Abstract: The focal mechanism solution,the coda wave value Q and the stress drop were obtained for the water injection-induced earthquakes with M_L>2.0 which occurred in a period from sept. 1986,in the Renqiu oil field of North China.The obtained result indicates that the focal machanism of induced earthquakes under the effect of movement along the primary fault close to water injection well is different from that of natural earthquakes. The average coda wave value Q₀ is 75 within the oil field which is smaller than that in the neardy areas. The stress drop by induced earthquakes changes from 0.2 to 3.0 bars. It shows that the stress background level in the oil field is not high.

Key words: Induced earthquake, Coda wave Q value, Stress drop

摘要： 利用区域性台网记录测定了任邱油田注水诱发地震的震源应力场和尾波衰减特征,结果表明地壳上层有很大水平应力,断层面解受注水井附近局部原生断层影响与华北现代应力场的优势破裂方向和错动方式有差别。地震应力降分布范围为0.2—3.0巴。平均尾波Q₀值为75,属于地壳上部沉积岩层的正常情况,发现在时间上表现出与注水量增减有关的波动。在空间上表现出震群密集区Q₀值较外围区偏低的特点。

关键词: 注水诱发地震, 尾波Q值, 应力降