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71.
Naoki Kabeya Nick A. Chappell Wlodek Tych Akira Shimizu Shiho Asano Hiroaki Hagino 《水文科学杂志》2016,61(9):1716-1727
ABSTRACTA new method known as Unobserved Components–Dynamic Harmonic Regression (UC-DHR) was applied to a 39-year record of rainfall and streamflow for three sub-catchments of the Sarukawa Experimental Watershed in southwestern Japan. Some 25% of the timber was harvested from one of the sub-catchments in May–July 1982 and the objective was to quantify the magnitude of this effect relative to the effects of climate cycles (e.g. Southern Oscillation Index). The observed effects of inter-annual climate cycles (i.e. 0.89–1.36 mm/d) were seen to be comparable (i.e. 0.70–1.17 mm/d) to the effects of harvesting 25% of the standing timber. This result underlines the importance of always quantifying the effect of climate on streamflow response when harvesting impacts are studied.
Editor D. Koutsoyiannis; Associate editor T. Okruszko 相似文献
72.
Sayaka Sogawa Takashi Kidachi Masahumi Nagayama Tadafumi Ichikawa Kiyotaka Hidaka Tsuneo Ono Yugo Shimizu 《Journal of Oceanography》2017,73(5):603-622
A continuous survey examined short-term variations in the zooplankton community and physical ocean environment from the northeastern Izu Islands to Boso Peninsula in Japan. High copepod abundance and small upwellings in the surface layer and salinity minimum layer in the subsurface were observed on the north side of coastal fronts in the westernmost transect, moving southward as the Kuroshio Current left the Boso Peninsula. Thus, the salinity minimum layer might be a key factor forming upwelling and the fronts, leading to large abundance of coastal copepods off the northeastern Izu Islands. A community structure analysis of calanoid copepods revealed an intermediate belt assemblage between coastal and offshore (Kuroshio) assemblages. Copepod abundance was remarkably low and Ctenocalanus vanus dominated (nearly 37%) in the intermediate belt zone, indicating that C. vanus has a relatively high tolerance to adverse environments for calanoid copepods. As the Kuroshio Current left the Boso Peninsula, the coastal assemblage expanded in the same direction, and the intermediate belt assemblage off the northeastern Izu Islands disappeared. The largest population of Calanus sinicus was found along the two western transects off the northeastern Izu Islands (>1000 m depth), which was assumed to be transported from Sagami Bay and advanced southwestward while growing from copepodite stages CIII to CV. Larvae of C. sinicus would be an important food for fish larvae in addition to Paracalanus parvus s.l., the numerically dominant species in the coastal assemblage, and C. vanus under the adverse conditions for coastal copepods. 相似文献
73.
For the appropriate management and restoration of rivers, isolated vegetation is often a practical means for improving stream habitat and ecology. The effect of a finite vegetation patch on flow and bed morphology in an open channel was investigated using laboratory experiments. The patch containing emergent and submerged vegetation was modeled using circular cylinders and located mid‐channel along a side wall. Several configurations of the patch and submergence ratio (i.e. water depth to the height of vegetation), and two flow conditions (i.e. below and above the sediment motion threshold) were considered. For flows below the sediment motion threshold, erosion occurred primarily on the opposite side of the patch and near the leading edge of the patch. The degree of scouring depth observed in both these regions was affected by the submergence ratio and it increased with the non‐dimensional flow blockage (i.e. the product of the patch density and width). In contrast, for flows above the sediment motion threshold, sediment accumulated within and around the patch due to a reduction in bed shear stress, which was strongly influenced by the flow blockage and the obstruction ratio (i.e. the ratio of patch width to channel width). The eroded area observed within the patch was consistent with the interior adjustment region where the deceleration and diversion of flow occurred through the patch. As the flow blockage increased or as the obstruction ratio decreased, the deposition rate within and behind the patch decreased. Furthermore, the deposition rate increased with an increase in the ratio of flow rate through the patch to total flow rate regardless of the submergence ratio. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
74.
