珊溪水库M_L4.6震群精确定位与发震构造研究
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摘要
利用浙江、福建区域地震台网和珊溪水库台网给出的P波走时资料,通过震源位置和速度结构联合反演方法,重新确定了珊溪水库地震的震源参数。并通过假设发震断层可以用一个平面进行拟合的思路,利用重新确定的震源参数拟合得到了发震断层面参数。收集了2267条P波到时数据,求解了ML4.0以上地震震源机制解,结合水库区的断层活动性特征和宏观调查资料,讨论了珊溪水库地震序列的发震构造。
Using P-wave's travel time recorded by Shanxi-Reservoir Seismological Network,Zhejiang Seismological Network,and Fujian Seismological Network,we implemented a simultaneous inversion of the earthquake relocation and velocity structure,and got the new location of the ML4.6 earthquake in Shanxi-Reservoir area.Assuming the seismogenic fault can be fitted with a plane,we fitted the fault parameters with the new source parameters of the shanxi-resevoir earthuqake.We collected P-wave's first-motion data of 313 earthquakes to calculate the focal-mechanism solutions of the ML4.0 earthuqakes.Refering to the characteristics of fault zones crossing the reservoir and the data of the seismic macro-survey of the reservior area,we discussed the seismogenic structure of the Shanxi Reservoir area.We find that:① The focal depth of the earthquake sequence in Shanxi-Reservoir area is at an average of 5.4 km,smaller than the one in South China.② Beside the reservoir the focus is shallower,but deeper in the reservoir inundation area.In the beginning of the reservoir-induced seismicity,the focal depth increased gradually,because the deep infiltration of water gradually induced an earthquake with a greater depth.③ By fitting the epicenters of Shanxi earthquake sequence,we got the earthquake fault plane parameters:fault strike 132°,dip 85°,tend direction southwest.The fault parameters were broadly consistent with the ones of the Shuangxi-Jiaoxiyang fault.The ML≥4.0 focal mechanism solutions of the nodal plane,strike,dip,P-axis azimuth and elevation were generally in good agreement.
Using P-wave's travel time recorded by Shanxi-Reservoir Seismological Network,Zhejiang Seismological Network,and Fujian Seismological Network,we implemented a simultaneous inversion of the earthquake relocation and velocity structure,and got the new location of the ML4.6 earthquake in Shanxi-Reservoir area.Assuming the seismogenic fault can be fitted with a plane,we fitted the fault parameters with the new source parameters of the shanxi-resevoir earthuqake.We collected P-wave's first-motion data of 313 earthquakes to calculate the focal-mechanism solutions of the ML4.0 earthuqakes.Refering to the characteristics of fault zones crossing the reservoir and the data of the seismic macro-survey of the reservior area,we discussed the seismogenic structure of the Shanxi Reservoir area.We find that:① The focal depth of the earthquake sequence in Shanxi-Reservoir area is at an average of 5.4 km,smaller than the one in South China.② Beside the reservoir the focus is shallower,but deeper in the reservoir inundation area.In the beginning of the reservoir-induced seismicity,the focal depth increased gradually,because the deep infiltration of water gradually induced an earthquake with a greater depth.③ By fitting the epicenters of Shanxi earthquake sequence,we got the earthquake fault plane parameters:fault strike 132°,dip 85°,tend direction southwest.The fault parameters were broadly consistent with the ones of the Shuangxi-Jiaoxiyang fault.The ML≥4.0 focal mechanism solutions of the nodal plane,strike,dip,P-axis azimuth and elevation were generally in good agreement.
引文
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Aki K,Lee W H K.1976.Determination of three-dimensional velocity a-nomalies under a seismic array using P arrival times from local earth-quakes,1A homogeneous initial model[J].J Geophys Res,81(23):4381-4399.
孔祥儒,熊绍柏,周文星,等.1995.浙江省深部地球物理研究新进展——屯溪温州、诸暨临海地学断面及区域重力研究成果[J].浙江地质,11(1):50-62.
刘福田,李强,吴华,等.1989.用于速度图像重建的层析成像法[J].地球物理学报,32(1):46-61.
万永革,沈正康,刁桂苓,等.2008.利用小震分布和区域应力场确定大震断层面参数方法及其在唐山地震序列中的应用[J].地球物理学报,51(3):793-804.
王椿镛,陈运泰,邵占英.1998.中国东南陆缘的深部结构与动力学过程[J].地壳形变与地震,18(2):1-8.
王椿镛,林中洋,陈学波.1995.青海门源—福建宁德地学剖面的综合地球物理研究[J].地球物理学报,39(3):590-598.
熊绍柏,刘宏兵,王有学.2002.华南上地壳速度分布与基底、盖层构造研究[J].地球物理学报,45(6):784-791.
熊绍柏,刘宏兵.2000.浙皖地区地壳—上地幔结构和华南与扬子块体边界[J].地球物理学进展,15(4):3-17.
张国民,汪素云,李丽,等.2002.中国大陆地震震源深度及其构造含义[J].科学通报,47(9):663-668.
周龙泉,刘福田,陈晓非.2006.三维介质中速度结构和界面的联合成像[J].地球物理学报,49(4):1062-1067.
Aki K,Lee W H K.1976.Determination of three-dimensional velocity a-nomalies under a seismic array using P arrival times from local earth-quakes,1A homogeneous initial model[J].J Geophys Res,81(23):4381-4399.
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