| 近地表密度估计的重力贝叶斯分析方法及在云南地区的应用 |
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| 引用本文： | 牛源源,郭良辉,石磊,陈石,庄建仓.近地表密度估计的重力贝叶斯分析方法及在云南地区的应用[J].地球物理学报,2019,62(6):2101-2114. |
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| 作者姓名： | 牛源源 郭良辉 石磊 陈石 庄建仓 |
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| 作者单位： | 1. 中国地质大学(北京)地球物理与信息技术学院, 北京 100083;
2. 中国地震局地球物理研究所, 北京 100081;
3. 日本国立统计数理研究所, 东京 1908562 |
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| 基金项目： | 中国地震局地球物理研究所基本科研业务费专项资助（DQJB18B03），国家自然科学基金面上项目（41774098，41874097，41774090），中国-东南亚毗邻区大震活动地球动力学研究（科技部国际合作项目，2015DFA21206），中央高校基本科研业务费专项资金和中国地震局震情跟踪面上课题（2018020201）联合资助. |
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| 摘 要： | 基于布格重力异常相对于地形起伏光滑分布的约束条件,从一维自由空气重力异常数据出发,采用贝叶斯方法估算近地表岩石密度,同时采用三次B样条函数拟合布格重力异常,获取光滑分布的布格重力异常.数据拟合和光滑约束之间的权重采用Akaike贝叶斯准则(ABIC准则)自动确定.均匀剖分模型和不均匀剖分模型数据试验都验证了该方法的有效性.相关参数评价表明,足够多的样条系数可以提高估计结果的准确性,样条系数的个数接近测点数时可获得较稳定的估计结果.增大异常的噪声水平时,ABIC准则可有效地自动增大先验光滑约束的权重.云南地区两条重力剖面应用结果表明,剖面沿线的近地表密度值起伏变化明显(达2.45~2.8g·cm^-3),前寒武纪和古生代地层密度相对较高(主要为2.53~2.75g·cm^-3),而中生代密度较低(2.45~2.73g·cm^-3);本文估计的近地表密度结果与区域物性资料及地表地质特征较吻合;估计的剖面布格重力异常具有光滑性;红河断裂两侧近地表密度差异较大,可达0.4g·cm^-3.本文获得的两条剖面近地表密度结构和布格重力异常为该区深部结构与构造研究提供更可靠的重力基础数据.
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| 关 键 词： | 重力异常 近地表密度 贝叶斯分析 ABIC准则 |
| 收稿时间： | 2018-12-26 |
Estimation of near-surface density based on gravity Bayesian analysis and its application in Yunnan area |
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| NIU YuanYuan,GUO LiangHui,SHI Lei,CHEN Shi,ZHUANG JianCang.Estimation of near-surface density based on gravity Bayesian analysis and its application in Yunnan area[J].Chinese Journal of Geophysics,2019,62(6):2101-2114. |
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| Authors: | NIU YuanYuan GUO LiangHui SHI Lei CHEN Shi ZHUANG JianCang |
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| Institution: | 1. School of Geophysics and Information Technology, China University of Geosciences, Beijing 100083, China;
2. Institute of Geophysics, China Earthquake Administration, Beijing 100081, China;
3. The Institute of Statistical Mathematics, Tokyo 1908562, Japan |
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| Abstract: | Bouguer gravity anomalies are calculated by terrain correction and Bouguer correction to free-air gravity anomaly data. Near-surface density is an important parameter in these two corrections. Assuming that Bouguer gravity anomalies vary smoothly with surficial topography, we estimate the near-surface density from 1-D free-air gravity anomalies by using the Bayesian method and simultaneously obtain the smooth Bouguer anomalies fitted by the cubic B-spline function. We determine the trade-off parameters between the data misfit and prior constraints automatically by the Akaike's Bayesian Information Criterion (ABIC). Synthetic data tests by using uniform and non-uniform subdivisions verify the effectiveness of the presented method. Relevant parameter evaluations show that more of the spline coefficients are involved in the method, better results will be produced. When the number of spline coefficients are close to the number of observed stations, a more stable estimation can be obtained. More noise in the data, higher weight for smooth constraints will be determined automatically by the ABIC algorithm. The application of this method to two gravity profiles in the Yunnan area shows that near-surface density along the profiles varies significantly (2.45~2.80 g·cm-3). The Proterozoic and Paleozoic strata have relatively high density (mainly 2.53~2.75 g·cm-3), and the Mesozoic strata have relatively low density (2.45~2.73 g·cm-3). The estimated near-surface density in this paper is in a good agreement with regional physical data and surface geological characteristics, and the estimated Bouguer gravity anomalies have good smoothness. The density differences between both sides of the Honghe fault are as large as 0.4 g·cm-3. The near-surface density structure and Bouguer gravity anomalies obtained in this paper provide reliable basic data for the study of deep structure in this area. |
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| Keywords: | Gravity anomaly Near-surface density Bayesian analysis ABIC |
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