TritiogenicHe in groundwater in Takaoka     

Nobuo Takaoka  Yoshihiko Mizutani 《Earth and Planetary Science Letters》1987,85(1-3)

³He/⁴He ratios up to 3.5 times the ratio of atmospheric He were found in groundwater samples. The³He enrichment can be attributed to radiogenic³He produced by in-situ beta-decay of³H. This shows that tritiogenic³He is accumulating in confined waters. From tritiogenic³He and³H concentrations, ages of groundwaters can be calculated. Detection of tritiogenic³He gives a tool to trace a tritium contamination which occurred in the past and cannot be assessed only by the³H counting method.  相似文献   

Streaming potential observations, using geothermal wells and in situ electrokinetic coupling coefficients under high temperature     

Tsuneo Ishido  Hitoshi Mizutani  Kenzo Baba 《Tectonophysics》1983,91(1-2)

In an attempt to detect streaming potentials induced by subsurface water flows, we have observed the horizontal electric field (self-potential) variations across stationary electric dipoles near geothermal wells in the Takinoue geothermal area, Japan. We observed variations of self-potential which seem to be associated with the water flows in the aquifer, induced by turning on and off the flow of the wells. Amplitudes of the variations are 3–5 mV across 60–200 m dipoles, and can be explained well with a proposed electrokinetic model: the streaming potential coefficient of − 15 mV/bar and/or the ζ-potential of −50 to −100 mV in the aquifer are appropriate to explain the observed data by the model. The obtained electrokinetic coupling coefficients are in situ ones and determined for crustal rock-water system under high temperature (˜200°C) condition. The present results, together with a laboratory study by Ishido and Mizutani (1981), give fundamental information on electrokinetic coupling coefficients in the earth's interior, and are very important when we make quantitative interpretations of self-potentials generated by geothermal activity on the basis of electrokinetic effects.  相似文献   

Influence of surface and vegetation characteristics on C-band radar measurements for soil moisture content   总被引：1，自引：0，他引：1  

Shakil Ahmad Romshoo  Masahiro Koike  Sadayukihir Onaka  Taikan Oki  Katumi Musiake 《Journal of the Indian Society of Remote Sensing》2002,30(4):229-244

Soil moisture estimation using microwave remote sensing faces challenges of the segregation of influences mainly from roughness and vegetation. Under static surface conditions, it was found that Radarsat C-band SAR shows reasonably good correlation and sensitivity with changing soil moisture. Dynamic surface and vegetation conditions are supposed to result in a substantial reduction in radar sensitivity to soil moisture. A C-band scatterometer system (5.2 GHz) with a multi-polarization and multi-angular configuration was used 12 times to sense the soil moisture over a tall vegetated grass field. A score of vegetation and soil parameters were recorded on every occasion of the experiment. Three radar backscattering models Viz., Integral Equation Model (IEM), an empirical model and a volume scattering model, have been used to predict the backscattering phenomena. The volume scattering model, using the Distorted Born Approximation, is found to predict the backscattering phenomena reasonably well. But the surface scattering models are expectedly found to be inadequate for the purpose. The temporal variation of soil moisture does show good empirical relationship with the observed radar backscattering. But as the vegetation biomass increases, the radar shows higher sensitivity to the vegetation parameters compared to surface characteristics. A sensitivity analysis of the volume scattering model for all the parameters also reveals that the radar is more sensitive to plant parameters under high biomass conditions, particularly vegetation water content, but the sensitivity to surface characteristics, particularly to soil moisture, is also appreciable.  相似文献   

Thermal diffusivity of lunar rocks under atmospheric and vacuum conditions     

Naoyuki Fujii  Masahiro Osako 《Earth and Planetary Science Letters》1973,18(1):65-71

Thermal diffusivity, k, of three lunar rocks (10049 and 10069; Type A, Apollo 11 and 14311; Apollo 14) and a terrestrial basalt (alkaline olivine basalt, Oki-do?go, Japan) was measured under one atmosphere and in vacuum conditions (10^?3 ～ 10^?5 mmHg) in the temperature range from 85 to 850°K. The semi-empirical curve of k =A + B/T +CT³ is fitted to the data in each condition. The porosity of rocks strongly affects the thermal diffusivity at low temperature ( T ? 500°K) in vacuum condition. At 150°K, thermal diffusivity of lunar rocks with porosity of 5.5% (10049) and 11% (10069) at one atmosphere is about 1.7 and 3.2 times of that in vacuum, respectively. The difference between the values at one atmosphere and those in vacuum decreases as the temperature increases. Measurements of k should be made at gas pressures at least lower than 10^?3 mmHg to estimate the value under lunar surface conditions.  相似文献   

