Prestate of Stress and Fault Behavior During the 2016 Kumamoto Earthquake (M7.3)

Fault behavior during an earthquake is controlled by the state of stress on the fault. Complex coseismic fault slip on large earthquake faults has recently been observed by dense seismic networks, which complicates strong motion evaluations for potential faults. Here we show the three‐dimensional prestress field related to the 2016 Kumamoto earthquake. The estimated stress field reveals a spatially variable state of stress that forced the fault to slip in a direction predicted by the “Wallace and Bott Hypothesis.” The stress field also exposes the pre‐condition of pore fluid pressure on the fault. Large coseismic slip occurred in the low‐pressure part of the fault. However, areas with highly pressured fluid also showed large displacement, indicating that the seismic moment of the earthquake was magnified by fluid pressure. These prerupture data could contribute to improved seismic hazard evaluations

Seismicity controlled by resistivity structure : the 2016 Kumamoto earthquakes, Kyushu Island, Japan

The M JMA 7.3 Kumamoto earthquake that occurred at 1:25 JST on April 16, 2016, not only triggered aftershocks in the vicinity of the epicenter, but also triggered earthquakes that were 50–100 km away from the epicenter of the main shock. The active seismicity can be divided into three regions: (1) the vicinity of the main faults, (2) the northern region of Aso volcano (50 km northeast of the mainshock epicenter), and (3) the regions around three volcanoes, Yufu, Tsurumi, and Garan (100 km northeast of the mainshock epicenter). Notably, the zones between these regions are distinctively seismically inactive. The electric resistivity structure estimated from one-dimensional analysis of the 247 broadband (0.005–3000 s) magnetotelluric and telluric observation sites clearly shows that the earthquakes occurred in resistive regions adjacent to conductive zones or resistive-conductive transition zones. In contrast, seismicity is quite low in electrically conductive zones, which are interpreted as regions of connected fluids. We suggest that the series of the earthquakes was induced by a local accumulated stress and/or fluid supply from conductive zones. Because the relationship between the earthquakes and the resistivity structure is consistent with previous studies, seismic hazard assessment generally can be improved by taking into account the resistivity structure. Following on from the 2016 Kumamoto earthquake series, we suggest that there are two zones that have a relatively high potential of earthquake generation along the western extension of the MTL

Prestate of Stress and Fault Behavior During the 2016 Kumamoto Earthquake (M7.3)

Fault behavior during an earthquake is controlled by the state of stress on the fault. Complex coseismic fault slip on large earthquake faults has recently been observed by dense seismic networks, which complicates strong motion evaluations for potential faults. Here we show the three‐dimensional prestress field related to the 2016 Kumamoto earthquake. The estimated stress field reveals a spatially variable state of stress that forced the fault to slip in a direction predicted by the “Wallace and Bott Hypothesis.” The stress field also exposes the pre‐condition of pore fluid pressure on the fault. Large coseismic slip occurred in the low‐pressure part of the fault. However, areas with highly pressured fluid also showed large displacement, indicating that the seismic moment of the earthquake was magnified by fluid pressure. These prerupture data could contribute to improved seismic hazard evaluations

2011年霧島火山の噴火に伴って発生した火山性微動の時空間的特徴に関する研究

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Spatial heterogeneities in tectonic stress in Kyushu, Japan and their relation to a major shear zone Seismology

We investigated the spatial variation in the stress fields of Kyushu Island, southwestern Japan. Kyushu Island is characterized by active volcanoes (Aso, Unzen, Kirishima, and Sakurajima) and a shear zone (western extension of the median tectonic line). Shallow earthquakes frequently occur not only along active faults but also in the central region of the island, which is characterized by active volcanoes. We evaluated the focal mechanisms of the shallow earthquakes on Kyushu Island to determine the relative deviatoric stress field. Generally, the stress field was estimated by using the method proposed by Hardebeck and Michael (2006) for the strike-slip regime in this area. The minimum principal compression stress (σ3), with its near north-south trend, is dominant throughout the entire region. However, the σ 3 axes around the shear zone are rotated normal to the zone. This result is indicative of shear stress reduction at the zone and is consistent with the right-lateral fault behavior along the zone detected by a strain-rate field analysis with global positioning system data. Conversely, the stress field of the normal fault is dominant in the Beppu-Shimabara area, which is located in the central part of the island. This result and the direction of σ3 are consistent with the formation of a graben structure in the area

