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491.
492.
沈阳的郊区化—兼论中西方郊区化的比较 总被引:68,自引:0,他引:68
在我国80年代才开始郊区化过程,研究刚刚起步。亟待城市学界对我国郊区化的特点、机制、发展规律以及与西方的异同进行深入研究,发掘它对城市发展有利的一面,本文正是出于这目的,研究了沈阳的郊区,内容包括地域划分,80年代是否开始、大体的强度,90年代的 状况,机制分析和调控建议。 相似文献
493.
494.
Abstract Recent paleomagnetic studies are reviewed in an effort to clarify the relationship between the intra-arc deformation of central Japan and the collision tectonics of the Izu-Bonin Arc. The cusp structure of the pre-Neogene terranes of central Japan, called the Kanto Syntaxis, suggests a collisional origin with the Izu-Bonin Arc. The paleomagnetic results and newly obtained radiometric ages of the Kanto Mountains revealed the Miocene rotational history of the east wing of the Kanto Syntaxis. More than 90° clockwise rotation of the Kanto Mountains took place after deposition of the Miocene Chichibu Basin (planktonic foraminiferal zone of N.8: 16.6–15.2 Ma). After synthesizing the paleomagnetic data of the Japanese Islands and collision tectonics of central Japan, it appears that approximately a half rotation (40–50°) probably occurred at ca 15 Ma in association with the rapid rotation of Southwest Japan. The remainder (50-40°) continued until 6 Ma, resulting in the sharp bent structure of the pre-Neogene accretionary complexes (Kanto Syntaxis). The latter rotation seems to have been caused by the collision of the Izu-Bonin Arc on the northwestward migrating Philippine Sea Plate. 相似文献
495.
Abstract Indications of transient crustal displacement associated with the 3 March 1985, M, = 7.8, Central Chile earthquake are evidenced by various observational devices. Almost half a meter of coastal uplift at localities close to the epicentral region was detected by repeated leveling lines. A tide gauge at Valparaiso revealed minor coseismic coastal subsidence (∼ 10 cm) continuously developing after the earthquake. Two limnigraphs, 27 km apart, that were situated at the extremes of Rapel Lake to the south of the leveling line, have recorded continuously the equipotential lake level for more than 10 years, providing a permanent very-long-base tiltmeter. The water level difference at the two limnigraphs as a function of time resembles a ramp function, beginning approximately at the time of the earthquake occurrence and gradually developing over a period of 10 months with a maximum amplitude of 120 mm or 4.4 p radians in tilt. The shape of the time-dependent tilt is mimicked by the sea level signal recorded at Valparaiso, ∼ 100 km away from Rapel Lake, showing a maximum coastal subsidence of 0.6 m. Comparisons of sea level changes produced by the 1971, M, = 7.5, earthquake indicates that they represent rupture in different portions along the seismogenetic region as well as a different rupture mode. Gravity surveys carried out in three different pre- and post-seismic epochs, along the segment of the leveling line which shows major coseismic uplift, indicate that the whole region has subsided, post-seismically, 10 em in 5 years. These observations are interpreted in terms of a variable slip dislocation model. Inversions show that it is the more than 2 m of fault displacement in 10 months of post-seismic movement along the contact between the Nazca and South America plates, which is interpreted to be responsible for the time-dependent elevation changes. 相似文献
496.
Estimation of spectral reflectance of snow from IRS-1D LISS-III sensor over the Himalayan terrain 总被引:1,自引:0,他引:1
The sensor onboard the satellite views the earth as a plain surface and consequently the satelliteobtained spectral radiances
cannot represent true values over a mountainous terrain. The relative magnitudes of terrain slope and its aspect with respect
to the sun's position will determine the amount of direct solar radiation incident on an undulating surface. Estimation of
spectral reflectance from satellite data forms an important component in many of the snow and glacier studies. The spectral
reflectance of snow is influenced by its various parameters. The changes in snowpack characteristics as a result of various
metamorphic processes, with age, can cause variations in its spectral reflectances. Since, the terrain geometry also modifies
the amount of reflected radiation from a rugged surface, one has to correct the estimated spectral reflectances for terrain
topography so as to use them in deriving the snowpack characteristics accurately. Also, the amounts of melt runoff originating
from glaciers having different slopes and orientations will not be the same. Considering these aspects, a model has been developed
to estimate the terrain corrected spectral reflectances over the Himalayan terrain using the Linear Imaging Self Scanner-III
data of the Indian Remote Sensing Satellite. The model computes spectral reflectances from satellitebased radiance measurements
and includes the effect of the terrain topography on the incident solar radiation. The terrain slope and its aspect are generated
from the digital elevation model of the region. The analysis carried out over the Beas Basin, Himachal Pradesh, India, indicated
a variation of 22% in the amount of incident solar radiation for an increase of 10‡ in terrain slope. Further, the terrain
with south-east aspect received maximum amount of solar radiation. The large differences observed between the uncorrected
and terrain corrected reflectances in the shortwave infrared band (B5), which is not saturated over the snow covered region,
suggest that the terrain slope and its aspect cannot be neglected in estimating the accurate spectral reflectances over the
Himalayan terrain. 相似文献
497.
