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大容量气枪震源子波时频特性及其影响因素
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,哈尔滨市南岗区学府路29号 150080;2)中国地震局地震工程与工程振动重点实验室,哈尔滨市南岗区学府路29号 150080;3)福建省地震局,福州 350003
摘要:
通过分析福建街面水库气枪实验的近场水听器记录,研究气枪子波时频特性及其受沉放深度和工作压力的影响,并结合气泡模型解释气泡振荡过程。数据分析表明:①气枪子波由主脉冲和气泡脉冲组成。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。②随着沉放深度的增加,主脉冲振幅变化很小,而气泡脉冲振幅增加,初泡比减小,气泡周期减小,低频段主频增加。沉放深度为10m时,主脉冲振幅和初泡比最大,可应用于浅部探测;沉放深度为25m时,气泡脉冲振幅很大,初泡比最小,可应用于深部探测。③工作压力增加时,主脉冲振幅、气泡脉冲振幅、初泡比、气泡周期等随之增大,低频段主频则减小。
关键词:  气枪子波 时频特性 子波参数 沉放深度 工作压力
DOI:
分类号:
基金项目:中国地震局公益性行业科研专项(2015419015)、国家自然科学基金(41474071)联合资助
The time­frequency characteristic of large volume air­gun source wavelet and its influencing factors
Xia Ji1,2) Jin Xing1,2,3) Cai Huiteng3) Xu Jiajun3)
1)Institute of Engineering Mechanics,China Earthquake Administration,Harbin 150080,China;2)Key Laboratory of Earthquake Engineering and Engineering Vibration,CEA,Harbin 150080,China;3)Earthquake Administration of Fujian Province,Fuzhou 350003,China
Abstract:
Through analyzing the near-field hydrophone records of the air-gun experiment in the Jiemian reservoir,Fujian,we study the time-frequency characteristic of air-gun source wavelet and the influence of gun depth and firing pressure,and explain the process of bubble oscillation based on the Johnson(1994)bubble model. The data analysis shows that: (1)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. (2)With gun depth increasing,the variation of main pulse amplitude is very small,bubble pulse amplitude and the dominant frequency increase,peak-bubble ratio and bubble period decrease. When gun depth is 10m,main pulse amplitude and peak-bubble ratio are maximum,which is suitable in shallow exploration;when gun depth is 25m,bubble pulse amplitude is large,and peak-bubble ratio is minimum,which is suitable in deep exploration. (3)With firing pressure increasing,main pulse amplitude,bubble pulse amplitude,peak-bubble ratio,and bubble period increase,the dominant frequency decreases.
Key words:  Air­gun wavelet  Time­frequency characteristic  Wavelet parameters  Gun depth  Firing pressure