Response of a summertime anticyclonic eddy to wind forcing in Funka Bay,Hokkaido, Japan

Flow fluctuations inside an anticyclonic eddy in summertime Funka Bay were examined using three moorings and hydrographic data. The flow pattern above a sharp pycnocline with a concave isopycnal structure during the mooring period was characterized by high mean kinetic energy and relatively low eddy kinetic energy. The ratios of eddy to mean kinetic energy were equal to or less than one, and the mean flow field and isopycnal structure indicated the existence of a stable anticyclonic eddy above the sharp pycnocline under approximate geostrophic balance. Larger flow fluctuations with periods longer than 7 days were dominant inside the eddy. The low-frequency flow fluctuations are accompanied by north to northeastward movement of the eddy with deepening of the pycnocline and spin-up of the anticyclonic circulation. The wind field over Funka Bay is characterized by bay-scale wind fluctuations. The bay-scale winds are greatly influenced by the land topography around Funka Bay, resulting in non-uniform structure with significant wind stress curl. The bay-scale wind fluctuations are termed “locally modified wind” in the present study. The locally modified wind has a negative (positive) wind stress curl in the central–northeastern (southwestern) region of Funka Bay. The north to northeastward movement of the eddy is caused by horizontal non-uniform supply of vorticity from the locally modified wind forcing by the Ekman pumping process. Through this process, the anticyclonic circulation is enhanced (weakened) in the central–northeastern (southwestern) part of the eddy, resulting in the eddy moving north to northeastward with the pycnocline deepening and spin-up of the anticyclonic circulation. The locally modified wind forcing induces low-frequency flow fluctuations through the movement of the eddy in summertime Funka Bay.     

Simulation of rockfalls triggered by earthquakes

Summary A computer program to simulate the downslope movement of boulders in rolling or bouncing modes has been developed and applied to actual rockfalls triggered by the Mammoth Lakes, California, earthquake sequence in 1980 and the Central Idaho earthquake in 1983. In order to reproduce a movement mode where bouncing predominated, we introduced an artificial unevenness to the slope surface by adding a small random number to the interpolated value of the mid-points between the adjacent surveyed points. Three hundred simulations were computed for each site by changing the random number series, which determined distances and bouncing intervals. The movement of the boulders was, in general, rather erratic depending on the random numbers employed, and the results could not be seen as deterministic but stochastic. The closest agreement between calculated and actual movements was obtained at the site with the most detailed and accurate topographic measurements.     

Diurnal variations in streamflow and water quality during the summer dry season

In a headwater basin covered with boreal forest in northern Japan, the summer dry flow was monitored each summer from 1985 to 1993. Streamflow and specific electrical conductance fluctuated diurnally and these variations were attributed to daytime evapotranspiration. In 1989, the daytime reduction in streamflow and conductance were accompanied by a reduction in the HCO^?₃ concentration. The low flow hydrograph was separated into two components using HCO^?₃ and Cl^? concentrations in August 1989, assuming low flow to be a mixture of delayed subsurface flow and of quick shallow flow. The slight diurnal variation in the ratio of shallow flow to subsurface flow caused the diurnal variation in conductance by changing the HCO^?₃ concentration.     

Two overlapping plates subducting beneath central Japan as revealed by strontium isotope data

In central Japan, the Pacific plate subducts westward beneath the Eurasian plate and the Philippine Sea plate subducts northwestward into the mantle wedge between the Eurasian plate and the subducted Pacific slab. There, the Northeast Japan arc is joined to the Izu-Ogasawara arc. We determined ⁸⁷Sr/⁸⁶Sr ratios and Rb and Sr contents for 47 volcanic rock samples from 15 Quaternary volcanoes in central Japan and summarized the geographical distribution of the ratios. The general trend of slowly increasing ⁸⁷Sr/⁸⁶Sr ratio from the back-arc side toward the volcanic front in the Northeast Japan arc is broken by a marked high ratio (above 0.7060) centered around Akagi volcano located at the southernmost region of the arc. Elsewhere, the ratio along the volcanic front in this arc varies within the range 0.7038 to 0.7045. The marked high ⁸⁷Sr/⁸⁶Sr ratio is considered to be due to the addition of slab-derived components transported by the Philippine Sea plate to the magma-generating region in the mantle wedge beneath central Japan. Therefore, the geographical distribution of the high ratio may correspond to that of the Philippine Sea slab-derived components in the mantle wedge and we may draw the underground outline of the Philippine Sea plate. This outline implies that an aseismic portion of the Philippine Sea plate continues a few tens km ahead of the seismic one. A belt of low ⁸⁷Sr/⁸⁶Sr ratios from the Izu Peninsula northwestward along the northern end of the Izu-Ogasawara arc coincides with the zone where the subducting Philippine Sea plate is not observed seismologically, while it is detected seismologically on both sides of the belt.     

Sub-Moho seismic profile in the Mariana Basin — Ocean bottom seismograph long-range explosion experiment

Ocean bottom seismograph (OBS) long-range explosion experiments were carried out in the Mariana Basin in 1973 and 1976. Seven large shots (8.5–1.5 ton) as well as several tens of small shots were fired. The maximum range of observation was about 1900 km. As many as 25 OBS stations were deployed in an array of about 800 km. It is found that the sub-Moho P-wave velocity structure is of stratified nature, being composed of alternating high- and low-velocity layers. High-velocity layers with apparent velocities of 8.1, 8.2, 8.4, 8.6 and 8.7 km/s are identified. Low-velocity layers, sandwiched between the high-velocity layers of 8.4, 8.6 and 8.7 km/s, are very prominent. The sub-Moho high-velocity lid with an apparent velocity of 8.4 km/s is very thin. Thinning of this lid, thickening of the low-velocity layer, and the presence under it of another high-velocity layer (8.6 km/s) appear to characterize the uppermost mantle structure beneath the Mariana Basin.     

