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气枪震源弱信号提取的可靠性初步分析
武安绪1) 叶泵2) 李红1) 李云1) 郑轶文1) 张宏艳1) 李妍1)
1)北京市地震局,北京市海淀区苏州街28号 100080;2)中国地震局滇西地震预报实验场办公室,云南大理 671000
摘要:
基于数据合成仿真、气枪震源激发信号的实际处理,由叠加信噪比、波形相关系数及相位偏移等3个定量指标,系统评价线性、相位加权和S变换等3种叠加方法提取强背景噪声下弱信号的实际性能,并定量估计叠加结果的可靠性。通过对以上3种方法叠加结果的综合探讨,初步对比分析后认为,线性叠加虽然信噪比较低,但波形畸变最小;相位加权叠加信噪比较高,相位偏移小,但波形质量与线性叠加的结果相比偏离较大;S变换叠加可获得相对较高的信噪比,波形幅度损失小,但存在一定的相位偏移现象。因此建议,当波形质量和时间精度均要求较高时宜用线性叠加。但气枪震源激发有限时选择叠加方法应有所偏重,若要求波形高保真,宜选择S变换叠加;若要求时间高精度,可选择相位加权叠加方法,以合理实现弱信号的有效提取。
关键词:  气枪震源 弱信号提取 线性叠加 相位加权叠加 S变换叠加
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基金项目:地震科技星火计划项目(XH16003)资助
The preliminary analysis of reliability on weak signal extraction for air­gun source surveys
Wu Anxu1) Ye Beng2) Li Hong1) Li Yun1) Zheng Yiwen2) Zhang Hongyan1) Li Yan1)
1)Earthquake Administration of Beijing Municipality,Beijing 100080,China;2)Western Yunnan Earthquake Prediction Study Area,CEA,Dali 671000,Yunnan,China
Abstract:
Based on data synthesis simulation and air-gun source signal processing,weak signal extraction performances under strong background noise of three different stack methods of linear,phase weighted and S transform are evaluated systemically and reliability of stack results are estimated quantitatively with the indexes of signal to noise ratio,waveform correlation coefficient and phase shift. After a comprehensive discussion and comparative analysis of stack results with above three methods,we conclude that linear stack has the minimum waveform distortion though its signal-to-noise ratio is lower;phase weighted stack has highest signal-to-noise ratio and small phase shift,but its waveform quality has larger deviation compared with linear stack results;S transform stack obtains a relatively higher signal-to-noise ratio and small waveform amplitude loss,but with the certain existence of the phase shift phenomenon. Therefore,linear stack technique is proposed when waveform amplitude and time precision requirements are higher,but the selection of stack methods should be biased when air-gun source firings are limited;S transform stack method should be chosen when there is requirement of high waveform fidelity;and phase weighted stack method should be chosen when there is high time precision in order to achieve effective extraction of weak signal reasonably.
Key words:  Air­gun source  Weak signal extraction  Linear stack  Phase weighted stack  S transform stack