基于广义同步挤压方向时频的VSP最优滤波研究

For the characteristics in direction and time-frequency of vertical seismic profile (VSP) field, that mainly refers to the direction difference between upward wave and downward wave and the different time-frequency characteristic among P-wave and P-S wave et al. This application proposes a directional time-frequency based on generalized synchrosqueezing transform which is applied to the optimal filtering research of VSP. In this research, it brings the generalized synchrosqueezing technology into the time-frequency representation of Directionlet, thereby obtains a high resolution directional time-frequency filtering method. Directionlet possesses strong ability in direction representing and shows extremely sparse representation for the information of all directions. The generalized synchrosqueezing transform comprehensively improves the resolution of time-frequency distribution through generalized demodulation that is eliminating the fuzzy caused by time-varying, and through squeezing and rearranging the spectrum of time-scale coefficients decomposed by Directionlet. Therefore, it could make the time-frequency curves more elaborate to be identified, and then it is more beneficial to the separation and extraction of each wave in VSP. Simultaneously, it suppresses the background noise when extracts the valid waves. Optimizing the filtering process continuously to make the filtering performance to be fully played, until it realizes the optimal filtering of VSP by the directional time-frequency based on generalized synchrosqueezing. At last, the whole method system will be established.

针对垂直地震剖面（Vertical Seismic Profile, VSP)波场的方向特性和时频特性，主要指上、下行波在方向上具有差异性，纵波、转换横波等具有不同的时频特性，申请书提出基于广义同步挤压方向时频的VSP最优滤波研究。该研究中，将广义同步挤压技术引入方向波Directionlet的时频表示，得到一种高分辨率方向时频滤波方法。Directionlet具有强方向表征能力，能够对各个方向信息进行极为稀疏的表示，而广义同步挤压变换可通过广义解调来消除时移产生的模糊，并通过对Directionlet分解所得的时间—尺度系数谱沿频率方向进行挤压重排，使时频分辨率全面提高，使时频曲线更精细易于辨识，从而更有利于VSP中波的分离提取，同时也对背景噪声进行了有力压制。不断优化滤波过程使滤波性能得到充分发挥，直至实现广义同步挤压方向时频对VSP的最优滤波并建立其方法体系。

该项目提出基于方向波Directionlet变换的广义同步挤压时频滤波方法，对垂直地震剖面（VSP）资料进行波场分离与提取。该滤波方法结合了方向波Directionlet变换的强方向表征能力和广义同步挤压技术的高分辨能力，使其对不同方向且具有不同时频特性的有效信号所做的时频分布达到很高的分辨率，瞬时频率曲线更精细而易于辨识，从而更有利于不同波场信息的分离提取，同时也可对背景噪声进行有力的压制。为该滤波方法设置最优滤波的目标函数，即以最小均方误差函数和L2范数正则项为衡量准则，使其取值最小。根据方向波与广义同步挤压变换理论对滤波方法进行建模，并对VSP记录进行多种情况下的模拟，然后编程实现滤波方法并先应用于模拟VSP记录的处理，分析评价滤波结果，不断优化滤波方法，然后将其应用于实际资料的处理。该方法为地震勘探资料处理提供了新思路，其所能达到的波场分离及背景噪声压制效果优于传统滤波方法。