Predominant hosting lead(II) in ternary mixtures of heavy metal ions by a novel of diethylaminomethyl-calix[4]resorcinarene

Heavy metal ions from single and ternary systems of Pb(II), Cu(II), and Ni(II) adsorbed by calix[4]resorcinarenes in water–chloroform extraction were studied. Comparison was made of calix[4]resorcinarenes, 2,8,14,20-tetraundecyl calix[4]resorcinarene-4,6,10,12,16,18,22,24-octol, and diethylaminomethyl-calix[4]resorcinarene, 5,11,17,23-tetra(diethylaminomethyl)-2,8,14,20- tetraundecylcalix[4]resorcinarene-4,6,10,12,16,18,22,24-octol, for predominant extraction of their ions from the ternary mixture of aqueous solution at different pH in a water layer. The hosting of Pb(II) by the diethylaminomethyl-calix[4]resorcinarene occurred efficiently at pH 6–7. The hosting of Pb(II), Cu(II), and Ni(II) ions for the ternary aqueous mixture was applied to the Langmuir isotherm. Adsorption was studied using nuclear magnetic resonance spectroscopy in a water–deuterium chloroform extraction system. Results showed that as the heavy metal ions were included into the host cavity, the observation of shifted peaks of water molecules from downfield to higher field was visible in the nuclear magnetic resonance spectra, meaning that water molecules were included with heavy metal ion into the host cavity. The spectra also showed that the diethylamino group expressed formation of the coordination complex between the diethylaminomethyl-calix[4]resorcinarene and Pb(II) for the purpose of predominant hosting of Pb(II).     

Trace element composition and degree of partial melting of pelitic migmatites from the Aoyama area, Ryoke metamorphic belt, SW Japan: Implications for the source region of tourmaline leucogranites

Degree of partial melting of pelitic migmatites from the Aoyama area, Ryoke metamorphic belt, SW Japan is determined utilizing whole-rock trace element compositions. The key samples used in this study were taken from the migmatite front of this area and have interboudin partitions filled with tourmaline-bearing leucosome. These samples are almost perfectly separated into leucosome (melt) and surrounding matrix (solid). This textural feature enables an estimate of the melting degree by a simple mass-balance calculation, giving the result of 5–11 wt.% of partial melting. Similar calculations applied to the migmatite samples, which assume average migmatite compositions to be the residue solid fraction, give degree of melt extraction of 12–14 wt.% from the migmatite zone. The similarity of the estimated melting degree of 5–11 wt.% with that in other tourmaline–leucogranites, such as Harney Peak leucogranite and Himalayan leucogranites, in spite of differences in formation process implies that the production of tourmaline leucogranites is limited to low degrees of partial melting around 10 wt.%, probably controlled by the breakdown of sink minerals for boron such as muscovite and tourmaline at a relatively early stage of partial melting. Because the amount of boron originally available in the pelitic source rock is limited (on average 100 ppm), 10 wt.% of melting locally requires almost complete breakdown of boron sink mineral(s) in the source rock, in order to provide sufficient boron into the melt to saturate it in tourmaline. This, in turn, means that boron-depleted metapelite regions are important candidates for the source regions of tourmaline leucogranites.     

Interaction between wind and snow surface

The horizontal and vertical wind velocity fluctuations were measured using two sonic anemometers at a height of 135 cm above a snow surface under a transverse snow wave-forming condition. A snow-wave was formed when the wind at a height of 1 m blew at a speed of more than 7 m s^–1 after an approximate accumulation of from 10 to 20 cm of new snow on a snowfield. For example, when a snow-wave had a wavelength of 10 m and a wave height of 15 to 20 cm, the measured horizontal and vertical velocity components showed that they had a frequency peak of 0.7 Hz in coherence and co-spectrum corresponding to this wavelength. The results suggest that wind turbulence and snow-wave formation interact with each other.     

Post-collisional magmatism of western Chukotka and Early Cretaceous tectonic rearrangement in northeastern Asia

The paper presents new data on the isotopic age and chemical composition of volcanic rocks from the Tytyl’veem and Mangazeika basins of western Chukotka superposed on Mesozoides of the Verkhoyansk–Chukotka Tectonic Region. The results of SIMS U–Pb zircon dating (121.4 ± 2.8 and 118.0 ± 2.0 Ma) corroborate the Aptian age of the Tytyl’veem Formation. This age, in turn, indicates its formation after closure of the South Anyui ocean (Neocomian), but before origination of the Okhotsk–Chukotka Belt (Albian–Campanian). Post-collisional Aptian igneous rocks are widespread in the northern Verkhoyansk–Chukotka Tectonic Region; the legth of the corresponding igneous province is no less than 1400 km. In geochemical characteristics, the post-collisional volcanic rocks occurring in Western Chukotka are similar with the rocks from Andean-type igneous belts.     

利用TDR对土壤含水量及土壤溶液电导率的同步连续测量

土壤含水量和可溶解的土壤盐分浓度的测定, 对了解土壤盐分的分布及移动具有重要的意义. 在内蒙古黄河流域灌溉玉米田的一个野外实验中, 利用TDR对土壤含水量及土壤溶液电导率进行了同时连续测量. 结果表明: 在降雨量较少的时期内, 当土壤水分从地下含水层向地表面移动的同时, 地下水中含有的盐分也通过作物根区层向地表移动;当灌溉或有强降雨存在时, 土壤表面蓄积的盐分在未能完全溶解于灌溉水及雨水之前, 大量的灌溉水及降雨通过土壤内的大空隙快速渗入土壤下层;余下的水分在完全溶解了土壤表面的盐分之后, 缓慢通过土壤小空隙下渗.