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41.
O. T. Matsuura 《Astrophysics and Space Science》1976,41(1):195-211
A stationary state of production of solid material in the coma of a comet is sought by assuming a production and dynamics of solid grains liberated during the vaporization of cometary nuclei under the action of solar radiation. 相似文献
42.
O. T. Matsuura 《Solar physics》1969,9(1):173-182
A magnetohydrodynamic (MHD) approach is presented that appears to be comprehensive for the interpretation of the recently discovered microwave solar events, in which only the degree of circular polarization changes, without any increase in the output of the total solar flux. On the basis of this explanation experimental evidence is suggested for Alfvén waves, in relation to the velocity fields in the solar chromosphere. 相似文献
43.
At Shiotani, SW Japan, rhyolitic welded tuff forms a steep-sided funnel-shaped body, confined by Paleogene granitic rocks
to an elliptical area 1–1.5 km across. The Shiotani welded tuff is pervasively welded and foliated concordantly with the contact
that dips inward at angles of 70–90°. In contrast, nearby contemporary volcaniclastic deposits are non-welded and gently inclined.
Near the contact with the granite, the tuff is plastically deformed and shows lineations that plunge inward at angles of 40–65°.
Lithic and crystal clasts in the rheomorphic outer part are rotated in a plane normal to the foliations and parallel to the
lineations indicating downward flow of the welded tuff. The geometry and internal structures suggest that the Shiotani welded
tuff was emplaced and welded in a funnel-shaped eruption conduit. Upon collapse of a plinian or phreatoplinian eruption column,
the majority of the conduit-filling pyroclasts probably fell back en masse into the conduit. Heat and steam from underlying
magma and diffusion of interstitial volatiles into the glass perhaps reduced the viscosity of juvenile pyroclasts and facilitated
welding in the conduit, especially at deep levels. The hot welded pyroclasts then flowed down the conduit wall during welding
compaction and retreat of the magma. These processes resulted in increased welding toward the contacts and welding foliations
concordant with the steep wall. Emplacement of nearby correlative volcaniclastic mass-flow deposits in a shelf to upper bathyal
environment suggests a possibility that, when active, the Shiotani conduit was under the sea. Welding compaction would occur
even under the sea provided that the steam generated in the upper part of the conduit fill prevented water access.
Received: 28 February 1996 / Accepted: 5 May 1997 相似文献
44.
Tomonori Matsuura 《Journal of Oceanography》1986,42(5):362-372
Effects of the Ekman friction on the prograde (eastward) flows past a cylinder on a-plane are investigated when
(=R
2/U, whereR is the cylinder radius andU the freestream speed)O(1) and(=2E
k
1/2/R
0·O(1) where
is the non-dimensional beta parameter and the ratio of the square root of the Ekman numberE
k
multiplied by 2 to the Rossby numberRo multiplied by the aspect ratio(=H/R, whereH is the fluid depth). Previous studies without the Ekman friction have shown that the-effect inhibits flow separation for pragrade flows through the asymptotic boundary condition by shifting the region of the adverse pressure gradient toward the rear stagnation point. It is found that the Ekman friction alleviates this-effect on the exterior flow. In the Ek
1/4-boundary layer, on the other hand, Ekman friction suppresses the vorticity advection along the wall, which tends to make the boundary layer thickness thin and delay the flow separation. The Ekman friction thus affects flow separation in a complicated manner. Details of the boundary layer structures and the separation angles are described for 0.3<
<4.0 and 0.1<<1.5. 相似文献
45.
Tomonori Matsuura 《Journal of Oceanography》1980,36(1):39-45
The dynamics of decaying, isolated, intense vortices are investigated numerically using a highly idealized model. It is found that the cyclonic vortex decays while keeping the ratio TKE/TAPE nearly constant. Meanwhile the anticyclonic vortex decays rapidly within about two years and subsequently decays gradually. This difference is discussed in terms of momentum, vorticity and energy. The limitations of the model are also discussed. 相似文献
46.
47.
Aiming Lin Mikako Sano Maomao Wang Bing Yan Di Bian Ryoji Fueta Takashi Hosoya 《Journal of Seismology》2017,21(4):683-703
The Mw 6.2 (Mj 6.8) Nagano (Japan) earthquake of 22 November 2014 produced a 9.3-km long surface rupture zone with a thrust-dominated displacement of up to 1.5 m, which duplicated the pre-existing Kamishiro Fault along the Itoigawa–Shizuoka Tectonic Line (ISTL), the plate-boundary between the Eurasian and North American plates, northern Nagano Prefecture, central Japan. To characterize the activity of the seismogenic fault zone, we conducted a paleoseismic study of the Kamishiro Fault. Field investigations and trench excavations revealed that seven morphogenic paleohistorical earthquakes (E2–E8) prior to the 2014 Mw 6.2 Nagano earthquake (E1) have occurred on the Kamishiro Fault during the last ca. 6000 years. Three of these events (E2–E4) are well constrained and correspond to historical earthquakes occurring in the last ca. 1200 years. This suggests an average recurrence interval of ca. 300–400 years on the seismogenic fault of the 2014 Kamishiro earthquake in the past 1200 years. The most recent event prior to the 2014 earthquakes (E1) is E2 and the penultimate and antepenultimate faulting events are E3 and E4, respectively. The penultimate faulting event (E3) occurred during the period of AD 1800–1400 and is associated with the 1791 Mw 6.8 earthquake. The antepenultimate faulting event (E4) is inferred to have occurred during the period of ca. AD 1000–700, likely corresponding to the AD 841 Mw 6.5 earthquake. The oldest faulting event (E8) in the study area is thought to have occurred during the period of ca. 5600–6000 years. The throw rate during the early Holocene is estimated to be 1.2–3.3 mm/a (average, 2.2 mm/a) with an average amount of characteristic offset of 0.7–1.1 m produced by individual event. When compared with active intraplate faults on Honshu Island, Japan, these slip rates and recurrence interval estimated for morphogenic earthquakes on the Kamishiro Fault along the ISTL appear high and short, respectively. This indicates that present activity on this fault is closely related to seismic faulting along the plate boundary between the Eurasian and North American plates. 相似文献
48.
