苏门达腊大地震激发的地球自由振荡及其谱线分裂的检测与讨论
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摘要
2004年12月26日的苏门达腊大地震不仅产生了印度洋大海啸,还激发了地球自由振荡.武汉台C0-32超导重力仪记录到这次大地震激发的地球自由振荡信号.通过对C0-32超导重力仪观测资料的预处理和谱分析,不仅检测到42个基频振型和2个径向振型,还较系统地检测到49个谐频振型和12个振型的谱峰分裂.通过对检测到的谐频振型及异常谱峰分裂现象的讨论,发现内核顶部的刚度是低于目前地球模型的理论估值,但内核顶部压缩波速的各向异性却是高于目前学者的估测值.这表明地球内核的各向异性远比目前所认识的复杂,可能在地球内核的形成及演化过程中还存在新的地球物理现象.
引文
1)http://www-gpi.physik.uni-karlsruhe.de/pub/widmer/Modes/modes.html MINOS程序,下同
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6孙和平,陈晓东,许厚泽,等.GWR超导重力仪潮汐观测标定因子的精密测定.地震学报,2001,23(6):651—658
7郗庆文.固体潮汐理论值计算.地球物理学报,1982,25(增刊):632—643
8Tamura Y.A Harmonic Development of the tide-Generating Poten-tial.Bull D’infor Marees Terrestres,1987,101:6813—6824
9许厚泽,孙和平,徐建桥,等.武汉国际重力潮汐基准研究.中国科学D辑:地球科学,2000,30(5):549—553
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14雷湘鄂.液核自由章动常数和地球自由振荡的研究与检测.博士学位论文.北京:中国科学院研究生院,2003.1—170
15Niebauer T M.Correcting Gravity Measurements for the Effects of Local Air Pressure.J Geophys Res,1988,93(B7):7989—7991
16Farrell W E.Deformation of the earth by the surface loads.Rev Geophys Space Phys,1972,(10):761—797
17Merriam J B.Atmospheric Pressure and Gravity.Geophys J Ints,1992,(109):488—500
18孙和平.大气重力格林函数.科学通报,1997,42(5):1640—1646
19徐建桥,郝兴华,孙和平.武汉基准台气压对重力潮汐观测的影响.测绘学报,1999,28(1):21—27
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23雷湘鄂,许厚泽,孙和平.由5个国际超导重力仪台站观测资料检测到的秘鲁8.2级大地震所激发的球型自由振荡现象.中国科学D辑:地球科学,2004,34(5):483—491
24Dziewonski A,Anderson D.Preliminary reference earth model.Phys Earth Planet Inter,1981,(25):297—356
25Widmer R,Masters G,Gilbert F.Spherically symmetric attenua-tion within the earth from normal mode data.Geophys J Int,1991,104:541—553
26Dahlen F A.The normal modes of a rotating,elliptical earth.Geo-phys J R Astr,1968,(16):329—367
27Ishii M,Tromp J.Normal-mode and free-air gravity constraints on lateral variations in velocity and density of Earth's mantle.Science,1999,285(5431):1231—1236
28Ishii M,Tromp J,Dziewonski A M,et al.Joint inversion of normal mode and body wave data for inner core anisotropy:laterally ho-mogeneous anisotropy.J Geophys Res,2002,107(B12):2379—2395
29He X,Tromp J.Normal-mode constraints on the structure of the Earth.J Geophys Res,1996,110(B9):20053—20082
30Masters G,Gilbert F.Structure of the inner core inferred from ob-servations of its spheroidal shear modes.Geophys Res Lett,1981,(8):569—571
31Woodhouse J H,Giardini D,Li X D.Evidence for inner core ani-sotropy from free oscillations.Geophys Res Lett,1986,13:1549—1552
32Giardini D,Li X D,Woodhouse J H.Splitting Functions of Long-Period Normal Modes of the Earth.J Geophys Res,1988,93:13716—13742
33Laske G,Masters G.Limits on differential rotation of the inner core from an analysis of the Earth's free oscillations.Nature,1999,402(6757):66—69
34Tromp J.Inner-core anisotropy and rotation.Ann Rev Earth Planet Sci,2001,29:47—69
1Stein S,Okal E A.Speed and size of the Sumatra earthquake.Na-ture,2005,434(7033):581—582
2Park J,Song TRA,Tromp J,et al.Earth's free oscillations excited by the26December2004Sumatra-Andaman earthquake.Science,2005,308(5725):1139—1144
3Crossley D J,Hinderer J.Global Geodynamics Project——GGP:status report1994.In:Proceeding of the Workshop on Non-tidal Gravity Changes(Ed.Poitevin).Luxembourg:Conseil de L'Europe Cahiers du Centre Européen de Géodynamique et de Séismologie,1995.244—269
4Rosat S,Hinderer J,Crossley D,et al.Performance of supercon-ducting gravimeters from long-period seismology to tides.J Geo-dyn,2004,38(3-5):461—476
