Strain and tilt changes measured during a water injection experiment at the Nojima Fault zone, Japan

Abstract In order to make geophysical and geological investigations of the Nojima Fault on Awaji Island, Japan, three boreholes measuring 1800 m, 800 m and 500 m deep were drilled into the fault zone. The fault is one of the seismic source faults of the 1995 Hyogo-ken Nanbu earthquake of M 7.2. A new multicomponent borehole instrument was installed at the bottom of the 800 m borehole and continuous observations of crustal strain and tilt have been made using this instrument since May 1996. A high-pressure water injection experiment within the 1800 m borehole was done in February and March 1997 to study the geophysical response, behavior, permeability, and other aspects of the fault zone. The injection site was located approximately 140 m horizontally and 800 m vertically from the instrument. Associated with the water injection, contraction of approximately 0.7 × 10⁻⁷ str (almost parallel to the fault) and tilt of approximately 1 × 10^-7 rad in the sense of upheaval toward the injection site were observed. In addition to these controlled experiments, the strainmeter and tiltmeter also recorded daily variations. We interpret strain and tilt changes to be related to groundwater discharge and increased ultra-micro seismicity induced by the injected water.     

Numerical study of the oxidation process of dimethylsulfide in the marine atmosphere

A box model, involving simple heterogeneous reaction processes associated with the production of non-sea-salt sulfate (nss-SO ₄ ^2– ) particles, is used to investigate the oxidation processes of dimethylsulfide (DMS or CH₃SCH₃) in the marine atmosphere. The model is applied to chemical reactions in the atmospheric surface mixing layer, at intervals of 15 degrees latitude between 60° N and 60° S. Given that the addition reaction of the hydroxyl radical (OH) to the sulfur atom in the DMS molecule is faster at lower temperature than at higher temperature and that it is the predominant pathway for the production of methanesulfonic acid (MSA or CH₃SO₃H), the results can well explain both the increasing tendency of the molar ratio of MSA to nss-SO ₄ ^2– toward higher latitudes and the uniform distribution with latitude of sulfur dioxide (SO₂). The predicted production rate of MSA increases with increasing latitude due to the elevated rate constant of the addition reaction at lower temperature. Since latitudinal distributions of OH concentration and DMS reaction rate with OH are opposite, a uniform production rate of SO₂ is realized over the globe. The primary sink of DMS in unpolluted air is caused by the reaction with OH. Reaction of DMS with the nitrate radical (NO₃) also reduces DMS concentration but it is less important compared with that of OH. Concentrations of SO₂, MSA, and nss-SO ₄ ^2– are almost independent of NO _x concentration and radiation field. If dimethylsulfoxide (DMSO or CH₃S(O)CH₃) is produced by the addition reaction and further converted to sulfuric acid (H₂SO₄) in an aqueous solution of cloud droplets, the oxidation process of DMSO might be important for the production of aerosol particles containing nss-SO ₄ ^2– at high latitudes.     

An Improved Mellor–Yamada Level-3 Model: Its Numerical Stability and Application to a Regional Prediction of Advection Fog

This note describes a numerically stable version of the improved Mellor–Yamada (M–Y) Level-3 model proposed by Nakanishi and Niino [Nakanishi, M. and Niino, H.: 2004, Boundary-Layer Meteorol. 112, 1–31] and demonstrates its application to a regional prediction of advection fog. In order to ensure the realizability for the improved M–Y Level-3 model and its numerical stability, restrictions are imposed on computing stability functions, on L/q, the temperature and water-content variances, and their covariance, where L is the master length scale and q ²/2 the turbulent kinetic energy per unit mass. The model with these restrictions predicts vertical profiles of mean quantities such as temperature that are in good agreement with those obtained from large-eddy simulation of a radiation fog. In a regional prediction, it also reasonably reproduces the satellite-observed horizontal distribution of an advection fog.     

Integrated magnetobiochronology of the Pliocene–Pleistocene Miyazaki succession,southern Kyushu,southwest Japan: Implications for an Early Pleistocene hiatus and defining the base of the Gelasian (P/P boundary type section) in Japan

An integrated magnetobiochronology of the Miyazaki Pliocene–Pleistocene succession in the Miyazaki area, southwest Japan, was established using planktic foraminiferal and calcareous nannofossil biostratigraphy together with paleomagnetic data. The upper Miyazaki succession in the northern Miyazaki region can be divided into the Takanabe, Hisamine (redefined), and Higoyashiki (new) Formations, in ascending order. A depositional hiatus between the Hisamine Formation and the Takanabe and/or older formations was also identified based on integrated magnetobiostratigraphy from five sections including the Nagatani River (NGT) section through the uppermost Miyazaki succession. The hiatus, herein called the Hisamine unconformity, is equivalent to the Kurotaki unconformity between the Miura and Kazusa groups of the Boso Peninsula in central Japan. The depositional hiatus recognised in the lower Pleistocene of Pacific coastal areas in southwestern and central Japan may have resulted from tectonic activity associated with a change in the subduction direction of the Philippine Sea plate, which commenced prior to ca. 2.2 Ma. The youngest unit just below the hiatus is the upper part of the Takanabe Formation in the NGT section. The NGT section represents the continuous Late Pliocene to earliest Pleistocene sequence including the Gauss/Matuyama boundary and is here proposed as the type section for the Pliocene/Pleistocene boundary in Japan, which the IUGS ratified as the base of the Gelasian in 2009.     

