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排序方式: 共有163条查询结果,搜索用时 250 毫秒
91.
Naoki Uchida Satoshi Yui Satoshi Miura Toru Matsuzawa Akira Hasegawa Yoshinobu Motoya Minoru Kasahara 《Gondwana Research》2009,16(3-4):527-533
We analyzed small repeating earthquakes recorded over a 13-year period and GPS data recorded over an 8-month period to estimate interplate quasi-static slip associated with the 2003 Tokachi-oki earthquake (M8.0) and the 2004 off-Kushiro earthquake (M7.1). The repeating-earthquake analysis revealed that the slip rate near the source region of the Tokachi-oki earthquake was relatively low (< 5 cm/year) prior to the earthquake; however, in the last 3 years leading up to the event, a minor acceleration in slip occurred upon the deeper extension of the coseismic slip area of the earthquake. Repeating-earthquake and GPS data indicate that large amounts of afterslip occurred around the rupture area following the earthquake; the afterslip mainly propagated to the east of the coseismic slip area. We also infer that the occurrence of the 2004 off-Kushiro earthquake, located about 100 km northeast of the epicenter of the Tokachi-oki earthquake, was advanced by the afterslip associated with the Tokachi-oki earthquake. 相似文献
92.
Mass depletion from the nucleus of a disk galaxy and its effect on the outer structure of the galaxy
High-energy explosions in the nuclei of galaxies throw out large amount of gas with sufficiently large velocities. This high-velocity ejections of gas is observed in Seyfert galaxies and in many normal spiral galaxies. The ejected gas flows continuously in the outer region and builds the outer structure of the galaxy. The degree of influence of the outflowing gas on the outer structure depends on the energy released during the explosion and on the damping rate of flow. These two parameters may essentially determine the type of galaxy to be evolved to including the Hubble-type. The physical interpretation of some such observed phenomena has been achieved on the basis of the solution of gas dynamical equations with viscosity. 相似文献
93.
Mita Rajaram B. P. Singh N. Nityananda A. K. Agrawal 《Geophysical Journal International》1979,56(1):127-138
Summary. Transient geomagnetic variations like SSCs, Bays, Sq and storm-time variations show anomalously large Z amplitudes at the three permanent magnetic observatories in India under the equatorial electrojet. Our earlier studies have shown that these anomalies cannot be explained in terms of the usual coastal effect. Another unique feature of this area is the small equatorial enhancement of all magnetic fluctuations, which still remains to be completely understood. It is also noticed that Z/H ratio at Annamalainagar is very large for night-time variations but becomes insignificant for day-time fluctuations, whereas no such large difference is seen at Trivandrum, the other coastal station. All the above features have been explained here by introducing the presence of a conducting channel in the lower crust or upper mantle between India and Sri Lanka Island. The anomalies of the equatorial electrojet in the Indian region thus do not necessitate the conducting surface of the mantle to be deeper in this area as has been suggested by earlier workers. A less conducting mantle in the Indian region otherwise could be difficult to incorporate in the present theories of mantle convection when this area is known to be tectonically active. The presence of the conducting channel is further confirmed by analogue model experiments of Papamastorakis. We further observe that the equatorial electrojet does have an associated internal part in the Indian region. 相似文献
94.
An evaporation experiment on matrix material of the Murchison (C2) meteorite up to 1900°C in vacuo has revealed the evaporation sequence of primitive dust material and the associated evolution of residual solid phases from hydrous silicates through magnesium silicates and iron-metal to calcium-aluminum oxides. The comparison with primitive meteorites suggests that the evaporation metamorphism coupled with the re-condensation may have played an important role in the generation of diverse primitive meteorites in the early solar nebula. 相似文献
95.
Robert N. Clayton Naoki Onuma Toshiko K. Mayeda 《Earth and Planetary Science Letters》1976,30(1):10-18
On the basis of18O/16O and17O/16O ratios, meteorites and planets can be grouped into at least six categories, as follows: (1) the terrestrial group, consisting of the earth, moon, differentiated meteorites and enstatite chondrites; (2) types L and LL ordinary chondrites; (3) type H ordinary chondrites; (4) anhydrous minerals of C2, C3, C4 carbonaceous chondrites; (5) hydrous matrix minerals of C2 carbonaceous chondrites; (6) the ureilites. Objects of one category cannot be derived by fractionation or differentiation from the source materials of any other category. 相似文献
96.
