Detection of 2011 Tohoku tsunami induced changes in Rikuzentakata using Normalized Wavelet Fusion and Probabilistic Neural Network

Mehrotra Akansha and Singh Krishna Kant

On March 11, 2011 an earthquake of magnitude 9.0 occurred off the northeast coast of Japan. The earthquake was followed by a massive and destructive tsunami that hit the coastal areas of Japan. In this paper, tsunami induced changes in Rikuzentakata city using ASTER VNIR satellite images of the area are identified using the proposed method. The proposed method is based on Undecimated Discrete Wavelet Transform (UDWT) and Probabilistic Neural Network (PNN). UDWT is applied on two difference images log ratio and Change Vector Analysis image to obtain a multi resolution analysis of the difference images. The wavelet decompositions are fused together using normalized wavelet fusion rule to obtain a change map. The changes are then classified into different change classes using PNN to create a classified image showing different change classes. The different change classes represent the changes in urban area, vegetation and water. The performance of the method was tested using different accuracy elements like error matrix, overall accuracy and kappa coefficient. The results ensure that the method has high accuracy and identifies almost all the tsunami induced changes.

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Wavelet based Denoising of Non-Stationary Strong Ground Motion Signals using Bayes Technique

Beena Mol M., Prabavathy S. and Mohanalin J.

Accelerograms are the important source of strong ground motion information in the field of earthquake engineering and engineering seismology. The strong ground motion records are always contaminated by low and high frequency disturbances called noise. The presence of noise in the signal of interest of strong ground motion will affect the effective use of accelerograms for further earthquake and seismological engineering applications. Therefore the noise present in the accelerograms has to be processed and removed. In this study, time-frequency representation of accelerograms using wavelet transforms has been used for removing the noise. The efficiency of Bayes technique in determining the threshold separating the wavelet coefficients of noise and of the signal of interest in accelerograms has been proposed. The efficiency of Bayes threshold in denoising the strong ground motion has been experimentally investigated using synthetic and real accelerograms. The real accelerograms used in this study are recorded from the earthquakes of high magnitude with high frequency pulses. The quality of the signals denoised using Bayes threshold has been compared with the denoised signals using universal and sure thresholds.

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Numerical Simulations of Tsunamis in the East Sea, Korea

Cho Yong-Sik

A composite numerical model consisting of the propagation and associated run-up process models is presented in this study. The governing equations are the linear shallow-water equations in the propagating model, while they are the nonlinear shallow-water equations in the run-up model. In the propagation model, the physical dispersion is mimicked by the numerical dispersion resulting from a finite difference scheme. In the run-up model, a second-order upwind scheme is employed to predict the run-up heights of tsunamis along the Eastern Coast of the Korean Peninsula and the obtained run-up heights are compared with the available field observed data and numerical results of a first-order upwind scheme. The target events are both 1983 Central East Sea and 1993 Hokkaido Tsunami events. The predicted maximum run-up heights agree reasonably with field observed run-up heights.

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Characteristics of Landslides occurring below Warning Criteria for the Last Ten Years in Korea

Lee S.W., Kim G., Yune C.Y., Choi B.K. and Shin J.H.

Landslide damage caused by localized heavy rainfall and storms has been frequently reported in many areas throughout the world. As urban life and infrastructures have increasingly expanded into mountainous areas, losses for human and property from landslides have become common occurrences. In this study, the characteristics of rainfall-induced landslides are investigated based on 455 landslides database set. Thirty-three factors such as rainfall, soil, forest, geological and topographic information that may affect landslide occurrences were included in the database. The rainfall threshold for landslide occurrence of Korea Forest Service that is the most widely used in domestic area is employed as landslide-inducing criteria in order to detect erratic occurrences of landslide. Finally relations between landslides occurred below rainfall thresholds and specific factors affecting landslide occurrences were examined to understand characteristics of such landslide occurrences.

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Assessment of soil erosion probability in Kodaikanal, India using GIS and remote sensing

Bagyaraj M., Ramkumar T., Venkatramanan S., Chung S. Y. and Gurugnanam B.

Soil erosion hazard zone was demarcated with the help of Remote sensing data. Geographical Information System (GIS) has been integrated with the weighted index overlay (WIO) methods for the identification and delineation of soil erosion susceptibility zones in the Kodai Hills. The parameters considered for identifying the soil erosion probability zone of factors that are considered to influence the soil erosion are: soil series, land use/land cover, normalized difference vegetation index (NDVI), landform, drainage density, drainage frequency, lineament density, slope and relative relief generated using the resource sat (IRS P6 LISS IV MX) data and survey of India (SOI) toposheets of scale 1:50,000 and integrated them with weight index overlay (WIO) model based on GIS to identify the soil erosion probability zone of the study area. In the present analysis the area is divided into three zones representing low (38.12%), moderate (50%) and high (11.89%) erosion proneness. The high soil erosion probability zone was observed in areas with high terrain alteration, high relief and slopes with the intensity and duration of heavy precipitation during the monsoons.

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The Prediction of Blasting Vibration Waveform and its use

Chen Shihai, Zhang Wei , Zhang Zihua and Lin Congmou

The propagation of surface blasting vibration wave can be considered according to geometrical and viscoelastic attenuation of vibrations. The viscoelastic attenuation can be estimated by use of the Kjartansson theory and the distance from the source to the point of interest. The geometrical attenuation can be considered combined with the geometric similarity principle of explosion and the surface particle vibration velocity is supposed to have the Sadov's formula form that is widely applied at present. Hereby, the waveform function of surface vibration is constructed. This time history waveform function prediction model of blasting vibration can synthetically reflect the amplitude attenuation, spectrum structure and duration of blasting vibration propagation. The mathematic model of blasting vibrations of multi-holes millisecond blasting is also constructed according to single hole blasting vibration waveform characteristics and system response transfer function. Blasting parameters can be optimized combining this prediction model with blasting vibration safety criterion.

