﻿ 基于KiK-net数据的偏振分析方法计算震中方位角影响因素分析
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 大地测量与地球动力学  2019, Vol. 39 Issue (2): 215-220  DOI: 10.14075/j.jgg.2019.02.020

### 引用本文

FAN Tao, LI Shanyou, CHEN Zhigao, et al. Analysis of Factors Impacting Polarization Analysis Method in Determining Epicentral Azimuth Based on Data from KiK-net[J]. Journal of Geodesy and Geodynamics, 2019, 39(2): 215-220.

### Foundation support

National Natural Science Foundation of China, No.U1534202, 51408564; Science and Technology Innovation Fund of Hubei Province, No.2016ACA159; Scientific Research Fund of Institute of Seismology and Institute of Crustal Dynamics, CEA, No.IS201456151.

### Corresponding author

SONG Jindong, associate researcher, majors in strong motion observation and earthquake early warning, E-mail: jdsong@iem.ac.cn.

### 第一作者简介

FAN Tao, engineer, majors in strong motion observation and earthquake early warning, E-mail: fant_cea@163.com.

### 文章历史

1. 中国地震局地震研究所地震预警湖北省重点实验室, 武汉市洪山侧路40号, 430071;
2. 中国地震局工程力学研究所地震工程与工程振动重点实验室，哈尔滨市学府路29号, 150080

1 方法原理

 图 1 地震波极化特性示意图 Fig. 1 Sketch map of polarization characteristics of seismic wave

 图 2 质点在三维空间偏振的轨迹示意图 Fig. 2 Sketch map of three-dimensional particle polarization trajectory

 ${m_x} = \frac{1}{N}\sum\limits_{i = {N_1}}^{{N_2}} {{x_i}, {m_y} = \frac{1}{N}\sum\limits_{i = {N_1}}^{{N_2}} {{y_i}, {m_z} = \frac{1}{N}\sum\limits_{i = {N_1}}^{{N_2}} {{z_i}} } }$

 ${\mathit{\boldsymbol{M}}_C} = \frac{1}{N}\left[{\begin{array}{*{20}{c}} {\sum {{A^2}} }&{\sum {AB} }&{\sum {AC} }\\ {\sum {BA} }&{\sum {{B^2}} }&{\sum {BC} }\\ {\sum {CA} }&{\sum {CB} }&{\sum {{C^2}} } \end{array}} \right]$ (1)

 $\left\{ {\begin{array}{*{20}{c}} {\cos \alpha (t) = {\mathit{\Lambda }_X}}\\ {\cos \beta (t) = {\mathit{\Lambda }_Y}}\\ {\cos \gamma (t) = {\mathit{\Lambda }_Z}} \end{array}} \right.$ (2)

 ${\rm{azi}} = {\rm{ta}}{{\rm{n}}^{-1}}(\frac{{{\mathit{\Lambda }_Z}{\rm{sign}}({\mathit{\Lambda }_X})}}{{{\mathit{\Lambda }_Y}{\rm{sign}}({\mathit{\Lambda }_X})}})$ (3)
2 数据及处理

1) 对三分量记录进行基线校正，并进行数字滤波，滤波频带0.1~20 Hz；

2) 通过积分获得速度和位移记录；

3) 利用STA/LTA方法结合AIC方法确定P波到时点[7]

4) 读取P波到时点后固定窗长(定义窗长为选定记录的时间长度)的三分量记录；

5) 利用协方差矩阵法求取震中方位角，同时，根据台站的经纬度和震中的经纬度可以得到实际方位角。

3 影响因素分析

3.1 参量形式的影响

 图 3 计算方位角与实际方位角散点图 Fig. 3 Scatter diagram of actual azimuth and calculated azimuth

 图 4 计算方位角残差直方图 Fig. 4 Histogram of azimuthal residuals

3.2 时窗长度的影响

 图 5 计算方位角残差标准差随时窗长度变化的曲线 Fig. 5 Curves of azimuth residual's standard deviation vary with time window length

 图 6 偏差所占比例随窗长变化的曲线 Fig. 6 Curves of deviation percentage vary with time window length
3.3 滤波频带的影响

 图 7 标准差随滤波频带范围变化的曲线 Fig. 7 Curves of standard deviation vary with filter band

 图 8 偏差所占比例随滤波频带变化的曲线 Fig. 8 Curves of deviation percentage vary with filter band

4 震例验证

 图 9 计算方位角示例 Fig. 9 The example of azimuth

5 结语

1) 当采用位移记录时，计算方位角与实际方位角的线性相关性较加速度记录和速度记录取得的结果更高。

2) 计算时间窗取1 s时，计算方位角的偏差最小。

3) 当滤波频带为0.1~20 Hz时，计算方位角的结果较好。

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Analysis of Factors Impacting Polarization Analysis Method in Determining Epicentral Azimuth Based on Data from KiK-net
FAN Tao1     LI Shanyou2     CHEN Zhigao1     SONG Jindong2     LU Jianqi2
1. Hubei Key Laboratory of Earthquake Early Warning, Institute of Seismology, CEA, 40 Hongshance Road, Wuhan 430071, China;
2. Key Laboratory of Earthquake Engineering and Engineering Vibration, Institute of Engineering Mechanics, CEA, 29 Xuefu Road, Harbin 150080, China
Abstract: In this paper, three main factors which directly influence the precision of determining the epicentral azimuth, namely ground-motion type, time window length and filter band, are analyzed by the polarization analysis method, based on part of KiK-net strong motion data. Results show that azimuth determined by ground displacement is outstanding compared to that determined by ground acceleration and ground velocity. Meanwhile, with calculation-time window to be valued around 1 s and filtering band to be valued between 0.1-20 Hz makes the epicentral azimuth determination results best. The results of 45-degree deviation percentage can be 88%.
Key words: polarization analysis; epicenter azimuth; earthquake early warning (EEW) of high speed railway