A seismic data denoising method based on complete ensemble empirical mode decomposition with adaptive noise and Hurst exponent
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摘要: 在地震观测中,地震数据中普遍包含有噪声信号。由于噪声信号的干扰,地震分析的效率会受到不同程度的影响。传统的去噪方法通常需要噪声的先验知识,并且滤波时会造成部分有效信号丢失。针对这一问题,本文提出一种将自适应噪声完全集合经验模态分解(CEEMDAN)算法与Hurst指数相结合的地震数据去噪方法。首先通过CEEMDAN方法将信号分解为一系列本征模函数(IMF),然后利用Hurst指数对滤波后的IMF分量进行识别,最后对地震数据IMF分量进行重构,从而实现数据去噪。与传统方法的去噪效果对比表明,本文方法可将低信噪比波形的去噪效果提高32%,将高信噪比波形的去噪效果提高6倍。同时对地磁数据的去噪结果表明,本文方法能够较完整地将地铁噪声从地磁信号波形中滤除。
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关键词:
- 地震数据去噪 /
- 地磁数据去噪 /
- 自适应噪声完全集合经验模态分解 /
- Hurst指数
Abstract: In seismic observation, seismic data generally contain ambient noise, which reducesthe efficiency of seismic analysis. Traditional denoising methods usually need a priori knowledge of noise, and some effective data will be lost when filtering. To solve this problem, this paper proposes a seismic data denoising method based on complete ensemble empirical mode decomposition with adaptive noise (CEEMDAN) and Hurst exponent. Firstly, the signal is decomposed into a series intrinsic mode functions (IMF) by CEEMDAN method. Secondly, the Hurst exponent is used to identify the filtered IMF component. Finally, the IMF component of seismic data is reconstructed to realize data denoising. Compared with the denoising effect of traditional methods, the filtering ability of this method for low SNR waveforms is improved by 32%, and the filtering ability for high SNR waveforms is 6 times higher. At the same time, as shown in the denoising results of geomagnetic data, this method can completely filter subway noise from geomagnetic signal waveform. -
图 4 使用本文方法所得四个事件的去噪结果
左侧为原始波形,右侧为去噪后波形。(a) 百色地震波形;(b) 灵川地震波形;(c) 南宁爆破事件波形;(d) 桂林坍塌事件波形
Figure 4. Denoising results of the four events by the method proposed in this paper
The left column stands for original waveforms and the right column stands for denoising waveforms. (a) Baise earthquake waveform;(b) Lingchuan earthquake waveform;(c) Nanning blasting waveform;(d) Guilin collapse waveform
表 1 本文所选事件的信息
Table 1. The information of events selected in this paper
事件序号 事件类型 发震日期 震中位置 记录台站 震中距/km ML a 天然地震 2021-04-28 广西百色 FUN 73 1.3 b 天然地震 2017-11-25 广西灵川 YOF 148 1.9 c 人工爆破 2021-04-04 广西南宁 DAQ 88 2.0 d 山体坍塌 2020-06-23 广西桂林 GUL 36 2.3 表 2 表1中四个事件的IMF分量的Hurst指数
Table 2. The Hurst exponents of different IMF components for four events in Table 1
分量序号 事件a 事件b 事件c 事件d IMF1 0.302 5 0.294 6 0.258 9 0.359 4 IMF2 0.322 6 0.407 5 0.425 5 0.325 4 IMF3 0.307 0 0.287 5 0.356 1 0.466 3 IMF4 0.418 9 0.333 7 0.306 3 0.487 1 IMF5 0.483 8 0.384 6 0.515 9 0.361 1 IMF6 0.655 8 0.640 8 0.612 2 0.647 8 IMF7 0.686 0 0.686 2 0.658 9 0.683 1 IMF8 0.763 8 0.792 9 0.796 6 0.653 0 IMF9 0.806 2 0.877 7 0.870 9 0.864 5 IMF10 0.969 3 0.916 5 0.992 9 0.908 0 IMF11 0.973 3 0.966 8 1.007 0 0.955 1 IMF12 0.985 1 1.009 2 1.004 0 IMF13 0.994 9 表 3 不同去噪方法的质量因子Q值和均方根误差RMSE
Table 3. Quality factor Q and root-mean-square error RMSE of different denoising methods
去噪方法 灵川地震事件 桂林坍塌事件 Q值 RMSE Q值 RMSE 带通滤波器 0.723 9 0.380 1 1.360 1 0.076 1 小波包变换 0.718 5 0.375 6 1.193 9 0.073 3 EMD方法 0.854 9 0.374 7 7.344 2 0.040 0 本文方法 0.955 9 0.373 9 9.606 9 0.025 7 表 4 地磁数据IMF分量的Hurst指数
Table 4. The Hurst exponent of different IMFs from geomagnetic data
序号 Hurst指数 序号 Hurst指数 序号 Hurst指数 IMF1 0.284 6 IMF5 0.497 9 IMF9 0.954 7 IMF2 0.323 2 IMF6 0.583 0 IMF10 0.989 9 IMF3 0.208 0 IMF7 0.702 9 IMF11 0.997 1 IMF4 0.352 4 IMF8 0.861 3 IMF12 1.006 3 -
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