A 100 m laser strainmeter system installed in a 1 km deep tunnel at Kamioka, Gifu, Japan

We have installed a laser strainmeter system in a deep tunnel about 1,000 m below the ground surface at Kamioka, Gifu, Japan. The system consists of three types of independent interferometers: (1) an EW linear strainmeter of the Michelson type with unequal arms, (2) an NS-EW differential strainmeter of the Michelson type with equal arms and (3) a NS absolute strainmeter of the Fabry–Perot type. These are configured in L-shaped vacuum pipes, each of which has a length of 100 m. (1) and (2) are highly sensitive (order of 10⁻¹³ strain) and have wide dynamical range (10⁻¹³–10⁻⁶). Observations with strainmeters (1) and (2) started on June 11, 2003. (3) is a new device for absolute-length measurements of the order of 10⁻⁹ of a long-baseline (100 m) Fabry–Perot cavity by the use of phase-modulated light. This third strainmeter will be ready for operation before the end of 2004. The laser source of strainmeters (1) and (2) is a frequency-doubled YAG laser with a wavelength of 532 nm. The laser frequency is locked onto an iodine absorption line and a stability of 2 × 10⁻¹³ is attained. The light paths of the laser strainmeter system are enclosed in SUS304 stainless steel pipes. The inside pressure is kept to be 10⁻⁴ Pa. Consequently, quantitative measurement of crustal strains of the order of 10⁻¹³ can be attained by employing the laser strainmeter system of (1) and (2) at Kamioka. This resolving power corresponds to that of a superconducting gravimeter. Using the laser strainmeter system, we expect to determine parameters related to fluid core resonance, core modes and core undertone as well as other geodynamic signals such as slow strain changes caused by silent earthquakes or slow earthquakes.     

Element partitioning between olivine and silicate melt under high pressure

Element partitioning between olivine and silicate melt has been investigated at pressures 1–14 GPa, by using a 6–8 type multi-anvil high pressure apparatus. In order to observe systematics in the partitioning of trivalent ions, Li was added to the starting materials in order to increase the concentration of trivalent ions in olivine. With increasing pressure, it was found that partition coefficients of most of the elements gradually decreased. Trivalent ions generally showed parabolic pattern on partition coefficient — ionic radius diagram. When pyrolite-like material was used as the starting material, partition coefficient of Al, D_Al, gradually increased with increase in pressure while the partition coefficients of the other elements decreased, and the D_Al deviated from the parabolic pattern of other trivalent ions. The deviation of D_Al from the D pattern of the other trivalent ions was also found when olivine was employed as main component of the starting material. This result may be ascribed to the compositional change of coexisting silicate melt with increase in pressure.     

Turbulence structure of sea breeze front and its implication in air pollution transport — Application of k-ɛ turbulence model —

A k- turbulence model was applied to a numerical simulation of sea breeze. The dynamical behaviors of eddy diffusivity, turbulent kinetic energy and its dissipation rate, associated with moving sea breeze front, were predicted and analyzed. Results demonstrated, for example, difference of the turbulence structure between thermal internal boundary layer and inland mixed layer, and the double maxima structures of turbulence-related quantities in their vertical profiles just behind sea breeze front. The properties of the computed sea breeze front agreed qualitatively with those of a gravity current in unstable environment, observed by Simpson et al. (1977). Furthermore, the possibility that air pollutants released in the sea breeze layer might be trapped within small circulating flow at the sea breeze front, and move with it was shown in an advection simulation of hypothetical fluid particles using flows obtained.     

Excitation processes of infrared atmospheric emissions

Excitation rates of the infrared emissions which are likely to occur in the mesosphere and thermosphere are quantitatively evaluated. They include the 9.6 μm band of O₃, the 15 and 4.3 μm bands of CO₂ and the 5.3 and 2.8 μm bands of NO. These emissions may be excited through nonthermal processes such as chemiluminescent reactions and resonant fluorescence in the thermosphere, whereas they are of thermal origin in the stratosphere and mesosphere. Increase of the non-thermal excitation rate caused by precipitating electrons could be responsible for the enhancement of the 4.3 μm band of CO₂, and the 5.3 and 2.8 μm bands of NO observed in the auroral thermosphere.     

