微地震观测系统及震源定位目标函数研究

doi:10.13209/j.0479-8023.2016.091

摘要/Abstract

摘要：

通过模型试验, 分别讨论地面、井下观测系统以及二者的组合对于定位结果的影响。试验结果表明, 联合采用地面与井下观测系统能够有效提高震源定位精度。在采用井下观测系统的基础上, 对比几种常用目标函数的应用效果, 并在更有效的走时残差计算方法基础上, 提出一种新的目标函数。模型数据及实际资料的处理结果表明, 提出的目标函数在水平方向以及垂向上均具有较好的收敛性, 其震源定位结果也更准确、可靠。

关键词: 微地震, 震源定位, 观测系统, 目标函数

Abstract:

Through synthetic data tests, the influence on source location results of surface and downhole recording systems are discussed, as well as the combination of both. The results indicate that joint use of surface and downhole recording systems can significantly improve the location accuracy. With the downhole recording system, the location results obtained by adopting different objective functions in source location algorithm are compared. Moreover, a new objective function is also proposed. The effectiveness of the new objective function is tested on synthetic and real data sets. The results demonstrate that this objective function shows better convergency in both horizontal and vertical directions, and it can produce more reliable location results.

Key words: microseismic, source location, recording system, objective function

中图分类号:

P315

李罗兰, 何川, 谭玉阳. 微地震观测系统及震源定位目标函数研究[J]. 北京大学学报自然科学版, 2017, 53(2): 329-343.

Luolan LI, Chuan HE, Yuyang TAN. Study of Recording System and Objective Function for Microseismic Source Location[J]. Acta Scientiarum Naturalium Universitatis Pekinensis, 2017, 53(2): 329-343.

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链接本文: https://xbna.pku.edu.cn/CN/10.13209/j.0479-8023.2016.091

https://xbna.pku.edu.cn/CN/Y2017/V53/I2/329

图/表 19

表1 微地震不同观测方式特点的比较

Table 1 Comparison of the features of different microseismic recording systems

观测方式	仪器要求	检测周期	检测范围	数据质量	可操作性	成本花费
井下观测	高	短期	小	好	复杂	高
地面观测	低	短期/长期	大	较差	简便	低
浅井观测	低	长期	大	较好	较简便	较低

图1 地面(a)及井下(b)观测系统布设示意图及其对应的目标函数等值线倒三角形表示检波器位置, 矩形框表示网格搜索的目标区域, 圆点表示真实震源位置, “×”号表示目标函数最小值点的位置(即反演得到的震源位置), 下同

Fig. 1 Geometries of the surface (a) and downhole (b) recording systems and their corresponding objective function contour plots

图2 不同地面观测系统布设示意图及其对应的目标函数等值线

Fig. 2 Geometries of different surface recording systems and their corresponding objective function contour plots

图3 不同观测系统组合及其对应的目标函数等值线

Fig. 3 Combinations of different recording systems and their corresponding objective function contour plots

图4 目标函数等值线(单层模型结果) (a)~(d)分别为采用式(1)、(3)、(5)和(6)作为目标函数的等值线

Fig. 4 Contour plots of the objective functions (results of single layer model)

图5 测试网格点位置

Fig. 5 Locations of the test grid points

图6 理论P波到时(a)及 P-S 波到时差(b) 灰色和黑色曲线分别对应图5中“×”和“+”所表示的网格点的理论P波到时和P-S波到时差

Fig. 6 Calculated P-wave arrival times (a) and P-S separation times (b)

图7 合成数据震源定位结果(a)~(d)分别为采用式(1)、(3)、(5)和(6)作为目标函数时的震源定位结果

Fig. 7 Source location results of the synthetic data set

图8 不同目标函数的震源定位误差平均值及方差对比

Fig. 8 Comparison of the means and variances of the location errors of different objective functions

图9 多层模型介质及震源、观测系统布设示意图

Fig. 9 Multi-layer model and geometry of the source location and recording system

图10 目标函数等值线(多层模型结果) (a)~(d)分别为采用式(1)、(3)、(5)和(6)作为目标函数的等值线

Fig. 10 Contour plots of the objective functions (results of multi-layer model)

表2 地层模型参数

Table 2 Layer model parameters

层位	D/m	v_P /(m · s^-1)	v_S/(m · s^-1)
1	0~1200	2000	1200
2	1200~1400	2400	1500
3	1400~1600	2800	1800
4	1600~1800	3200	2100
5	1800~2000	3600	2400

图11 合成数据震源定位结果(a)~(d)分别为采用式(1)、(3)、(5)和(6)作为目标函数时的震源定位结果

Fig. 11 Source location results of the synthetic data set

图12 震源右移后的多层模型介质及震源、观测系统布设示意图

Fig. 12 Multi-layer model and geometry of the source location and recording system with the source moved right

图13 震源下移后的多层模型介质及震源、观测系统布设示意图

Fig. 13 Multi-layer model and geometry of the source location and recording system with the source moved down

图14 震源右移后的目标函数等值线(多层模型结果) (a)~(d)分别为采用式(1)、(3)、(5)和(6)作为目标函数的等值线

Fig. 14 Contour plots of the objective functions with the source moved right (results of multi-layer model)

图15 震源下移后的目标函数等值线(多层模型结果) (a)~(d)分别为采用式(1)、(3)、(5)和(6)作为目标函数的等值线

Fig. 15 Contour plots of the objective functions with the source moved down (results of multi-layer model)

图16 实际资料震源定位结果俯视图(a)~(d)分别为采用式(1)、(3)、(5)和(6)作为目标函数时的震源定位结果

Fig. 16 Plan view of the source location results of the real data set

图17 实际资料震源定位结果侧视图(a)~(d)分别为采用式(1)、(3)、(5)和(6)作为目标函数时的震源定位结果

Fig. 17 Side view of the source location results of the real data set

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