Effective Stress Analysis for Evaluating the Effect of the Sand Compaction Pile Method During the 1995 Hyogoken-Nambu Earthquake

The effect of the sand compaction pile method as a countermeasure for liquefaction mainly consists of three factors: increase in the density, increase in the horizontal effective stress and stabilization of microstructure. Proper evaluation of the effect of improvement is important for estimating the seismic behavior of the ground improved by the sand compaction pile method. How to incorporate the effect and its factors into an analytical model was investigated by simulating the seismic behavior of the ground at two sites during the 1995 Hyogoken-Nambu earthquake with the effective stress analysis method “FLIP.” It was found that not only the increase in the density but also increase in the horizontal effective stress were important in explaining the effect of the sand compaction pile method. Moreover, a model taking account of both sand piles and the improved ground between them suggested a possibility of reproducing the behavior of improved ground under large ground motions more properly

PRENOLIN project. Results of the validation phase at sendai site

One of the objectives of the PRENOLIN project is the assessment of uncertainties associated with non-linear simulation of 1D site effects. An international benchmark is underway to test several numerical codes, including various non-linear soil constitutive models, to compute the non-linear seismic site response. The preliminary verification phase (i.e. comparison between numerical codes on simple, idealistic cases) is now followed by the validation phase, which compares predictions of such numerical estimations with actual strong motion data recorded from well-known sites. The benchmark presently involves 21 teams and 21 different non-linear computations. Extensive site characterization was performed at three sites of the Japanese KiK-net and PARI networks. This paper focuses on SENDAI site. The first results indicate that a careful analysis of the data for the lab measurement is required. The linear site response is overestimated while the non-linear effects are underestimated in the first iteration. According to these observations, a first set of recommendations for defining the non-linear soil parameters from lab measurements is proposed. PRENOLIN is part of two larger projects: SINAPS@, funded by the ANR (French National Research Agency) and SIGMA, funded by a consortium of nuclear operators (EDF, CEA, AREVA, ENL)

Psychiatric disorders and clinical correlates of suicidal patients admitted to a psychiatric hospital in Tokyo

<p>Abstract</p> <p>Background</p> <p>Patients admitted to a psychiatric hospital with suicidal behavior (SB) are considered to be especially at high risk of suicide. However, the number of studies that have addressed this patient population remains insufficient compared to that of studies on suicidal patients in emergency or medical settings. The purpose of this study is to seek features of a sample of newly admitted suicidal psychiatric patients in a metropolitan area of Japan.</p> <p>Method</p> <p>155 suicidal patients consecutively admitted to a large psychiatric center during a 20-month period, admission styles of whom were mostly involuntary, were assessed using Structured Clinical Interviews for DSM-IV Axis I and II Disorders (SCID-I CV and SCID-II) and SB-related psychiatric measures. Associations of the psychiatric diagnoses and SB-related characteristics with gender and age were examined.</p> <p>Results</p> <p>The common DSM-IV axis I diagnoses were affective disorders 62%, anxiety disorders 56% and substance-related disorders 38%. 56% of the subjects were diagnosed as having borderline PD, and 87% of them, at least one type of personality disorder (PD). SB methods used prior to admission were self-cutting 41%, overdosing 32%, self-strangulation 15%, jumping from a height 12% and attempting traffic death 10%, the first two of which were frequent among young females. The median (range) of the total number of SBs in the lifetime history was 7 (1-141). Severity of depressive symptomatology, suicidal intent and other symptoms, proportions of the subjects who reported SB-preceding life events and life problems, and childhood and adolescent abuse were comparable to those of the previous studies conducted in medical or emergency service settings. Gender and age-relevant life-problems and life events were identified.</p> <p>Conclusions</p> <p>Features of the studied sample were the high prevalence of affective disorders, anxiety disorders and borderline PD, a variety of SB methods used prior to admission and frequent SB repetition in the lifetime history. Gender and age appeared to have an influence on SB method selection and SB-preceding processes. The findings have important implications for assessment and treatment of psychiatric suicidal patients.</p

Use of Fourier phase characteristics and effective stress analyses for post-earthquake ground motion estimation: application to ESG6 blind prediction steps 2&3 dataset and JMA accelerometric data

Abstract After the occurrence of a large earthquake, engineering seismologists are often requested to estimate strong ground motions at a site where strong motion data were not obtained. The goal of this study was to test the ability of a class of methods that uses Fourier phase characteristics for the post-earthquake ground motion estimation, making use of the precious opportunity provide by the ESG6 Blind Prediction Steps 2&3. It was also part of the goal of this study to test the performance of the effective stress analyses to account for soil nonlinearity. In addition to the dataset provided by the organizer of the blind prediction, the author used additional accelerometric data from a nearby JMA site. To simulate ground motions for an M5.9 earthquake at the target site “KUMA”, the Fourier amplitude spectrum was estimated from the spectral ratio between KUMA and the nearby JMA site. The Fourier phase spectrum was approximated by the spectrum of another event at KUMA. Comparison between the estimated and recorded ground motions after the blind prediction revealed that the estimated ground motions were fairly consistent with the observed ground motions, indicating the effectiveness of the method when the rupture process of the target event is simple and the soil nonlinearity at the target site is not significant. To simulate ground motions at KUMA for the M6.5 foreshock and the M7.3 mainshock of the 2016 Kumamoto earthquake sequence, the author conducted effective stress analyses using a program called “FLIP” to account for soil nonlinearity. Comparison between the estimated and recorded ground motions after the blind prediction indicated that the low-frequency components were overestimated and the high-frequency components were underestimated. The strong soil nonlinearity considered in the effective stress analyses was the main cause of the discrepancy. One explanation for this result could be that the nonlinear soil behavior at KUMA during the foreshock and the mainshock was not a strong one. Another explanation could be that the effect of soil nonlinearity was already included in the records at JMA and the effect of soil nonlinearity was double counted in the results submitted by the author. Graphical Abstrac

The region of large site amplification in Northern Hokkaido, Japan, extends to the eastern Soya Region

Abstract In the document titled “predominant period of long-period ground motions and the natural period of deep subsoil” by the Central Disaster Management Council, the west part of Northern Hokkaido facing the Sea of Japan is categorized as a region, where long-period (> 6 s) ground motions are predominant. In contrast, the document categorizes the east part of Northern Hokkaido as a region where short-period (< 1 s) ground motions are predominant. The J-SHIS velocity structure model also implies that a deep sedimentary basin is located in the west part of Northern Hokkaido, but not in the east part. However, the result of a past generalized inversion analysis was inconsistent with these general understanding and suggested that the region of large site amplification in the low-frequency range in Northern Hokkaido extends to the eastern Soya Region. It was preferable to check this result with an independent dataset. Therefore, in this study, the records of the May 24, 2013, MW8.3, Sea of Okhotsk earthquake were used to investigate the distributions of site amplification factors in Northern Hokkaido. Because this is a distant earthquake and the epicentral distance was greater than 1300 km even at the closest station in Hokkaido, it was assumed that the difference of ground motions at different stations represents the difference of the site effects. The Fourier spectra for the S wave part of this earthquake at K-NET and KiK-net stations clearly indicated that the region of large site amplification in the low-frequency range in Northern Hokkaido does extend to the eastern Soya Region. It is desirable in a future study to reveal the cause of the discrepancy between this amplification pattern and the existing velocity structure models. Graphical Abstrac