M. Tahara K. Uehira H. Shimizu M. Nakada T. Yamada K. Mochizuki M. Shinohara M. Nishino R. Hino H. Yakiwara H. Miyamachi K. Umakoshi M. Goda N. Matsuwo T. Kanazawa 《Physics of the Earth and Planetary Interiors》2008,167(1-2):19-33
The Hyuganada region, a forearc region of Southwest Japan, is characterized by several interesting geological and geophysical features, i.e., significant aseismic crustal uplift of 120 m during the past 120 thousand years at the Miyazaki Plain, negative free-air gravity anomalies with the maximum magnitude of −130 mgal, and relatively less cohesive interplate coupling compared with that for off the Shikoku and Kii Peninsula. In order to examine the causes of these observations, we determined a detailed three-dimensional seismic velocity structure based on the seismic data observed by ocean bottom seismometers (OBS) and land stations. P- and S-wave tomographic velocity structures clearly indicate the subducting slab and also the zones of high Poisson's ratio at 25–35 km depth along the coastline of the northeastern part of the Hyuganada. The region with high Poisson's ratio may correspond to the serpentinized mantle wedge as suggested for other mantle wedges, and appears to be coincident with the zone for observed aseismic slips such as the slow-slip and after-slip events. Also, the detection may be related to a relatively weak interplate coupling in the Hyuganada region. The tomographic structures also indicate low velocity zones with a horizontal scale comparable to the Kyushu-Palau Ridge in and around the subducting slab. If we assume that the low velocity zones correspond to the subducted Kyushu-Palau Ridge, then the predicted gravity anomaly due to the density contrast between the low velocity zones and the surrounding region can explain about 60% of the gravity anomaly in the Hyuganada region. The buoyancy is probably an important factor for the crustal uplift observed in the Miyazaki Plain, the steep bending of the subducting slab and the normal fault-type earthquakes around the Hyuganada region. 相似文献
75.
Reaction between slab-derived melts and peridotite in the mantle wedge: experimental constraints at 3.8 GPa 总被引:75,自引:0,他引:75
Laboratory experiments on natural, hydrous basalts at 1–4 GPa constrain the composition of “unadulterated” partial melts of eclogitized oceanic crust within downgoing lithospheric slabs in subduction zones. We complement the “slab melting” experiments with another set of experiments in which these same “adakite” melts are allowed to infiltrate and react with an overlying layer of peridotite, simulating melt:rock reaction at the slab–mantle wedge interface. In subduction zones, the effects of reaction between slab-derived, adakite melts and peridotitic mantle conceivably range from hybridization of the melt, to modal or cryptic metasomatism of the sub-arc mantle, depending upon the “effective” melt:rock ratio. In experiments at 3.8 GPa, assimilation of either fertile or depleted peridotite by slab melts at a melt:rock ratio 2:1 produces Mg-rich, high-silica liquids in reactions which form pyrope-rich garnet and low-Mg# orthopyroxene, and fully consume olivine. Analysis of both the pristine and hybridized slab melts for a range of trace elements indicates that, although abundances of most trace elements in the melt increase during assimilation (because melt is consumed), trace element ratios remain relatively constant. In their compositional range, the experimental liquids closely resemble adakite lavas in island-arc and continental margin settings, and adakite veins and melt inclusions in metasomatized peridotite xenoliths from the sub-arc mantle. At slightly lower melt:rock ratios (1:1), slab melts are fully consumed, along with peridotitic olivine, in modal metasomatic reactions that form sodic amphibole and high-Mg# orthopyroxene. 相似文献
76.
E. Hiei Y. Shimizu H. Miyazaki H. Imai K. Sato S. Kuji W. Sinambela 《Astrophysics and Space Science》1986,119(1):9-15
From the photographs taken at the total solar eclipse of 11 June 1983, we derived the electron density for the north polar rays and for the thread-like fine structures above the active region, which are 108 at 1.4 solar radii and 3×109 at 1.15 solar radii, respectively. The brightness distributions of the corona at the polar region and above the active region, and the flattening index were also derived.Paper presented at the IAU Third Asian-Pacific Regional Meeting, held in Kyoto, Japan, between 30 September–6 October, 1984. 相似文献
77.
