Numerical Modeling of Near Fault Seismic Ground Motion for Denali Fault

An effective earthquake (Mw 7.9) struck Alaska on 3 November, 2002. This earthquake ruptured 340 km along Susitna Glacier, Denali and Totschunda faults in central Alaska. The peak ground acceleration (PGA) was recorded about 0.32 g at station PS10, which was located 3 km from the fault rupture. The PGA would have recorded a high value, if more instruments had been installed in the region. A numerical study has been conducted to find out the possible ground motion record that could occur at maximum horizontal slip during the Denali earthquake. The current study overcomes the limitation of number of elements to model the Denali fault. These numerical results are compared with observed ground motions. It is observed that the ground motions obtained through numerical analysis are in good agreement with observed ground motions. From numerical results, it is observed that the possible expected PGA is 0.62 g at maximum horizontal slip of Denali fault.

A Practical and Effective Solution to Earthquake (EQ) Catastrophe

About 50-year direct observation indicated that any civil structure founded in/on rock do not get damage from earthquakes without tsunami effect. The main reason behind this is that the modulus of elasticity of saturated rocks is million times greater than that of saturated soil units. Furthermore, all saturated soil units are susceptible to liquefaction at varying degrees. Based on the past observations, none of the structures founded in/on rocky ground, has been affected from the recent destructive earthquakes studied by the authors in/and abroad. The studied earthquake cases highlighted again that the civil structures in/on rocky grounds, even adjacent to the epicenter, have not been affected from shaking of destructive earthquakes. In Turkey, the land needed for housing is one hundredth of the country. However, 57% is proper for housing. The remaining 43% consists mainly of forest, restricted zones, rugged terrains, and soil land which bears essentially plains and very locally landslides. Thus, earthquake disasters could be alleviated by implementing practical land use planning.

Predicting Probability of Liquefaction Susceptibility based on a wide range of CPT data

In the present study, three efficient soft computing techniques i.e. GP, RVM, and MARS are utilized to predict the probabilistic liquefaction susceptibility of soils based on reliability analysis. For this, a sum of 253 Cone Penetration Test (CPT) data of nineteen major earthquakes occurred between 1964 and 2011 has been collected from the literature. Six liquefaction parameters such as corrected cone penetration resistance, total vertical stress, total effective stress, maximum horizontal acceleration, magnitude moment, and depth of penetration. To evaluate the overall performance of the proposed models, rank analysis has been carried out. Based on the values of performance indices, the GP model outperforms the other two models in terms of RMSE=0.15, R2 =0.77, and VAF=76.86 in the training stage while the same has been found 0.14, 0.81, and 80.46 in the testing phase. Also, the Rank Analysis confirms the superiority of the GP model in predicting the probability of liquefaction susceptibility of soils at all stages.

Analysis of a Monopile under Two-Way Cyclic Loading

A large diameter monopiles are commonly used as an offshore wind turbine (OWT) foundation to withstand lateral cyclic loads due to wind and wave action. In the present study, a two-dimensional finite element analysis was performed to evaluate the behavior of a monopile under two-way lateral cyclic loading. The centrifuge test carried out on a 0.7m diameter pile was being used to validate the constituent model. The parametric study was carried out on a monopile by varying the slenderness ratio (L/D = 4, 5, and 6) and load amplitudes (30%, 40%, and 50% of the ultimate pile capacity). From the load-displacement response of a monopile, it was observed that the measured accumulated displacement increases drastically for the first load cycle. For a given embedded length, the lateral displacement was observed to increase with an increase in load amplitude. For an embedded length of L/D = 4, the increase in load amplitude from 30% - 40% resulted in an increase in lateral displacement to 24%.

Modelling of Seismic Liquefaction Using Classification Techniques

Liquefaction susceptibility of soil is a complex problem due to non-linear behaviour of soil and its physical attributes. The assessment of liquefaction potential is commonly assessed by the in-situ testing methods. The classification problem of liquefaction is non-linear in nature and difficult to model considering all independent variables (seismic and soil properties) using traditional techniques. In this study, four different classification techniques, namely Fast k-NN (F-kNN), Naïve Bayes Classifier (NBC), Decision Forest Classifier (DFC), and Group Method of Data Handling (GMDH), were used. The SPT-based case record was used to train and validate the models. The performance of these models was assessed using different indexes, namely sensitivity, specificity, type-I error, type-II error, and accuracy rate. Additionally, receiver operating characteristic (ROC) curve were plotted for comparative study. The results show that the F-kNN models perform far better than other models and can be used as a reliable technique for analysis of liquefaction susceptibility of soil.

