长白山天池火山区介质速度非均匀性谱结构  

Spectral structure of velocity inhomogeneity of crust medium in Changbaishan Tianchi volcano

作　　者：范小平[1] 李清河[1] 杨从杰[1] 金淑梅[1] 

机构地区：[1]江苏省地震局,南京210014

出　　处：《地球物理学报》2011年第5期1215-1221,共7页Chinese Journal of Geophysics

基　　金：国家科技支撑计划项目(2006BAC01B04);国家自然科学基金(40974031)资助

摘　　要：观测和研究表明,非均匀介质RMS(Root Mean Square)速度微扰动ε,特征尺度相关距离a以及幂指数κ的空间分布特征可描述介质非均匀性特征.本文选用长白山天池火山区的小震记录,运用S波包络展宽法对长白山天池火山区地壳浅部介质速度非均匀性谱结构进行了研究.结果发现长白山天池火山区地壳浅部介质呈现强烈的介质非均匀性,且其具有明显的频率特性.在2～4 Hz及4～8 Hz频带范围内,小尺度弱非均匀性介质基本上分布在天池火山口的东南角和西北角,大尺度强非均匀性介质基本上分布在天池火山口的西南角和东北角,这一特征在0～2km和2～5 km深度范围内均体现;在8～16 Hz频带内,0～2 km深度范围内弱非均匀性介质分布在火山口西部,而2～5 km深度范围内弱非均匀性介质基本上分布在火山口周围区域;在16～30 Hz频带内,0～2 km深度范围小尺度弱非均匀性介质分布在火山口的东北角及西南角,而2～5 km深度范围内小尺度弱非均匀性介质集中分布在火山口的东南角,西北角有少量分布.Observation and study show that the RMS （Root Mean Square） fractional velocity fluctuation e, correlation distance a, and order k can be used to evaluate the medium inhomogeneity of crust. Based on the analysis of small local earthquake waveforms, the spectral structure of velocity inhomogeneity in Changbaishan Tianchi volcano area was studied by the peak delay time of S-wave envelope broadening method. The results show that the shallow crust medium of Changbaishan Tianchi volcano area presents strong inhomogeneity and frequency dependence. In 2-4 Hz and 4-8 Hz bands, the small-scale and weak inhomogeneities lie in the southeast and northwest of Changbaishan Tianchi volcano and the large-scale and strong inhomogeneities lie in the northeast and southwest at the depth of 042 km and 245 km. In 8-16 Hz, the small-scale and weak inhomogeneities lie on the west of volcano at the depth of 0- 2 kin, but at the depth of 245 kin, the weak inhomogeneities lie around the volcano. In 16- 30 Hz, the small-scale and weak inhomogeneities lie in the southeast and northwest of Changbaishan Tianchi volcano at the depth of 0-2 km, and they lie on the southeast at the depth of 2-5 kin, only a little lie on the northwest of Changbaishan Tianchi volcano.

关 键 词：介质非均匀性谱结构 S波包络展宽 长白山天池火山 

分 类 号：P315[天文地球—地震学]