武岩, 丁志峰, 朱露培. 2014: 利用接收函数研究渤海湾盆地沉积层结构. 地震学报, 36(5): 837-849. DOI: 10.3969/j.issn.0253-3782.2014.05.008
引用本文: 武岩, 丁志峰, 朱露培. 2014: 利用接收函数研究渤海湾盆地沉积层结构. 地震学报, 36(5): 837-849. DOI: 10.3969/j.issn.0253-3782.2014.05.008
Wu Yan, Ding Zhifeng, Zhu Lupei. 2014: Sedimentary basin structure of the Bohai Bay from teleseismic receiver functions. Acta Seismologica Sinica, 36(5): 837-849. DOI: 10.3969/j.issn.0253-3782.2014.05.008
Citation: Wu Yan, Ding Zhifeng, Zhu Lupei. 2014: Sedimentary basin structure of the Bohai Bay from teleseismic receiver functions. Acta Seismologica Sinica, 36(5): 837-849. DOI: 10.3969/j.issn.0253-3782.2014.05.008

利用接收函数研究渤海湾盆地沉积层结构

Sedimentary basin structure of the Bohai Bay from teleseismic receiver functions

  • 摘要: 对布设于渤海湾盆地地区的70个台站2006年9月—2009年9月记录到的895个远震数据进行接收函数计算,发现位于沉积层上的台站记录的接收函数震相较为复杂,由沉积层基底的转换波、多次波及莫霍面转换波、多次波共同构成,且随着沉积层厚度的增加,沉积层基底转换波、多次波与莫霍面转换波、多次波震相相互叠加,使之无法分辨出莫霍面转换波及多次波到时.为此,本文利用相邻算法对沉积层模型进行搜索, 以获取与实际波形误差最小的波形相对应的模型,即台站下方的沉积层结构.结果显示:① 渤海湾盆地由NNE向展布的坳陷带与隆起带组成,冀中坳陷带的沉积层厚度为3—6 km, 坳陷带内沿NE-NNE向分布着带状凹陷带与凸起带相间的次级构造,而且其东侧靠近沧县隆起区的凹陷带沉积层基底埋深最大,体现了渤海湾盆地基底受正断层控制而形成的半地堑(地堑)-半地垒(地垒)构造;② 隆起带的波速比vP/vS大于坳陷带的波速比,推测与隆起带下第三系地层的缺失有关, 坳陷带内高波速比地区与地热田的分布相对应, 说明沉积层内高温环境下波速比较高;③ 隆起带内的S波平均速度较坳陷带内的S波平均速度小,且冀中坳陷带内沉积层较厚地区对应的S波平均速度比其它地区更大, 说明渤海湾地区沉积层厚度与沉积层内的S波平均速度成反比关系,推测与下第三系地层的厚度有关,且下第三系地层越厚的地区,S波平均速度越大.以上结果表明,利用接收函数研究的结果与通过地质、地热等方面的研究结果存在着良好的对应关系.

     

    Abstract: We calculated P wave receiver functions using 895 teleseismic events from September 2006 to September 2009 recorded by 70 temporary stations located in the Bohai Bay basin.We found that it is difficult to identify the P to S converted phases from the Moho discontinuity.The first few seconds after the direct P arrival are mainly controlled by the sedimentary structure response which includes the Ps phase generated by the bottom of the basin and its multiple reverberations in the basin.Based on these characteristics, we used the neighborhood algorithm to invert the data and try to find the best basin velocity model that produces the best fit between the theoretical receiver functions and observed ones in the least-squares sense.The results show that there is a series of depressions and uplifts orienting in the NNE direction in the Bohai Bay basin.The sedimentary depth in the Jizhong Depression is about 3-6 km.There are several secondary depressions and uplifts alternating in the NNE or NE direction in the Jizhong depression.The thickest sedimentary layer is located in the eastern Jizhong depression.The above shows the characteristics of a half rift valley (rift valley)-half horst (horst) structure.The ratio of the P velocity to S velocity in the uplifts is larger than that in the depressions, which may be caused by the lack of the Paleogene stratum in the uplifts.The proximity of geothermal fields to the high vP/vS ratio depressions shows a close relationship between the high temperatures of the stratum and the large vP/vS ratios .The average of S velocity of the sedimentary in the uplift is smaller than that in the depression, and the thicker sedimentary area always has a higher average S velocity.These characteristics show a relationship between thick sedimentary and high average S velocity.It may be because that the thicker sedimentary area has a thicker Paleogene stratum and the S velocity of the Paleogene stratum is much higher than that of the Neogene and Quaternary stratums.The sedimentary structure provides a base to determine crustal structure beneath the Bohai Bay basin.

     

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