute distributions of f0 for each of the surficial geologic units mapped in New England. We find that the thick glaciofluvial ice-contact sediments and thick proglacial sediments of Cape Cod and Long Island are characterized by f0 distributions with the lowest medians (1.06 and 1.03 Hz respectively) and narrowest interquartile ranges (0.23 and 0.28 Hz respectively) in New England, which we interpret as being the thickest sediments in the region. The f0 distribution of the thin, proglacial sediments, mostly fine-grained in the Boston Basin, the coast of Lake Champlain and the Maine coast has a relatively low median (2.70 Hz), however it has high variability (3.65 Hz interquartile range) since the sediment thickness varies widely in this geologic unit. The f0 distribution of the thin alluvial sediments of the Connecticut River Valley also has a low f0 median (1.83 Hz) however, it has less variability than the proglacial sediments, mostly fine-grained thin (1.59 Hz). We present maps of the median and interquartile range of the f0 distributions and their corresponding Vs30 distribution approximations. Vs30 distributions are developed for each of the surficial geologic units by assuming a layer-over-halfspace model for site response and establishing estimates of sediment average shear-wave velocity (Vsavg) for each of the units based on a limited number of shear wave velocity profiles from the region. We compare our results against two existing site characterization maps for the region, Wald and Allen (2007) and Becker et al. (2011) and find that our updated maps result in median Vs30 values that tend to be higher than Becker et al. (2011) except in geologies with consistently deep profiles, and lower than Wald and Allen (2007) median values, with the exception of coastal zone sediments.

Assessment of the effects of strong earthquakes on the city of Plovdiv

The assessment of the effects of strong earthquakes is based on procedures for integrating the seismic hazard and the seismic vulnerability of the load-bearing structures of the building stock. The analyses are made for seismic excitation, determined by the analysis of seismic hazard - a deterministic earthquake scenario (expressed in macroseismic intensity). The scenario takes into account the effects of soil amplification, using the geotechnical information for the considered urban area. Based on the collected information about the building stock and the performed analysis, an assessment of the direct damages and destructions is obtained. The distribution of the buildings is graphically presented, respectively by number and by total built-up area, at different degrees of damage. Economic losses are calculated based on the results obtained for damage and destruction in three main groups of buildings. The main task of this study is to quantify the effects of strong earthquakes for the city of Plovdiv based on an accurate assessment of seismic hazard. This information will enable the municipal administration to make informed management decisions about planning of rescue equipment and people, hospital beds, shelter for the homeless people and financial resources to restore the damaged buildings.

Experimental Study on the Dynamic Characteristics of a New Long-Short Pile Composite Foundation under Long-Term Train Load

Long-short pile composite foundation (PC-LSPCF) composed of part-screw pile and cement-soil compaction pile is a new railway foundation treatment method, which has been widely used in high-speed railway construction projects in China. To explore the dynamic characteristics and deformation characteristics of railway PC-LSPCF under long-term train loads, the dynamic characteristics of long piles, short piles, and soil between piles under long-term train loads are tested by an indoor dynamic model test. The dynamic amplification of pile and soil under dynamic load and the temporal and spatial distribution of peak response are analyzed, and the stress and deformation development mechanism of PC-LSPCF under cyclic loading of large-cycle trains is revealed. The results show that the neutral point of the long pile is at 1/2 of the pile length and that of the short pile is at 3/8 of the pile length. The part-screw pile has a certain absorption effect on vibration energy. The deformation of a long-short pile composite foundation under long-term train loads can be divided into three stages: extreme growth, transition, and stability. The train speed is negatively correlated with the cumulative settlement of the long-short pile composite foundation. The higher the train speed, the smaller the cumulative settlement, and the smaller the number of cycles of the N-S curve entering the gentle period. As the number of train cyclic loads increases, the load-sharing relationship of the long pile-short pile-soil system will be redistributed. The research results have important reference significance for the optimization design of high-speed railway foundation treatment.

