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Title:: The Time-frequency Characteristic of Large Capacity Air-gun Array Wavelet and its Influencing Factors

作者:: 夏季¹; 2; 金星¹; 2; 3; 蔡辉腾³; 徐嘉隽³; 1.中国地震局工程力学研究所,黑龙江哈尔滨 150080; 2.中国地震局地震工程与工程振动重点实验室,黑龙江哈尔滨150080; 3.福建省地震局,福建福州 350003

Author(s):: XIA Ji¹; 2; JIN Xing¹; 2; 3; CAI Huiteng³; XU Jiajun³; 1.Institute of Engineering Mechanics,China Earthquake Administration,Harbin 150080,Heilongjiang,China2.Key Laboratory of Earthquake Engineering and Engineering Vibration,China EarthquakeAdministration,Harbin 150080,Heilongjiang,China3.Fujian Earthquake Ad

Keywords:: air-gun array; time-frequency characteristic of wavelet; the quantity of air-gun; the size of air-gun array

摘要:: 通过分析福建街面水库气枪实验的OBS竖向速度记录,研究大容量气枪阵列子波时频特性及其受气枪数量和枪阵尺寸的影响。数据分析结果表明:(1)气枪子波由主脉冲和气泡脉冲组成,同时伴随有水面虚反射引起的负脉冲。主脉冲振幅大、持时短、频带宽,通常应用于浅部探测; 气泡脉冲能量集中在低频段,垂直穿透深,水平传播远,通常应用于深部探测。在频谱上可以看到气泡振荡引起的频谱波动和虚反射引起的陷波点。(2)气枪数量增加,主脉冲振幅和气泡脉冲振幅相应增加,初泡比震荡变小,气泡周期和低频段主频主要受单枪容量影响,变化很小,频谱形状较为一致。(3)街面水库气枪阵列的枪阵尺寸远大于单枪气泡半径,各枪子波之间相互作用很小,枪阵子波近似为各枪子波线性叠加,子波参数随枪阵尺寸变化影响不大。

Abstract:: Through analyzing the far-field OBS velocity records of the air-gun experiment in Fujian Jiemian reservoir,we study the time-frequency characteristic of large capacity air-gun array wavelet and the influence of the quantity of air-gun and the size of air-gun array.Data analysis results showed that:(1)The air gun wavelet is composed of main pulse and bubble pulse.Main pulse,which is of large amplitude,short duration and wide frequency band,is usually used in shallow exploration; Bubble pulse,which is concentrated in low-frequency band,is usually used in deep exploration with deep vertical penetration and far horizontal propagation.It can be seen that spectrum fluctuation caused by bubble oscillation and notch point caused by ghost wave in the frequency spectrum.(2)With the quantity of air-gun increasing,main pulse amplitude and the bubble pulse amplitude increase,peak-bubble ratio decreases.Bubble period and the dominant frequency in low-frequency band are mainly affected by single gun capacity and their changes are very small.The frequency spectral shape is consistent.(3)The size of air-gun array in the air-gun experiment in Fujian Jiemian reservoir is much larger than single gun bubble radius.The interaction between every air-gun wavelet is very small.The air-gun array wavelet shows approximately linear superposition of every air-gun wavelet.Wavelet parameters changes little with the variation of the size of air-gun array.