Effects of urbanization and groundwater flow on the subsurface temperature in Osaka, Japan     

Makoto Taniguchi  Takeshi Uemura 《Physics of the Earth and Planetary Interiors》2005,152(4):305-313

Subsurface temperatures were analyzed to evaluate the effects of urbanization and groundwater flow in Osaka, the second largest metropolitan in Japan. The temperature-depth profiles were classified into three (recharge, intermediate and discharge) types based on the thermal gradient, shape of the profiles, and temperature itself. The locations of the three types of profiles represent the places of regional and local groundwater flow systems in Osaka plain. The analyses of subsurface temperature using heat conduction-convection theory under the condition of surface warming showed that the depth of minimum temperature in the profile increased with the groundwater recharge rate and time lapse from the beginning of surface warming due to urbanization. Comparisons between observed and estimated temperature profiles showed that the surface warming due to urbanization is larger and occurred earlier in the middle of the city than those in surrounding area, which agreed with the air temperature records.  相似文献   

Climatic and environmental changes at southeastern coast of Lake Biwa over past 3000 years, inferred from borehole temperature data     

Shusaku Goto  Hideki Hamamoto  Makoto Yamano 《Physics of the Earth and Planetary Interiors》2005,152(4):314-325

In order to infer past climatic change in central Japan, we measured temperatures in a borehole at the Karasuma site, on the southeastern coast of Lake Biwa, and reconstructed sediment surface temperature history during the last 3000 years. The reconstructed temperature history shows apparent Medieval Warm Period, Little Ice Age, and contemporary temperature warming. However, the large amplitude of the temperature changes up to 4-5 K cannot be explained by past climatic change only, suggesting that there was some other cause of the larger amplitude temperature changes. The onsets of temperature decrease in the late 12th century a.d. and temperature increase in the mid 17th century a.d. appear to coincide with occurrences of two destructive earthquakes (1185 and 1662 a.d.) that caused water level changes of Lake Biwa. It suggests that the reconstructed sediment surface temperature history reflects the environmental change due to tectonically induced water level changes of the lake. If the annual mean of the ground surface temperature was higher than that of the bottom water temperature in a shallow part of the lake, which is consistent with the present-day data, the large amplitude of the sediment surface temperature change may be attributed to a combined effect of past climatic and environmental changes. Thus, we suggest that the borehole temperature at the Karasuma site preserves information not only on past climate changes but also on environmental changes due to tectonically induced water level changes.  相似文献   

Long-term monitoring of the temperature profile in a deep borehole: Temperature variations associated with water injection experiments and natural groundwater discharge     

Makoto Yamano  Shusaku Goto 《Physics of the Earth and Planetary Interiors》2005,152(4):326-334

Long-term temperature monitoring was carried out in a borehole drilled for investigation of the Nojima fault, an active fault in SW Japan, using the distributed optical fiber temperature sensing (DTS) technique. Temperatures in the borehole had been measured every 1 m along an optical fiber cable with a resolution of about 0.1 K over a period of 6 years. Water injection experiments were conducted in this borehole in 1997, 2000 and 2003. Monitoring of the temperature profile was started after the first injection experiment, and the temperature profile remained very stable until the start of the second injection experiment. During the second and third experiments, the temperatures in the borehole dropped due to cooling by the injected water but no appreciable temperature change was observed below about 580 m. It clearly shows that the water leaked out of the hole around this point and the leaking depth is estimated to be about 540 m based on the shape of the temperature profile. After the injection was stopped, the recovery of the temperature to the undisturbed profile was exceptionally slow around the leaking point, resulting in a local temperature anomaly, probably because the water leaking out of the hole had cooled the surrounding formations extensively. A very similar temperature anomaly was observed at the beginning of temperature monitoring, which suggests that water leaked out at the same depth in the first injection experiment as well. Between the second and third injection experiments, the top of the borehole was kept open to allow groundwater discharge for about 1 month in 2000 and 2003. In both periods, groundwater flowed out continuously and the shapes of the observed temperature profiles indicate that the groundwater entered in the hole at the same depth as the leaking point during the injection experiments. The temperature records also show that the rate of discharge had been nearly constant through the two test periods. The water discharge appears to have been little affected by the water injection. These results demonstrate that the optical fiber temperature monitoring system is a very effective tool for hydrological experiments.  相似文献   

Seismicity changes related to a water injection experiment in the Nojima Fault Zone   总被引：2，自引：0，他引：2  

Keiichi Tadokoro  Kin'Ya Nishigami  Masataka Ando  Naoshi Hirata  Takashi Iidaka  Yukihiro Hashida  Kunihiko Shimazaki  Shiro Ohmi  Yasuyuki Kano  Makoto Koizumi  Shigemitsu Matsuo  Hiroo Wada 《Island Arc》2001,10(3-4):235-243

