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101.
This paper briefly reviews main progress in the research on lithospheric structure and continental geodynamics made by Chinese geophysicists during last 4 years since 22nd IUGG general assembly in July 1999. The research mainly covers the following fields: investigations on regional lithospheric structure, DSS survey of crust and upper mantle velocity structure, study on present-day inner movement and deformation of Chinese mainland by analyz-ing GPS observations, geodynamics of Qingzang plateau, geophysical survey of the Dabie-Sulu ultra-high pressure metamorphic belt and probing into its formation mechanism, geophysical observations in sedimentary basins and study on their evolution process, and plate dynamics, etc. 相似文献
102.
Based on Coulomb static stress variation, the stress trigging action of the Mani ( Ms7.9, Nov.1997) earthquake on the West Kuulun Mountains Pass (MsS.1, Nov. 2001 ) earthquake is researched. Results of different source mechanism resolutions show that a 10_3 MPa Coulomb stress due to the Mani earthquake was added to the fracture fault of the Kunlun earthquake, and this may shift the broken date to about 10 years earlier, and infer that the stress level in the crust is not low. Comparing the relationship between strong earthquake strength and frequency and earth rotation change, it is shown that the strength‘s decrease and the variation period‘ s shortening of earth rotation are important controlling factors on strong earthquake activity. This great event with Ms = 8.1 took place probably due to a gradual strengthening background of regional stress field within the Qinghai-Xizang block in the period of acceleration of change of day‘s length and stress triggering from the Mani earthquake. 相似文献
103.
In this paper, we briefly describe the general destruction caused by historic earthquakes in major cities of China, preliminarily analyze the heaviness and widespread occurrence of earthquakes in cities of China, and suggest that research on scenario earthquakes in cities should be developed as a part urban disaster reduction research. 相似文献
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105.
Petrology, geochemistry and isotopic ages of eclogites from the Dulan UHPM Terrane, the North Qaidam, NW China 总被引:35,自引:0,他引:35
The Dulan eclogite–gneiss region is located in the eastern part of the North Qaidam eclogite belt, NW China. Widespread evidence demonstrates that this region is a typical ultrahigh-pressure (UHP) metamorphic terrane. Eclogites occur as lenses or layers in both granitic and pelitic gneisses. Two distinguished sub-belts can be recognized and differ in mineralogy, petrology and geochemistry. The North Dulan Belt (NDB) has tholeiitic protoliths with high TiO2 and lower Al2O3 and MgO contents. REE patterns and trace element contents resemble those of N-type and E-type MORB. In contrast, eclogites in the South Dulan Belt (SDB) are of island arc protoliths with low TiO2, high Al2O3 and show LREE-enriched and HFSE-depleted patterns. Sm–Nd isotope analyses give isochron ages of 458–497 Ma for eclogite-facies metamorphism for the two sub-belts. The ages are similar to those of Yuka and Altun eclogites in the western extension of the North Qaidam-Altun eclogite belt. The Dulan UHP metamorphic terrane, together with several other recently recognized eclogite-bearing terrenes within the North Qaidam-Altun HP-UHP belt, constitute the key to the understanding of the tectonic evolution of the northern Tibetan Plateau. The entire UHP belt extends for more than 1000 km from the Dulan UHP terrane in the southeast to the Altun eclogite–gneiss terrane in the west. This super-belt marks an early Paleozoic continental collision zone between the Qaidam Massif and the Qilian Massif. 相似文献
106.
Cretaceous deformation history of the middle Tan-Lu fault zone in Shandong Province, eastern China 总被引:13,自引:0,他引:13
Based on field analysis of fault-slip data from different rock units of the Cretaceous basins along the middle part of the Tan-Lu fault zone (Shandong Province, eastern China), we document polyphase tectonic stress fields and address the changes in sense of motion of the Tan-Lu fault zone during the Cretaceous. The Cretaceous deformation history of the Tan-Lu fault zone can be divided into four main stages. The first stage, during the earliest Cretaceous, was dominated by N-S extension responsible for the formation of the Jiaolai basin. We interpret this extension to be related to dextral strike-slip pull-apart opening guided by the Tan-Lu fault zone. The second stage, during the middle Early Cretaceous, was overwhelmingly rift-dominated and characterized by widespread silicic to intermediate volcanism, normal faulting and basin subsidence. It was at this stage that the Tan-Lu-parallel Yi-Shu Rift was initiated by E-W to WNW-ESE extension. The tectonic regime then changed during the late Early Cretaceous to NW-SE-oriented transpression, causing inversion of the Early Cretaceous rift basin and sinistral slip along the Tan-Lu fault zone. During the Late Cretaceous, dextral activation of the Tan-Lu fault zone resulted in pull-apart opening of the Zhucheng basin, which was subsequently deformed by NE-SW compression. This deformation chronology of the Tan-Lu fault zone and the associated Cretaceous basins allow us to constrain the regional kinematic models as related to subduction along the eastern margin of Asia, or related to collision in the Tibet region. 相似文献
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109.
中国西部退耕还林(草)和沙漠化土地绿化的区域性气候效应 总被引:10,自引:0,他引:10
中国正在实施的西部大开发必将导致较大规模的土地利用和地表覆盖(LULC)变化,其中最重要的两类LULC变化是退耕还林(草)和沙漠化土地绿化工程。利用最新的全球地表特征资料数据库(GLCCD)识别以上两项生态建设工程的实施规模与范围,并以此更新了目前比较流行的区域气候模式的下边界条件,利用修正了的区域气候模式研究上述大规模LULC变化可能对中国区域性气候造成的影响。使用的卫星资源数据库是由美国地质测绘局(USGS)和Nebraska-Lincoln大学牵头,根据NOAA卫星的AVHRR资料、USGS掌握的高分辨率数字化地图,以及生态区划和植被分布等资料组建的。 相似文献
110.
2001年11月14日在昆仑山口西发生了8.1级地震,震中位置为90.9E、36.2N.分析表明,8.1级地震前一些主要地震活动性异常都出现了,例如空区、条带、增强、平静和震群等,且与7级大震比较,这些前兆图象的演变具有类似的过程,所不同的是8.1级地震的前兆地震活动图象涉及的区域范围更大、地震震级更高,这为特大地震的前兆识别和预报提供了依据.最后回顾了对这次大震的粗略预测,并讨论了有关大震预测的某些问题. 相似文献