基于环境噪声的地震响应重建方法及应用

被动源地震干涉能够从环境噪声中重建有用的地震响应,如面波甚至体波,以用于建立地下速度模型。但由于环境噪声源具有随机分布的特征,记录混沌而杂乱无序,如何进行资料预处理并从中重建地震响应是一件具有挑战性的工作。为此,针对地表噪声源记录特点以及噪声源分布不均匀而导致重建因果格林函数与逆时格林函数不相等等问题,提出了振幅规则化和求和虚源道集构建方法,显著改善和增强了重构地震响应中的面波信号。利用高铁线附近采集的环境噪声数据,进行了地震响应重建试验,结果表明:振幅规则化和求和虚源道集构建方法能有效地从环境噪声中恢复直达波和面波响应,可进一步用于走时层析成像和面波反演以及近地表纵波和横波速度模型的建立。

Useful seismic responses such as direct arrivals and surface waves can be retrieved from ambient noise using passive interferometry,which can be further used for building near-surface velocity models.Unfortunately,ambient noise occurs randomly,and its record shows obvious chaos and disorder.Hence,it is challenging to preprocess the ambient noise and retrieve a valuable seismic response.In this study,to overcome the shortcoming of using only the causal Green function to retrieve virtual source gather,an improved method for virtual source gather retrieval by summation processing is proposed,which mainly includes amplitude regularization,seismic traces mutual coherence or cross-correlation,and summing the causal and non-causal Green functions.The surface wave signals in the retrieved seismic responses were improved and enhanced.Finally,the method is applied to ambient noise data acquired along a railway line to retrieve seismic responses.The results indicate that direct arrivals and surface waves can be effectively retrieved from ambient noise,which could be further used for travel-time tomography and surface wave inversion as well as building near-surface P-wave and S-wave velocity models.

中国石化科技部项目(P13030)资助。