Abstract A water injection experiment was carried out by the scientific drilling program named the 'Nojima Fault Zone Probe' during the two periods 9–13 February and 16–25 March 1997. The pumping pressure at the surface was approximately 4 MPa. The total amount of injected water was 258 m³. The injection was made between depths of 1480 m and 1670 m in the Disaster Prevention Research Institute, Kyoto University (DPRI) 1800 m borehole drilled into the Nojima Fault zone. A seismic observation network was deployed to monitor seismic activity related to the water injections. Seismicity suddenly increased in the region not far from the injection hole 4 or 5 days after the beginning of each water injection. These earthquakes were likely to be induced by the water injections. Most of the earthquakes had magnitudes ranging from −2 to +1. Numerous earthquakes occurred during the first injection, but only one could be reliably located and it was approximately 2 km north of the injection site. Between the two injection periods, earthquakes concentrated in the region approximately 1 km northwest of the injection site. During and after the second injection experiment, earthquakes were located approximately 1.5 km west of the injection site. Those earthquakes were located approximately 3 km or 4 km from the injection point and between 2 km and 4 km in depth. Values of intrinsic permeability of 10⁻¹⁴–10⁻¹⁵ m² were estimated from the time lapse of the induced seismic activity. The coefficient of friction in the area where the induced earthquakes occurred was estimated to be less than 0.3.  相似文献   

Diopside-bearing EL6 EET 90102: insights from rare earth element distributions     

Christine Floss  Robert A Fogel  Makoto Kimura 《Geochimica et cosmochimica acta》2003,67(3):543-555

EET 90102 is the first known diopside-bearing EL6 chondrite. Diopside occurs in most aubrites and is occasionally found as rare small grains in unequilibrated enstatite chondrites, but is unknown from equilibrated enstatite chondrites. We have carried out a study of the rare earth element (REE) distributions in EET 90102, with a specific emphasis on diopside, in order to better understand its origin in this meteorite. We also present data for Ca-rich pyroxenes from two unequilibrated (EH3) enstatite chondrites for comparison.Our data show that diopside and other silicates in EET 90102 exhibit volatility-related anomalies indicative of formation under highly reducing conditions. Such anomalies have not previously been observed in EL6 chondrites, although they are common in unequilibrated enstatite chondrites. Diopside in EET 90102 probably formed by metamorphic equilibration of enstatite and oldhamite. The REE compositions of some grains, in particular the presence of positive Yb anomalies, indicate that they inherited their REE characteristics largely from CaS. Other grains have REE patterns that are more consistent with a derivation of diopside primarily from enstatite.In contrast to other EL6 chondrites, which experienced slow cooling, EET 90102 was quenched from high metamorphic temperatures. Thus, there may have been insufficient time to completely homogenize diopside REE compositions.The presence of diopside in EET 90102 simplifies one outstanding problem of aubrite formation. Melting of a diopside-bearing enstatite chondrite protolith provides a source for the abundant diopside in aubrites without requiring the oxidation of oldhamite, as suggested by previous research.  相似文献   

Deterioration of eelgrass,Zostera marina L., meadows by water pollution in Seto Inland Sea,Japan     

Tamaki H  Tokuoka M  Nishijima W  Terawaki T  Okada M 《Marine pollution bulletin》2002,44(11):1253-1258

Survival of transplanted Zostera marina L. (eelgrass) and environmental conditions (water quality, bottom sediments, sedimentation on leaves and flow regime) were studied concurrently in the center, edge, and at the outside of a eelgrass meadow located in a eutrophic coastal zone in northern Hiroshima Bay, Seto Inland Sea, Japan. Eelgrass transplants at the outside of the meadow declined significantly, whereas those at the center were consistently well established. Silt content in the bottom sediments at the outside was higher than that at the center. The sediment was oxic from the surface to 2 cm deep at the center, whereas those at the edge and the outside were reductive almost from the surface. The sediment characteristics typical in eutrophic water seemed to be a factor responsible for the deterioration of eelgrass meadows. Although suspended solid concentrations in the water columns were almost the same, the amount of sediments deposited on leaves of eelgrass at the outside was higher than that at the center of the meadow. The amount of the deposition at the outside seems to be enough to inhibit photosynthesis; i.e. photosynthetic photon flux density (PPFD) available for eelgrass was only 36% of that without any deposition. The deposition in the center, however, was small enough to allow 84% of the original PPFD. Flow rates, determined at 30 cm above the bottom, a half height of average eelgrass, suggested that the rate at the outside was not enough to remove deposited sediments from the surface of eelgrass leaves. Thus, the large amount of sediment deposition caused by water pollution and/or eutrophication seemed to be another factor to inhibit the survival of eelgrass at the outside edge of the meadow.  相似文献   

Three-dimensional P- and S-wave velocity structures beneath the Japan Islands obtained by high-density seismic stations by seismic tomography   总被引：1，自引：0，他引：1  

Makoto Matsubara  Kazushige Obara  Keiji Kasahara 《Tectonophysics》2008,454(1-4):86-103