On-going orogeny in the outer-arc of the Timor–Tanimbar region, eastern Indonesia     

Yoshiyuki Kaneko  Shigenori Maruyama  Ade Kadarusman  Tsutomu Ota  Masahiro Ishikawa  Tatsuki Tsujimori  Akira Ishikawa  Kazuaki Okamoto   《Gondwana Research》2007,11(1-2):218

The Timor–Tanimbar islands of eastern Indonesia form a non-volcanic arc in front of a 7 km deep fore-arc basin that separates it from a volcanic inner arc. The Timor–Tanimbar Islands expose one of the youngest high P/T metamorphic belts in the world, providing us with an excellent opportunity to study the inception of orogenic processes, undisturbed by later tectonic events.Structural and petrological studies of the high P/T metamorphic belt show that both deformation and metamorphic grade increase towards the centre of the 1 km thick crystalline belt. Kinematic indicators exhibit top-to-the-north sense of shear along the subhorizontal upper boundaries and top-to-the-south sense in the bottom boundaries of the high P/T metamorphic belt. Overall configuration suggests that the high P/T metamorphic rocks extruded as a thin sheet into a space between overlying ophiolites and underlying continental shelf sediments. Petrological study further illustrates that the central crystalline unit underwent a Barrovian-type overprint of the original high P/T metamorphic assemblages during wedge extrusion, and the metamorphic grade ranged from pumpellyite-actinolite to upper amphibolite facies.Quaternary uplift, marked by elevation of recent reefs, was estimated to be about 1260 m in Timor in the west and decreases toward Tanimbar in the east. In contrast, radiometric ages for the high P/T metamorphic rocks suggest that the exhumation of the high P/T metamorphic belt started in western Timor in Late Miocene time and migrated toward the east. Thus, the tectonic evolution of this region is diachronous and youngs to the east. We conclude that the deep-seated high P/T metamorphic belt extrudes into shallow crustal levels as a first step, followed by doming at a later stage. The so-called ‘mountain building’ process is restricted to the second stage. We attribute this Quaternary rapid uplift to rebound of the subducting Australian continental crust beneath Timor after it achieved positive buoyancy, due to break-off of the oceanic slab fringing the continental crust. In contrast, Tanimbar in the east has not yet been affected by later doming. A wide spectrum of processes, starting from extrusion of the high P/T metamorphic rocks and ending with the later doming due to slab break-off, can be observed in the Timor–Tanimbar region.  相似文献   

Preparation of Two New GSJ Geochemical Reference Materials: Basalt JB-1b and Coal Fly Ash JCFA-1   总被引：1，自引：0，他引：1  

Shigeru Terashima  Masahiro Taniguchi  Masumi Mikoshiba  Noboru Imai 《Geostandards and Geoanalytical Research》1998,22(1):113-117

  相似文献   

Extinction-angle distribution of plagioclase feldspars in clastic sediments     

S. Mizutani 《Mathematical Geosciences》1975,7(4):335-348

An extinction-angle distribution was computed for randomly oriented grains of plagioclase feldspar with a known An-composition. Expressed by a histogram with eighteen columns, the results are shown by an 18×19 data array for nineteen types of low-temperature plagioclase. In a mixture of grains with various An-compositions, the extinction-angle distribution is given by a linear combination of the obtained data matrix with the frequencies of An-composition. If we have a sample containing randomly oriented grains of plagioclase feldspars, a frequency distribution of those with An-composition can be calculated after measuring their extinction angles. By taking into account the constraints of inequalities, the calculation is treated with the dual method of linear programming. The procedure provides for a simpler and more expedient method for determining the frequency distribution of An-composition. This method was tested by applying it to a model sample containing randomly oriented plagioclase grains with known An-composition frequencies, whose extinction-angle distribution was determined by the Monte Carlo method. An example of application of this method to Permian sandstones from central Japan is presented.  相似文献   

Relations between load and settlement of circular foundations on or in a dense sand expressed by a function of diameter and depth     