Mg- and Al-rich granulites of the central Highland Complex,Sri Lanka preserve a range of reaction textures indicative ofa multistage PT history following an ultrahigh-temperaturemetamorphic peak. The granulites contain a near-peak assemblageof sapphirinegarnetorthopyroxenesillimanitequartzK-feldspar,which was later overprinted by intergrowth, symplectite andcorona textures involving orthopyroxene, sapphirine, cordieriteand spinel. Biotite-rims, kornerupine and orthopyroxene-rimson biotite are considered to be late assemblages. Thermobarometriccalculations yield an estimated PT of at least 1100°Cand 12 kbar for the near-peak metamorphism. Isopleths of Al2O3in orthopyroxene are consistent with a peak temperature above1150°C. The PT path consists of four segments. Initialisobaric cooling after peak metamorphism (Segment A), whichproduced the garnetsapphirinequartz assemblage,was followed by near-isothermal decompression at ultrahigh temperature(Segment B), which produced the multiphase symplectites. Furtherisobaric cooling (Segment C) resulted in the formation of biotiteand kornerupine, and late isothermal decompression (SegmentD) formed orthopyroxene rims on biotite. This evolution canbe correlated with similar PT paths elsewhere, but thereare not yet sufficient geochronological and structural dataavailable from the Highland Complex to allow the tectonic implicationsto be fully assessed. KEY WORDS: central Highland Complex; granulites; multistage evolution; Sri Lanka; UHT metamorphism 相似文献
498.
ZHANG Guowei Dong Yunpeng Lai Shaocong GUO anlin Meng Qingren Liu Shaofeng CHENG Shunyou Yao Anping ZHANG Zongqing PEI Xianzhi Li Sanzhong 《中国科学D辑(英文版)》2004,47(4)
The Mianlue tectonic zone (Mianlue zone), an ancient suture zone in addition to theShangdan suture in the Qinling-Dabie orogenic belt, marks an important tectonic division geo-logically separating north from south and connecting east with west in China continent. To de-termine present structural geometry and kinematics in the Mianlue tectonic zone and to recon-struct the formation and evolution history involving plate subduction and collision in theQinling-Dabie orogenic belt, through a multidisciplinary study, are significant for exploring themountain-building orogenesis of the central orogenic system and the entire process of the majorChinese continental amalgamation during the Indosinian. 相似文献
499.
利用中心年代分别为1964、1979及1993的3期精密水准复测资料研究中轴(构造)带及其两侧(东经90.5°至113.5°,北纬21.5°至42.0°)的现代地壳垂直运动。结果表明中轴带及其两侧近30多年的运动趋势与最近十几年运动趋势十分一致。而且与该地区的地势地貌有良好的相关性,几个垂直形变的高梯度带均分布在本区两个大盆地(四川盆地与柴达木盆地)周边。整个形变态势表现出明显的继承性运动特征。但在70年代,该区的垂直运动经历了一次明显的变化或反向。联系到同一时期中轴带南部的一系列7级以上强震的发生,提示大区域的垂直形变的趋势变化可能是强震活跃的一种指示。文中还利用得到的地壳垂直形变图研究了区内南—北、东—西向穿切几个主要构造单元的9条剖面的地壳垂直运动特征和它们的时空演化,结果进一步证明1969~1979年间,我国中西部比较强烈的地壳垂直运动与我国地震活动高潮期一致。纬向剖面的运动特征清楚地显示出东经100~105度的经向带内,整个研究区可分为地壳垂直运动速率西高东低的东、西两区;而经向剖面又可将这东、西两区分出以某些纬向高变化窄带为界的纬向区块。文中还详细讨论了这些区块所对应的构造单元的现今运动特征。 相似文献
500.
特提斯喜马拉雅二叠纪-白垩纪中-基性火山岩研究进展 总被引:10,自引:1,他引:10
介绍了特提斯喜马拉雅带中—基性火山岩的研究进展,报道了新近在该带中部地区二叠系到白垩系地层中发现的11个层位的中—基性火山岩,讨论了在特提斯喜马拉雅火山岩研究中存在的一些问题及其在反演印度大陆北缘大地构造属性方面的意义。据目前已有的研究成果,认为特提斯喜马拉雅带的二叠纪火山活动可能与新特提斯洋的开启有成生联系,中生代火山事件则主要与印度大陆北缘不同时期的伸展活动有关。新近发现的中—基性火山岩的科学意义体现在3个方面:查明印度大陆北缘二叠纪—白垩纪长达225Ma时间跨度范围内的大地构造属性;了解印度大陆北缘构造活动的时空演化规律,重建特提斯的构造演化格架,为全球对比提供依据。 相似文献