A non-linear numerical model of the tuned liquid damper

The Tuned Liquid Damper (TLD) is modelled numerically as an equivalent tuned mass damper with non-linear stiffness and damping. These parameters are derived from extensive experimental results described in References 1 and 2. This Non-linear Stiffness and Damping (NSD) model captures the behaviour of the TLD system adequately under a variety of loading conditions. In particular, the NSD model incorporates the stiffness hardening property of the TLD under large amplitude excitation. Copyright © 1999 John Wiley & Sons, Ltd.     

Age and paleoclimatic implication of middle to upper Miocene plant-bearing strata in the southern Kanazawa area,Ishikawa Prefecture,Central Japan,based on refined Neogene palynostratigraphy in the Hokuriku district

13–8 Ma (middle to late Miocene) is a key period for understanding how the unique vegetation was established in Japan. Palynostratigraphy is useful for estimating the ages of plant-bearing strata deposited in shallow-marine and non-marine environments, but has low temporal resolution for this key period in Japan. We compiled Neogene and early Quaternary palynological records for the Hokuriku district of Central Japan to clarify palynostratigraphic events that may improve the temporal resolution. Our results showed that palynoassemblages changed considerably during 10–6.4 Ma in the Hokuriku district, following a relatively stable period during 13–10 Ma. We found that evergreen Quercus abundance increased at 11.5–10 Ma. We used these palynostratigraphic signatures, along with other biostratigraphic markers, to infer the ages of the Miocene plant-bearing Saikawa and Koderayama Formations in the southern Kanazawa area of Ishikawa Prefecture in the Hokuriku district. The ages of the Saikawa and Koderayama Formations were inferred as ~13 and 10–6.4 Ma, respectively. The palynoflora of the Koderayama Formation shows floristic similarity to that of present south China, implying that the unique flora of Japan established after the age of the Koderayama Formation.     

Imaging polarimetry of Comet 9P/Tempel before and after the Deep Impact

The NASA's Deep Impact mission was the first impact experiment to a cometary nucleus. The target of the mission was Comet 9P/Tempel, one of the Jupiter family comets. The impact was performed on July 4th, 2005. Imaging polarimetric observations were carried out by Polarimetric Imager for COmets (PICO) mounted on the Lulin One-meter Telescope (LOT) at Lulin Observatory, Taiwan. Intensity and linear polarization degree maps were obtained on July 3-5, 2005. Impact ejecta plume was clearly recognized in the enhanced intensity map. Furthermore, arc-shaped region of high polarization was recognized in the polarization map. Dust grains in this region had larger expansion velocity than the grains which provided the brightest area in the intensity map. comparing our results with the MIR spectroscopy obtained by Subaru Telescope we conclude that very small carbonaceous grains might be responsible for the region of high polarization.     

High pressure transitions in the system KAlSi3O8-NaAlSi3O8

Phase relations in the system KAlSi₃O₈-NaAlSi ₃O₈ have been examined at pressures of 5–23 GPa and temperatures of 700–1200° C. KAlSi₃O₈ sanidine first dissociates into a mixture of wadeite-type K₂Si₄O₉, kyanite and coesite at 6–7 GPa, which further recombines into KAlSi₃O₈ hollandite at 9–10 GPa. In contrast, NaAlSi₃O₈ hollandite is not stable at 800–1200° C near 23 GPa, where the mixture of jadeite plus stishovite directly changes into the assemblage of calcium ferrite-type NaAlSiO₄ plus stishovite. Phase relations in the system KAlSi₃O₈-NaAlSi₃O₈ at 1000° C show that NaAlSi₃O₈ component gradually dissolves into hollandite with increasing pressure. The maximum solubility of NaAlSi₃O₈ in hollandite at 1000° C was about 40 mol% at 22.5 GPa, above which it decreases with pressure. Unit cell volume of the hollandite solid solution decreases with increasing NaAlSi₃O₈ component. The hollandite solid solution in this system may be an important candidate as a host mineral of K and Na in the uppermost lower mantle