利用黏弹位错理论与GRACE数据研究2004年苏门答腊地震（Mw9.3）震后重力变化

发布时间：2018-03-22 17:27

  本文选题：GRACE卫星　切入点：黏弹球体位错理论　出处：《中国地震局地震预测研究所》2015年硕士论文　论文类型：学位论文

【摘要】：地震导致的地壳变形是研究地球内部构造,地震孕育发生机理的重要研究方向。随着现代大地测量技术的不断发展,除了可以用GPS和InSAR观测到震后地壳形变外,重力卫星GRACE能够观测到特大的俯冲型地震引起的~300 km空间分辨率的长波长同震和震后重力变化。自2002年成功发射以来,GRACE卫星已经连续提供超过十年的全球重力场数据,为研究震源机制、发震机理、地球内部构造、地震预测、断层反演、大地测量结果解释以及确定震源参数等提供了丰富的资料。对于震后变形机制解释目前主要有黏弹性松弛,震后余滑、空隙流体回弹等理论。震后变形机制需要结合地震位错理论进行解释,Tanaka等(2006)提出的黏弹性球体位错理论可以同时考虑地球的可压缩性和无限分层的影响,是目前最为完备的震后位错理论之一。本文的主要目的是研究利用GRACE卫星数据提取苏门答腊地震(Mw9.3)导致的同震和震后重力变化信号,并结合Tanaka等(2006)的黏弹性球体位错理论对其进行解析,为研究地球内部构造研究和地震孕育机理研究等提供支持。本文主要研究工作如下:1)GRACE Release05数据预处理方法的研究对CSR(Center for Space Research University of Texas)发布的GRACE Level02Rlease05重力场数据进行去相关滤波处理,去除重力场球谐系数奇偶阶次之间的相关误差,削弱重力场空间分布中的南北条带现象,并利用高斯平滑方法处理GRACE数据中的偶然误差,不同的平滑半径对平滑结果影响很大,平滑半径需要根据研究区域大小慎重选取,建议结合去相关滤波和高斯平滑方法同时进行处理。2)GRACE数据提取同震和震后重力信号的方法研究分别利用差分法和最小二乘拟合法提取了苏门答腊地震(Mw9.3)同震重力变化空间分布,并结合弹性球体位错理论结果比较了两种方法的优劣:差分法较最小二乘方法能更好的提取地震重力信号;然后利用差分法提取了苏门答腊地震(Mw9.3)同震和震后七年的重力变化,结果显示断层两侧地幔黏度存在较大差异;此外,本文还提取了断层两侧单点A(95.0°E,1.5°N)和B(97.0°E,7.0°N)地震前后重力场时间序列,分析了其时间序列特征。3)黏弹性球体位错理论研究了黏弹性球体位错理论的理论基础和计算思路,给出北极任意断层在任意点产生的震后变形(垂直位移和空间固定点重力变化)计算公式和在地球任意点任意断层在地表任意点产生的震后变形计算公式。4)黏弹球体位错积分程序改进指出黏弹球体位错积分程序计算近场变形误差较大的缺陷,并利用Sun和Okubo(1998)的有限断层积分方法对其改进,比较了两种理论震源深度为10 km和32 km四种独立震源垂直位移和重力变化格林函数,二者基本一致;改进后的程序模拟结果与弹性球体位错理论同震模拟结果垂直位移和重力变化平均差异分别为0.05%和0.03%,并分析了四种独立震源在震源深度为32 km,地幔黏度为1×1018 Pa?s的0~0.7年和0~7年的重力变化格林函数。5)改进后的黏弹性球体位错理论的应用利用改进后的黏弹性位错积分程序对苏门答腊地震(Mw9.3)震后重力变化进行模拟,并将其与GRACE观测结果进行比较,模拟结果与GRACE观测结果在峰值空间分布和震后变化趋势上基本一致。该地区地幔黏度存在明显横向差异,下盘区域地幔取内黏度系数约为1×1018 Pa?s,上盘区域地幔黏度系数约为8×1018Pa?s。
[Abstract]:The earthquake caused the crustal deformation is the internal structure of the earth, an important research direction of earthquake occurrence mechanism. With the continuous development of modern geodetic techniques, except for GPS and InSAR observed postseismic crustal deformation, gravity satellites can be observed GRACE long wavelength ~300 km spatial resolution of large subduction earthquakes caused by the same after the earthquake, earthquake and gravity changes. Since 2002 the successful launch of the GRACE satellite has a continuous supply of global gravity field data of more than ten years, for the study of focal mechanism, earthquake mechanism, the internal structure of the earth, earthquake prediction, fault inversion, geodetic measurement interpretation and provides a wealth of information to determine the source parameters for post earthquake deformation mechanism. Explain the current mainly viscoelastic relaxation, afterslip, interstitial fluid rebound theory. After the deformation mechanism requires a combination of dislocation theory to explain Tana Ka (2006) proposed the theory of viscoelastic spherical dislocation can be considered at the same time the earth compressibility and infinite layered effect, is one of the most complete earthquake dislocation theory. The main purpose of this paper is to study the extraction of Sumatra earthquake GRACE satellite data (Mw9.3) caused by the coseismic and postseismic gravity change signal, and according to Tanaka (2006) of the viscoelastic spherical dislocation theory to analyze the mechanism of inoculation, provides support for the study of the internal structure of the earth and the earthquake. The main research work are as follows: 1) the number of GRACE Release05 according to the study of pretreatment methods on CSR (Center for Space Research University of Texas) GRACE Level02Rlease05 gravity field data released to the related filter, remove the gravitational field of spherical harmonic coefficients of correlation between parity order error, weakening the North South gravity field spatial distribution of strip in the present Like, and use the Gauss smoothing method to process error in GRACE data, different smoothing radius has great influence on the smoothing result, smoothing radius according to research area carefully selected, combining with correlation filtering and smoothing method to Gauss and.2) GRACE data extraction method of coseismic and postseismic gravity signal respectively by differential method and the least square fitting method to extract the Sumatra earthquake (Mw9.3) distribution of coseismic gravity changes in space, and combined with the elastic sphere dislocation theory results compares two methods: signal extraction of seismic gravity difference method can be better than the least squares method; then using difference method to extract the Sumatra earthquake (Mw9.3) with gravity change seven years after the earthquake and earthquake, results show that there is a big difference on both sides of the fault mantle viscosity; in addition, this paper also extracts on both sides of the fault point A (95 E, 1.5 N) and B (97 ~ E, 7 ~ N) before and after the earthquake gravity field time series analysis of the time sequence characteristics of.3) viscoelastic spherical dislocation theory to study the theoretical basis and calculation method of viscoelastic spherical dislocation theory, given any faults at any point in the Arctic earthquake (change of vertical displacement and deformation space fixed point gravity) calculation formula of.4 deformation formula and at any point at any point on the earth's surface of arbitrary fault earthquake) sticky dislocation process improvement that Pinball integral calculation near field deformation errors of the sticky Pinball dislocation integration process, and the use of Sun and Okubo (1998) improved finite integral method of fault the comparison of two kinds of theories, the focal depth of 10 km and 32 km four independent source vertical displacements and gravity changes of Green function, the two are basically the same; the improved simulation result and elastic dislocation theory with the ball 闇囨ā鎷熺粨鏋滃瀭鐩翠綅绉诲拰閲嶅姏鍙樺寲骞冲潎宸�寮傚垎鍒�涓，

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