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91.
A three-dimensional seismometer array was installed in the Chiba Experiment Station of the Institute of Industrial Science, University of Tokyo in 1982. The array system consists of 44 three-component accelerometers densely placed both on the ground surface and in boreholes. A complementary system for the measurement of ground and buried pipe strains was also installed at the same site. The array system has been successfully in operation, and more than 160 earthquakes have been recorded. Considering a wide use of these seismograms, the Chiba array database has recently been created comprising twenty-seven major events. This paper describes the Chiba array system and its strong motion database. Results of engineering analysis using the selected records are also presented. 相似文献
92.
We have carried out multi-station TV observations since 1994 in order to determine the orbit of the Arietid daytime meteor
stream. In 1999, one possible Arietid meteor was recorded by our simultaneous observations and its orbit was determined. In
2003, two Arietid meteors were observed from two stations of our observing site, those orbits were determined precisely, the
orbital elements were in good agreement with each other. This is the first time that determination of the precise orbit of
the Arietids has been made from optical observations. The orbit of these Arietid meteors, and comparison with the orbit obtained
from radar observations are discussed. 相似文献
93.
Raulin Jean Pierre Makhmutov Vladimir S. Kaufmann Pierre Pacini Alessandra Abe Lüthi Thomas Hudson Hugh S. Gary Dale E. 《Solar physics》2004,223(1-2):181-199
We present a report on the strong X5.3 solar flare which occurred on 25 August 2001, producing high-level γ-ray activity, nuclear lines and a dramatic long-duration white-light continuum. The bulk of millimeter radio fluxes reached a peak of ∼100 000 solar flux units at 89.4 GHz, and a few thousands of solar flux units were detected in the submillimeter range during the impulsive phase. In this paper we focus on and discuss (i) the implications inferred from high frequency radio observations during the impulsive phase; (ii) the dynamics of the low corona active region during the impulsive phase. In particular we found that 4–5 × 1036 accelerated (>20 keV) electrons s−1 radiating in a 1000–1100 G region, are needed to explain the millimeter to submillimeter-wave emissions. We present evidence that the magnetic field in the active region was very dynamic, and that strong non-thermal processes were triggered by the appearance of new, compact, low-lying (few thousand kilometers) loop systems, suggesting the acceleration site(s) were also located in the low solar atmosphere. 相似文献
94.
Morphometrical analysis of two tropical mountain river basins of contrasting environmental settings, the southern Western Ghats, India 总被引:8,自引:4,他引:4
Jobin Thomas Sabu Joseph K. P. Thrivikramji George Abe N. Kannan 《Environmental Earth Sciences》2012,66(8):2353-2366
The morphometric analysis of river basins represents a simple procedure to describe hydrologic and geomorphic processes operating on a basin scale. A morphometric analysis was carried out to evaluate the drainage characteristics of two adjoining, mountain river basins of the southern Western Ghats, India, Muthirapuzha River Basin (MRB) in the western slopes and Pambar River Basin (PRB) in the eastern slopes. The basins, forming a part of the Proterozoic, high-grade, Southern Granulite Terrain of the Peninsular India, are carved out of a terrain dominantly made of granite- and hornblende-biotite gneisses. The Western Ghats, forming the basin divide, significantly influences the regional climate (i.e., humid climate in MRB, while semi-arid in PRB). The Survey of India topographic maps (1:50,000) and Shuttle Radar Topographic Mission digital elevation data were used as the base for delineation and analysis. Both river basins are of 6th order and comparable in basin geometry. The drainage patterns and linear alignment of the drainage networks suggest the influence of structural elements. The Rb of either basins failed to highlight the structural controls on drainage organization, which might be a result of the elongated basin shape. The irregular trends in Rb between various stream orders suggest the influence of geology and relief on drainage branching. The Dd values designate the basins as moderate- to well-drained with lower infiltration rates. The overall increasing trend of Rl between successive stream orders suggests a geomorphic maturity of either basins and confirmed by the characteristic I hyp values. The Re values imply an elongate shape for both MRB and PRB and subsequently lower vulnerability to flash floods and hence, easier flood management. The relatively higher Rr of PRB is an indicative of comparatively steeply sloping terrain and consequently higher intensity of erosion processes. Further, the derivatives of digital elevation data (slope, aspect, topographic wetness index, and stream power index), showing significant differences between MRB and PRB, are useful in soil conservation plans. The study highlighted the variation in morphometric parameters with respect to the dissimilarities in topography and climate. 相似文献
95.
