The waveform inversion method is applied-- using synthetic ocean-bottom seismometer （OBS） data--to study oceanic crust structure. A niching genetic algorithm （NGA） is used to implement the inversion for the thickn...The waveform inversion method is applied-- using synthetic ocean-bottom seismometer （OBS） data--to study oceanic crust structure. A niching genetic algorithm （NGA） is used to implement the inversion for the thickness and P-wave velocity of each layer, and to update the model by minimizing the objective function, which consists of the misfit and cross-correlation of observed and synthetic waveforms. The influence of specific NGA method parameters is discussed, and suitable values are presented. The NGA method works well for various observation systems, such as those with irregular and sparse distribu- tion of receivers as well as single receiver systems. A strategy is proposed to accelerate the convergence rate by a factor of five with no increase in computational complex- ity; this is achieved using a first inversion with several generations to impose a restriction on the preset range of each parameter and then conducting a second inversion with the new range. Despite the successes of this method, its usage is limited. A shallow water layer is not favored because the direct wave in water will suppress the useful reflection signals from the crust. A more precise calculation of the air-gun source signal should be considered in order to better simulate waveforms generated in realistic situa- tions; further studies are required to investigate this issue.展开更多
鉴于国内外海洋地震台网的缺乏,本文介绍了一种面向全球海域应用的漂浮式海底地震接收系统(mobile earthquake recording in marine areas by independent divers,MERMAID).针对潜浮式地震仪MERMAID浮标的研发过程,建立了浮标的总体设...鉴于国内外海洋地震台网的缺乏,本文介绍了一种面向全球海域应用的漂浮式海底地震接收系统(mobile earthquake recording in marine areas by independent divers,MERMAID).针对潜浮式地震仪MERMAID浮标的研发过程,建立了浮标的总体设计要求与典型工作循环流程,设计了液压式浮力调节系统、机械结构等,并对比分析了不同转速及负浮力下潜过程,最后进行了实验室压力检测和千岛湖湖试。试验结果表明,该浮标能在15MPa压力下保持良好的密封性与稳定性,利用水听器可以有效地采集到天然地震纵波(P波),同时计算各模块单个周期的能耗,以验证设计指标。展开更多
基金supported by the National Natural Science Foundation grant No.41174034the Major State Basic Research Development Program of China(973 Program)
文摘The waveform inversion method is applied-- using synthetic ocean-bottom seismometer （OBS） data--to study oceanic crust structure. A niching genetic algorithm （NGA） is used to implement the inversion for the thickness and P-wave velocity of each layer, and to update the model by minimizing the objective function, which consists of the misfit and cross-correlation of observed and synthetic waveforms. The influence of specific NGA method parameters is discussed, and suitable values are presented. The NGA method works well for various observation systems, such as those with irregular and sparse distribu- tion of receivers as well as single receiver systems. A strategy is proposed to accelerate the convergence rate by a factor of five with no increase in computational complex- ity; this is achieved using a first inversion with several generations to impose a restriction on the preset range of each parameter and then conducting a second inversion with the new range. Despite the successes of this method, its usage is limited. A shallow water layer is not favored because the direct wave in water will suppress the useful reflection signals from the crust. A more precise calculation of the air-gun source signal should be considered in order to better simulate waveforms generated in realistic situa- tions; further studies are required to investigate this issue.
文摘鉴于国内外海洋地震台网的缺乏,本文介绍了一种面向全球海域应用的漂浮式海底地震接收系统(mobile earthquake recording in marine areas by independent divers,MERMAID).针对潜浮式地震仪MERMAID浮标的研发过程,建立了浮标的总体设计要求与典型工作循环流程,设计了液压式浮力调节系统、机械结构等,并对比分析了不同转速及负浮力下潜过程,最后进行了实验室压力检测和千岛湖湖试。试验结果表明,该浮标能在15MPa压力下保持良好的密封性与稳定性,利用水听器可以有效地采集到天然地震纵波(P波),同时计算各模块单个周期的能耗,以验证设计指标。
