Abstract: The Shanxi graben system is one of the important specific morphotectonic types in the eastern part of China.It is located in the crustal attenuation zone and the region ofintense crustal movement with high intensity, high frequency, shallow focus (10-30km) and Quaternary volcanic activity which is similar to that of Rhine graben and East African rift. The earthquake distribution in the graben system is regular. Large earthquakes (M > 6) occurred inside the graben. Twelve of the seventeen earthquakes (M > 5) in Linfen region in history (about 70%) occurred inside the graben. Seventeen earthquakes (M > 8) occurred in recorded history in China, six of them in North China block and three of the six in fen-wei graben. The earthquakes are closely related to active faults: (1) All of the earthquakes occurred along active faults; (2) The earthquakes occurred along strike slip fault having the characteristics of low frequency and high intensity; (3) All causative faults are steep (dip angle >= 65^o); (4) Strong earthquakes occurred at the cross section of shear segment and tensile segment or compressional segment. The origin and development of the graben system may be roughly divided into three stages: (1) The large scale uplifts, thrust faults and fractures were formed by left lateral shearing caused by NW-SE trend compressional pressure in the Yanshan movement stage; (2) NNE and NE trend tensile fractures were formed and half grabens were produced by right lateral shearing under the action of NE-SW trend compressional pressure which were caused by the sudden change of compressional pressure trend; (3) Half grabens keep developing under the action of mantle uplifting and crustal surface extension caused by the subduction of Pacific plate.

Key words: graben system, seismicity, active faults, tectonic stress

摘要： 山西地堑系是中国东部重要独特构造地貌类型之一。中国有史以来记载了17次8级以上大地震，而华北断块就有6次，其中3次集中于汾渭地堑。地堑系的形成大致分为3个阶段：(1) 燕山期在NW-SE向主压应力作用下，使区内岩石破裂；(2) 新生代以来，在NE-SW向主压应力作用下，断裂倾向一侧，形成半地堑系；(3) 由于太平洋板块和印度板块的俯冲作用，在断块下陷曲率最大处产生张性断裂，整个断块不均匀下陷，形成完整断陷地堑构造，而且仍在继续发展扩大之中。

关键词: 地堑系, 地震活动性, 活动断层, 构造应力