Excitation of Resonant Modes along the Japanese Coast by the 1993 and 1983 Tsunamis in the Japan Sea
Kuniaki Abe 《Pure and Applied Geophysics》2009,166(1-2):117-130
We observed seiches at 55 ports in Japan facing the Japan Sea and obtained dominant periods from their maximum spectral amplitudes. These periods were mostly determined ranging from 10 to 40 minutes. They were compared with dominant periods of the 1993 Hokkaido Nansei-oki tsunami and the 1983 Nihonkai Chubu-oki tsunami at the same ports. As a result, relations of dominant periods between seiches and tsunamis are classified into three types. The first one is fundamental mode excitation, the second is higher mode excitation and the third is no excitation. Plotting the maximum spectral amplitude normalized at an epicentral distance of 50 km versus the ratio of the tsunami dominant period to the seiche dominant period, we obtained resonance curves having maxima at one. This fact shows a contribution of resonance to the amplification. Thus it is recognized that the dominant period of seiching is an important factor in interpreting amplification and resonance of tsunami. 相似文献
96.
Akira Tsuchiyama Masayuki Uesugi Kentaro Uesugi Tsukasa Nakano Ryo Noguchi Toru Matsumoto Junya Matsuno Takashi Nagano Yuta Imai Akira Shimada Akihisa Takeuchi Yoshio Suzuki Tomoki Nakamura Takaaki Noguchi Masanao Abe Toru Yada Akio Fujimura 《Meteoritics & planetary science》2014,49(2):172-187
In this study, the three‐dimensional (3‐D) microstructure of 48 Itokawa regolith particles was examined by synchrotron microtomography at SPring‐8 during the preliminary examination of Hayabusa samples. Moreover, the 3‐D microstructure of particles collected from two LL6 chondrites (Ensisheim and Kilabo meteorites) and an LL5 chondrite (Tuxtuac meteorite) was investigated by the same method for comparison. The modal abundances of minerals, especially olivine, bulk density, porosity, and grain size are similar in all samples, including voids and cracks. These results show that the Itokawa particles, which are surface materials from the S‐type asteroid Itokawa, are consistent with the LL chondrite materials in terms of not only elemental and isotopic composition of the minerals but also 3‐D microstructure. However, we could not determine whether the Itokawa particles are purely LL5, LL6, or a mixture of the two. No difference between the particles collected from Rooms A and B of the sample chamber, corresponding to the sampling sequence of the spacecraft's second and first touchdowns, respectively, was detected because of the statistically small amount of particles from Room B. 相似文献
97.
When river water mixes with sea water in estuary area, the concentrations of the dissolved element in river water may be changed
by either a simple physical mixing process or some complex chemical processes. It has been clarified in the Chikugogawa River
estuary area that the change in concentrations of SO
4
2−
, BO
3
3−
, Mg2+, Ca2+ and F− is only due to the mixing process but the change in concentrations of SiO
3
2−
and Al3+ is due to the chemical process in addition to the mixing process.
相似文献
98.
99.
The effect of solar radiation on the near-term rotation rate of Asteroid Itokawa via the YORP effect is predicted using the detailed shape model, rotation pole, mass estimate, and optical properties derived from the Hayabusa mission to Itokawa. Based on these estimates Itokawa is decelerating at a rate which will halve its rotation rate in only 50-90 thousand years, a large deceleration that should be detectable in a future appartion. The implications of such a large deceleration for Itokawa's past history are discussed and related to possible seismic shaking. 相似文献
100.
Sensitivity of the central Asian climate to uplift of the Tibetan Plateau in the coupled climate model (MRI-CGCM1) 总被引:2,自引:0,他引:2
Abstract The relationship between the altitude of the Tibetan Plateau and climate change in central Asia was investigated through a numeric experiment using the Meteorological Research Institute (MRI) coupled atmosphere–ocean general circulation model I (MRI-CGCM1). The results suggest that summer precipitation in central Asia decreased significantly as the Tibetan Plateau rose in height. Spring precipitation, however, increased during initial growth stages when the plateau height was up to 40% of its present-day height, and then decreased with further plateau growth. During the Tibetan Plateau uplift, the difference between precipitation and evaporation was minimal during spring. When the plateau attained a height exceeding 60% of its present height, relatively low precipitation but high evaporation in spring led to a lower amount of ground moisture. In the case of the high plateau, sensible heat flux during summer and fall largely exceeded latent heat flux. Change was particularly significant for cases when the plateau reached 40–60% of its present-day height. The duration of the predominant sensible heat flux became longer with the uplift of the Tibetan Plateau. The period in which latent heat exceeded sensible heat seems to have been restricted to winter and early spring. The numeric experiments suggest that a significant drying of central Asia corresponded to the period in which the Tibetan Plateau exceeded approximately half its present-day height. 相似文献