Dimensional Ground Response Analysis Research Articles

One Dimensional Ground Response analysis in Patan: Implications to Damage Pattern due to the 2015 Mw 7.8 Gorkha Earthquake

The 2015 Mw 7.8 Gorkha earthquake caused extensive damages in Kathmandu Valley located about 78 km SE from the epicenter. The damage patterns in the city clearly indicated the subsurface geology of the city had strongly modified the ground motion causing typical damages to tall structures. In this contribution, following one-dimensional approach, a ground response analysis is performed in Patan utilizing the deep borehole, shear wave profile and dynamic soil properties adopting both equivalent linear and non-linear approaches. The results of both equivalent linear and non-linear analyses were compared with the measured ground motions at soil site. It is found that the non-linear analysis better simulates the deamplification of the peak ground acceleration and strong shaking at longer period than the equivalent linear analysis. The obtained results confirm that the deamplification of PGA was due to the strong non-linear behavior of the fluvio-lacustrine deposits.

Liquefaction Potential Assessment of Guwahati City Using One Dimensional Ground Response Analysis

Guwahati city which lies in the North Eastern region of India, falls in the highest seismic risk zonal level i.e. zone V in India. However, there are very few works on seismic hazard analysis of Guwahati soil considering the local site effects. The effect of large modifications in seismic waves that occur due to variation in soil properties near the surface of the earth is of great importance in geotechnical earthquake engineering. Seismic soil liquefaction, a soil seismic hazard, is evaluated in Guwahati city in terms of factor of safety against liquefaction along the soil profiles using ground response analysis. One dimensional ground response analysis has been conducted using equivalent linear and non linear method using the Deepsoil software. The input motion of 2011 Sikkim earthquake (Mw = 6.9) having bedrock PGA of 0.152 g at 30 m depth is considered. A comparative study has been made of the equivalent linear and non linear analysis in terms of surface PGA (g), maximum strain (%), maximum stress ratio and liquefaction potential using soil profiles of Guwahati city. It has been observed that stiffer soil layer results in similar PGA from both the analysis however non linear analysis generally gives a lesser surface PGA than by equivalent linear analysis. Non linear analysis generally gives a higher strain range and a lower maximum stress ratio as compared to the equivalent linear method. A slightly higher factor of safety is obtained using non linear analysis than using equivalent linear analysis. A soil database of 200 bore holes was used for the study. Spatial distribution of soil liquefaction potential is presented in the form of GIS based maps of factor of safety values.

Reliability on ProSHAKE 2.0 in the Assessment of One Dimensional Ground Response Analysis through Verification Example

It is understood from the recent destructive earthquakes, topography, nature of the bedrock and geometry of the soil deposits are the prime factors that made modifications to the underlying earthquake motion. The influence of such confined soil states on the strong earthquake motion plays a significant task in accessing the uniqueness of ground action. In this paper, the response of the soil layers to the earthquake action of the bedrock directly under it is determined. The analysis is done through frequency domain approach. Pro-shake software 2.0 is used to arrive the reliability of the ground response study. A wide variety of output parameters such as time histories of acceleration, velocity, displacement, shear stress, shear strain, response spectra and maximum amplitude of various parameters with depth are plotted and the other scalar parameters such as peak acceleration, peak velocity, peak displacement, RMS acceleration, arias intensity, predominant period and bracketed duration was computed.

Determination of Shear Wave Velocity in Offshore Terengganu for Ground Response Analysis

Amount of vibration received in any location can be analysed by conducting ground response analysis. Even though there are three different methods available in this analysis, One Dimensional ground response analysis method has been widely used. Shear wave velocity is one of the key parameters in this analysis. A lot of correlations have been formulated to determine shear wave velocity with cone penetration test. In this study, correlations developed for Quaternary geological age have been selected. Six equations have been adopted comprise of all soil and soil type dependent correlations. Two platforms sites consist of clay and combination of clay and sand have been analysed. Shear velocity to be used in ground response analysis has been obtained. Results have been illustrated in graphs where shear velocity for each case has been plotted. In avoiding under or over predicting of shear wave velocity, the average of all soil and soil type dependent results will be used as final Vs value.