Hiroaki Nagaoka  Masahiro Yamazaki  Naoto Kubota  Takashi Okamoto 《国际地质力学数值与分析法杂志》2005,29(6):551-576

When load acts on a circular foundation on or in a dense sand, average contact pressure on the lower surface of the foundation is q and settlement of the foundation is s. Diameter and depth of the foundation are B and D_f. When the sand, B and D_f are given, we can know the relation between q and s/B by, e.g. a loading test, i.e. the relation is determined by B and D_f for the sand. Using the results of numerical analyses, we express a relation between q and s/B up to s=0.1B by functions of a single variable which is a linear combination of B and D_f. Consequently when two foundations have different B's and different D_f's but have the same value of the variable, the relations are the same. Then we examine whether the functions can express the results of eleven tests of model foundations of wide range of B and/or D_f. In all the tests, the relations are expressed with sufficient accuracy. Copyright © 2005 John Wiley & Sons, Ltd.  相似文献   

Response of a simple two-layer ocean to divergent and rotational wind stress     

Masahiro Endoh 《Journal of Oceanography》1971,27(3):116-120

Response of an unbounded two-layer ocean to traveling atmospheric disturbances is analytically investigated. Under the assumption that (1) lower layer is motionless, (2) each layer is homogeneous and in hydrostatic balance, (3) the Coriolis parameter is constant, and (4) the density difference between the two layers is small compared to the density itself, the one-dimensional Klein-Gordon's equation is solved analytically for both the divergent and rotational wind stress. Numerical examples of the wake pattern of the upwelling behind the regional divergent and rotational wind fields are also represented.The results may be summarized as follows: (1) the effect of the divergent wind stress is dominant when the forced Rossby numberR ₀ (the ratio of the frequency of the wind stress to the Coriolis parameter) is larger than unity unless the Mach numberM (the ratio of the traveling velocity of the wind stress to the internal gravitational velocity) is far less than unity, (2) the effect of the rotational wind stress is important, when the forced Rossby numberR ₀ is less than unity.  相似文献   

Impact fragmentation experiments of basalts and pyrophyllites     

Yasuhiko Takagi  Hitoshi Mizutani  Shin-Ichi Kawakami 《Icarus》1984,59(3):462-477

Results of impact fragmentation experiments for basalts and pyrophyllites are reported. Aluminum cylindrical projectiles were impacted on cubic basalt and pyrophyllite targets at velocities of 70 to 990 m/sec. The targets and projectiles were 20 g to 3.3 kg and 2 to 20 g in weight respectively. Weights of the fragments produced by impacts were measured and the size distributions of fragments were examined. Data of the largest fragment mass (m_L) normalized to the original target mass (M_t), m_L/M_t, correlate better with the nondimensional impact stress, P_I, a new scaling parameter introduced by H. Mizutani, Y. Takagi, and S. Kawakami (1984, in preparation) than the conventional projectile's kinetic energy per unit target mass, E/M_t, used in the previous studies. All the m_L/M_t data for basalts obtained in the present study are summarized by m_L/M_t = 2.95 × 10^?2P_I^?1 where P_I = P₀L³/YR³, P₀ = peak shock pressure, L = projectile size, R = target size and Y = material strength of target. For aluminum targets, however, the m_L/M_t is 2.5 orders of magnitude larger than that for brittle targets at impacts with the same P_I. Size distributions of fragments expressed in a log N - log (m/M_t) diagram divided into three regimes bounded by two inflection points. In each regime the curve is expressed by $\text{N (>}\text{m}\text{M}{}_{\mathrm{t}}\text{) = A (}\text{m}\text{M}{}_{\mathrm{t}}\text{)}{}^{\mathrm{?a}}$. The slopes, a, of the log $\text{N -}\text{log}\text{(}\text{m}\text{M}{}_{\mathrm{t}}\text{)}$ curves in the regimes of a large and a medium size range are positively correlated with the nondimensional impact stress, P_I, and expressed as a = C₃ + a₃log P_I. The slopes, a, in the smallest size range are, on the other hand, nearly constant and have values of $\text{0.5}\text{to}\text{0.7 (}\text{1}\text{2}\text{?}\text{2}\text{3}\text{)}$. Present results indicate that the impact fragmentation is scaled well by the new scaling parameter, P_I, of Mizutani, Takagi, and Kawakami and that the present experimental data may shed new light on planetary impact processes.  相似文献