Temporal change in permeability of the Nojima fault zone by repeated water injection experiments   总被引：8，自引：1，他引：8  

Yuichi Kitagawa  Kunio Fujimori  Naoji Koizumi   《Tectonophysics》2007,443(3-4):183

Three boreholes were drilled near the Nojima fault, which the 1995 Hyogoken–Nanbu earthquake occurred on. In order to research the properties and the healing process of the fault, water injection experiments were conducted every 3 years. In this report, we researched the permeability of the fault as a measurement of crack density or porosity of the fault zone. Pore water pressure changes in rock due to the water injections at one borehole were observed as discharge changes or groundwater level changes at the other borehole. Using numerical calculations, the permeability of the fault fracture zone was estimated for each experiment. The permeability has been decreasing as time passed, which is thought to show the fault healing process of the Nojima fault after the 1995 Hyogoken–Nanbu earthquake.  相似文献   

Oceanic crust production and climate during the last 100 Myr   总被引：2，自引：0，他引：2  

Kunio Kaiho  Saneatsu Saito 《地学学报》1994,6(4):376-384

In order to evaluate the possible influence of oceanic crust production on climatic changes during the past 100Myr variations in total oceanic crust for this period including production at mid-ocean ridges, oceanic plateaus, and back-arc basins were calculated using the most recent and accurate time-scales. The rates presented here differ from those of Larson (1991a, b) on Cenozoic fluctuations and show that (1) maximum production values occurred during the Cenomanian, Palaeocene, and late Oligocene-early Miocene and (2) minimum values occurred in Campanian-Maastrichtian, late Eocene, and middle Miocene. Significantly, variations of oceanic crust production correspond with variations in the δ¹⁸O of deep-water benthic foraminifera: maximum values of oceanic crust production correspond with minimum values of δ¹⁸O, and minimum production values with maximum values of δ¹⁸O. This latter synchronism suggests that changes in land-sea relationships and atmospheric CO₂ related to major fluctuations in oceanic crust production were the main cause of mid-Cretaceous warming and Late Cretaceous cooling, and of climatic quasi-cycles having a periodicity of 33–38 million years over the last 100 Myr. This is the first report showing variations of ocean crust production synchronized with the Cenozoic climate changes.  相似文献   

Is water-ice the carrier of the 3μm-absorption in infrared objects?     

Tadashi Mukai  Sonoyo Mukai  Kunio Noguchi 《Astrophysics and Space Science》1978,53(1):77-84

It is shown that Mie theory predictions of extinction for pure water-ice with the optical constant measured at 100 K do not fit in detail the observed ice absorption feature in infrared objects, although we attempt to explain the observations by considering size distribution and shape of the grains.In addition, based on a similarity between the ice band and the absorption band found in carbon stars, we feel it is questionable whether or not the ice band can really be attributed to the interstellar water-ice.  相似文献   

Vertical material flux under seasonal sea ice in the Okhotsk Sea north of Hokkaido, Japan     

Takehiko Hiwatari  Kunio Shirasawa  Yasushi Fukamachi  Ryuichi Nagata  Tomoyoshi Koizumi  Hiroshi Koshikawa  Kunio Kohata 《Polar Science》2008,2(1):41-54

Downward material fluxes under seasonal sea ice were measured using a time-series sediment trap installed at an offshore site in the Okhotsk Sea north of Hokkaido, Japan, from 13 January to 23 March 2005. The maximum fluxes of lithogenic material (753 mg m⁻² day⁻¹) and organic matter (mainly detritus; 333 mg m⁻² day⁻¹) were recorded during the period in which sea ice drifted ashore and increased in extent, from 13 January to 9 February. Organic matter as fecal pellets (81–93 mg m⁻² day⁻¹) and opal as biosilica (51–67 mg m⁻² day⁻¹), representing diatom fluxes, were abundant in sediment trap samples obtained during the period of full sea ice coverage from 10 February to 9 March. Microscopic observations revealed that fecal pellets were largely diatom frustules, suggesting that zooplankton actively grazed on ice algae during the period of full sea ice coverage. During the period of retreating sea ice, from 10 to 23 March, the phytoplankton flux showed a rapid increase (from 9.5 to 22.5 × 10⁶ cells m⁻² day⁻¹), reflecting their release into the water column as the sea ice melted. Our results demonstrate that the quantity and quality of sinking biogenic and lithogenic materials vary with the seasonal extent of sea ice in mid-winter.  相似文献   

Quasi-2-Day Signals Observed in the Warm Pool Region during TOGA/COARE IOP     

Iwao Ueki  Kunio Kutsuwada  Hideo Inaba  Arata Kaneko 《Journal of Oceanography》2000,56(5):539-552

