【摘要】 地震海啸的形成要具备3个条件:一是有深海盆地,可以容纳巨量海水;二是海底地形隆起与拗陷反差强烈;三是存在倾滑型活断层,可发生6级以上倾滑型的地震。查南海及其周边地形地貌,北西南三面都有宽阔的大陆架,中部又是平坦的深海平原,都不具备发生地震海啸的条件,惟独东侧马尼拉海沟才具备产生地震海啸的条件。南海地壳属于大洋型地壳与大陆型地壳之间的过度类型。其断裂构造非常发育,不同地段具有明显差异。北部为拉张型,南部为挤压型,西部为剪切型,东部为俯冲型,中部是扩张型。按断裂展布方向可分为NE向、NW向、EW向、SN向4组;按断裂切割深度,可分为岩石圈断裂、地壳断裂、基底断裂和盖层断裂。这些断裂多数为活动断裂,而东缘俯冲型断裂又是发震断裂。从地震分布、震源机制解分析,南海北、西、南以及中部都不具备引发地震海啸的条件,只有台南—菲律宾地震带东西两侧的贝尼奥夫带发生的倾滑型或具倾滑分量的走滑型6级以上地震,才有可能引发海啸,并可能对南海及我国东南沿海诸省以及港澳地区产生影响。更多还原

【Abstract】 To form seismic tsunami should possess three conditions:firstly,the deep sea basin which can contain a great volume of seawater;secondly,a great contrast between apophysis and depression of the seafloor topographty;thirdly,the dip-slip fault to cause the dip-slip earthquake with magnitude above 6 being existent.By investigating the topographty of the South China Sea and its circumference,we find that only the Manila trench in the east is qualified to cause seismic tsunami.The earth′s crust of the South China Sea belongs to the transitional type between the oceanic crust and continental crust.Its fracture structure has developed very much and is of the obvious differences in the different sections.It is the tenso-pull type in the north,the compression type in the south,the shear type in the west,the subduction type in the east and the expanding type in the middle part.It can be divided into 4 groups,NE direction,NW direction,EW direction and SN direction according to the fracture direction and can be divided into the lithosphere fracture,the earth′s crust fracture,the basement fracture and cover fracture according to the cutting depth of the fracture.These fractures are mostly the active ones,otherwise the subduction fracture in the east edge is the seismogenic one.According to the analysis of the earthquake distribution and the focal mechanism solution,it is not qualified to cause seismic tsunami in the north,the west,the south and the middle part of the South China Sea.Only the seismicity of the Benioff zone in the east and the west sides of Tainan-Philippines seismic belt,which is in addition the dip-slip or strike-slip earthquake with magnitude above 6,may cause tsunami,thereby to have an influence on all the South China Sea,the coastal provinces in the southeast of China,Hongkong and Macao.更多还原