| 华北及周边地区上地幔P波速度结构 |
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| 引用本文： | 关俊辉.华北及周边地区上地幔P波速度结构[J].地球物理学进展,2009,24(5):1582-1592. |
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| 作者姓名： | 关俊辉 |
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| 作者单位： | 中国科学院地质与地球物理研究所,北京,100029 |
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| 摘 要： | 本文基于层析成像方法研究了华北及其邻区(30°N~43°N，100°E~130°E)的上地幔P波速度结构.该区域是我国地震活动强烈的地区之一，曾多次发生破坏性地震，地质构造十分复杂.本研究采用中国数字化地震台网1996~2002年和中国科学院地质与地球物理所（IGGCAS）流动地震台阵2001~2003年地震记录中的P波走时，挑选了6870个地震事件，其中包括1382个区域地震事件，5488个远震事件.在对实际资料反演之前，进行了分辨率测试以确定反演结果的可靠性，对反演中不同参数对结果的影响做了分析，以确定最佳的的模型和参数.根据上述分析，以水平方向1°×1°，垂直方向以5 km、15 km、30 km为间隔划分网格，并建立初始速度模型，采用伪弯曲射线追踪方法计算走时和射线路径，通过基于LSQR算法的反演重建了研究区域40 km以下、480 km以上的三维P波速度结构.成像结果显示：（A）研究区域西南部的四川盆地北部在40 km以上为明显的低速异常，40 km以下一直到360 km均为高速异常；（B）华北盆地在90 km之上高速异常比较明显，而在120 km~360 km的深度，低速异常为区域主要特征，它与渤海湾地区的低速区连接，形成地幔楔，随着深度的增加，由于太平洋俯冲板块的影响，华北盆地和渤海湾地区下的高速异常突出.
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| 关 键 词： | 层析成像 P波速度构造 伪弯曲射线追踪方法 LSQR算法 |
| 收稿时间： | 2008-12-29 |
| 修稿时间： | 2009-5-22 |
Upper mantle structure of North China and surrounding regions from P-wave traveltime tomography |
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| GUAN Jun-hui.Upper mantle structure of North China and surrounding regions from P-wave traveltime tomography[J].Progress in Geophysics,2009,24(5):1582-1592. |
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| Authors: | GUAN Jun-hui |
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| Institution: | (InstituteofGeologyandGeophysics,ChineseAcademyofSciences,Beijing100029,China) |
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| Abstract: | A three-dimensional P wave velocity model is developed for the upper mantle of North China and surrounding regions (30°N～43°N, 100°E～130°E) by applying the tomography method of Zhao et al, where many earthquakes occurred in history. Although many researchers had studied this area, their results are mainly about crust and uppermost mantle or have a low resolution. In this study, 5870 earthquake events including 1382 local events and 5488 teleseismic events are extracted from P wave records of China Earthquake Networks Center during 1996 ～ 2002 and seislab of IGGCAS during 2001 ～ 2003. Before the inversion, checkerboard resolution test and restoring resolution test have been made to confirm the reliability of results, also analysis of different parameters to the result has been done to make the initial model. Based analysis above, we chose the spatial resolution of 1°×1°in the horizontal direction and 5～30 km in depth. Using the pseudobending method to calculate the ray traveling path and residual of travel time; LSQR method to inverse, we got the final 3-D P wave velocity structure in this area. The result reveals that: (A)Under the Sichuan Basin, the perturbation of P wave velocity above 40 km is high, beneath 40 km to 360 km, the perturbation of P wave velocity is low. (B) Above 90 km, the perturbation of P wave velocity under the North China Basin is high, while at the depth between 120 ～ 360 km, low perturbation of P wave is the
main feature, it connects with the low velocity area under the Bohai Bay, forming a mantle wedge. With the increasing of depth, the perturbation of P wave under this area becomes high. |
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| Keywords: | tomography P-wave velocity model preudobending method LSQR method |
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