We construct fine-scale 3D P- and S-wave velocity structures of the crust and upper mantle beneath the whole Japan Islands with a unified resolution, where the Pacific (PAC) and Philippine Sea (PHS) plates subduct beneath the Eurasian (EUR) plate. We can detect the low-velocity (low-V) oceanic crust of the PAC and PHS plates at their uppermost part beneath almost all the Japan Islands. The depth limit of the imaged oceanic crust varies with the regions. High-V_P/V_S zones are widely distributed in the lower crust especially beneath the volcanic front, and the high strain rate zones are located at the edge of the extremely high-V_P/V_S zone; however, V_P/V_S at the top of the mantle wedge is not so high. Beneath northern Japan, we can image the high-V subducting PAC plate using the tomographic method without any assumption of velocity discontinuities. We also imaged the heterogeneous structure in the PAC plate, such as the low-V zone considered as the old seamount or the highly seismic zone within the double seismic zone where the seismic fault ruptured by the earthquake connects the upper and lower layer of the double seismic zone. Beneath central Japan, thrust-type small repeating earthquakes occur at the boundary between the EUR and PHS plates and are located at the upper part of the low-V layer that is considered to be the oceanic crust of the PHS plate. In addition to the low-V oceanic crust, the subducting high-V PAC plate is clearly imaged to depths of approximately 250 km and the subducting high-V PHS zone to depths of approximately 180 km is considered to be the PHS plate. Beneath southwestern Japan, the iso-depth lines of the Moho discontinuity in the PHS plate derived by the receiver function method divide the upper low-V layer and lower high-V layer of our model at depths of 30–50 km. Beneath Kyushu, the steeply subducting PHS plate is clearly imaged to depths of approximately 250 km with high velocities. The high-V_P/V_S zone is considered as the lower crust of the EUR plate or the oceanic crust of the PHS plate at depths of 25–35 km and the partially serpentinized mantle wedge of the EUR plate at depths of 30–45 km beneath southwestern Japan. The deep low-frequency nonvolcanic tremors occur at all parts of the high-V_P/V_S zone—within the zone, the seaward side, and the landward side where the PHS plate encounters the mantle wedge of the EUR plate. We prove that we can objectively obtain the fine-scale 3D structure with simple constraints such as only 1D initial velocity model with no velocity discontinuity.  相似文献   

Two-stage model for chemical evolution of galactic halo     

Yasuki Kumai  Yutaka Sabano  Makoto Tosa 《Astrophysics and Space Science》1988,143(2):257-268

We propose a model of chemical evolution of the galactic halo which consists of a succession of two different evolutionary stages; each stage is characterized by different outflow rate of gas from the star-forming region so that different metal-enrichment rate is resulted. The low-metal stars with [Fe/H]<–0.8 are formed mainly during the first 3×10⁸ yr, and most of the high-metal stars with [Fe/H]–0.8 are formed during the succeeding 2×10⁹ yr. This model naturally explains the metallicity distribution of globular clusters in the galactic halo including both the metal-rich and the metal-poor clusters. We also discuss the implications of the present model on the formation and evolution of the galactic halo.  相似文献   

Atmospheric observations of liquid water in cloud and of chemical species in aerosols and gases near the ground and in fallen snow at Svalbard, Arctic     

Makoto Wada  Makoto Igarashi 《Atmospheric Research》1998,46(3-4)

Columnar observations of liquid water and of radar echo intensity in cloud were carried out, using a microwave radiometer and a vertically pointing radar respectively, in Ny-Ålesund, Svalbard. Chemical concentrations were also measured in aerosols, gases and snowfalls. Clouds with a large proportion of liquid water moved over the site after snow clouds, with a much lower liquid water content, had been present for about 16 h. The mass concentrations of most chemical species in snowfalls were lower from the first set of clouds than the second. The NO₃⁻ and SO₄²⁻ concentrations in gases and aerosols associated with the first set of clouds were higher than in the second set, but Cl⁻ concentration was less for the first set than the second.  相似文献   

Effects of temperature and chlorinity on the microdistribution ofFavella taraikaensis Hada (Ciliata) in Maizuru Bay     

Akihiko Kuwahara  Makoto Kashiwai  Masatosi Sinoda 《Journal of Oceanography》1975,31(3):109-114

Continuous sampling of the plankton with a pump sampler was carried out along a 960 m straight-line course in Maizuru Bay. The 25 collections of plankton were successively obtained at a depth of 1.5 m along the course, each of the collections covering a horizontal distance of 38 m. Vertical samplings of the plankton were done at five different depths (90, 120, 150, 180 and 210 cm) at 13 stations along the course. In both kinds of samplings temperature and chlorinity were measured.In the horizontal distribution ofF. taraikaensis, it was demonstrated that the counts of plankton had no correlation with the temperature and chlorinityin situ. There was a correlation between the counts and the differences of temperature and chlorinity between two successive sampling stations. It seemed thatF. taraikaensis was most abundant in the locations where the temperature difference was greater than +0.2C and the chlorinity difference was greater than +0.04 . This species was more abundant around the steep thermocline and the steep halocline. When the vertical profiles of temperature and chlorinity did not show steep gradients, this species was more abundant near the surface.  相似文献