| 南北地震带南段地壳厚度重震联合最优化反演 |
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| 引用本文： | 陈石,郑秋月,徐伟民.南北地震带南段地壳厚度重震联合最优化反演[J].地球物理学报,2015,58(11):3941-3951. |
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| 作者姓名： | 陈石 郑秋月 徐伟民 |
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| 作者单位： | 中国地震局地球物理研究所, 北京 100081 |
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| 基金项目： | 地震行业科研专项(201508006),中国地震科学台阵探测项目(201308011),国家自然科学基金青年项目(41104046),中国地震局地球物理研究所基本科研业务专项(DQJB13B19),地震科技星火计划项目(XH14014Y)联合资助. |
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| 摘 要： | 重力反演方法是研究地壳结构和物性界面起伏的有效地球物理手段之一.本文收集了南北地震带南段67个已有的固定台站接收函数反演的Moho面深度结果,并使用基于EGM2008重力异常模型计算的布格重力异常,验证了本文提出的重震联合密度界面反演方法的有效性.利用接收函数对台站下方Moho面深度估计作为先验约束,定义了一类评价函数,通过对重力反演算法中尺度因子,平移因子和稳定性因子的最优选择,最小化重力反演结果与接收函数模型之间的差异.结果表明,本文提出的方法,可以有效地同化不同地球物理方法获得的反演模型,且通过重震联合反演可以改进由于对空间分布不均匀的接收函数结果插值可能而引起的误差.本文还通过引入Crust1.0的Moho面深度为初值,同时考虑地壳密度的横向不均匀分布,通过模型之间的联合反演有效改善了地球物理反演模型间的不一致性问题.本文反演得到的最优化Moho面深度模型与已知67个台站位置接收函数模型之间的标准差约1.9km,小于Crust1.0与接收函数结果模型之间标准差为3.73km的统计结果.本文研究结果对于同化重震反演结果、精化地壳密度界面模型,都具有十分重要的参考意义.
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| 关 键 词： | 重震联合反演 地壳厚度 多约束反演 异常分离 界面反演 最优解 |
| 收稿时间： | 2014-12-25 |
Joint optimal inversion of gravity and seismic data to estimate crustal thickness of the southern section of the north-south seismic belt |
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| CHEN Shi,ZHENG Qiu-Yue,XU Wei-Min.Joint optimal inversion of gravity and seismic data to estimate crustal thickness of the southern section of the north-south seismic belt[J].Chinese Journal of Geophysics,2015,58(11):3941-3951. |
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| Authors: | CHEN Shi ZHENG Qiu-Yue XU Wei-Min |
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| Institution: | Institute of Geophysics, China Earthquake Administration, Beijing 100081, China |
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| Abstract: | The south section of the north-south seismic belt is located in the southeast of the eastern Himalayan syntaxis, which has a complicated crustal structure, crustal deformation history and fault system, where earthquakes frequently occur. We used the joint optimal inversion approach, which includes gravity and seismology, with the known observation dataset and model to study the Moho interface deformation in the crust of this area. The aim of our study is to minimize the uncertainties and model discrepancies in different geophysical approaches. The methodology and results would help understand the mechanics on deformation in deep crust. The refined model of Moho interface may help us to reveal earthquake generation conditions, which have important geological and geophysical significance.#br#In this paper, we propose a kind of the joint optimal inversion method using gravity and seismic data. We take advantage of the receiver function which accurately estimates the crustal thickness beneath seismic stations and define a new kind of evaluation function. We also find an effective way to control the inversion process by adjusting the scale and shifting factors. This new approach can effectively reduce the discrepancies between the gravity inversion and the receiver function. The results show that this approach can reduce the uncertainty in the results derived by the interpolated method due to the spatial non-uniform distribution of seismic stations.#br#On the basis of above data and methods, our results show that the regional Bouguer gravity anomalies along the south section of the north-south seismic belt can be estimated by means of the EGM2008 gravity anomaly model. The constrained crustal thickness derived from the seismic receiver function at the 67 seismic stations are compared with the Crust 1.0 model. The standard errors in the 67 crustal thickness values are about 3.73 km between the Crust 1.0 model and the receiver functions. We present a joint model based on gravity and seismic data. Its standard error is about 1.9 km between the gravity inversion and the receiver function model using our approach. This optimal model also introduces the Moho depth of Crust1.0 crustal model as the initial values to estimate the lateral density distribution. #br#The joint optimal inversion in this study can help us overcome the known non-uniqueness problem in geophysical inversion models and refine the crustal subsurface model derived by the geophysical methods. It is very difficult to build seismic stations with the uniform distribution in the region of the north-south seismic belt due to the limit of topographic relief. Our approach can provide a solution to optimally estimate the Moho interface. And the results based on our test at the south section of the north-south seismic belt are better than the existing models. It can serve as an alternative solution for refining the crustal density model. Its efficiency is better than the known interpolation method. The refined Moho interface model at the study area has the minimum discrepancies and will help us to better study deep crustal deformation and the seismogenic mechanism in this region. |
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| Keywords: | Joint inversion of gravity and seismic Crustal thickness Anomaly separation Subsurface inversion Optimal model |
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