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青藏高原东南缘的龙门山断裂两侧具有陡峭的地形特征，在约50~100 km的水平距离内，地形高程从2000 m增加到4000 m，该区强烈的壳幔变形特征及地球动力学模式一直是研究的热点问题.本文从四川地区49个固定台站记录的远震资料提取了P波接收函数，获得了四川盆地及周边的地壳厚度和泊松比，并以此构建反演的初始模型.在线性反演的基础上，引入了分别拟合低频和高频接收函数的两步反演技术，用以反演台站下方的地壳S波速度结构.数字试验表明，该方法可以有效抑制接收函数反演的不唯一性，为了得到最优解，最后用Bootstrap重采样技术估计解的不确定性.结果表明，四川盆地的地壳厚度在40~46 km，松潘-甘孜块体北部的地壳厚度为46~52 km，而南部增厚到50~60 km.从四川盆地向西跨过龙门山断裂，地壳厚度增加了10~15 km.在四川盆地及周边地区，地壳泊松比在0.26~0.32之间，呈块体分布特征，高泊松比（0.28~0.32）主要沿龙门山断裂以及安宁河-小江断裂分布.地壳S波速度结构表明，来自青藏高原中部的中下地壳低速层可能受到了坚硬的四川盆地阻挡，改变原来的运动方向并沿龙门山断裂展布，由于低速层的囤积导致该区地形陡峭和下地壳增厚. 相似文献
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We investigate quantitatively how the peak emission frequency of the overall energy spectrum is at work in distinguishing
RBL-like and XBL-like objects. We employ the sample of Giommi et al. (1995) to study the distribution of BL Lacertae objects with various locations of the cutoff of the overall energy spectrum.
We find that the sources with the cutoff located at lower frequency are indeed sited in the RBL region of the αro-αoxplane, while those with the cutoff located at higher frequency are distributed in the XBL region. For a more quantitative
study, we employ the BL Lacerta esamples presented by Sambruna et al. (1996), where the peak emission frequency, νp, of each source is estimated by fitting the data with a parabolic function. In the plot of αrx -log νp we find that, in the four different regions divided by the αrx = 0.75 line and thelogνp = 14.7 line, all the RBL-like objects are inside the upper left region, while most XBL-like objects are within the lower
right region. A few sources are located in the lower left region. No sources are in the upper right region. This result is
rather quantitative. It provides an evidence supporting what Giommi et al. (1995) suggested: RBL-like and XBL-like objects can be distinguished by the difference of the peak emission frequency of
the overall energy spectrum.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
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