During Tropical Ocean and Global Atmosphere (TOGA)/Coupled Ocean and Atmosphere Research Experiment (COARE) Intensive Observing Period (IOP), upward-looking acoustic Doppler current profilers (ADCP) and current meters were moored at two equatorial sites (147°E and 154°E) and two off-equatorial sites (2°N and 2°S, 156°E) in the warm pool region of the western equatorial Pacific. Using current data obtained by these moorings, we have shown that there is a dominant signal with a period of about 2 days from the end of November to the middle of December in 1992, except at the equatorial site on 147°E (Ueki et al., 1998). The energy of this quasi-2-day signal for the meridional current is larger than that for the zonal one and the signal has a high coherence between two off-equatorial sites. In this paper, using band-passed time series of the meridional curerent, we investigated characters of the quasi-2-day signal and attempted to interpret this signal as an equatorially trapped wave. Complex empirical orthogonal function (CEOF) analysis reveals two different phase propagating features between the equatorial and off-equatorial site. One is an upward propagating signal, which is dominant near the surface at two off-equatorial sites, and the other is a downward propagating signal, which is dominant near 200 m at the equatorial site. If one interprets the quasi-2-day signal as an equatorially trapped wave, it is suggested that it cannot be explained as a single wave but can be described as the superimposition of several wave signals. The main part of these signals consists of two signals, one caused by a meteorological forcing and another by another factor in the ocean field.  相似文献   

Transport of chemical components in sea ice and under-ice water during melting in the seasonally ice-covered Saroma-ko Lagoon,Hokkaido, Japan     

Daiki Nomura  Toru Takatsuka  Masao Ishikawa  Toshiyuki Kawamura  Kunio Shirasawa  Hisayuki Yoshikawa-Inoue 《Estuarine, Coastal and Shelf Science》2009

Physico-chemical properties in the brine and under-ice water were measured in Saroma-ko Lagoon on the northeastern coast of Hokkaido, Japan, which is connected to the Sea of Okhotsk, during the period from mid-February through mid-March 2006. The brine within brine channels of the sea ice was collected with a new sampling method examined in this study. Salinity, dissolved inorganic carbon (DIC), total alkalinity (TA), dissolved oxygen (DO), nutrients and oxygen isotopic ratio (δ¹⁸O) contained in the brine within brine channels of the sea ice and in the under-ice water varied largely in both time and space during the ice melt period, when discharge from Saromabetsu River located on the southeast of the lagoon increased markedly due to the onset of snow melting. The under-ice plume expands as far as 4.5 km from the river mouth at mid-March 2006, transporting chemical components supplied from the river into the lagoon. The under-ice river water was likely transported into the sea ice through well-developed brine channels in the sea ice due to upward flushing of water through brine channels occurred by loading of snowfalls deposited over the sea ice. These results suggest that the river water plume plays an important role in supplying chemical components into the sea ice, which may be a key process influencing the biogeochemical cycle in the seasonally ice-covered Saroma-ko Lagoon.  相似文献   

Verification of the wind-driven transport in the North Pacific subtropical gyre using gridded wind-stress products   总被引：1，自引：1，他引：0  

Kunihiro Aoki  Kunio Kutsuwada 《Journal of Oceanography》2008,64(1):49-60

Wind-stress products supplied by satellite scatterometers carried the European Remote-sensing Satellite (ERS) and QuikSCAT (QSCAT), together with numerical weather predictions from the European Centre for Medium Range Weather Forecasting (ECMWF) and the National Centre for Environmental Prediction (NCEP) were used to estimate wind-driven transports of the North Pacific subtropical gyre. At 30°N, we compared the wind-driven transports with geostrophic transports calculated from World Ocean Database 2005. The wind-driven transports for QSCAT and NCEP are in good agreement with the geostrophic transport within reasonable error, except for a regional difference in the eastern part of the section. The difference in the eastern part suggests an anti-cyclonic deviation of the geostrophic transport, resulting from an anti-cyclonic anomalous flow in the surface layer. It is suggested that this anomalous flow is the Eastern Gyral, produced by the thermohaline process associated with the formation of the Eastern Subtropical Mode Water. To investigate the validity of QSCAT and NCEP data, we examined whether or not the Sverdrup transports for these products are consistent with the transport of the western boundary current estimated by past studies. The net southward transport, given by the sum of the Sverdrup transport for QSCAT and NCEP and the thermohaline transport, agrees well with the net northward transport of the western boundary current. From this result, together with the fact that the wind-driven transports for these products are in good agreement with the geostrophic transport, we conclude that the Sverdrup balance can hold in the North Pacific subtropical gyre.  相似文献   

