| 华北地区地下介质波速比值(VP/VS)研究 |
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| 引用本文： | 张学民,刁桂苓,束沛镒,刘素英.华北地区地下介质波速比值(VP/VS)研究[J].地震地质,2004,26(2):305-317. |
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| 作者姓名： | 张学民 刁桂苓 束沛镒 刘素英 |
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| 作者单位： | 中国地质大学地球物理与信息技术学院,北京,100083;河北省地震局,石家庄,050021;河北省地震局,石家庄,050021;中国科学院地质与地球物理研究所,北京,100029 |
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| 基金项目： | 国家重点基础研究发展计划(973计划)，G1998040704， |
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| 摘 要： | 文中利用分别独立反演得到的华北地区 16个台的S波和P波速度结构 ,计算了各台站下方分层速度结构各层的波速比值 ,发现在强震区的波速比总体上高于弱震区 ,且地壳中的一些低速层位会出现 >1 8的波速比值 ,而在弱震区或稳定块体内部 ,各层波速比一般都低于正常波速比 1 732 ,平均值甚至 <1 7;在过渡区域 ,如位于盆地边缘或稳定块体边缘的台站 ,其波速比值有高有低 ,一般情况下 >1 732。在此基础上 ,最后我们对位于不同地质构造体的台站下方的介质性质进行了讨论
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| 关 键 词： | 波速比低速层 强震区 弱震区 地质构造 |
| 文章编号： | 0253-4967(2004)02-0305-13 |
| 修稿时间： | 2003年6月30日 |
STUDY ON WAVE VELOCITY RATIO(V_P/V_S) OF UNDERGROUND MEDIA IN NORTH CHINA |
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| ZHANG Xue-min , DIAO Gui-ling SHU Pei-yi LIU Su-ying School of Geophysics and Information Technology,China University of Geosciences,Beijing ,China Earthquake Administration of Hebei Province,Shijiazhuang ,China Institute of Geology and Geophysics,Chinese Academy of Science,Beijing ,China.STUDY ON WAVE VELOCITY RATIO(V_P/V_S) OF UNDERGROUND MEDIA IN NORTH CHINA[J].Seismology and Geology,2004,26(2):305-317. |
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| Authors: | ZHANG Xue-min DIAO Gui-ling SHU Pei-yi LIU Su-ying School of Geophysics and Information Technology China University of Geosciences Beijing China Earthquake Administration of Hebei Province Shijiazhuang China Institute of Geology and Geophysics Chinese Academy of Science Beijing China |
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| Affiliation: | ZHANG Xue-min 1,2) DIAO Gui-ling 2) SHU Pei-yi 3) LIU Su-ying 2) 1)School of Geophysics and Information Technology,China University of Geosciences,Beijing 100083,China 2)Earthquake Administration of Hebei Province,Shijiazhuang 050021,China 3)Institute of Geology and Geophysics,Chinese Academy of Science,Beijing 100029,China |
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| Abstract: | In this paper,based on available S wave and P wave velocity structures beneath16seismic stations in North China,wave velocity ratios for every velocity layer beneath these stations are calculated.According to their seismicity and geographic locations,these stations are divided into three types and discussed sepa-rately.In macroseismic area,the V P /V S ratio is systematically higher than that in microseismic area,and the V P /V S ratio of some low-velocity layers in mid-lower crust is greater than1.8.In seismically quiet area or at interior of stable block,however,the V P /V S ratio is relatively stable for the whole crust and upper man-tle,in many layers of which the ratio is less than the normal V P /V S ratio(1.732).In transitional area,such as the marginal area of basins or stable blocks,the number of layers with high V P /V S value becomes less,but the average V P /V S values beneath the stations are generally still greater than1.732.Moreover,beneath the stations in microseismic area,a layer of more than10km thickness is recognized,which has never been found in macroseismic area and may reflect the old continental nucleus or crystalline basement.Stations in the same tectonic unit of transitional area have the same S wave velocity structure,which might be the result of regional tectonic activities. In addition,the contour maps of V P /V S and S wave velocity at10km,15km,20km and25km depths were plotted and analyzed.The results showthat at10km depth,taken the TaihangMountains as a bound-ary,the V P /V S values in the western area are higher than those in the eastern area;but at greater depth,the V P /V S is higher in the eastern area,and especially much higher in Xingtai earthquake area at25km depth.It can be seen from S wave velocity images,that the velocity differences between the eastern and western areas separated by the TaihangMountains are very significant all the time,and there is no evidence of mixing-up even at25km depth.This may indicate that the Taihang Mountains is an evident material variation belt,which extends to a great depth. The apparent differences of V P /V S in macroseismic and microseismic areas are of great significance to prediction of potential risk area of strong earthquake,while the differences in velocity structures and wave velocity ratio beneath various geological structures may provide some leads for the study of the history of lo-cal tectonic activities. |
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| Keywords: | wave velocity ratio lowvelocity layer macroseimic area microseismic area geological structure |
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