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Attenuation Characteristics of Earthquake Ground Motion for Large Volume Airgun 
CAI Huiteng^{1,2}, CHEN Yong^{1}, JIN Xing^{2}, XU Yihe^{1,3}, LI Wen^{4}

1.School of Earth Sciences and Engineering, Nanjing University, Nanjing 210046, China;2.Fujian Earthquake Agency, Fuzhou 350003, China;3.Institute of Geophysics, CEA, Beijing 100081, China;4.Geophysical Exploration Center, CEA, Zhengzhou 450003, China


摘要: 
In order to further deepen the understanding of seismic wave propagation characteristics induced by the large volume airgun source, experimental data from multiple fixed excitation points in Fujian Province were used to obtain the equivalent single excitation high signaltonoise ratio velocity and displacement records through linear stacking and simulation techniques. Then the peak displacements of different epicentral distances were used to calculate the equivalent magnitude of the airgun source excitation at different fixed excitation points so as to establish the attenuation relationship between equivalent magnitude, epicenter distance and velocity peak. Our results show that:① Within 270km of epicentral distance, for the largevolume airgun's single shot, the peak velocity range is about 7004nm/s, and the peak displacement range is about 200.00.2nm; ② The equivalent magnitude of the Pwave from the airgun source with a total capacity of 8,000in^{3} is 0.1810.760, and the equivalent magnitude of the Swave is 0.2940.832. By contrast, the equivalent magnitude of the Pwave from the airgun source with a total capacity of 12,000in^{3} is 0.5330.896, and the equivalent magnitude of the Swave is 0.6110.946. The Swave energy is greater than the Pwave energy, and the excitation efficiency varies greatly with different excitation environment; ③ The peak velocity increases with the equivalent magnitude, and decreases with the epicentral distance. The vertical component of the Pwave peak velocity is the largest among those three components, while the Swave has the smallest vertical component and similar horizontal components. Hence, our research can provide an important basis for the quantitative judgment of the seismic wave propagation distance using the airgun and the design of the observation system in deep exploration or monitoring with airgun. 
关键词: Largevolume airgun source Velocity peak value Displacement peak value Equivalent magnitude Attenuation characteristics 
DOI：10.19743/j.cnki.08914176.201904010 
分类号: 
基金项目:This project is sponsored by the National Natural Science Foundation of China (41790461). 

Attenuation Characteristics of Earthquake Ground Motion for Large Volume Airgun 
CAI Huiteng^{1,2}, CHEN Yong^{1}, JIN Xing^{2}, XU Yihe^{1,3}, LI Wen^{4}

1.School of Earth Sciences and Engineering, Nanjing University, Nanjing 210046, China;2.Fujian Earthquake Agency, Fuzhou 350003, China;3.Institute of Geophysics, CEA, Beijing 100081, China;4.Geophysical Exploration Center, CEA, Zhengzhou 450003, China

Abstract: 
In order to further deepen the understanding of seismic wave propagation characteristics induced by the large volume airgun source, experimental data from multiple fixed excitation points in Fujian Province were used to obtain the equivalent single excitation high signaltonoise ratio velocity and displacement records through linear stacking and simulation techniques. Then the peak displacements of different epicentral distances were used to calculate the equivalent magnitude of the airgun source excitation at different fixed excitation points so as to establish the attenuation relationship between equivalent magnitude, epicenter distance and velocity peak. Our results show that:① Within 270km of epicentral distance, for the largevolume airgun's single shot, the peak velocity range is about 7004nm/s, and the peak displacement range is about 200.00.2nm; ② The equivalent magnitude of the Pwave from the airgun source with a total capacity of 8,000in^{3} is 0.1810.760, and the equivalent magnitude of the Swave is 0.2940.832. By contrast, the equivalent magnitude of the Pwave from the airgun source with a total capacity of 12,000in^{3} is 0.5330.896, and the equivalent magnitude of the Swave is 0.6110.946. The Swave energy is greater than the Pwave energy, and the excitation efficiency varies greatly with different excitation environment; ③ The peak velocity increases with the equivalent magnitude, and decreases with the epicentral distance. The vertical component of the Pwave peak velocity is the largest among those three components, while the Swave has the smallest vertical component and similar horizontal components. Hence, our research can provide an important basis for the quantitative judgment of the seismic wave propagation distance using the airgun and the design of the observation system in deep exploration or monitoring with airgun. 
Key words: Largevolume airgun source Velocity peak value Displacement peak value Equivalent magnitude Attenuation characteristics 