Effect of macropores on soil freezing and thawing with infiltration   总被引：3，自引：0，他引：3       下载免费PDF全文

Kunio Watanabe  Yuki Kugisaki 《水文研究》2017,31(2):270-278

An understanding of heat transport and water flow in unsaturated soils experiencing freezing and thawing is important when considering hydrological and thermal processes in cold regions. Macropores, such as cracks, roots, and animal holes, provide efficient conduits for enhanced infiltration, resulting in a unique distribution of water content. However, the effects of macropores on soil freezing and thawing with infiltration have not been well studied. A one‐directional soil‐column freezing and thawing experiment was conducted using unsaturated sandy and silt loams with different sizes and numbers of macropores. During freezing, macropores were found to retard the formation of the frozen layer, depending on their size and number. During thawing, water flowed through macropores in the frozen layer and reached the underlying unfrozen soil. However, infiltrated water sometimes refroze in a macropore. The ice started to form at near inner wall of the macropore, grew to the centre, and blocked flow through the macropore. The blockage ice in the macropore could not melt until the frozen layer disappeared. Improving a soil freezing model to consider these macropore effects is required. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

Evaluation of Vector Winds Observed by NSCAT in the Seas around Japan     

Harunobu Masuko  Kohei Arai  Naoto Ebuchi  Masanori Konda  Masahisa Kubota  Kunio Kutsuwada  Teruko Manabe  Akira Mukaida  Tetsuo Nakazawa  Atsushi Nomura  Akira Shibata  Yoshihiko Tahara 《Journal of Oceanography》2000,56(5):495-505

In order to validate wind vectors derived from the NASA Scatterometer (NSCAT), two NSCAT wind products of different spatial resolutions are compared with observations by buoys and research vessels in the seas around Japan. In general, the NSCAT winds agree well with the wind data from the buoys and vessels. It is shown that the root-mean-square (rms) difference between NSCAT-derived wind speeds and the buoy observations is 1.7 ms^–1, which satisfies the mission requirement of accuracy, 2 ms^–1. However, the rms difference of wind directions is slightly larger than the mission requirement, 20°. This result does not agree with those of previous studies on validation of the NSCAT-derived wind vectors using buoy observations, and is considered to be due to differences in the buoy observation systems. It is also shown that there are no significant systematic trends of the NSCAT wind speed and direction depending on the wind speed and incidence angle. Comparison with ship winds shows that the NSCAT wind speeds are lower than those observed by the research vessels by about 0.7 ms^–1 and this bias is twice as large for data observed by moving ships than by stationary ships. This result suggests that the ship winds may be influenced by errors caused by ship's motion, such as pitching and rolling.  相似文献   

Effects of a large convective storm on Saturn's equatorial jet     

Kunio M. Sayanagi  Adam P. Showman 《Icarus》2007,187(2):520-539

Hubble Space Telescope observations revealed that Saturn's equatorial jet at the cloud level blows at ∼275 m s⁻¹ today, approximately half the ∼470 m s⁻¹ wind during the Voyager flybys in 1980-1981. Radiative transfer calculations estimate the clouds to be significantly higher today than in 1980. The higher clouds make it difficult to observationally isolate any true slowdown from the vertical wind shear because Voyager and Cassini observations show that the winds become slower with altitude. Here, we test the hypothesis that the large equatorial storm in 1990 called the Great White Spot (GWS) decelerated the equatorial jet. We first use order of magnitude estimates to show: (1) if the GWS triggers vertical momentum redistribution, a minor speed change in the troposphere can lead to a substantial stratospheric wind speed change; (2) storm-triggered turbulent mixing slows a prograde equatorial jet; and (3) a prograde equatorial jet inhibits turbulent mixing in latitude. To test whether a GWS-like large storm decelerates the equatorial jet, we perform numerical experiments using the Explicit Planetary Isentropic Coordinate (EPIC) atmosphere model. Our simulation results are consistent with our order of magnitude predictions. We show that the storm excites waves, and the waves transport westward momentum from the troposphere to the stratosphere and decelerate the equatorial jet by as much as ∼40 m s⁻¹ at the 10-mbar level. However, our results show that the storm's effect is too weak at the cloud levels to halve the jet's speed from ∼470 m s⁻¹. Our results suggest that a combination of higher clouds and a true slowdown is necessary to explain the apparent equatorial jet slowdown. We also analyze the effect of waves on the apparent cloud motions, and show that waves can influence cloud-tracking wind speed measurements.  相似文献