| 论华北地区的均衡状态(二)——复合补偿与深部构造 |
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| 引用本文： | 冯锐,张若水,郑书真,王均,黄桂芳,严惠芬,周海南.论华北地区的均衡状态(二)——复合补偿与深部构造[J].地震学报,1988,10(4):385-395. |
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| 作者姓名： | 冯锐 张若水 郑书真 王均 黄桂芳 严惠芬 周海南 |
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| 作者单位： | 1. 国家地震局地球物理研究所
2. 国家地震局地震技术学校
3. 国家地震局地球物理勘探大队 |
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| 摘 要： | 由试验均衡的理论出发,得到了该区的均衡响应函数并建立了复合补偿模式。地形高度对重力场的影响很复杂,波长小于300km的地形起伏具有偏高的均衡响应值。 局部补偿是华北地区的主要补偿机制,所占比例达90%。区域补偿的等效弹性板厚度偏小,仅18km, 表明了华北地壳破裂程度严重和下地壳流变性突出。 均衡重力异常具有块体分布和均衡调整方向同新生代构造运动方向不完全符合等特点,其中一些成分是由于表浅层地质体的非均匀载荷所造成,不能简单地归因于欠补偿或过补偿。均衡异常的垂直导数分布清晰地揭示了华北地区几条重要的断块分界线。从深部构造上看,均衡补偿过程发生在下地壳特别是上地幔中。本文从均衡的角度探讨了地震危险性。
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| 关 键 词： | 试验均衡 复合补偿 壳内非均匀载荷 均衡异常的垂直导数 华北断块 |
ISOSTATIC STATUS IN NORTH CHINA (2)--COMPOSITE COMPENSATION AND DEEP STRUCTURE |
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| Institution: | 1. Institute of Geophysics, State Seismological Bureau;
2. Seismological Technique College, State Seismological Bureau;
3. Geophysical Exploration Brigade, State Seismological Bureau;
4. Institute of Geophysics, State Seismological Bureau |
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| Abstract: | From the theory of experimental isostasy, an isostatic response function and composite compensation model are derived for that region. There is a quite complicated relationship between topography and gravitational field, in which the topographical relief with a wavelength shorter than 300 km is of relatively high isostatic response. In the isostatic compensation process of North China local compensation is essential, and the ratio of its gravitational effects to that of the total compensation is 90%, in contrast to this, the thickness of equivalent elastic plate of regional compensation is small, being only 18 km. This indicates that in North China there exist serious crustal cracking and prominent rheological property in the lower crust. It is found that the distribution of isostatic anomaly shows blockwise pattern, furthermore the direction of isostatic adjustment is not completely identical to that of Cenozoic tectonic movement. Some isostatic anomalies come from inhomogeneous internal loads distributed in the shallower crust or at the surface, and can not be interpreted simply in terms of under- or over-compensation. The vertical derivative of isostatic anomaly distinctly reveals several important tectonic boundaries within North China. In the aspect of deep structure, the isostatic compensation process takes place in the lower crust and especially in the upper mantle. The seismic risk in North China is also discussed from the view point of isostaty. |
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