分布式光纤声波传感系统在近地表成像中的应用Ⅰ：主动源高频面波

Distributed Acoustic Sensing for imaging shallow structureⅠ:active source survey

近年来发展的新型地震观测系统--分布式光纤声波传感器(DAS,Distributed Acoustic Sensing)可以实现低成本高密度观测,有望提高浅层结构成像的精度以及分辨率.最近国内研发了一系列具有自主知识产权的DAS设备,为验证国产设备在浅层结构研究中的可行性以及应用效果,2018年7月我们开展了一次DAS观测实验.实验采集了50kg落锤震源激发的地震信号,并采用多道面波分析方法提取了8~20Hz频段的主动源Rayleigh波相速度频散曲线,得到了实验区浅层30m的S波速度结构.获得的主动源面波频散曲线与共址检波器的结果吻合,也与背景噪声提取的结果具有较好的一致性,表明国产设备的可靠性和DAS在浅层结构主动源面波成像研究中的可行性.

In recent years,the internationally developed new seismic acquisition system,distributed acoustic sensing(DAS),has realized low-cost and high-density observation,which is expected to improve the resolution and quality of shallow-structure imaging.A series of DAS equipment with independent intellectual property rights have been developed in China,but the related testing works have yet to be carried out.In order to verify the feasibility of the distributed acoustic sensing in the study of shallow structure,we conducted a DAS observation experiment in July 2018.The seismic signal generated by a 50 kg falling source is collected in the experiment.The multi-channel surface wave analysis method is used to extract the Rayleigh wave phase velocity dispersion curve in the 8~20 Hz band.Using the data,this paper calculated the S-wave velocity structure of the shallow 30 min the experimental area.The obtained surface wave dispersion data is in good agreement with the results of the co-located geophone,and is also consistent with the ambient noise calculation results,which shows the reliability of the domestic equipment and the feasibility of the DAS in active surface wave imaging in the shallow structure.