【摘要】 亚洲内陆的强地震密集地发生在天山-贝加尔一线,但该处并不存在一条连续的大断裂,学术界对这个问题的认识长期相左。文中分析了这条地震带的时空分布、分区特点、应力状态和活动周期,计算了欧亚大陆的布格重力异常场、均衡重力异常场,反演了上地幔的密度分布和剪切波速分布。发现在这个部位的70~250km的深部有一条北东向的密度、速度陡变带,它是新生代的冷地幔和热地幔的交界带,与浅部构造存在立交关系,对亚洲大陆的现今构造运动和应力场具有重要的控制作用。这个带的地震不同于传统意义上的板缘地震和板内地震,是一种因为深浅构造不同而造成的结构性地震,性质上为大陆内缘地震。文中还就深浅构造的空间立交关系、时间镜像关系进行了讨论,指出在南北地震带和伊朗东侧地震带的立交结构也与上地幔构造有关。天山-贝加尔活动构造带是正在发展中的板块边界,是大陆内部的一个典型构造,北侧为稳定的俄罗斯-西伯利亚次板块,南侧为活动的中国-东南亚次板块。更多还原

【Abstract】 It is obvious that a great amount of strong earthquakes in central Asia occurred densely along Tianshan-Baykal belt; however, none huge continuous fault has been revealed on the surface along the belt. It caused academic argument related to their relationship. The authors analyzed its seismic activity in terms of seismicity in time-space domain, zoning feature, stress field, and recurrence period of earthquakes. In addition, we studied the Bouguer gravity and isostatic anomaly, and calculated the distribution of density and shear wave velocity in the upper mantle. It is found that there is a gradient belt of density and velocity along NE direction at the depths of 70-250 km, which is actually a Cenozoic boundary of cold mantle and hot mantle, and has an overpass relation with the structure existed in the upper lithosphere. It is inferred that this gradient belt in the upper mantle played an important role in controlling present tectonic movement and stress field in Eurasia continent. As far as the earthquake nature in this belt is concerned, it is neither an interplate earthquake nor an intraplate one in the traditional sense. Such kind of earthquake caused by overpass structure actually belongs to the structural earthquake, and is of interplate within a continent. In this paper, the overpass relation and mirror relation in time-space domain between deep and shallow structures are discussed briefly. It is also noted that the overpass structures shown in the areas of both north-south seismic belt of China and eastern seismic belt of Iran are related to a special structure in the upper mantle. We conclude that the Tianshan-Baykal active tectonic belt is a developing boundary of plates, a typical tectonic within a continent, which separates Eurasian plate into two parts, i.e., the stable Russian sub-plate to the north and the active East Asia sub-plate to the south.更多还原