The July 27, 1976 Tangshan, China earthquake—A complex sequence of intraplate events
The July 27, 1976 Tangshan, China earthquake—A complex sequence of intraplate events
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DOI：
10.1785/bssa0690010207
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发表时间：
1979-02
影响因子：
3
通讯作者：
R. Butler;G. S. Stewart;H. Kanamori
中科院分区：
文献类型：
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作者：
R. Butler;G. S. Stewart;H. Kanamori
1976年7月27日，唐山大地震（Ms = 7.7）及其主余震（Ms = 7.2）在主震后15小时发生，造成中国东北地区65万多人丧生。这是历史上第二大地震灾害，仅次于1556年造成至少83万人死亡的中国陕西省地震。对唐山地震的远震面波和体波进行了详细的分析。主要结论是：(1)唐山地震序列是一个复杂的地震序列，包括走滑、逆冲和正断层事件。(2)从表面波判断，主震发生在近垂直的右旋走滑断层上，走向N40°E。(3)得到1.8 × 1027达因-cm的地震矩。根据余震带的范围和主震震中的相对位置，可以推断出全长140 km的对称（1:1）双侧断裂。假设断层宽度为15公里，则平均偏移量估计为2.7米，平均应力降约为30巴。(4)主震由一个相对缓慢的事件引发，地震矩为4 × 1026 dyne-cm。根据表面波分析，优选的断平面解表明走向为220°，倾角为80°，倾角为- 175°。(5)两次逆冲活动分别比走滑活动晚11和19秒。它们位于初始事件的南向西南方向，总力矩为8 × 1025达因-厘米。这个序列之后还有几个事件。(6)主余震为正断层双事件，断层面不受p波初动的约束。表面波对产生走向N120°E、倾角45°SW、倾角- 30°的斜滑解的机制提供了额外的约束。得到的总力矩为8 × 1026 dyne-cm。(7)唐山层序中大型走滑事件对小逆冲断层和正断层的触发对其他复杂走滑系统（如圣安德烈亚斯）的地震危险性评价具有重要意义。
The Tangshan earthquake (Ms = 7.7), of July 27, 1976 and its principal aftershock (Ms = 7.2), which occurred 15 hr following the main event, resulted in the loss of life of over 650,000 persons in northeast China. This is the second greatest earthquake disaster in recorded history, following the 1556 Shensi Province, Chinese earthquake in which at least 830,000 persons lost their lives. Detailed analyses of the teleseismic surface waves and body waves are made for the Tangshan event. The major conclusions are: (1) The Tangshan earthquake sequence is a complex one, including strike-slip, thrust, and normal-fault events. (2) The main shock, as determined from surface waves, occurred on a near vertical right-lateral strike-slip fault, striking N40°E. (3) A seismic moment of 1.8 × 1027 dyne-cm is obtained. From the extent of the aftershock zone and relative location of the main shock epicenter, symmetric (1:1) bilateral faulting with a total length of 140 km may be inferred. If a fault width of 15 km is assumed, the average offset is estimated to be 2.7 meters with an average stress drop of about 30 bars. (4) The main shock was initiated by an event with a relatively slow onset and a seismic moment of 4 × 1026 dyne-cm. The preferred fault-plane solution, determined from surface-wave analyses, indicates a strike 220°, dip 80°, and rake −175°. (5) Two thrust events follow the strike-slip event by 11 and 19 sec, respectively. They are located south to southwest of the initial event and have a total moment of 8 × 1025 dyne-cm. This sequence is followed by several more events. (6) The principal aftershock was a normal-fault double event with the fault planes unconstrained by the P-wave first motions. Surface waves provide additional constraints to the mechanism to yield an oblique slip solution with strike N120°E, dip 45°SW, and rake −30°. A total moment of 8 × 1026 dyne-cm is obtained. (7) The triggering of lesser thrust and normal faults by a large strike-slip event in the Tangshan sequence has important consequences in the assessment of earthquake hazard in other complex strike-slip systems like the San Andreas.