A Systematic Toxicological Analysis for Hallucinogenic Tryptamines in Seized and Biological Material

近年，外国人の流入増加やITの発達と普及により，違法薬物の入手が容易になり，重要事件の原因となっている。これら違法薬物は化学的に同じ基本骨格を有するが，置換基の異なる多種類の薬物が存在する。本稿では，最近違法薬物として関心の高い5-メトキシ-N,N-ジイソプロピルトリプタミンなどを含むトリプタミン系違法薬物に焦点を当て，標準物質および内部標準物質（IS）の合成，迅速検査法の開発，ガスクロマトグラフ-質量分析計（GC-MS）を用いた分析条件などを検討し，分析システムを構築した。　 　 トリプタミン系違法薬物を含む粉末試料は，3種の試薬（エールリッヒ，マルキス，シモン）による呈色反応で検査したところ，覚せい剤や催眠薬など乱用される頻度の高い薬物24種類との識別が可能であった。また，置換基の位置により同色調を示す傾向が観察された。　　 尿中の薬物をイオン会合性試薬（TBPE試液）と抗原抗体反応による検査キットで検出したところ， TBPE試液では0.5-2.0μg/mlで，検査キットではα-メチルトリプタミン，5-メトキシ-α-メチルトリプタミンが5.0μg/ml以上で検出可能であった。また，尿中の薬物を重水素ラベル化したISを用いて顆粒状珪藻土カラムによる抽出とTFAA誘導体化後，GC-MS分析したところ，検出下限は0.05μg/ml，直線性は0.05-2.0μg/ml，相関係数は0.981-0.999であった。尿中の薬物濃度0.1と1.0μg/mlでの日内変動は1.2-30%と1.2-16%であり，日間変動は3.2-20%と1.5-25%であった。　　 本研究で確立した分析システムは，薬物捜査に貢献する一方，中毒患者の治療方針決定の一助となることが期待される。また，これら検査法の普及により，薬物乱用の未然防止にも役立つと考える。A systematic toxicological analysis for hallucinogenic tryptamines in seized and biological materials was developed.　　 First, there were domestic problem that it was difficult to obtain standard sample of a controlled substance for analysis. So the standard (5-MeO-DPT) that were not obtained and internal standard (5-MeO-DPT-d14) were synthesized in our laboratory. Screening of powders was carried out using the combination of several spot test, Simon's, Marquis and Ehrlich's reagent. It was possible to distinguish from 24 kinds of abused drugs such as stimulants and psychotropic drugs. Also, the tendency that the same color tone was shown by the position of the substitution on the indole ring was observed. Screening of urine was carried out using ion association reagent (tetrabromophenolphthaleine ethyl ester) and immunoassay kits. For identification and quantitative determination in urine was carried out using isotope dilution gas chromatographymass spectorometry. The calibration curves showed linearity in the range of 0.05-2.0μg/ml. When urine samples containing two different concentrations ( 0.1 and 1.0μg/ml) of the drugs were analyzed, the coefficients of variation for intraday and interday testing ranged form 1.2 % to 30 %.　　 The developed systematic methods for toxicological analysis would be contributed to the investigation and help for treatment of patients

モノリス型カラムを用いた尿中メタンフェタミンの抽出

We have established a simple screening method for methamphetamine (MA) in urine using a monolithic silica capillary column for extraction and using the Simon's reagent for colorimetric determination. Urine was mixed with borate buffer solution (50 mM, pH 10.2) and the mixture was passed through the column connected with the needle of a gas-tight syringe. MA in urine was adsorbed to the column, then eluted with 10 µl of ethyl acetate, and directly spotted on a thin-layer chromatographic plate by dividing the eluate into several aliquots. To separate MA from urine impurities and detect it clearly, a 2-µl volume of a solvent mixture (chloroform : methanol = 95 : 5, v/v, saturated with 28-0x1.fa060bfff8bbp+0mmonium hydroxide) was applied to the spot for concentrically development of the analyte. After drying the solvent, 0.5% sodium nitroprusside solution containing 10% sodium carbonate was sprayed on the plate. The plate was put in a bottle saturated with acetaldehyde, and the ring was changed purple (Simon's reaction) when MA existed in urine. The macroscopic detection limit of MA in urine by this method was 0.5 µg/ml. To confirm efficiency of this method, the eluate from the column was analyzed by GC/MS using penta-deuterated MA as internal standard. By analysis of 30 urine samples, the results obtained by the present spot test agreed well with those by GC/MS