Application of Probabilistic Seismic Hazard Assessment to Understand the Earthquake Hazard in Attock City, Pakistan: A Step towards Linking Hazards and Sustainability

Within the last three decades, twelve major earthquakes (Mw > 6.0) have jolted Pakistan and contributed to a heavy death toll and an economic loss of billions of dollars, which is immense for any underdeveloped country. Despite the generalized description of seismic hazards in various regions of Pakistan, densely populated cities still require a detailed and integrated vulnerability analysis to overcome the impact of a significant earthquake. This study aims to integrate seismic hazard assessment schemes to understand the vulnerability of Attock city against an earthquake. It initially evaluates the threat from an earthquake due to tectonic activity in the region, splits the region (about 200 km radius) into six seismic zones and uses area source parameters. The ground motion prediction equations compatible with the study area’s seismotectonic environment are also used in this study. Peak horizontal ground acceleration (PGA) and 5% damped spectral acceleration are critical features of ground motions. The site classification is carried within Attock city, indicating the presence of SB (foundation condition with Vs30 = 760 m/s), SC (foundation condition with Vs30 = 400 m/s) and SD (foundation condition with Vs30 = 300 m/s). The peak ground accelerations for a return period of 475 years at the SB, SC and SD sites are estimated as 0.23 g, 0.28 g and 0.30 g, respectively. Uniform hazard spectra are obtained for each site classification at three return periods (475, 975 and 2475 years). Another possible threat can be the local site conditions of the study area, as Attock city exists on the unlithified sediments of upper Pleistocene to Recent alluvial deposits. That is why microtremor recordings are conducted at 20 sites within Attock city to understand the fundamental frequency (f0), horizontal to vertical spectral amplitude (A0) and Kg parameter, a seismic vulnerability index. The values of f0 are found between 0.6 and 9 Hz and A0 is observed between 2.1 and 5 Hz, whereas the Kg is estimated between 0.24 and 20 Hz. Despite evidence of the seismic vulnerability of Attock city, the current building designs and infrastructure development are not synchronized with the uniform hazard response spectra and the soil amplification, thus enhancing the exposure of the study area to disaster during a major earthquake. This study will be instrumental in pre-disaster mitigation strategies for urban planners and policymakers.

Soil–Structure Interaction and Earthquake Input Models Effect on the Structural Response of the Santa Maria Church and Guesthouse Building

ABSTRACT The fragility and capacity of historical structures can be evaluated under seismic loads with the help of a rigid-base assumption by neglecting soil–structure interaction effects. However, this approach may not be accurate because earthquake waves reach the structure by spreading through a soil medium. Wave propagation, soil amplification, and deformability of the subsoil may affect the seismic response of structures. Therefore, soil–structure interaction should be considered in the finite element model, especially in historical structures that require detailed analyses to determine the structural behavior. This paper focuses on the structural behavior of the Santa Maria Church and its Guesthouse Building, which are two of the historical landmarks in Trabzon, Turkey. The church, which has features that distinguish it from similar structures belonging to its period, is one of the important symbols for the city of Trabzon and continues its religious function. The seismic performance of the building was evaluated based on the soil – structure interactions for different soil conditions. The finite element models of the buildings were generated based on earthquake input models (rigid-base free earthquake input, massless-soil-free earthquake input, massed-soil-free earthquake input, and massed-soil deconvolved earthquake input models) and different soil conditions (hard, medium, and soft soil). Time-history analyses were conducted based on earthquake input models (rigid-base free earthquake input, massless-soil-free earthquake input, massed-soil-free earthquake input, and massed-soil deconvolved earthquake input models) and different soil conditions (hard, medium, and soft soil). Time-history analyses were conducted with respect to the horizontal components of the 1992 Erzincan Earthquake. Evaluating the effects of earthquake input models on the seismic responses was done with respect to the obtained maximum displacement and principal stress. The results show that the soil–structure interaction and the soil types have significantly altered the structural responses of both buildings.

