地震研究

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2 267条P波到时数据,求解了M_L4.0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 M_L4.6 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 M_L4.0 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 M_L≥4.0 focal mechanism solutions of the nodal plane,strike,dip,P-axis azimuth and elevation were generally in good agreement.

引言
1 地震定位
2 定位结果及其分析
3 震源机制解和地震主破裂面
4 结论

图1 珊溪水库库区震中与断裂分布图<br/>Fig.1 Epicenter and fault distribution in Shanxi reservoir area(triangle:station,circle:epicenter)

图1 珊溪水库库区震中与断裂分布图
Fig.1 Epicenter and fault distribution in Shanxi reservoir area(triangle:station,circle:epicenter)

图2 用于反演的P波走时<br/>Fig.2 P wave's travel time for inversion

图2 用于反演的P波走时
Fig.2 P wave's travel time for inversion

表1 珊溪水库地区地壳初始P波速度值<br/>Tab.1 P-wave's initial velocity in Shanxi reservoir area

表1 珊溪水库地区地壳初始P波速度值
Tab.1 P-wave's initial velocity in Shanxi reservoir area

图3 珊溪水库地震重新定位前后震中分布(a)重新定位前震中分布及网格划分;(b)重新定位后震中分布(淡绿:2002～2003年,绿:2004～2005年,紫:2006年2月,红:2006年3月后)<br/>Fig.3 Earthquake epicenters before(a)and after(b)relocation in Shanxi reservoir

图3 珊溪水库地震重新定位前后震中分布(a)重新定位前震中分布及网格划分;(b)重新定位后震中分布(淡绿:2002～2003年,绿:2004～2005年,紫:2006年2月,红:2006年3月后)
Fig.3 Earthquake epicenters before(a)and after(b)relocation in Shanxi reservoir

图4 沿图3b所示剖面AB(a)和CD(b)的地震分布<br/>Fig.4 Earthquake distribution along the section AB(a)and section CD(b)of Figure 3b

图4 沿图3b所示剖面AB(a)和CD(b)的地震分布
Fig.4 Earthquake distribution along the section AB(a)and section CD(b)of Figure 3b

图5 地震分布在水平面(a)、断层面(b)和垂直于断层面的横断面(c)上的投影和小震距断层面距离的分布(d)(圆圈表示精确定位的小震,粗线表示确定的断层面边界)<br/>Fig.5 Earthquake distribution in the horizontal plane(a),fault plane(b),cross-section perpendicular to the fault plane on the projection(c)and the distance distribution for small earthquakes from fault plane(d)(circles stand for precise position of small earthquake,thick lines stand for the fault plane boundary)

图5 地震分布在水平面(a)、断层面(b)和垂直于断层面的横断面(c)上的投影和小震距断层面距离的分布(d)(圆圈表示精确定位的小震,粗线表示确定的断层面边界)
Fig.5 Earthquake distribution in the horizontal plane(a),fault plane(b),cross-section perpendicular to the fault plane on the projection(c)and the distance distribution for small earthquakes from fault plane(d)(circles stand for precise position of small earthquake,thick lines stand for the fault plane boundary)

图6 ML≥4.0地震震源机制解<br/>Fig.6 Focal mechanism solutions of the ML≥4.0 earthquakes (a)2006-02-04 11:00,ML4.0;(b)2006-02-04 16:00,ML4.1;(c)2006-02-08 01:00,ML4.4;(d)2006-02-09 03:00,ML4.6;(e)2006-02-09 18:00,ML4.2;(f)2006-02-10 07:00,ML4.2;(g)2006-02-10 14:00,ML4.1;

图6 ML≥4.0地震震源机制解
Fig.6 Focal mechanism solutions of the ML≥4.0 earthquakes (a)2006-02-04 11:00,ML4.0;(b)2006-02-04 16:00,ML4.1;(c)2006-02-08 01:00,ML4.4;(d)2006-02-09 03:00,ML4.6;(e)2006-02-09 18:00,ML4.2;(f)2006-02-10 07:00,ML4.2;(g)2006-02-10 14:00,ML4.1;

表2 ML≥4.0地震震源机制解<br/>Tab.2 Focal mechanism solutions of the ML≥4.0 earthquakes

表2 ML≥4.0地震震源机制解
Tab.2 Focal mechanism solutions of the ML≥4.0 earthquakes

图7 2006年2月9日ML4.6地震等震线分布图<br/>Fig.7 Isoseismal map of Feb.9,2006,ML4.6 earthquake

图7 2006年2月9日ML4.6地震等震线分布图
Fig.7 Isoseismal map of Feb.9,2006,ML4.6 earthquake

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备注

引言

1 地震定位

2 定位结果及其分析

3 震源机制解和地震主破裂面

4 结论

期刊信息