Yukiyo Saitoh Kenshi Kuma Yutaka Isoda Hiroshi Kuroda Hiromi Matsuura Taku Wagawa Hyoe Takata Naoto Kobayashi Seiya Nagao Takeshi Nakatsuka 《Journal of Oceanography》2008,64(6):815-830
We report measurements of iron, nutrients, dissolved oxygen, humic-type fluorescence intensity and chlorophyll a concentrations in the coastal waters at the inflow (western) and outflow (eastern) ends of Tsugaru Strait (Japan) in June
2003 and 2004. Two different water masses (intensive eastward flow “subtropical Tsugaru Warm Current Water (TWCw)” and weak
westward flow “subarctic Oyashio Water (OW)”) were observed at the eastern end of the strait. TWCw at the southern part of
the eastern strait was vertically homogeneous with a uniform concentrations of iron (0.7–1.1 nM for labile dissolved Fe and
14–20 nM for total dissolvable Fe in 2003) as well as other chemical, biological and physical components throughout the water
column of 200 m due to strong vertical mixing in the strait. The degree of mixing in the Tsugaru Warm Current (TWC) is predominantly
affected by diurnal tidal current, which is strong during the period of tropical tides and weak during the period of equinoctial
ones. The especially strong vertical water mixing in 2003 is caused by large dissipation energy input due to the bottom friction
of passage-flow through the strait and tidal current. At the northern part of the eastern strait, the fresh surface layer
overlying the OW and the deep-bottom waters in 2003 contained large concentrations of dissolved iron, resulting from iron
supplied from river runoff and shelf sediments, respectively. These results suggest that the most important mechanism for
transporting iron in the strait is the strong vertical water mixing due to the tidal current, and that the iron sources in
the coastal waters are the organic-associated, iron-rich freshwater input into the surface water. 相似文献
49.
A mechanism of interdecadal variability of tropical cyclone activity over the western North Pacific 总被引:7,自引:0,他引:7
Tropical cyclone (TC) activity in the western North Pacific (WNP) has changed interdecadally with an approximately 20-year period between 1951 and 1999. The cause and mechanism of interdecadal variability of TC frequency in the WNP is investigated using NCEP/NCAR reanalysis and the result obtained from a high-resolution coupled general circulation model (CGCM). The interdecadal variability of TC activity in the WNP correlates with long-term variations in sea surface temperatures (SSTs) in the tropical central Pacific and with those of westerly wind anomalies associated with the monsoon trough that appears over the tropical WNP during the typhoon season of July to October. The westerly wind anomalies at near 10°N show positive feedback with the SST anomalies in the central Pacific. Therefore, the interdecadal variability of TC frequency is related to long-term variations in atmosphere–ocean coupling phenomena in the tropical North Pacific. A 50-year long-run simulation using the high-resolution CGCM showed the robustness of interdecadal variability of TC frequency. 相似文献
50.
Seasonal transition of hydrological processes in a slow‐moving landslide in a snowy region
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Hikaru Osawa Yuki Matsushi Sumio Matsuura Takashi Okamoto Tatsuya Shibasaki Hiroyuki Hirashima 《水文研究》2018,32(17):2695-2707
A comprehensive understanding of seasonal hydrological dynamics is required to describe the influence of pore‐water pressure on the stability of landslides in snowy regions. This study reports on the results of continuous meteorological and hydrological observations over 2 years on a landslide body comprising Neogene sedimentary rocks in northern Japan, where a thick (3–5 m) seasonal snowpack covers the land surface. Monitoring of the volumetric water content in shallow unsaturated zones (<0.8 m depth) and pore‐water pressure in saturated bedrock at depths of 2.0 and 5.2 m revealed clear seasonality in hydrological responses to rainfall and meltwater supply. During snow‐free periods, both the shallow soil moisture and deep pore‐water pressure responded rapidly to intense rainwater infiltration. In contrast, during snowmelt, the deep pore pressure fluctuated in accordance with the daily cycle of meltwater input, without notable changes in shallow moisture conditions. During occasional foehn events that cause intense snow melting in midwinter, meltwater flows preferentially through the layered snowpack, converging to produce a localized water supply at the ground surface. This episodically triggers a significant rise in pore‐water pressure. The seasonal differences in hydrological responses were characterized by a set of newly proposed indices for the magnitude and quickness of increases in the pressure head near the sliding surface. Under snow‐covered conditions, the magnitude of the pressure increase tends to be suppressed, probably owing to a reduction in infiltration caused by a seasonal decrease in the permeability of surface soils, and effective pore‐water drainage through the highly conductive colluvial layer. Deep groundwater flow within bedrock remained in a steady upwelling state, enhanced by increasing moisture in shallow soils under snow cover, reflecting the convergence of subsurface water from surrounding hillslopes. 相似文献