Abstract: High-frequency S-wave seismogram envelopes of microearthquakes are broadened with increasing travel distance,which is called S-wave envelope broadening.Multiple forward scattering and diffraction for the random inhomogeneities along seismic ray path are the main reasons to cause the S-wave envelope broadening,so the phenomenon of S-wave envelope broadening is used to study the inhomogeneity of medium.The peak delay time of S-wave,which is defined as the time lag from the direct S-wave onset to the maximum amplitude arrival of its envelope,is accepted to quantify the phenomenon of S-wave envelope broadening.The 204 small earthquake records in Changbaishan Tianchi volcano were analyzed by S-wave envelope broadening algorithm.The results show that the phenomenon of S-wave envelope broadening in Changbaishan Tianchi volcano is obvious,and the peak delay time of S-wave has a positive correlation with hypocenter distance and frequency of S-wave.The relationships between the peak delay time of S-wave and the hypocenter distance for different frequency bands were got by statistics method.The results are beneficial to the understanding of the S-wave envelope broadening phenomena and the quantitative research on the inhomogeneities of the crust medium in the Changbaishan Tianchi volcano region.

Key words: Changbaishan Tianchi volcano, S-wave envelope broadening, peak delay time of S-wave

摘要： 高频S波随着传播距离的增大其均方根(RMS)包络逐渐变宽,把这种现象称为S波的包络展宽现象。S波传播路径上随机分布的非均匀体对S波的多次前向散射和绕射作用是导致S波包络展宽现象的主要原因,因此可用S波的包络展宽现象来研究介质的非均匀性。采用S波包络峰值延时对S波包络展宽现象进行量化。S波包络峰值延时定义为S波初至与其RMS包络峰值最大值之间的时间差。文中对长白山天池火山区204个小震记录进行了S波包络展宽分析,研究发现长白山天池火山区小震S波包络展宽现象明显,S波包络峰值延时与震中距、频率呈正相关;运用统计学方法获取了长白山天池火山区不同频带下S波包络峰值延时与震中距之间的关系。研究结果对认识S波包络展宽的特征以及定量研究长白山天池火山区介质的非均匀性具有重要意义。

关键词: 长白山天池火山, S波包络展宽, S波包络峰值延时