5Rosat S,Sato T,Imanishi Y,et al.High-resolution analysis of the gravest seismic normal modes after the2004M-w=9Sumatra earthquake using superconducting gravimeter data.Geophys Res Lett,2005,32(13):L13304
6孙和平,陈晓东,许厚泽,等.GWR超导重力仪潮汐观测标定因子的精密测定.地震学报,2001,23(6):651—658
7郗庆文.固体潮汐理论值计算.地球物理学报,1982,25(增刊):632—643
8Tamura Y.A Harmonic Development of the tide-Generating Poten-tial.Bull D’infor Marees Terrestres,1987,101:6813—6824
9许厚泽,孙和平,徐建桥,等.武汉国际重力潮汐基准研究.中国科学D辑:地球科学,2000,30(5):549—553
10Ness N R,Harrison C T,Slichter L B.Observation of the free oscillation of the earth.J Geophys Res,1961,66(2):621—629
11van Camp M.Measuring Seismic normal modes with the GWR C021Superconducting gravimeter.Phys Earth Planet Inter,1999,116:81—92
12Neumeyer J,Bathelmes F,Combrinck L,et al.Analysis results from the SG registration with the dual sphere superconducting gravimeter at SAGOS(South Africa).Bull D’infor Marees Ter-restres,2002,135:10607—10616
13雷湘鄂,许厚泽,孙和平.利用超导重力观测资料检测地球自由振荡.科学通报,2002,47(18):1432—1436
14雷湘鄂.液核自由章动常数和地球自由振荡的研究与检测.博士学位论文.北京:中国科学院研究生院,2003.1—170
15Niebauer T M.Correcting Gravity Measurements for the Effects of Local Air Pressure.J Geophys Res,1988,93(B7):7989—7991
16Farrell W E.Deformation of the earth by the surface loads.Rev Geophys Space Phys,1972,(10):761—797
17Merriam J B.Atmospheric Pressure and Gravity.Geophys J Ints,1992,(109):488—500
18孙和平.大气重力格林函数.科学通报,1997,42(5):1640—1646
19徐建桥,郝兴华,孙和平.武汉基准台气压对重力潮汐观测的影响.测绘学报,1999,28(1):21—27
20罗少聪.大气负荷效应问题研究.博士学位论文.北京:中国科学院研究生院,2003.1—141
21Zürn W,Widmer R.On noise reduction in vertical Seismic records below2mHz using local barometric pressure.Geophys Res Lett,1995,(22):3537—3540
22Banka D,Jentzsch G,Crossley D.Investigations of superconduct-ing gravimeter records in the frequency range of the free oscilla-tions of the Earth-the noise magnitude.In:Proceedings of the13th Symp.Brussels:Earth Tides(Ducarme and Paquet,eds),Serie Geophysique,Observatorire Royal de Belgique,1998.641—648
23雷湘鄂,许厚泽,孙和平.由5个国际超导重力仪台站观测资料检测到的秘鲁8.2级大地震所激发的球型自由振荡现象.中国科学D辑:地球科学,2004,34(5):483—491
24Dziewonski A,Anderson D.Preliminary reference earth model.Phys Earth Planet Inter,1981,(25):297—356
25Widmer R,Masters G,Gilbert F.Spherically symmetric attenua-tion within the earth from normal mode data.Geophys J Int,1991,104:541—553
26Dahlen F A.The normal modes of a rotating,elliptical earth.Geo-phys J R Astr,1968,(16):329—367
27Ishii M,Tromp J.Normal-mode and free-air gravity constraints on lateral variations in velocity and density of Earth's mantle.Science,1999,285(5431):1231—1236
28Ishii M,Tromp J,Dziewonski A M,et al.Joint inversion of normal mode and body wave data for inner core anisotropy:laterally ho-mogeneous anisotropy.J Geophys Res,2002,107(B12):2379—2395
29He X,Tromp J.Normal-mode constraints on the structure of the Earth.J Geophys Res,1996,110(B9):20053—20082
30Masters G,Gilbert F.Structure of the inner core inferred from ob-servations of its spheroidal shear modes.Geophys Res Lett,1981,(8):569—571
31Woodhouse J H,Giardini D,Li X D.Evidence for inner core ani-sotropy from free oscillations.Geophys Res Lett,1986,13:1549—1552
32Giardini D,Li X D,Woodhouse J H.Splitting Functions of Long-Period Normal Modes of the Earth.J Geophys Res,1988,93:13716—13742
33Laske G,Masters G.Limits on differential rotation of the inner core from an analysis of the Earth's free oscillations.Nature,1999,402(6757):66—69
34Tromp J.Inner-core anisotropy and rotation.Ann Rev Earth Planet Sci,2001,29:47—69
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