Analysis Of Liquifaction Potential Using The Method Microzonation in Coastal Zone at North Aceh District

Liquefaction is a natural phenomenon that occurs when previously sandy soil turns into mush as a result of an earthquake and has the potential to become a natural disaster if not anticipated early. the coastal zone of Dewantara District is included in the earthquake-prone area (referring to the results of previous studies, the value of the seismic vulnerability index is between 0.41 to 18.3 Kg, with the potential for damage caused to be medium and high risk) because most of the area is an area that has alluvial plains a wide beach and located on a tectonic route so that it is estimated that there is a potential follow-up threat after an earthquake occurs, in the form of liquefaction. Determination of the distribution of liquefaction potential due to earthquakes is determined based on data obtained from microtremor measurements. The specific objective of this study is to provide information regarding the potential and vulnerability of liquefaction to Policy Makers/Local Governments in evaluating plotting areas and/or preparing regional spatial plans based on disaster risk reduction/mitigation aspects. Based on the results of the processed data analysis, several important conclusions can be identified in this study. The character of soil vulnerability is related to the value of dominant frequency (f0), soil amplification (A0), and seismic vulnerability index (seismic vulnerability index). This relationship can be used to formulate whether an area has the potential to experience lateral ground motion (liquefaction) which potentially can affect the coastal area of ​​Dewantara District. Based on microseismic data analysis (standard deviation), several disaster-prone zone points were obtained in the north and east of the measurement point. In detail, this is shown by the map of the distribution of SVI values ​​in the Coastal Area which is in the range of 20-100, especially in the north it is at a value above 75, which allows for a higher chance of liquefaction on the condition that there are major earthquakes accompanied by with rock pores filled with fluid.

Investigation of site effect of Lake Van region (eastern Turkey) by using strong ground motion records

The site effect plays a very important role in determining the structural damage that may occur in a possible major earthquake. In this study, seventy-nine strong ground-motion records (M > 4.5) from past earthquake events in the Lake Van region, recorded by 14 accelerometer stations located on dissimilar geological units, were analyzed for local soil properties using horizontal-to-vertical spectral ratio (EHVSR) method. In addition, EHVSR results were compared with Standard Spectral Ratio (SSR) results, which is another method used to determine soil amplification. The obtained predominant period, amplification factor, seismic vulnerability index (Kg) and bedrock depth values were examined. The EHVSR results show that the predominant frequencies of the sites and the amplification factor values were estimated as 0.58–5.77 Hz and 1.84–7.5, respectively. The seismic vulnerability index (Kg) values, which are crucial parameter in hazard assessment, change from 1.6 to 30. The bedrock depths range between 11 and 186 m for the study area. From the results of this study it is found that the damage may be high after a possible destructive earthquake in the study area where the predominant period, amplification, Kg values and bedrock depth are high.

Efficacy and Safety of Nasal Immunisation with Somatostatin DNA Vaccine for Growth Promotion in Fattening Pigs.

This study aimed to evaluate the efficacy and safety of the SS DNA vaccine on growing pigs. Randomly, 147 pigs were divided into four groups, treatment 1 (T1, 3 × 109 CFU/mL, n = 39), T2 (3 × 108 CFU/mL, n = 35), T3 (3 × 107 CFU/mL, n = 35) and control group (phosphate-buffered saline, n = 38). All animals received two vaccinations separated by 45 days and the same diet and management. The results showed that all treatment groups (T1, T2 and T3) had significantly higher slaughter weight (d 185) than the Ctrl group (p < 0.05), and daily gain between 50 and 110 days of age was significantly higher in all treatment groups than in the Ctrl group (p < 0.05). Antibody-positive pigs have significantly higher daily weight gain than that in antibody-negative pigs (p < 0.05). The results of the meat quality analysis showed no significant changes between the P (antibody-positive pigs) and N (antibody-negative pigs) groups. Furthermore, the results showed that antibody titres at 110 and 185 days had a significant positive correlation with the daily weight gain (p < 0.05) and a significant negative correlation with the backfat thickness (p < 0.05). Evaluating the safety of vaccines by PCR amplification of target genes (GS/2SS), faecal, soil and water samples had no target genes detected by PCR amplification in these samples after 5 days, and no GS/2SS were detected in the blood and tissues for the experimental period. Moreover, no abnormalities were found in pathological sections of the P group compared with the N group. In conclusion, SS DNA vaccines can promote the growth of fattening pigs to a certain extent without altering the meat quality, and it has no effects on the safety of the surrounding environment.

