近地表衰减的影响因素

Influence factors of near surface attenuation

近地表衰减是影响地震记录质量的重要因素。在陆上进行地震勘探时,地震波需要穿过近地表,由于近地表传播介质通常为非均匀、各向异性和非完全弹性体,导致地震波衰减十分严重,使检波器接收到的地震波能量弱、频率低。近地表衰减的影响因素主要包括品质因子、低降速带速度、低降速带厚度和炮检距。正演模拟地震记录在各种影响因素不同取值下的情况,对地震子波及其对应振幅谱进行详细分析,并阐述了各个因素对近地表衰减的影响作用。

Near surface attenuation is an important factor influencing the quality of seismic records. The seismic waves pass through the near surface when a seismic exploration is conducted on land. The seismic wave attenuation is very serious due to near surface media is usually inhomogeneous, anisotropic and wholly nonelastic body, and seismic wave received by detectors has the characteristics of weak energy and low frequency. The influence factors of near surface attenuation mainly include the quality factor, the velocity of weathering, the thickness of weathering and offset. Forward modeling seismic record is done in the case of various influence factors under different values, the seismic wavelets and their corresponding amplitude spectrum are analyzed in details, and the impact of each factor on the near surface attenuation are introduced.