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地震预警中基于HHT的P波震相识别方法研究
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摘要
针对地震信号非线性,非平稳性等特征,引入HHT方法对地震信号进行预处理,通过经验模态分解得到IMF分量,采用过零尺度阈值算法实现IMF分量的自适应选择,重构阈值范围内的IMF分量达到降噪效果。对有效信号的IMF分量作Hilbert变换得到瞬时频率和瞬时幅值,基于时频分析构建识别P波STA/LTA法的新特征函数。为提高震相识别精度,对STA/LTA法长短时窗内的幅值信号求标准差进一步放大地震到达后的特征函数比值,通过联合AIC准则,开展了P波震相自动识别。为了验证所建议P波震相自动识别算法,以人工捡拾为基准,应用KIK—NET数据,评价了本文提出方法的精度。结果表明,在处理信噪比较高的地震记录时,三种P博震相识别方法的捡拾精度基本一致;对于信噪比较低的地震信号,与传统STA/LTA—AIC算法相比,基于HHT的P波震相自动识别加权算法有更高的识别精度,同时具有较强抗噪性。
In view of nonlinear and non—stationary seismogram,HHT was introduced to preprocess the seismogram.A series of IMFs are obtained by empirical mode decomposition and are adaptively selected by zero — crossing scale thresholding adaptive denoising algorithm.The IMFs within the threshold range are reconstructed to reduce noise.Calculate the instantaneous amplitude and instantaneous frequency in a new STA/LTA characteristics function.The new STA/LTA method was applied jointly with AIC method in the identification of P wave.At the same time,a weighting factor was used to improve the STA/LTA algorithms.Considering the manual picking results as a benchmark,apply the seismic data from Japanese KIK—NET,verify the proposed algorithm in this paper.Results show that,compared with the traditional method,the P wave identification algorithm based on HHT has higher picking accuracy and better noise resistance.
引文
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