| 重力与地形数据揭示的巴颜喀拉块体东缘垂向构造应力场 |
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| 引用本文： | 佘雅文,付广裕,王灼华,高原.重力与地形数据揭示的巴颜喀拉块体东缘垂向构造应力场[J].地球物理学报,2017,60(6):2480-2492. |
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| 作者姓名： | 佘雅文 付广裕 王灼华 高原 |
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| 作者单位： | 1. 中国地震局地球物理研究所, 北京 100081;2. 中国地震局地震预测研究所, 北京 100036;3. 河北省地震局, 石家庄 050021 |
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| 基金项目： | 国家自然科学基金（41574071），地震预测研究所基本科研业务费专项（2016IES010204、2016IES0305、2015IES0201）和实验场专项经费项目（20150117）联合资助. |
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| 摘 要： | 利用基于消去-恢复原理的最小二乘配置方法,对2009-2013年相对重力/GPS联合观测数据与EGM2008模型数据进行融合,更新了巴颜喀拉块体东缘地区的自由空气与布格重力异常场.基于该布格重力异常数据,以CRUST1.0地壳密度模型为初始条件,使用二维多边形棱柱体正演与非线性最小二乘反演方法,获取了巴颜喀拉块体东缘地壳分层密度结构.基于地壳不可压缩和均衡调整原理提出了计算垂向构造应力新方法,并结合上述地壳分层密度结构和地形数据计算了巴颜喀拉块体东缘垂向构造应力分布.结果表明,龙门山断裂带中南段蓄积了较高的正向构造应力(约40 MPa),马尔康周边地区蓄积了较高的负向构造应力(约—30 MPa).对研究区域1970年以来5级(Ms)以上地震进行统计发现,地震多发生在垂向构造应力梯度带上,垂向构造应力为正的地区易触发浅源地震,为负的地区易触发深源地震.在地壳横向变形强烈的区域,垂向构造应力与地震深度的对应关系减弱.
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| 关 键 词： | 巴颜喀拉块体 布格重力异常 地壳密度结构 垂向构造应力 |
| 收稿时间： | 2016-11-14 |
Vertical tectonic stress in eastern margin of Bayan Har block revealed by gravity and terrain data |
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| SHE Ya-Wen,FU Guang-Yu,WANG Zhuo-Hua,GAO Yuan.Vertical tectonic stress in eastern margin of Bayan Har block revealed by gravity and terrain data[J].Chinese Journal of Geophysics,2017,60(6):2480-2492. |
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| Authors: | SHE Ya-Wen FU Guang-Yu WANG Zhuo-Hua GAO Yuan |
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| Institution: | 1. Institute of Geophysics, China Earthquake Administration, Beijing 100081, China;2. Institute of Earthquake Science, China Earthquake Administration, Beijing 100036, China;3. Hebei Seismological Bureau, Shijiangzhuang 050021, China |
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| Abstract: | In the eastern margin of Bayan Har block, the Gravity/GPS measurement data from 2009 to 2013 and the EGM2008 model gravity data are merged by the least square collocation based on the remove and restore method. Simultaneously, the free-air gravity anomalies (FGAs) and the Bouguer gravity anomalies (BGAs) in the study area are updated. According to the new BGA field above and the Crust 1.0 data, the density structure of the crust is inverted by using the two-dimension polygon method and the nonlinear least square method. Based on the incompressible crust and the isostatic adjustment method, we propose a new method to calculate the vertical tectonic stresses. Furthermore, the distribution of the vertical tectonic stresses around the eastern margin of the Bayan Har block is calculated by using the density structure above. Through the vertical tectonic stress field, we find that the high positive vertical stresses (~40 MPa) are around the southern segment of the Longmen Shan faults, and the high negative vertical stresses (~-30 MPa) are around Barkam. According to the distribution of 99 earthquakes (MS>5) since 1970 in the study area, we find that the gradient belts of the vertical stresses are corresponding to the lateral distribution of the earthquakes, and the area of the negative and positive vertical stresses corresponds to the deep and shallow earthquakes, respectively. However, when the horizontal deformation of the crust is large, the corresponding relation between vertical tectonic stresses and the focal depth of earthquakes is weak. |
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| Keywords: | Bayan Har block Bouguer gravity anomaly Structure of the crustal density Vertical tectonic stress |
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