塔克拉玛干沙漠区浅表层对地震波的吸收衰减作用

人们普遍认为疏松沙丘对地震波的吸收衰减是导致塔克拉玛干沙漠区地震资料信噪比及分辨率均较低的重要因素,因此探究沙漠区近地表对地震波的吸收衰减程度,对地震数据现场采集及后续处理中采取有针对性的措施具有指导意义。以塔克拉玛干沙漠古城地区为实例,总结分析了近地表疏松沙丘的特点,采用蜂窝状放置法对不同厚度沙丘进行吸收衰减调查试验,通过谱比法探讨了该区沙漠表层对地震波的吸收衰减规律。试验结果表明:疏松沙丘对主频在40Hz以内的地震波的能量和频率的吸收衰减并不严重;在沙漠地表区,若未采用检波器组合接收,即使将其埋置于疏松沙层之下的高速层中,仍难以获得高品质地震资料。

Seismic wave absorption caused by near-surface in Taklimakan Desert

It is generally believed that seismic wave absorption caused by loose near-surface such as sand dunes is the main factor which damages both data S/N ratio and resolution in Taklimakan Desert. Therefore, clearly understanding seismic wave attenuation in the desert is significant for taking appropriate measures in seismic acquisition and data processing. For this purpose, we have conducted field tests in Gucheng, Taklimakan Desert with "honey comb" geophone arrays and analyzed wave absorption caused by loose near-surface with spectral ratio method. It is concluded that loose near-surface in the desert would not very severely damage seismic energy and frequency when the dominant frequency is below 40Hz. Our experiment shows that high quality seismic data cannot be acquired without geophone arrays, even though geophones are buried in high velocity layer(HVL) under loose sand dunes.