福建水口水库M_L4.8地震序列的精定位及其活动图像分析
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摘要
应用双差定位法对2008年福建古田水口水库ML4.8地震序列进行重新定位,得到539次地震的相对定位结果,减小了定位误差,得到了较精细的地震活动图像。并结合库区地震构造背景和几个较大地震的震源机制解,对水库诱发地震序列的时空特征进行了讨论。结果表明:①震中活动图像呈现出北西向的条带状分布,分布范围为北西向宽4.5km,北东向宽2.9km;②地震序列在时间进程的发展中,前震主要发生于水库岸边,在余震密集期的地震主要发生于水库水域内,余震衰减后期,地震主要发生于水库岸边,形成了岸边—水域—岸边的迁移过程;③震源深度在北西向剖面显示深度由岸边向水域逐渐加深,在时间上,震源深度经历了深—浅—深的过程。最后结合求解的最大前震和最大余震的震源机制解和当地的地震地质背景资料,推测此次序列的发震构造应为北西向的闽江断裂。
Using the double-difference earthquake location algorithm,we relocated hypocenters of 539 earthquakes for the Shuikou reservoir ML4.8 earthquake sequence in Fujian,reduced the location residuals,obtained the fine earthquake activity images.Spatial and temporal characteristics of the earthquake sequence was discussed.We concluded that: ① Epicenter moving image shows a banded distribution trending north west,4.5 km wide in north-west and 2.9 km wide in north-east;② Foreshocks mainly occurred in the reservoir shore,in the intensive phase,aftershocks occurred mainly in the reservoir waters,the late decay of aftershocks occurred mainly in the reservoir shore,forming a shore-water-shore migration process;③ Focal depth profile of North-West show that the depth from the shore to the water gradually deepened,in time,the focal depth experienced a deep-shallow-deep process.At last,combining the largest foreshock and the largest aftershock focal mechanisms,and the local geological background,we speculated that the seismogenic structure of this sequence should be the Minjiang fault.
Using the double-difference earthquake location algorithm,we relocated hypocenters of 539 earthquakes for the Shuikou reservoir ML4.8 earthquake sequence in Fujian,reduced the location residuals,obtained the fine earthquake activity images.Spatial and temporal characteristics of the earthquake sequence was discussed.We concluded that: ① Epicenter moving image shows a banded distribution trending north west,4.5 km wide in north-west and 2.9 km wide in north-east;② Foreshocks mainly occurred in the reservoir shore,in the intensive phase,aftershocks occurred mainly in the reservoir waters,the late decay of aftershocks occurred mainly in the reservoir shore,forming a shore-water-shore migration process;③ Focal depth profile of North-West show that the depth from the shore to the water gradually deepened,in time,the focal depth experienced a deep-shallow-deep process.At last,combining the largest foreshock and the largest aftershock focal mechanisms,and the local geological background,we speculated that the seismogenic structure of this sequence should be the Minjiang fault.
引文
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[3]杨智娴,陈运泰.用双差地震定位法再次精确测定1998年张北一尚义地震序列的震源参数[J].地震学报,2004,26(2):115-120.
[4]黄嫒,杨建思,张天中.2003年新疆巴楚一伽师地震序列的双差法重新定位研究[J].地球物理学报,2006,49(1):162-169.
[5]陈文明,杨贵,陈祥熊,等.福建顺昌ML4.9地震序列的精确定位、震源机制及其地震构造背景景分析[J].华南地震,2011,31(2):37-44.
[6]陈文明,杨贵,陈祥熊.1999年9月24日福州震群活动与地震构造的关系[J].地震地磁观测与研究,2006,27(4):23-28.
[7]郑钰,杨建思.双差算法的剖析及参数对定位的影响[J].地震地磁观测与研究,2008,29(3):85-93.
[8]陈祥熊,林树,李祖宁,等.福建—台湾地区一维地壳速度结构的初始模型[J].地震,2005,25(2):61-68.
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