【摘要】 利用收集的地震深度数据,讨论了南海北部及周缘陆区不同地壳结构地震震源深度的分布特征,结果表明:(1)华南大陆、大陆架、大陆坡区壳内地震分布的下界深度在30 km左右,平均深度华南大陆最浅、大陆架区次之,大陆坡区最深;(2)华南沿海大陆型地壳区地震集中分布于5￣15 km的“优势层”内;大陆架和大陆坡区地震的垂向分布也具有“优势层,”但厚度明显增加;而在南海海盆区,地震深度分布范围较大,有相当数量的地震分布于地幔内;(3)地震震源深度的分布特征与岩石圈热—流变结构密切相关,地震主要分布于地壳(岩石圈)的脆性层内。由于南海北部由陆向海脆性层底界深度加深,导致了地震“优势层”厚度加厚。(4)地壳上层的流变结构可能对南海北部及周缘陆区地震的发生有重要影响。更多还原

【Abstract】 In this paper,the characteristics of the focal depth in the northern South China Sea are discussed.The statistic of the focal depth of the earthquakes shows that :(1) although from the South China Margin to the South China Basin the depth of Moho increases gradually,the depth for the border of the earthquakes distribution layer for every region in the northern SCS are adjacent,about 30 km.The average depth of the earthquakes in every region is different,the South China Sea Margin′s is shallowest;the South China Basin′s is deepest.(2) in the South China Margin most of the earthquakes occur in the depth of 5～15 km;in the continental shelf and continental slope of the northern SCS,there is also a seismogenic layer in the crust,but the thickness of this layer is thicker than that in the South China Margin;in the South China Sea Basin,the focal depths distribution is dispersed,some earthquakes occur in the mantle.(3) the characteristic of the focal depth is a good indicator of the the rheological structure of the lithosphere: the earthquakes occur in the brittle layer of the lithosphere.Because the base of the brittle layer burys more deeply from the South China to the South China Basin,the thickness of the seismogenic layer in the crust increases.(4) the rheological structure of the upper crust may be one of the main factors controlling the distribution of earthquakes in the northern South China Sea.更多还原