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Allocation of Infrared Imaging Sensor for Fire Detection

Min Cheol Jeon, Hyun Seung Song, Jae Hong Oh and Yang Dam Eo

The optimal allocation of a fire surveillance system for a mixed urban and forest area was studied. A fire detection probability estimation algorithm was developed taking into consideration the weather conditions, forest environmental factors and infrared imaging system specifications. For computing the visible area reduction caused by forest, the canopy closures of trees were measured in the test field. Infrared energy transmittance for particular temperature and precipitation values was used as an input parameter for the generation of detection probability. We also introduced an optimum equipment allocation method that maximizes the computed detection probability for evenly distributed locations of the equipment. The experiment showed that the automated method produces better results than the manual allocation method. We expect this method to contribute to reducing the costs of installing infrared imaging-based early fire alarm systems.

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Response of Shallow Foundation in Rocks subjected to Underground Blast Loading using FLAC3D

Kumar Ranjan, Choudhury Deepankar and Bhargava Kapilesh

Blast loadings caused by terrorist activities, mining, quarrying, construction activities and all other operations which involve the use of explosives for rock breaking etc. can create severe problems to adjacent shallow foundations. A better understanding is required to protect shallow foundations to prevent failure of supported superstructure subjected to underground blast loadings under different rock conditions. Peak particle velocity (PPV) is important parameter in evaluating underground blast loading. PPV should be within permissible limit to avoid damage to the foundation. There are various methods available to evaluate PPV. The aim of the paper is to investigate the applicability of two methods namely Drake and Little7 and IS 692210. Typical square shaped shallow footing is modeled in three types of rocks namely, basalt, limestone and shale under saturated conditions. Finite difference based FLAC3D software is used to simulate the underground blast loads for foundations in rocks. Peak stress is calculated by using aforementioned two methods. Responses below footing have been obtained. Results in terms of time history records for pore pressure ratio, stresses, displacements, velocities and accelerations are presented. Free field peak stresses for various rocks calculated from Drake and Little7 method are greater than those calculated from IS 692210. PPV below foundations has been measured by these methods and compared with threshold limit for damage. This study shows that FLAC3D results provide useful information on behavior of shallow foundations in rocks subjected to underground blasts and can be used for practical design of such foundations.

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Stress Inversion and Prediction of Casing Deformation for X832 Block in Daqing Oilfield based on Genetic Algorithm

Ji Youjun, Yue Jiannan and Liu Jun

Dynamic analysis of ground stress flied of oil and prediction of casing deformation are directly influenced by the accuracy of initial ground stress. There are many factors that have been influenced in reservoir stress that is a complex non- steady stress field. And it generally cannot be given directly to the reservoir initial ground stress field distribution but direct measurement has too much workload. However, it is not realistic to measure the majority of the oil region. So, numerical analysis being an effective means obtains stress field. Mathematical and mechanical models of development process of reservoir, including solving ideas of models, are obtained by the basic theory of fluid mechanic and elastic-plastic mechanic. Reservoir initial stress should be obtained by genetic algorithm and the calculation models of the reservoir initial stress are determined by optimization objective function of measuring point of displacement in reservoir. The reservoir stress in Daqing Oilfield X832 block and casing deformation during 20-year development process are predicted by geological model inversion.

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Stability analysis of left slope of Baihetan hydropower station in Jinshajiang River

Guan Rong, Jun Peng, Taiqing Lin, Di Hou and Gaung Liu

The proposed Baihetan hydropower station is in the downstream of Jinsha River. The maximum dam height is 289 m and the total installed capacity is 14004 MW. It is the second largest hydropower station in China at present. Geological condition of the river valley in Baihetan hydropower station is complex and the slope of two banks is high and steep. Discontinuity in the slope is well developed and several potential sliding blocks can be formed by these discontinuities. Stability of large-scale blocks in the left bank is one of the main engineering geological issues in Baihetan hydropower station. Based on research on geologic feature and spacial partition of key discontinuity, mechanical properties of main discontinuities are proposed. Irregular wedge analysis method is proposed based on classical wedge limit equilibrium method. According to analysis of geological condition and stability calculation results, reinforcement of the slope in the left bank is proposed for design. (1) The left bank is an oblique consequent slope. The typical sliding mode in the left bank is the potential unstable block consisting of a bottom slipping surface which is gently inclined interformational disturbed belts and intraformational fault zones that dip to SE (C3-1, LS337 etc.), the cutting edges of the lateral surface which are tension cracks with steep dip and faults that dip to NW (F33, f320, f114, etc.) and the cutting edges of the posterior surface which are tension cracks that dip to NE-NNE (J101, J110 etc.). (2) LS337 and C3-1 in the left bank are mainly rock fragment mingling little mud and moist. They are the controlling discontinuities for stability of blocks in the left bank. (3) Stability of blocks 1# and 2# is bad so they are key reinforcement object. It is suggested that concrete plug, excavation, anchoring, drainage in the slope and slope protection are used to ensure stability of the slope. For blocks 1# and 2#, concrete plug and drainage in the slope is recommended.

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