地下爆炸Rg波低谷点激发机理  

Generation of null in Rg wave by underground explosions

作　　者：何永锋[1] 陈晓非[1] 何耀峰[1] 靳平[2] 

机构地区：[1]北京大学地球与空间科学学院,北京100871 [2]西北核技术研究所,西安710024

出　　处：《地球物理学报》2005年第3期643-648,共6页Chinese Journal of Geophysics

基　　金：国家自然科学基金项目 (4 0 13 40 10 )资助

摘　　要：目前普遍认为Rg_S散射是地下核爆炸短周期Lg波的主要能量来源,其主要依据为由线性偶极补偿源(CLVD)激发的Rg波谱的低谷点随深度变化的特征与区域震相Lg波谱的低谷点随深度变化的特征具有一致性.本文利用简正振型理论,分析了Rg波谱中低谷点的形成机理,给出了各种速度模型下CLVD源深度与低谷点频率之间的关系,并分析了利用公式hCLVD=V (16fNull)估计震源深度的局限性.本文的研究结果进一步支持了CLVD源是激发Lg波的主要因素的观点,并得到重要结论:CLVD源形式下的本征位移函数及其导数的叠加所形成的极小值,即源的空间分布特征,是形成Rg波低谷点的原因,而不能仅用水平向基频本征位移函数过零点来解释.It is widely accepted that the near-source scattering of explosion-generated Rg into S is the primary contributor to the low-frequency Lg from nuclear explosions, because the prominent low-frequency spectral null in Lg coincides with that in Rg from a compensated linear vector dipole (CLVD) source. In this study, the mechanism of the excitation of the spectral null of Rg generated by the CLVD source is analyzed in detail with the normal mode method. The most important result in this study is that the spectral null is due to a combination of displacement eigenfunction and its derivative of the fundamental-mode Rayleigh wave controlled by CLVD source, not only the zero-crossing can fully explain the excitation of the spectral null.

关 键 词：Rg波 LG波 CLVD源 低谷点 简正振型 

分 类 号：P315[天文地球—地震学]