Anomalies in total field, horizontal, and vertical components over the Indian region derived from MAGSAT measurements have been inverted through the ridge-regression method, basically to test: (1) the application of the method in deriving a stable estimate of crustal magnetisation, and (2) the relative amount of information on crustal magnetisation contained in scalar vis-a`-vis vector data. Results show that the instabilities in magnetisation solution that appear when Mayhew's conventional method is applied in low latitudes could be removed through the ridge-regression technique. It was also noticed that magnetisation distribution estimated through the inversion of the total field(B) does not relate well with the geological features in the equatorial region. Inversion of theZ-anomaly alone gives realistic results for the equatorial region but not over higher latitudes. We conclude that a joint inversion ofX- andZ-anomalies provides a magnetisation estimate consistent with known geological features both for equatorial and higher latitudes. 相似文献
97.
Naoki Niwa Takuji Kobori Motoichi Takahashi Hiroshi Midorikawa Narito Kurata Takayuki Mizuno 《地震工程与结构动力学》2000,29(6):789-812
A semi‐active hydraulic damper (SHD) for a semi‐active damper system, which is useful for practical structural control especially for large earthquakes, has been developed. Its maximum damping force is set to 1 or 2 MN, and it is controlled by only 70 W of electric power. An SHD with a maximum damping force of 1 MN was applied to an actual building in 1998. This paper first presents the results of a dynamic loading test to confirm the control performance of the SHD. Next, an analytical model of SHDs (SHD model) is constructed with the same concept for two kinds of SHDs based on the test results. Through simulation analyses of the test results using the proposed SHD model, the dynamic characteristics of the SHD can be well represented within practical conditions. Simulation analyses are also carried out using a simple structure model with the SHD model. It is shown that this SHD model can be used to precisely evaluate the control effect of the semi‐active damper system and is useful in practical SHD design under the applied conditions. Copyright © 2000 John Wiley & Sons, Ltd. 相似文献
98.
AbstractFollowing the Great East Japan Earthquake, a massive tsunami caused serious damage to coastal dikes. Local scour at the ground behind these dikes reportedly causes dike failures. It is important to reveal the scour process to establish methods for effective scour countermeasures. Herein, we focus on geogrids. To verify this proposal and examine its design, flume-model experiments were performed for non-liquefied and liquefied grounds behind coastal dikes. The results showed that the scour amount and area were reduced drastically when geogrids were present. Geogrids on the sand-bed surface changed the direction of overflow water. Thus, a scour hole developed away from a coastal dike model. Furthermore, geogrids exerted a scour-reduction effect even during liquefaction. 相似文献
99.
Masayuki Uesugi Motoo Ito Hikaru Yabuta Hiroshi Naraoka Fumio Kitajima Yoshinori Takano Hajime Mita Yoko Kebukawa Aiko Nakato Yuzuru Karouji 《Meteoritics & planetary science》2019,54(3):638-666
Carbonaceous materials in the sample catcher of the Hayabusa spacecraft were assigned as category 3 particles. We investigated the category 3 particles with a suite of in situ microanalytical methods. Possible contaminants collected from the cleanrooms of the spacecraft assembly and extraterrestrial sample curation center (ESCuC) were also analyzed in the same manner as category 3 particles for comparison. Our data were integrated with those of the preliminary examination team for category 3 particles. Possible origins for the category 3 particles include contamination before and after the operation of the Hayabusa spacecraft. 相似文献
100.
Fumiaki Nakata Kazuhiro Shimasaku Mamoru Doi Nobunari Kashikawa Wataru Kawasaki Yutaka Komiyama Sadanori Okamura Maki Sekiguchi Masafumi Yagi Naoki Yasuda 《Monthly notices of the Royal Astronomical Society》1999,309(4):L25-L29
We investigate pure luminosity evolution models for early-type (elliptical and S0) galaxies (i.e. no number density change or morphological transition), and examine whether these models are consistent with observed number counts in the B , I and K bands, and redshift distributions of two samples of faint galaxies selected in the I and K bands. The models are characterized by the star formation time-scale τ SF and the time t gw when the galactic wind starts to blow, in addition to several other conventional parameters. We find that the single-burst model ( τ SF =0.1 Gyr and t gw =0.353 Gyr), which is known to reproduce the photometric properties of early-type galaxies in clusters, is inconsistent with the redshift distributions of early-type galaxies in the field environment, owing to overpredictions of the number of galaxies at z ≳1.4 even with strong extinction which is at work until t gw . In order for dust extinction to be more effective, we treat τ SF and t gw as free parameters, and find that models with τ SF ≳0.5 Gyr and t gw >1.0 Gyr can be made consistent with both the observed redshift distributions and the number counts, if we introduce strong extinction [ E ( B − V )≥1 as a peak value]. These results suggest that early-type galaxies in the field environment do not have the same evolutionary history as described by the single-burst model. 相似文献