In order to propose an estimation formula for damage rates of water distribution pipes, the damage to water distribution pipelines caused by the Great East Japan Earthquake (formally the 2011 Touhoku-taiheiyo-oki Earthquake) is analyzed based on the database of pipeline network and damage to the pipes prepared by the Sendai City Waterworks Bureau.
Influences of topographical classification, pipe material and diameter to the water pipe damages are firstly analyzed. A damage rate defined by the number of damage occurrences per unit length (km) is utilized as a damage index in this paper. As a result of the analyses, the topographical classification is found to be the most influential factor among all. The damage rate of the artificially cut-and-fill grounds (mostly used as residential districts) is almost three times large as compared to that of the alluvium (flat) grounds. Furthermore, it is found that thickness of the fill and/or distance between the damage location and cut-and-fill boundary strongly affect the damage rate. Namely, the depth of fill from 3 to 7 m and the distance from 10 to 20 m (fill side) show the highest damage rate.
The relationship between the damage rates and surface ground motions (velocities) is analyzed in the same way, and a standard damage rate curve is established, that gives the damage rates in the alluvium (flat) grounds at some surface ground velocities.
Based on the result of the analyses, this paper describes a proposed estimation formula for the damage rates of water distribution pipes due to earthquakes.
The survey was carried out again two years later on buildings that were completely surveyed just after the 2016 Kumamoto earthquake. The purpose of the survey is to quantify the relationship between damage level, construction year, structure type, etc. and the usage of the buildings after two years. This study revealed that about half of the buildings surveyed areas in Mashiki town do not exist. In addition, it was found that the continuous use rate of buildings is higher as the construction year of the affected building is newer, or the damage level is lower. Also, 37% of the continuously used buildings have been repaired, and some of buildings judged to be no damage by the exterior survey have also been repaired. 84% of newly constructed buildings were wooden structure and 71% were single story.
Effects of magnitude, hypocenter distance and subsurface soil structure on the spatial variability of ground motions between adjacent sites are examined using observed records from the Chiba array and pairs of the K-NET and the KiK-net which are adjacent to each other. The statistical analysis of coherence and standard deviation of Fourier spectrum ratio of the ground motion show that the spatial variability of ground motion depends on magnitude, distance and subsurface soil structure. In particular, subsurface soil structure has the most significant influence on the variability. The decrease in S-wave velocity of subsurface soil causes a reduction of spatial coherence. And we also found that the longer the distance between observation sites, the deeper the soil properties effects to the spatial variability of ground motions.
This paper describes liquefaction response behaviors for foreshock, main shock and aftershocks of the 2011 Off the Pacific Coast of Tohoku Earthquake. Based on analyses of seismic observation records at a plate-shaped building constructed in the liquefied area at Chiba City of Chiba Prefecture, it focuses on change of properties of waveform at the ground surface and change of predominant frequencies of a soil-pile-foundation-superstructure system with spectral ratio of building to ground. The results of study were recognized following phenomena;
1) A liquefaction phenomenon occurred on the main shock and the maximum aftershock from ground records. From change of predominant frequencies of a soil-pile-foundation-superstructure system, the soil stiffness was almost recovered two hours after the maximum aftershock, which means an excess pore water pressure became low.
2) On the main shock and the maximum aftershock, predominant frequencies of a soil-pile-foundation-superstructure system were low and spectral ratio amplitude of building to ground was small, due to liquefaction phenomenon.
Strong ground motions recorded by the servo velocity seismographs deployed in Minoh City during the earthquake in Osaka-Fu Hokubu on 18 June 2018 (MJMA 6.1) were shown and compared with that published by public institutions in the neighboring region. Furthermore, the velocity records were partially clipped because ground motions exceeded the limitation of measurement of the seismograph, therefore the clipped records were restored using the newly proposed method.
It was shown that the area evaluated as JMA Seismic Intensity level 6 lower and/or approximately up to 100 cm/s in 5% pseudo velocity response spectrum may extend to Kayano located in the central part of Minoh City. It was found from the analysis results such as the band-pass filtered waveforms at a frequency band of 0.3-0.8 Hz, its particle motions, and the Fourier spectral ratios to an observation site located in the mountain area that, in the later phase behind the direct S-wave part, the amplitude in the east-west direction is greater than that in the north-south direction at the observation sites in the graben region.
This study reports on a horizontal bi-axial shake table test using a multi-supported piping system with a damaged support structure. After fracture of the support structure, the seismic response amplitude of the piping increased but that of the piping system remained relatively stable. The stress distributions on the piping before and after the fracture of the support structure, and the 45-directional stress on the vertical piping, were examined. In addition, the seismic response analysis of the shake table test was conducted. The numerical model of the response analysis, in which the fractured support structure was removed, effectively predicted the piping response after the fracture.
The authors are conducting a micro-tremor observation in Yangon City to evaluate the site effect (amplification function) of the ground. Yangon City is located at the confluence area of two large rivers, Yangon River and Bago River. In Yangon City, numbers of boring surveys have been conducted down to the engineering bedrock several tens of meters deep. However, exploration of the deep underground structure, under the engineering bedrock, using reflection method, gravity exploration, etc. have not been conducted, and there is little information about it. Therefore, in the micro-tremor observation we focused on long period micro-tremor (microseisms) which reflect the deep underground structure at several hundred meters to several kilometers deep. In this paper, we describe the H/V spectrum obtained by the single point (three components) micro-tremor observation and the phase velocity dispersion curve obtained by the array observation. In addition, we will describe estimation of the deep underground structure based on both results.
In prediction of seismic intensity distribution maps for scenario earthquake, several cases of source parameter settings are adopted in order to incorporate epistemic uncertainty associated with prediction results. In the previous study, the authors proposed a mode decomposition method to evaluate spatial variation and correlation reflected in a set of seismic intensity distribution maps by use of singular value decomposition technique. In this study, the proposed method was applied to four kinds of scenario earthquakes which can be potentailly caused by two kinds of reverse faults (Eastern Boundary Fault Zone of the Ishikari Lowland: 12 cases and Fukaya Fault Zone: 12 cases) and two kinds of left strike-slip faults (South Western segment of the Yamazaki Fault Zone, main part: four cases and Central North segment of Fault Zone of the Itoigawa-Shizuoka Tectonic Line: eight cases). Spatial variations derived as left-singular vectors in modal forms are visualized. Dominant factors, such as moment magnitude, spatial configuration of asperities and forward directivity effect, were listed for each mode with reference to source parameter settings and righ-singular vectors characterizing the seismic distribution of each case.