层裂对区域震相Lg波的影响  

THE EFFECT OF SPALL ON Lg WAVES

作　　者：何永锋[1] 陈晓非[1] 张海明[1] 

机构地区：[1]北京大学地球与空间科学学院理论与应用地球物理研究所

出　　处：《地震学报》2005年第3期309-316,355,共8页Acta Seismologica Sinica

基　　金：国家自然科学基金项目(40134010)资助.

摘　　要：地下核爆炸Lg波的激发机制,目前尚未十分清楚.普遍接受的观点是:伴随层裂源的补偿线性矢量偶极源激发的Rg波的散射形成的S波,是Lg波的最主要贡献因素.本文利用频谱比对方法,结合合成理论地震图方法,基于东哈萨克斯坦地区速度模型,分析了东哈萨克斯坦地壳速度模型下的层裂对区域震相Lg波的影响,并进一步分析了该地区的实际观测资料.结果表明,层裂时间函数对Lg波具有扇贝形调制作用;Lg波振幅谱的低谷点源自于补偿线性矢量偶极(CLVD)源激发的Rg波.这一结果也表明,东哈萨克斯坦速度模型下的Lg波受层裂的调制作用,与内华达试验区的Lg波是一样的,进一步支持了Patton和Taylor的观点,对于进一步理解及更好地利用Lg波具有重要理论指导意义.The generation mechanism of Lg wave from underground nuclear explosion is still not clear at present. The general viewpoint is that the S wave generated by the near-source scattering of explosion-generated Rg appears to be the primary contributor to the low-frequency Lg (0.2~2.0 Hz) from nuclear explosions. The viewpoint is supported by the analysis of regional data from several Yucca flats, NTS explosions by Patton and Taylor, who further indicated that the prominent low-frequency spectral null in Lg is due to Rg from a compensated linear vector dipole (CLVD) source. In this paper, the data from Kazakstan Test Sites are investigated by a spectral ratio method. We have found that the spectral ratio of Lg waves is characterized by a spectral scalloping and a pronounced null, and the spectral null does not shift with spall dwell times, showing a strong dependence on shot depth and a very good agreement with those expected from Rg due to a CLVD source.

关 键 词：频谱比 Lg波层裂 CLVD源 低谷点 

分 类 号：P315.02[天文地球—地震学]