Investigation of the soil amplification factor in the Adapazari region

Turkey is located on the highly active Eurasian plate. A very active strike slip fault, the North Anatolian Fault Zone (NAFZ), crosses Turkey from east to west; earthquakes occurred on this fault on August 17, 1999 (Kocaeli) and November 12, 1999 (Duzce). Regional geology and subsoil conditions can significantly change the characteristics of ground motion. For this reason, determining soil amplification during an earthquake, especially for soft soils, is a very important topic for researchers. In this study, one dimensional ground response analyses were performed for selected Adapazari sites using the August 17, 1999 Kocaeli earthquake strong ground motion record with SHAKE2000 software. Soil characteristics and depth to engineering bedrock at the selected sites are different and the observed level of structural damage at these sites during the Kocaeli earthquake was also different. Calculated soil surface response spectrums at these sites were compared with the recommended design spectra of the Turkish Earthquake Code and the Eurocode 8. According to one dimensional ground response analyses, the calculated response spectra of the selected sites exceed the recommended design spectra of the Turkish Earthquake Code and the Eurocode 8. Calculations show that higher amplification ratios occur at higher periods due to soil behaviour. Results of this study indicate that local geological conditions may amplify ground motion at some periods and, due to this amplification, the calculated response spectra may exceed the recommended design spectra. Therefore, it is clear that local site conditions must be considered for earthquake-resistant engineering designs on soft alluvial soil deposits.

Evaluation of the Effectiveness of Theoretical 1D Amplification Factors for Earthquake Ground-Motion Prediction

We investigate the use of site factors derived from theoretical one- dimensional ground-response analyses as a means by which to estimate seismic site effects for earthquake ground-motion prediction. We review a set of theoretical site factors derived from equivalent-linear analyses for specific geologic categories in the Los Angeles area and the San Francisco Bay area. The theoretical site factors are a function of the peak horizontal acceleration for the reference rock site condition and the depth to firm material (taken as depth to the 1 km/sec shear-wave isosurface). We apply the site factors to predict the response spectral acceleration of ground motions at recording sites in a manner that mimics how they would typically be used in engineering practice: empirical ground-motion prediction equations are used to estimate a reference (rock) spectrum that is then modified by using the theoretical site factors. Analysis of residuals between the data and model predictions indicates that the theoretical site factors are able to capture the average effects of sediment nonlinearity. The analyses also show that short-period spectral accelerations are underpredicted and that long-period spectral accelerations are overpredicted. The underprediction at short periods may result from overestimation of a soft-to-firm reference rock correction factor that is needed to apply the site factors. The overprediction bias at long periods varies with depth, suggesting that the depth term in the site factors may not fully account for the effect of basin geometry at long periods.

Comment on "Nonlinear Soil-Site Effects in Probabilistic Seismic-Hazard Analysis" by Paolo Bazzurro and C. Allin Cornell

The authors are to be commended for presenting clear and practical solutions to a problem that has long been vexing to engineers and seismologists—how to link probabilistic assessments of ground-motion hazard with the results of geotechnical ground-response analysis. The term “ground- response analysis” is used here to refer to one-dimensional modeling of shear-wave propagation through a soil column, the response of which will generally be nonlinear for engineering design applications. The purpose of this discussion is to point out some of the key assumptions made in the development of the authors’ solution and to offer a preliminary comparison with an alternative ground-response implementation procedure. The authors present two procedures for implementation of ground-response analysis results into probabilistic seismic- hazard analysis (psha). One procedure involves convolution of amplification factors (af) calculated from ground- response analysis with a site-hazard curve developed for reference-site conditions (usually rock). This solution is given by equations (2)–(4) for the case in which the amplification at frequency f [af( f )] is conditioned only on rock hazard for frequency f , and in equations (5)–(7) for the case in which af( f ) is conditioned on the rock-hazard curve at both frequency f and the fundamental frequency of the soil column ( f sc). The second procedure involves modifying the median and standard deviation of a ground-motion intensity measure estimated from an attenuation relationship for rock- site conditions. The median is modified to account for ground-response effects, including sediment nonlinearity, using equation (14). Standard deviation is similarly modified using equation (15). The modified median and standard deviation are then directly used within the hazard integral in lieu of those from the attenuation relation for rock. A critical assumption implicit to both of these procedures is that site effects are correctly simulated by one- dimensional ground-response analysis. More specifically, this …