利用GRACE卫星数据提取苏门答腊地震同震和震后重力变化
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摘要
基于GRACE重力卫星数据,采用P3M6去相关滤波技术、350km半径的高斯平滑技术与差分方法,提取2004年苏门答腊Mw9.3地震的同震和震后重力场时空演化过程。该地震断层下盘同震重力变化达到4.6μGal,上盘同震重力变化最大值为-8.3μGal,该结果与球体位错理论计算结果在量级和分布形态上具有较好的一致性。震后7a断层下盘重力变化累计达到5.6μGal,超过同震变化信号;而断层上盘震后重力变化只有0.6μGal,仅为同震变化信号的11%。该现象表明,断层下盘所在海洋地层的粘滞性较低,地层相对柔软,其地层在震后由于较大的粘滞性松弛效应而持续变形,并伴随较大的重力变化;而断层上盘所在的地层接近陆地地壳特性,地层相对脆硬,震后受地层的粘滞性响应而导致的重力变化相对较小。
Based on the GRACE data,we successfully extract the co-seismic and post-seismic gravity changes caused by the 2004 Sumatra Mw9.3 earthquake,using P3M6de-correlation filtering,Gaussian smoothing with a 350km radius,as well as the difference method.The peak co-seismic gravity changes in the uplift and subduction zones reach up to 4.6 and-8.3μGal,respectively.Such results agree well in both magnitude and distribution with those calculated by the dislocation theory for a spherical earth model.The total post-seismic gravity changes of 7 years are up to 5.6μGal in the uplift zone,which is bigger than the corresponding co-seismic gravity changes.On the other hand,the changes in the subduction zone are only 0.6μGal,just about 11% of corresponding co-seismic gravity changes.Our results imply that the viscosity of the marine strata in the uplift zone is relatively lower than in the strata of the subduction zone.It is the low viscosity in marine area that caused the continuous deformation and relatively bigger gravity changes after the earthquake.The little post-seismic gravity changes in the subduction zone imply the high viscosity of the continental strata.
Based on the GRACE data,we successfully extract the co-seismic and post-seismic gravity changes caused by the 2004 Sumatra Mw9.3 earthquake,using P3M6de-correlation filtering,Gaussian smoothing with a 350km radius,as well as the difference method.The peak co-seismic gravity changes in the uplift and subduction zones reach up to 4.6 and-8.3μGal,respectively.Such results agree well in both magnitude and distribution with those calculated by the dislocation theory for a spherical earth model.The total post-seismic gravity changes of 7 years are up to 5.6μGal in the uplift zone,which is bigger than the corresponding co-seismic gravity changes.On the other hand,the changes in the subduction zone are only 0.6μGal,just about 11% of corresponding co-seismic gravity changes.Our results imply that the viscosity of the marine strata in the uplift zone is relatively lower than in the strata of the subduction zone.It is the low viscosity in marine area that caused the continuous deformation and relatively bigger gravity changes after the earthquake.The little post-seismic gravity changes in the subduction zone imply the high viscosity of the continental strata.
引文
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[18]Swenson S,Wahr J.Post-processing Removal of Correlated Errors in GRACE Data[J].Geophysical Research Letters,2006,33(8):L08402
[19]Zhou X,Sun W K,Zhao B,et al.Geodetic Observations Detecting Coseismic Displacements and Gravity Changes Caused by the Mw=9.0 Tohoku-Oki Earthquake[J].Journal of Geophysical Research:Solid Earth,2012,117(B5):B05408
[20]Sun W K,Okubo S,Fu G Y,et al.General Formulations of Global Co-seismic Deformations Caused by an Arbitrary Dislocation in a Spherically Symmetric Earth Model—Applicable to Deformed Earth Surface and Space-Fixed Point[J].Geophysical Journal International,2009,177(3):817-833
[2]Tapley B D,Bettadpur S,Ries J C,et al.GRACE Measurements of Mass Variability in the Earth System[J].Science,2004,305(5 683):503-505
[3]Chen J L,Rodell M,Wilson C R,et al.Low Degree Spherical Harmonic Influences on Gravity Recovery and Climate Experiment(GRACE)Water Storage Estimates[J].Geophysical Research Letters,2005,32(14):L14405
