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地学长江计划安徽实验中低频可控震源地震波信号提取方法评估
顾庙元1) 姚佳琪1) 张伟1,2) 陶知非3) 张汝杰3)
1)中国科学技术大学地球与空间科学学院地震学与地球内部物理实验室,合肥市金寨路96号 230026;2)蒙城地球物理国家野外科学观测研究站,安徽亳州 233527;3)中国石油集团东方地球物理公司,河北涿州 072750
摘要:
可控震源的激发过程精确可控、可重复性高。本文评估了重复激发形成的多道记录的信号增强方法,包括叠加方法和有效信号直接分离方法。相比线性叠加,加权叠加充分利用了有效信号的一致性,能进一步压制噪声,提高叠加记录的信噪比。相比时间域相位加权叠加,Semblance加权叠加更加稳定。时频域相位加权叠加能在时频域压制随机分散分布的噪声信号,叠加信号更加清晰。本文中,采用标准SVD分离获得的信号同线性叠加结果类似。本文利用密集分布的临时台阵评价地学长江计划安徽实验中低频可控震源在庐江第2激发点的激发效果。对比不同的处理流程发现,先互相关检测信号再进行时频域相位加权叠加能够取得最佳的处理效果,通过200多次重复激发,可以在50km范围内提取到较清晰的有效信号。
关键词:  低频可控震源 信号检测 多道记录 信号增强 加权叠加 地震震相
DOI:
分类号:
基金项目:国家自然科学基金(41374056)、云南省陈颙院士工作站专项经费(2014IC007)联合资助
Evaluating different methods for retrieving seismic wave signals from low frequency vibrator in the Anhui experiment of “Yangtze River Geoscience Project”
Gu Miaoyuan1) Yao Jiaqi1) Zhang Wei1,2) Tao Zhifei3) Zhang Rujie3)
1)Laboratory of Seismology and Physics of Earth's Interior,School of Earth and Space Sciences,University of Science and Technology of China,Hefei 230026,China;2)Mengcheng National Geophysical Observatory,Hefei 230026,China;3)BGP Inc.,China National Petroleum Corporation,Zhuozhou 072750,China
Abstract:
The signal exciting process of vibrator is well controlled and resulting signals are of high repeatability. In recent years,low frequency vibrator,for which the lowest frequency could be 1.5Hz,has been developed and shows its potential for subsurface structure exploring in regional scale. Detecting and enhancing extremely weak signal is the key for processing vibrator seismic signal at long distance. We evaluate different signal enhancing methods for multichannel seismic records excited by repeating low frequency vibrator,including stacking methods and separating methods. Compared with linear stacking,weighted stacking utilizes coherence of signal in multichannel records to suppress noise and enhance the signal-to-noise ratio(SNR)of stacking result. Semblance weighted stacking is more stable and effective than time-domain phase weighted stacking. Compared with time domain weighted stacking,time-frequency domain phase weighted stacking is capable of protecting signal frequency-band and the stacked signal is clearer. Signal value decomposition(SVD)can separate signal from multichannel records. In this experiment,the result of linear standard SVD separation is similar to linear stacking result. During the Anhui experiment of “Yangtze River Geoscience Project”,the low frequency vibrator excited repeatedly at two locations. We analyze different processing sequences after preprocess. The best sequence is first to detect signal by correlation for each excitation then enhance signal by time-frequency domain phase weighted stacking. Using repeated signal more than 200 times,clear Pg and Sg phase can be retrieved within 50km.
Key words:  Low frequency vibrator  Signal detection  Multichannel records  Signal enhancement  Weighted Stacking  Seismic phase