利用主动震源直达波互相关时延检测技术监测小江断裂带浅层地震波波速变化
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摘要
为了监测云南小江断裂带附近地震波波速的连续变化,2006年4月在小江断裂带以西10 km布置了一条长235 m的主动震源浅勘测线,进行为期1个月的连续观测实验。采用前后互相关技术对直达波进行了高精度波速变化测量,分析得到以下结果和结论:(1)实验期间,实验点地下介质存在相对波速变化δv/v≈10-3~10-2;(2)波速变化随震中距增加迅速减小,这可能反映了较浅层波速变化与较深层相比更剧烈;(3)波速变化和大气压变化有很好的相关性,相对波速变化对大气压敏感系数为10-6Pa-1量级;(4)降雨会显著影响波速与气压的关系,降雨前相对波速变化随气压增加而增加,而降雨后相对波速则与气压呈负相关。
In order to monitor continuous variation of wave velocity around the Xiaojiang Fault Zone in Yunnan,we laid the survey line of active source of 235 m on Apr.,2006,and conducted the continuous observation field experiment in one month. By before and after correlation technique,we monitored the precise velocity variation of the direct wave,and got the follow ing conclusions:( 1) Throughout the experiment,there exit relative velocity variation of δv / v ≈10- 3~ 10- 2in the subsurface medium at the experiment site.( 2) The velocity decreased with the increasing of epicenter,which may reflect the velocity variation in the shallow layer varied stronger than that in the deeper layer.( 3) The measured velocity variation appeared the good correlation with barometric pressure,which had a stress sensitivity of 10- 6Pa- 1.( 4) The rainfall had the significant influence on the relationship betw een velocity variation and barometric pressure. The relative velocity variation increased with the increasing of the barometric pressure before the rain,while after the rainfall the estimated velocity changes showed a clear negative-correlation with barometric pressure.
引文
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