[4]Lovel W,Becker M,Cazenave A,et al.Global Land Water Storage Change from GRACE over 2002-2009;Inference on Sea Level[J].Comptes Rendus Geoscience,2010,342(3):179-188
[5]Chen J L,Wilson C R,Tapley B D,et al.2005Drought Event in the Amazon River Basin as Measured by GRACE and Estimated by Climate Models[J].Journal of Geophysical Research:Solid Earth,2009,114(B5):B05404
[6]鞠晓蕾,沈云中,张子占.基于GRACE卫星RL05数据的南极冰盖质量变化分析[J].地球物理学报,2013,56(9):2 918-2 927(Ju Xiaolei,Shen Yunzhong,Zhang Zizhan.Antarctic Ice Mass Change Analysis Based on GEACE RL05Data[J].Chinese Journal of Geophysics,2013,56(9):2 918-2 927)
[7]Jacob T,Wahr J,Pfeffer W T,et al.Recent Contributions of Glaciers and Ice Caps to Sea Level Rise[J].Nature,2012,482(7 386):514-518
[8]Matsuo K,Heki K.Time-Variable Ice Loss in Asian High Mountains from Satellite Gravimetry[J].Earth and Planetary Science Letters,2010,290(1):30-36
[9]Sun W,Okubo S.Coseismic Deformations Detectable by Satellite Gravity Missions:a Case Study of Alaska(1964,2002)and Hokkaido(2003)Earthquakes in the Spectral Domain[J].Journal of Geophysical Research:Solid Earth,2004,109(B4):B04405
[10]Han S C,Shum C K,Bevis M,et al.Crustal Dilatation Observed by GRACE after the 2004 Sumatra-Andaman Earthquake[J].Science,2006,313(5 787):658-662
[11]周新,孙文科,付广裕.重力卫星GRACE检测出2010年智利Mw 8.8地震的同震重力变化[J].地球物理学报,2011,54(7):1 745-1 749(Zhou Xin,Sun Wenke,Fu Guangyu.Gravity Satellite Detects Coseismic Gravity Changes Caused by 2010Chile Mw8.8Earthquake[J].Chinese Journal of Geophysics,2011,54(7);1 745-1 749)
[12]Linage C,Rivera L,Hinderer J,et al.Separation of Coseismic and Postseismic Gravity Changes for the 2004Sumatra-Andaman Earthquake from 4.6yr of GRACE Observations and Modelling of the Coseismic Change by NormalModes Summation[J].Geophysical Journal International,2009,176(3):695-714
[13]Chen J L,Wilson C R,Tapley B D,et al.GRACE Detects Coseismic and Postseismic Deformation from the SumatraAndaman Earthquake[J].Geophysical Research Letters,2007,34(13):L13 302
[14]周新.利用现代大地测量数据研究2011日本东北大地震(Mw9.0)的同震变形和断层滑动分布[D].北京:中国科学院大学.2012(Zhou Xin.Coseismic Deformation and Slip Characteristics from Modern Geodetic Data for the 2011Tohoku-Oki(Mw9.0)Megathrust Earthquake[D].Beijing:University of Chinese Academy of Sciences,2012)
[15]王武星,石耀霖,孙文科,等.利用GRACE观测数据研究苏门答腊区域的黏滞性结构[J].中国科学:地球科学,2011,41(6):773-783(Wang Wuxing,Shi Yaolin,Sun Wenke,et al.Viscous Lithospheric Structure beneath Sumatra Inferred from Post-seismic Gravity Changes Detected by GRACE[J].Science China Earth Sciences,2011,41(6):773-783)
[16]Tanaka Y,Okuno J,Okubo S.A New Method for the Computation of Global Viscoelastic Post-seismic Deformation in a Realistic Earth Model(I)—Vertical Displacement and Gravity Variation[J].Geophysical Journal International,2006,164(2):273-289
[17]Ogawa R,Heki K.Slow Postseismic Recovery of Geoid Depression Formed by the 2004 Sumatra-Andaman Earthquake by Mantle Water Diffusion[J].Geophysical Research Letters,2007,34(6):L06313
[18]Swenson S,Wahr J.Post-processing Removal of Correlated Errors in GRACE Data[J].Geophysical Research Letters,2006,33(8):L08402
[19]Zhou X,Sun W K,Zhao B,et al.Geodetic Observations Detecting Coseismic Displacements and Gravity Changes Caused by the Mw=9.0 Tohoku-Oki Earthquake[J].Journal of Geophysical Research:Solid Earth,2012,117(B5):B05408
[20]Sun W K,Okubo S,Fu G Y,et al.General Formulations of Global Co-seismic Deformations Caused by an Arbitrary Dislocation in a Spherically Symmetric Earth Model—Applicable to Deformed Earth Surface and Space-Fixed Point[J].Geophysical Journal International,2009,177(3):817-833
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