New Approach for Developing Correlation of NSPT and Shear-Wave Velocity (Vs): Bantul Case Study

DOI:10.17014/ijog.9.3.395-413Predictions of ground motion levels that, under certain conditions, may cause liquefaction require a sufficient knowledge of the underlying soil characteristics. The utilization of the seismic refraction method applies measurements of the subsurface shear-wave velocities (Vs) as a representation of the properties of stiffness and soil amplification. This study, carried out in Bantul, Yogyakarta Province, Indonesia, is conducted to determine the relationship between Standard Penetration Test N values (NSPT) and Vs by using data from eighty-eight drill sites and twenty-nine seismic reflection investigations with the statistical method, namely the Statistical Gradation Approach. The new equations, developed from a power regression analysis, are applied to all soil and eight soil types: silty sand, sand, gravelly sand, clay, silt, sandy clay, clay sand, and sandy silt. The equations, proposed to predict Vs, show a strong relationship between NSPT and Vs values, which applied to other regions with the shear-wave velocity of <300 m/sec, shallow groundwater depth, and dominant sandy soil.

Regional-scale assessment of earthquake-induced slope displacement considering uncertainties in subsurface soils and hydrogeological condition

Realistic prediction of coseismic landslides is crucial for the design of civil infrastructures and geotechnical systems in seismically active regions. Coseismic landslides are complicated nonlinear and large-deformation processes triggered by ground shaking. To date, many gaps still remain in the scientific understanding of the landslides, particularly in areas lacking information on the subsurface stratigraphy. Analytical methods for estimating coseismic landslides have been based on highly simplified models, where many key influential factors have been overlooked, leading to large uncertainty in using empirical models for landslide prediction. In addition, more evidence recently underscores the necessity of modeling coupled effects between topography and soil amplification, which gives rise to complex wave propagation patterns due to scattering and diffracting of waves within the low-velocity near-surface layers. Neglecting topographic amplification and soil layers could result in significantly underpredicted regional-scale hazards of landslides. In this study, a regional-scale coseismic landslide simulation is carried out using the integral Spectral Element Method (SEM)-Newmark method for Hong Kong Island to quantify the coupled effect of 3D topography, subsurface soil condition as well as hydrogeological conditions. By leveraging extensive geological borehole data, a rigorous statistical model that characterizes uncertainties associated with subsurface soils is established. Influence of key factors that are not well considered in previous coseismic landslide studies, such as variation in irregular rockhead and spatially distributed shear-wave velocity are quantitatively analyzed. Numerical results demonstrate that by rigorously incorporating multiple sources of subsurface soil uncertainties, the total area of landslides in the study region can increase up to 30% compared with benchmark model as evidenced in the physics-based numerical simulation. These case studies will provide a valuable opportunity to revisit key factors that influence coseismic landslides using measured field data.

PROPOSAL OF SEISMIC LOAD FOR TRADITIONAL HOUSES IN KYOTO

In this paper, first, an approximation formula for the amplification factor of the surface soil is proposed. However, since most of the traditional houses are located on good soil condition, the lower limit of surface soil amplification factor 1.23 may be acceptable in reality. On the other hand, the large amplification sites are hardly related to the large shaking area during the Hanaore-fault-zone earthquake which is deeply related to the safety of traditional houses in Kyoto. We also pointed out that increase in bearing capacity of houses may increase the deformation response in case of pulse-like ground motion input.

