| 遗传算法中的光滑约束反演及其在青藏高原面波研究中的应用 |
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| 引用本文： | 吴建平,明跃红,曾融生.遗传算法中的光滑约束反演及其在青藏高原面波研究中的应用[J].地震学报,2001,23(1):45-53. |
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| 作者姓名： | 吴建平 明跃红 曾融生 |
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| 作者单位： | （中国北京100081中国地震局地球物理研究所） |
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| 基金项目： | 国家自然科学基金! (4 9874 0 2 1) |
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| 摘 要： | 光滑约束技术在线性反演中具有重要的作用，但在遗传算法的反演中则很难直接施加于模型参数，其原因是采用光滑处理后的模型参与迭代后，模型的多样性受到很强的压制，并在少量的迭代过程中使种群的各个模型趋向一致，从而得不到满足条件的最优解．本文给出了一种可用于遗传算法反演的间接光滑约束方法．该方法将遗传算法迭代过程中产生的模型经处理后得到的光滑模型，作为误差函数计算的输入模型．迭代过程仍采用原模型，避免了模型的多样性损失，在面波反演和接收函数反演的试验中取得了良好的效果．我们利用该方法对青藏高原地区的瑞利波相速度资料进行了反演，揭示了青藏高原中部地区S波速度结构的横向变化特征．结果表明，青藏高原北部地区地壳Ｓ波速度较南部地区低；大多数路径在15～40ｋｍ 深度范围内，存在12～25ｋｍ 厚的地壳低速层；上地幔低速层位于100ｋｍ 深度以下，厚度主要在40～80ｋｍ 范围内变化，个别路径可达100ｋｍ 以上．安多台以北、玛沁和玉树以西之间，在上地幔90～230ｋｍ 深度范围存在明显的低速层，最低速度约4.2～ 4.3km／s．根据不同路径的S波速度结构和前人的资料，我们认为印度板块的俯冲可能以雅鲁藏布缝合带附近为界．
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| 关 键 词： | 遗传算法 光滑约束 面波 S波速度结构 青藏高原 |
| 文章编号： | 0253-3782(2001)01-0045-09 |
| 修稿时间： | 2000年4月14日 |
SMOOTH CONSTRAINT INVERSION TECHNIQUE IN GENETIC ALGORITHMS AND ITS APPLICATION TO SURFACE WAVE STUDY IN THE TIBETAN PLATEAU |
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| Wu Jianping,Ming Yuehong,Zeng Rongsheng.SMOOTH CONSTRAINT INVERSION TECHNIQUE IN GENETIC ALGORITHMS AND ITS APPLICATION TO SURFACE WAVE STUDY IN THE TIBETAN PLATEAU[J].Acta Seismologica Sinica,2001,23(1):45-53. |
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| Authors: | Wu Jianping Ming Yuehong Zeng Rongsheng |
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| Abstract: | WT5BZ]Smooth constraint is important in linear inversion, but it is difficult to apply directly to model parameters in genetic algorithms. If the model parameters are smoothed in iteration, the diversity of models will be greatly suppressed and all the models in population will tend to equal in a few iterations, so the optimal solution meeting requirement can not be obtained. In this paper, an indirect smooth constraint technique is introduced to genetic inversion. In this method, the new models produced in iteration are smoothed, then used as theoretical models in calculation of misfit function, but in process of iteration only the original models are used in order to keep the diversity of models. The technique is effective in inversion of surface wave and receiver function. Using this technique, we invert the phase velocity of Raleigh wave in the Tibetan Plateau, revealing the horizontal variation of S wave velocity structure near the center of the Tibetan Plateau. The results show that the S wave velocity in the north is relatively lower than that in the south. For most paths there is a lower velocity zone with 12~25 km thick at the depth of 15~40 km. The lower velocity zone in upper mantle is located below the depth of 100 km, and the thickness is usually 40~80 km, but for a few paths reach to 100 km thick. Among the area of Ando, Maqen and Ushu stations, there is an obvious lower velocity zone with the lowest velocity of 4.2~4.3 km/s at the depth of 90~230 km. Based on the S wave velocity structures of different paths and former data, we infer that the subduction of the Indian Plate is delimited nearby the Yalung Zangbo suture zone. |
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| Keywords: | genetic algorithm smooth constraint surface wave S wave velocity structure Tibetan Plateau |
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