R. Vannucci N. Shimizu G. B. Piccardo L. Ottolini P. Bottazzi 《Contributions to Mineralogy and Petrology》1993,113(4):437-449
Ion probe investigations on mineral phases forming the Al-Di pyroxenites from the Zabargad peridotite body indicate that porphyroclastic pyroxenes in composite mafic layers record an unusual HREE, Zr, Sc enrichment not registered by pyroxenes in spinel websterites. Orthopyroxene in the opx+sp clusters forming the inner, cpx-free zone of layered pyroxenites shows strongly fractionated REE patterns (HREEN/LREEN>1000; Yb>100xch) and very high Zr, Sc and Y abundances (up to 30,672 and 60ppm, respectively). In the outer, cpx-rich zone porphyroclastic clinopyroxene is strongly HREE enriched (HREEN/LREEN29; Yb 269xch) and displays very high Sc and Zr abundances (up to 819 and 164 ppm, respectively). It is suggested that the unusual trace element abundances are inherited from a precursor garnet. Composite pyroxenite layers are interpreted as former garnet clinopyroxenites characterized by gnt/cpx modal zoning. The sp+opx(cpx-free) assemblage in the inner part is a product of the break-down reaction of garnet upon decompression, with Ca of the original garnet completely entering the enstatite solid solution. The temperature at which the breakdown reaction occurred is estimated to be higher than 1000°C (P in the range 20–30 kbar). In the outer part, decompression caused the garnet to form a sp+opx assemblage; however, the grossularite component participated in the formation of new clinopyroxene which reacted with the clinopyroxene present in the original mode before the decompression reaction, thus forming a cpx2+sp+opx assemblage. As a result of garnet breakdown, pyroxenes have peculiar HFSE anomalies. Progressive upwelling during the Red Sea rifting produced incomplete reaction under pl-facies conditions. The geochemical signatures of precursor garnet in pyroxenes were partially crased during the recrystallization from granular spincl-bearing to granoblastic plagioclase-bearing assemblages, being preserved only in a few porphyroclast relies. The finding of pyroxenes with trace element characteristics of precursor garnet has important geodynamic and geochemical implications. Al-Di pyroxenite layers had a long history within the mantle, before the continental lithosphere rifting and thinning took place in the region. It is suggested that Al-Di pyroxenites were formed by deep-seated tholeiitic magmatism unrelated to the Red Sea evolution, thus representing the earliest event in the Zabargad upper mantle. Garnet breakdown significantly preceded the metasomatism induced by hydrous fluids (crystallization of Ti-rich pargasite) and the later intrusion of hydrous (Cr-Di) pyroxenite dykes. During the stages of mantle evolution, the HFSE anomalies in pyroxenes varied significantly. We note that the study of HFSE anomalies in mineral phases reveals complex geochemical histories which are not recorded by the whole-rock system. 相似文献
78.
G. Suhr H. A. Seck N. Shimizu D. Günther G. Jenner 《Contributions to Mineralogy and Petrology》1998,131(2-3):136-154
Up to 3 km of dunitic rocks occur below crustal gabbro in the Blow Me Down massif (Bay of Islands Ophiolite, Newfoundland).
Analyses of dunite- and gabbro-hosted clinopyroxene grains (cpx) for rare earth elements (REE), Zr, and Ti reveal three types
of chondrite-normalized patterns: N-group patterns are similar to cpx grains as they would form by fractionation from a range
of mid ocean ridge basalts (MORB). They are typical for a few higher level dunitic samples as well as mafic cumulates. F-group
patterns show light REE depletion, very strong middle REE fractionation and a positive Zr anomaly and occur in dunites only.
R-group patterns are severely depleted in both light and heavy REEs relative to MORB-like cpx and two samples of the group
display a positive Ti anomaly. They are also restricted to dunitic rocks. The patterns are explained in a two stage model
in which an established dunite sequence, dominated by MORB-type cumulate signatures (N-group), was infiltrated by extremely
refractory melts. During infiltration of the refractory melt chromatographic fractionation occurred, transforming N-group
dunites into F-group and R-group dunites. The F-group patterns are composite patterns: heavy REE, Ti ± Zr reflect the original
MORB-like cumulate dunite host, light REEs indicate equilibrium with the infiltrating, refractory melts. Steep slopes in the
middle REEs reflect the position of the chromatographic front. For more intense percolation of refractory melts, R-group patterns
with a positive Ti anomaly will form by the same process. The rest of the R-group patterns displaying no positive Ti anomaly
may represent either the most intensely reacted host rocks or these dunites derive directly as cumulates from refractory melts.
Only small volumes of refractory melt (a 5 m column) are required to imprint the observed trace element pattern on the thick
original dunite sequence. One of several possible origins for the refractory melts is transformation of original MORB-type
melts by way of chromatographic fractionation within the highly depleted, residual uppermost mantle. In the framework of an
oceanic spreading centre, the migrating, refractory liquids are considered a late event following the main constructive stage
dominated by aggregated melts. The study demonstrates that highly refractory melts can exist under oceanic spreading centres
dominated by a MORB-like cumulate and volcanic sequence.
Received: 2 September 1996 / Accepted: 20 November 1997 相似文献
79.
Mikio Shimizu 《Astrophysics and Space Science》1977,51(1):241-243
The argument for the similarity of the composition of cometary volatiles to that of interstellar molecules has been strengthened by the analysis of CO+ and CO
2
+
emission of the comet West. The strong 6300 Å emission of oxygen atoms can be interpreted in terms of photodissociation of OH by the solar Lyman-alpha radiation, and not as being due to photo-dissociation of CO2 of speculatively large amount. 相似文献
80.