EVALUATION OF SURFACE SOIL AMPLIFICATION FACTOR FOR SEISMIC DESIGN IN KYOTO CITY AREA

Based on the analysis results of the seismic diagnosis design of traditional houses in Kyoto, it has been considered that the surface soil amplification factor indicated in the guidelines may be overestimated. In this paper, we have analyzed the soil model used in the calculation of the amplification factor in the guidelines and that used in the earthquake damage estimation in Kyoto. As a result, the former soil model is not adequate for Kyoto city area. In addition, the lower limit of 1.23 is sufficient for the amplification factor used in the seismic diagnosis of traditional houses.

Structural challenges for seismic stability of buildings in hilly areas.

Buildings on hills behave dynamically, very different from buildings on flatlands. Due to irregularity in horizontal and vertical planes, they inhibit non-uniform mass and stiffness distribution and are subjected to torsional forces. Studies in various Indian cities in hilly terrains have highlighted serious concerns about existing construction practices. Lack of adequate planning and design has resulted in haphazard development in hilly regions. This state-of-the-art review investigates the factors that influence the structural performance of buildings on slopes while explaining reasons that have caused enormous damages and even collapse of hill buildings in the recent earthquake events. The work discusses building configurations, comparison of various vital building regulations, the major problems encountered in building stocks and associated structural deficiencies on hill slopes. The significance of intensification of earthquake-related losses due to soil amplification has been well documented in the past. Insights from experimental and numerical studies focusing on impacts of topographical and geological factors on damage amplification of hillside buildings are fetched, the results of which are in good corroboration with the findings of post-earthquake surveys and reviews. This study establishes that a higher slope gradient necessitates more slope cutting than a lower slope gradient to get the same building footprint, and many times, this value exceeds the permissible height of slope cutting given in existing building byelaws. Such excessive slope cutting makes the slope weak and unstable. Recommendations and solutions to help enhance structural resilience, reduce disproportionate damages and mitigate failure of hill buildings have been delineated.

Analysis of reinforced soil wall for c–ϕ backfill considering Rayleigh wave

Analytical methods to analyse the seismic stability of reinforced soil walls showing the effect of Rayleigh waves are not available to date. In this study, the pseudo-dynamic approach was used to determine the seismic behaviour of a reinforced soil wall considering the propagation of primary, shear and Rayleigh waves. A mathematical derivation is proposed to obtain the required strength of reinforcements, the critical angle of the failure wedge and the factor of safety (FS) of the reinforced soil wall. The non-linear distribution of tensile force in the reinforcements can easily be obtained for the case of c–ϕ backfill using the results from the present parametric study. A sizable effect of horizontal ground acceleration and soil amplification factor on the required strength of reinforcements, critical angle of failure wedge and FS was observed. The trends found for Kmax and FS clearly emphasise the prominence of Rayleigh wave consideration in the analysis.

Seismic Microzonation Map for a Fixed-Jacket Platform in the Malay Basin

The existence of soft soil in offshore areas may lead to the amplification of vibration received from offshore facilities, especially from the existing fixed-jacket platforms, which were designed without provision to seismicity, as in Malaysian water. Therefore, this study was designed to develop a seismic microzonation map and a soil amplification factor map according to soil type; we propose horizontal response spectra and site coefficient values (Ca and Cv) for the Malay Basin. A one-dimensional nonlinear analysis of layered soil (NERA) was used in the ground response analysis for six selected seismic events under five return periods of 100, 200, 500, 1000, and 2500 years. Soil amplification factors for soil types D and E showed a decreasing trend from 100 years to 2500 years. Two designed horizontal response spectra are proposed (for soil type D and E) under average and envelope conditions; a comparison with ISO showed that the proposed spectra were higher, especially for soil type E. To summarize, the seismicity effect should be included in the development of offshore industries as findings indicated that soil amplification occurred in soil types D and E at the Malay Basin.

