利用GRACE数据检测日本Mw9.0地震同震和震后重力变化
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摘要
基于德国地学中心(GFZ)发布的GRACE RL05月重力场模型数据,考虑全球陆地同化系统陆地水储量的影响,采用300 km的扇形滤波,利用叠积法提取了日本Mw9.0地震的同震和震后重力时变信号,并利用最小二乘拟合的方法计算了两个同震重力变化极值点在地震前后85个月的重力年变率。结果表明:土壤水分和雪水引起的重力变化为-0.34~0.09μgal;利用GRACE数据检测到的同震重力变化为-5.3~4.2μgal,与基于PSGRN/PSCMP模型计算的结果在空间分布和量级上具有较好的一致性;震后5 a震中附近区域的重力整体上呈现增加趋势,断层上盘所在的日本海域与下盘所在的太平洋区域重力增加的最大值分别为2.6、4.5μgal,下盘重力增加较大,可能与断层下盘所在地层的黏滞性相对较低有关。
Based on the RL05 earth gravity field model released by GFZ,considering the influence of the terrestrial water reserves in the global land data assimilation system,the co-seismic and post-seismic gravity changes caused by the 2011 Japan Mw9. 0 earthquake is successfully extracted by using the method of stacking and 300 km fan filter. The gravity annual variation rate of the two characteristic points around the epicenter is calculated as well by using the method of least squares fitting in 85 months before and after the earthquake.The results show that the gravity change caused by the soil moisture content and accum snow is-0.34 ~ 0.09 μgal; the coseismic gravity changes from the GRACE RL05 data is-5.3 ~ 4.2 μgal,which is consistent well with the result based on the PSGRN/PSCMP model in spatial distribution and order of magnitude; the gravity increasing trend is showed in the area around the epicenter in5 years after the earthquake,the maximum increase in gravity of the Sea of Japan the upper plate locates and the Pacific Ocean the subduction area locates is 2.6 μgal and 4.5 μgal,respectively,the gravity of the subduction area increases greater,indicating that the viscosity of the subduction area is relatively lower than that of the up-lift zone.
Based on the RL05 earth gravity field model released by GFZ,considering the influence of the terrestrial water reserves in the global land data assimilation system,the co-seismic and post-seismic gravity changes caused by the 2011 Japan Mw9. 0 earthquake is successfully extracted by using the method of stacking and 300 km fan filter. The gravity annual variation rate of the two characteristic points around the epicenter is calculated as well by using the method of least squares fitting in 85 months before and after the earthquake.The results show that the gravity change caused by the soil moisture content and accum snow is-0.34 ~ 0.09 μgal; the coseismic gravity changes from the GRACE RL05 data is-5.3 ~ 4.2 μgal,which is consistent well with the result based on the PSGRN/PSCMP model in spatial distribution and order of magnitude; the gravity increasing trend is showed in the area around the epicenter in5 years after the earthquake,the maximum increase in gravity of the Sea of Japan the upper plate locates and the Pacific Ocean the subduction area locates is 2.6 μgal and 4.5 μgal,respectively,the gravity of the subduction area increases greater,indicating that the viscosity of the subduction area is relatively lower than that of the up-lift zone.
引文
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[2]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(5787):658.
[3]CHEN J L,WILSON C R,TAPLEY B D,et al.GRACE Detects Coseismic and Postseismic Deformation from the Sumatra-Andaman Earthquake[J].Geophysical Research Letters,2007,34(13):173-180.
[4]RYOKO O,KOSUKE H.Slow Postseismic Recovery of Geoid Depression Formed by the 2004 Sumatra-Andaman Earthquake by Mantle Water Diffusion[J].Geophysical Research Letters,2007,34(6):160-166.
[5]ISABELLE P,VALENTIN M,MICHEL D,et al.Coseismic and Post-Seismic Signatures of the Sumatra 2004December and 2005 March Earthquakes in GRACE Satellite Gravity[J].Geophysical Journal of the Royal Astronomical Society,2007,171(1):177-190.
[6]DE LINAGE C,RIVERA L,HINDERER J,et al.Separation of Coseismic and Postseismic Gravity Changes for the2004 Sumatra-Andaman Earthquake from 4.6 yr of GRACE Observations and Modelling of the Coseismic Change by Normal-Modes Summation[J].Translated World Seismology,2010,176(3):695-714.
[7]周新,孙文科,付广裕.重力卫星GRACE检测出2010年智利Mw8.8地震的同震重力变化[J].地球物理学报,2011,54(7):1745-1749.
[8]KOJI M,KOSUKE H.Coseismic Gravity Changes of the2011 Tohoku-Oki Earthquake from Satellite Gravimetry[J].Geophysical Research Letters,2011,38(7):113-120.
[9]邹正波,罗志才,吴海波,等.日本MW9.0地震前GRACE卫星重力变化[J].测绘学报,2012,41(2):171-176.
[10]张克亮,甘卫军,周新.GRACE卫星重力场同震变化的经验正交函数分解:以日本MW9.0地震为例[J].地震地质,2014,36(3):763-774.
[11]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):57-76.
[12]ZHANG Z,CHAO B F,YANG L,et al.An Effective Filtering for GRACE Time-Variable Gravity:Fan Filter[J].Geophysical Research Letters,2009,36(17):1397-1413.
[13]HEISKANEN W A,MORITZ H.Physical Geodesy[J].Bulletin Géodésique(1946-1975),1967,86(1):491-492.
[14]WAHR J,MOLENAAR M,BRYAN F.Time Variability of the Earth’s Gravity Field:Hydrological and Oceanic Effects and Their Possible Detection Using GRACE[J].Journal of Geophysical Research Solid Earth,1998,103(B12):30205-30230.
[15]WEI S,SLADEN A,ARIA group.Updated Result[EB/OL].2011-11-03.http:∥www.tectonics.caltech.edu/slip_history/2011_taiheiyo-oki/.
[16]李进.基于GRACE时变重力梯度探测大地震的同震变化[D].武汉:武汉大学,2011.
[17]邹正波,李辉,吴云龙,等.尼泊尔M8.1地震震前卫星重力场时变特征[J].大地测量与地球动力学,2015,35(4):547-551.
[18]STEFFEN H,GITLEIN O,DENKER H,et al.Present Rate of Uplift in Fennoscandia from GRACE and Absolute Gravimetry[J].Tectonophysics,2009,474(1-2):69-77.
[19]WANG R,MARTN F,ROTH F.PSGRN/PSCMP—A New Code for Calculating Co-and Post-seismic Deformation,Geoid and Gravity Changes Based on the ViscoelasticGravitational Dislocation Theory[J].Computers&Geosciences,2006,32(4):527-541.
[20]SUN W,OKUBO S,FU G,et al.General Formulations of Global Co-seismic Deformations Caused by an Arbitrary Dislocation in a Spherically Symmetric Earth ModelApplicable to Deformed Earth Surface and Space-fixed Point[J].Geophysical Journal International,2009,177(3):817-833.
[21]HEKI K,MATSUO K.Coseismic Gravity Changes of the2010 Earthquake in Central Chile from Satellite Gravimetry[J].Geophysical Research Letters,2010,37(24):701-719.