A Re-Look Into Modified Scaled Distance Regression for Prediction of Blast-Induced Ground Vibration

Underground blasts are conducted for deep excavations, tunneling, or mining activities. Scaled distance regression analysis is performed in industry to estimate peak particle velocity from charge weight and distance. For addressing the uncertainties in estimating safe charge weight for controlled blasting, 95% confidence expression is generally used. For addressing inaccuracies arising from superimposition of blast waves in multi-hole blasting when using attenuation equation developed from single-hole blast data, a modified approach was proposed in literature. This article presents comparisons to establish that industrial practice of scaled distance regression would be as satisfactory as the proposed modified approach, when various performance measures (including parsimony) are considered together. Furthermore, industrial practice of using 95% confidence expression generated from sufficient data (say, 40 numbers) would result in safe charge weight estimation, whereas modified scaled distance approach (mean expression) could still result in few non-conservative values.

Seismic Evaluation of a Profile of Volcanic Ash From the South American Andes

Although soils derived from volcanic ash are only a small portion of the soils that cover the world's surface, cities have developed on some of these soils. This makes their study interesting, especially since soils derived from volcanic ash have special characteristics including a high void ratio, liquid limits that can be greater than 100%, and shear wave velocities close to 150 m/s. Cities on these soils in the South American Andes are in areas with frequent and intense seismic activity making an understanding of how earthquakes affect these soils a matter of importance. This paper analyzes site response by the equivalent linear method, taking into account the variability of these soils. The Monte Carlo method was used for degradation of the shear modulus and damping curves. The results of this study show factors that amplify spectral acceleration can cause this measurement to become greater than four. In addition, the authors found that maximum spectral accelerations are functions of high plasticity indexes whose influence increases when shear wave velocities are between 175 and 225m/s.

CodaQback

Attenuation study of a province is considered as a basic quantity for seismic hazard assessment. It has already been established that the study of two physical processes, namely the seismic sources and propagation of the waves, is essential for seismic-hazard mapping. Additionally, attenuation plays an important role towards scaling seismic hazard. Accordingly, a computational tool entitled CodaQback is presented. Based on back scattering model, this versatile software is equipped with user-friendly graphical user interface. It also allows quick picking of phases for computing coda attenuation parameter. All outputs after each execution step in CodaQback are efficiently exported step-wise into a separate folder in Excel and text formats. To validate the computing tool, it is tested in real data analysis and there is found to be good matching of computed values with already established ones. It is envisioned that this package will enable user to derive quick and reliable estimation of coda attenuation parameter irrespective of geological and geo-morphological units.

Characterization of Ground Response and Liquefaction for Kathmandu City Based on 2015 Earthquake Using Total Stress and Effective Stress Approach

This chapter presents the seismic vulnerability of Kathmandu City (Nepal), based on Nepal 2015 earthquake, in terms of the ground response and liquefaction potential. The spatially well-distributed 10-boreholes and ground motions of Mw 7.8 Nepal 2015 earthquake recorded at five different stations were adopted for the analysis. The range of peak ground acceleration and peak spectral acceleration were in the order of 0.21g-0.42g and 0.74g-1.50g, respectively. Liquefaction potential of the sites were computed using both semi-empirical approach and liquefaction potential index (LPI). LPI shows that the 6 sites out of 10 sites are at high risk of liquefaction.

Liquefaction Susceptibility Assessment Using Geotechnical and Geological Manners of Northern Thailand

Soil site investigations such as boring logs, basic soil properties, spectral analysis of surface wave, and the examinations of geologic and geomorphologic were performed in Mae Lao area to investigate the susceptibility of liquefaction after the 6.2 Mw Chiang Rai Earthquake 2014. The study area was found to lay on a complex geological formation and geotechnical behavior with a condition of the high groundwater table. Being located on a high seismicity area (intensity V-VII Mercalli) governs the study area as a concern for high liquefaction hazards. Liquefaction susceptibility-based compositional criteria, soil resistance, and geologic criteria have been established, and consequently, the character of liquefaction potential is defined.