贵阳地表水-地下水的硫和氯同位素组成特征及其污染物示踪意义

喀斯特地表水和地下水的交换活跃,地下水系统容易受到地表污染物的污染。为了解喀斯特城市地表水—地下水系统污染特征和污染物质来源,对贵阳市地表水、地下水、雨水和城市排污污水的硫同位素和氯同位素组成变化进行了研究。贵阳市不同类型水体的δ³⁷Cl值在-4.07‰～+2.03‰之间变化,δ34SSO4值变化为-20.4‰～+20.9‰。大气输入物质和城市排污污水的δ³⁷Cl、δ³⁴S及Cl^-/SO₄^2-比值与地表水和地下水的不同,稳定硫和氯同位素的结合研究为示踪地下水污染物来源提供了有效研究手段。贵阳市地下水中的Cl^-和SO^₄2-至少有4种来源,人为活动通过城市排污和大气输入向地下水系统大量输入了硫酸盐和氯离子。      

On the chondrite—achondrite transition: mineralogy and chemistry of Yamato 74160 (LL7)

We report on the petrology, mineralogic properties and contents of major elements and trace elements Ag, Au, Bi, Cd, Co, Cs, Ga, In, Rb, Se, Te, Tl, U and Zn (determined by radiochemical neutron activation analysis) in Yamato 74160, interpreted as an LL7 chondrite. All properties are consistent with this meteorite having been recrystallized and partially melted locally once at temperatures well above 1090°C under conditions such that some minerals (e.g. plagioclase, euhedral pyroxene, tetrataenite) grew from melt pockets and siderophilic and chalcophilic elements were lost by extraction into eutectic melt that drained away. Inhomogeneous plagioclase compositions and mobile element loss suggest shock as the most likely heat source. Yamato 74160, while inferentially chondritic, is a larval achondrite: even higher temperatures and longer times would have been required to cause the separations necessary to transform it to an identifiable achondrite type.     

Antiferromagnetic transition of fayalite under high pressure studied by Mössbauer spectroscopy

Néel temperature (Tm _N of α-Fe₂SiO₄ (fayalite) was measured as a function of pressure by means of Mössbauer spectroscopy in the pressure range 0–16 Gpa. High pressure was generated using a clamp-type miniature diamond anvil cell which was inserted into a cryostat. The Néel temperature increased linearly with increasing pressure at a rate of dT _N /dp=2.2±0.2 K/GPa. The result is discussed on the basis of the model proposed for the magnetic structure of fayalite by Santoro et al. (1966). The observed dT _N /dp suggests that the superexchange interactions vary as the ?10/3 power of the volume while the volume dependence of the direct exchange interactions is positive and small.     

Kinetics of reactions between aqueous sulfates and sulfides in hydrothermal systems

The rates of chemical reactions between aqueous sulfates and sulfides are essentially identical to sulfur isotopic exchange rates between them, because both the chemical and isotopic reactions involve simultaneous oxidation of sulfide-sulfur atoms and reduction of sulfate-sulfur. The rate of reaction can be expressed as a second order rate law: R = k·[∑SO₄^2?]·[∑S^2?], where R is the overall rate, k is the rate constant and [∑SO₄^2?] and [∑S^2?] are molal concentrations. We have computed the rate constants from the available experimental data on the partial exchange of sulfur isotopes between aqueous sulfates and sulfides using the rate law established by us: $\text{ln(}\text{α}{}^{\mathrm{e}}\text{? α}\text{α}{}^{\mathrm{e}}\text{? α}{}^0\text{) = ? kt([∑SO}{}_4{}^{\mathrm{2?}}\text{] + [∑S}{}^{\mathrm{2?}}\text{])}$, where t is time and α⁰, α, and α^e are, respectively, the fractionation factors at t = 0 (the initial condition), at the end of experiment, and at equilibrium. The equilibrium fractionation factor can be expressed as: $\text{1000 ln α}{}^{\mathrm{e}}\text{=}\text{6.463 × 10}{}^6\text{T}{}^2\text{+ 0.56 (±.5)}$ (T in Kelvin).The rate constants are strongly dependent on T and pH, but not in as simple a manner as suggested by Igumnov (1976). Our rate constants in Na-bearing hydrothermal solutions decrease by 1 order of magnitude with an increase in pH by 1 unit at pH's less than ~3, remain constant in the pH range of ~4 to ~7, and again decrease at pH >7. The activation energy for the reaction also depends on pH: 18.4 ± 1 kcal/mole at pH = 2, 29.6 ± 1 kcal/mole at pH = 4 to 7, and between 40 and 47 kcal/mole at pH around 9. The observed pH dependence of the rate constant and of the activation energy can be best explained by a model involving thiosulfate molecules as reaction intermediates, in which the intramolecular exchange of sulfur atoms in thiosulfates becomes the rate determining step.The rate constants obtained in this study were used to compute the changes in the isotopic fractionation factors between aqueous sulfates and sulfides during cooling of fluids. Comparisons with data of coexisting sulfate-sulfide minerals in hydrothermal deposits, suggest that simple cooling was not a likely mechanism for coprecipitation of sulfate and sulfide minerals at temperatures below 350°C. Mixing of sulfide-rich solutions with sulfate-rich solutions at or near the depositional sites is a more reasonable process for explaining the observed fractionation.The degree of attainment of chemical equilibrium between aqueous sulfates and sulfides in a hydrothermal system, and the applicability of a_O2-pH type diagrams to mineral deposits, depends on the ∑S content and the thermal history of the fluid, which in turn is controlled by the flow rate and the thermal gradient in the system.The rates of sulfate reduction by non-bacterial processes involving a variety of reductants are also dependent on T, pH, [∑SO₄^2?], and [∑S^2?], and appear to be fast enough to become geochemically important at temperatures above about 200°C.