Influence of Slope Amplification on the Pile Dynamic Behavior Based on the Data Mining Method

In this article, a centrifuge shaking table model test of anchored stabilizing piles for strengthening landslides was established, and the dynamic response characteristics of the pile–anchor–slope under earthquake action were analyzed. On this basis, combined with the fuzzy gray relational analysis and the rank-sum ratio method, the correlation between the amplification of the acceleration response of the heterogenous slope and the dynamic response of the support structure was explored. Based on the obtained results, relevant suggestions for engineering design were proposed. The results showed that the seismic amplification of the complex soil–rock slope reinforced by the pile–anchor structure was not uniform and the amplification coefficient had strong variability. Among them, the amplification coefficient of the slope, dynamic earth pressure, and dynamic bending moment of the pile near the connection of the pile–anchor cable continued to increase; the correlation between the seismic amplification and the seismic behavior of the pile–anchor structure is different at different positions of the slope. The measurement points with a higher comprehensive ranking of correlation are mainly concentrated in the pile–anchor connection, the middle of the slope, and the high-angle soil–rock interface. It is related to the geometric characteristics of the model and the high seismic amplification of the slope; for the pile–anchor connection part and the high-angle soil–rock structure surface of the slope, the shock absorption measures and grouting strength of the anchor cable’s anchoring section should be considered in the engineering design.

Influence of soil amplification and backfill angle on seismic earth pressure coefficients by pseudo dynamic method

ABSTRACT The knowledge of earth pressure concepts plays a major role to design a retaining wall. The most traditional pseudo-static methodology as proposed by Mononobe–Okabe gives the direct approximation of earth pressure in seismic condition. This paper utilised the pseudo-dynamic methodology to figure out the seismic earth pressure on rigid wall with cohesion less backfill along with considering the effects of time, phase difference, soil amplification factor along with the variation in seismic velocities. The main contribution is the soil amplification and backfill inclination which is not given much attention before. By considering the above factors coefficients the seismic earth pressure against retaining wall is determined. The coefficient of seismic passive earth pressure decreases with the increase of soil amplification keeping other properties as standard values. The value of coefficient of seismic active earth pressure increases with increase of soil amplification. The comparison is also done without taking backfill angle for both coefficients of seismic earth pressures. The influence of all the soil properties like backfill angle, wall friction angle, soil friction angle, non-dimensional parameters are shown in tabular format as well as in the graphical with respect to the soil amplification which is more realistic towards the design.

Unexpected soil amplification effect on seismic performance of highway bridges during the Aegean earthquake of October 2020, Mw 6.6

On October 30, 2020, an earthquake about 70 km away from the city center of Izmir with a 4.3 million population has shaken the city tremendously and has resulted in destruction of many building type of structures due to an unexpected high soil-amplified vibrations very similar to the Mexico City earthquake in 1985. The bridges at the soil-amplified sites has performed in elastic range with no damage at all. In the city of Izmir, the 42 year old twin bridges located on the main transportation route, were tremendously shaken by the earthquake had observed to have no seismic induced damage. Surprisingly twin bridges suffering from the alkali silica reaction (ASR) over the years did not even pound to each other despite the small size of longitudinal gap between them. As it has been known, the past performance of Turkish designed bridges are typically succesfull with almost no damage as observed in the Van 2011 and Sivrice 2020 earthquake mainly due to allowing movements at their joints and to flexible type of framing. The focus of the paper is given to understand the successful performance of bridges and to investigate the non-pounded twin bridges of the Izmir city. In this scope, a bridge inspection has been performed and the twin bridges have been analyzed for the recorded ground motion. The results have indicated that the structures have been subjected to 0.3 g at their vibration modes and the twin bridges have a synchronized motion due to having the identical vibration mode shape with a period of 1.5 seconds