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本文搜集了现在已知的关于青藏高原地区的各种地球物理场特征,即:该区的地壳与上地幔构造,地磁场要素的分布,航空磁测的结果,古地磁极移轨迹,重力异常与均衡补偿,地热活动与温泉分布,地震活动以及深地震探测等研究结果,来探讨它与大陆板块构造的关系。 研究的初步结果表明,印度洋板块与欧亚板块交接地带的北界为雅鲁藏布江,南界为恒河平原的北缘。喜马拉雅地带为这两大板块碰撞与挤压的过渡带,其宽度约300公里左右。这一地带的大、小地震绝大部分是浅源地震,只在弧形山系和东西弧顶及其转折部位有中源地震。在这一过渡带内水热活动剧烈,重力也不均衡。 雅鲁藏布江以北到当雄一带,地壳厚度为70—73公里,喜马拉雅地区则为68—45公里左右,并向南翘起。地壳由多层介质组成,在下地壳中存在着低速层。断层面解表现为向南逆冲,主压应力轴基本上为南北向和北东向,且与震源深度相关。现在构造活动与地震活动似均逐渐向南移到主边界大断层一带。 在雅鲁藏布江以北,小震震源深度向南递加,而在恒河平原以北,则向北递加。此外,在上述两个地区均有零星的中源地震发生。因此,喜马拉雅地带的南北两侧有相向“俯冲”之势。在兴都库什地区,中源地震震源面北倾;在帕米尔地带,中源地震震源面南倾。因此,震源面构成了“V”字?
This paper collects the various known characteristics of the geophysical fields in the Qinghai-Tibet Plateau nowadays: the crust and upper mantle structure, the distribution of geomagnetic field elements, the result of aeromagnetic survey, the paleomagnetic pole locus, the gravity anomaly And balanced compensation, geothermal activity and hot spring distribution, seismic activity and deep seismic exploration and other research results to explore its relationship with the continental plate tectonics. The preliminary results of the study show that the northern boundary of the Indian Ocean plate and the Eurasian plate is the Brahmaputra River and the southern boundary is the northern margin of the Ganges River. The Himalayan zone is the transition zone between the two plates that collide and crush, with a width of about 300 km. Most of the large and small earthquakes in this area are shallow-source earthquakes, with mid-source earthquakes occurring only in arc-shaped mountain systems and in the summits of eastern and western arcs and their turning points. In this transitional zone hydrothermal activity is intense, gravity is not balanced. To the north of the Brahmaputra to Dangxiong area, the crust thickness of 70-73 km, while the Himalayan region is about 68-45 km, and tilt to the south. The crust consists of multiple layers of media, with a low-velocity layer in the lower crust. The fault surface shows southward thrusting, and the main compressive stress axis is basically north-south direction and northeastward, and is related to the focal depth. Now tectonic activity and seismic activity are gradually moving south along the main fault area. North of the Yarlung Zangbo River, the magnitude of the epicenter of the small earth earthquake was increased southward, while to the north of the Ganges plain, it was added northward. In addition, sporadic Mien source earthquakes occurred in both areas. Therefore, the north and south sides of the Himalayas are oppositely “subducted”. In the Xingduku area, the source of the Zhongyuan earthquake is north-dipping; in the Pamir area, the source of the Zhongyuan earthquake is south-dipping. Therefore, the source surface constitutes a “V” word?