东亚及西太平洋边缘海高分辨率面波层析成像
|
摘要
根据欧亚大陆及西太平洋地区 58个数字地震台站约 1 2 0 0 0个长周期波形记录 ,挑选出 41 0 0条面波大圆传播路径 ,采用面波频散及波形拟合反演方法 ,对东亚及西太平洋边缘海地区 (60°E— 1 60°E ,2 0°S— 60°N)的地壳上地幔进行了高分辨率三维S波速度成像 .结果表明 ,从上地壳到 70km深 ,在东亚东部及西太平洋边缘海地区为高速分布 ,西部以青藏高原为中心呈极低速分布 .自地中海经土耳其、伊朗、喜马拉雅山到缅甸、印尼群岛的特提斯汇聚碰撞带 ,显示为低速异常链 .从 85km至 2 50km深 ,在东亚东部及西太平洋边缘海 ,自北向南显示出一条巨型低速异常带 ,西部地区为高速异常分布 .以东经 1 1 0°E为界 ,东西两部分岩石圈、软流圈的结构与深部动力过程有着巨大的差异 .此界线以西主要是印度板块与欧亚板块碰撞引起的岩石圈汇聚增厚区 ,东部则主要是由于软流圈上涌 (地幔热物质上升 )引起的岩石圈拉张减薄区
This paper deals with the high resolution surface wave tomography in East Asia and West Pacific marginal seas (60°-160°E,20°S-60°N). Twelve thousands long period digital seismic waveforms from 650 events (7.0≥ M ≥5.0) recorded at 58 digital seismic stations from CDSN, GSN, GDSN and GEOSCOPE network in Eurasia and west Pacific regions were used in this paper. Four thousands and one hundred accurate surface dispersion curves with periods ranging 8 to 250 seconds were selected and employed for inversion. The high resolution 3 D shear wave velocity images in this area was constructed by inversion of both dispersion and waveform and show a notable lateral variation in the crust and upper mantle.\;The images of S wave velocity indicate that from the upper crust to the depth of 70km, the high velocity is displayed in the region of eastern part of East Asia and West Pacific marginal seas, in contrast, extremely low velocity is in the Qinghai Xizang plateau and its surrounding areas. There exists a boundary of velocity decrease along the Mountain belt from Da Xingganling to Taihangshan, Wulinshan, which coincides with the gravity gradient belt in NNE-SSW trend in East China. The low velocity anomaly chain is located along the convergence belt of Tethys from Mediterranean Sea, Turkey, Iran, Himalayan orogens, Burma, Indonesian Islands.\;The evolution and geodynamic process is so different between the eastern part and western part of the East Asia and West Pacific marginal seas by the boundary of longitude 110°E. The western part is the thickening convergent lithosphere caused by Indian subcontinent collided with the Eurasian continent, and the eastern part is disassembly causing the lithosphere thinning and extension arising from intrusion of asthenospheric material.
This paper deals with the high resolution surface wave tomography in East Asia and West Pacific marginal seas (60°-160°E,20°S-60°N). Twelve thousands long period digital seismic waveforms from 650 events (7.0≥ M ≥5.0) recorded at 58 digital seismic stations from CDSN, GSN, GDSN and GEOSCOPE network in Eurasia and west Pacific regions were used in this paper. Four thousands and one hundred accurate surface dispersion curves with periods ranging 8 to 250 seconds were selected and employed for inversion. The high resolution 3 D shear wave velocity images in this area was constructed by inversion of both dispersion and waveform and show a notable lateral variation in the crust and upper mantle.\;The images of S wave velocity indicate that from the upper crust to the depth of 70km, the high velocity is displayed in the region of eastern part of East Asia and West Pacific marginal seas, in contrast, extremely low velocity is in the Qinghai Xizang plateau and its surrounding areas. There exists a boundary of velocity decrease along the Mountain belt from Da Xingganling to Taihangshan, Wulinshan, which coincides with the gravity gradient belt in NNE-SSW trend in East China. The low velocity anomaly chain is located along the convergence belt of Tethys from Mediterranean Sea, Turkey, Iran, Himalayan orogens, Burma, Indonesian Islands.\;The evolution and geodynamic process is so different between the eastern part and western part of the East Asia and West Pacific marginal seas by the boundary of longitude 110°E. The western part is the thickening convergent lithosphere caused by Indian subcontinent collided with the Eurasian continent, and the eastern part is disassembly causing the lithosphere thinning and extension arising from intrusion of asthenospheric material.
引文
[1] 朱介寿,曹家敏,李显贵等.中国及邻近区域地球三维结构初始模型的建立.地球物理学报,1997,40(5):627—648.ZHUJieShou,CAOJiaMin,LIXianGui,etal.Apreliminarythree dimensionalEarth’smodelofChinaandadjacentregionsanditsimplications.ChineseJ .Geophys.(InEnglish),1997,40(4):499—518.
[2] 朱介寿.全球地幔三维结构模型及动力学研究新进展.地球科学进展,1996,11(5):421—431.ZHUJieShou,Therecentdevelopmentofthree dimensionalmodelsandgeodynamicsoftheearth’smantle.AdvanceinEarthSciences(inChinese),1996,11(5):421—431.
[3] 刘福田,曲克信,吴 华等.中国大陆及其邻近地区的地震层析成像.地球物理学报,1989,32(3):281—291.LIUFuTian,QUKeXin,WUHua,etal.SeismictomographyoftheChineseContinentandadjacentregion.ChineseJ.Geophys.(ActaGeophysicaSinica),1989,32(3):281—291.
[4] 冯 锐,朱介寿,丁韫玉等.利用地震面波研究中国地壳结构.地震学报,1981,3(4):335—350.FENGRui,ZHUJieShou,DINGWenYu,etal.StudythecrustalstructureinChinabyusingtheseismicsurfacewave.ChineseJ.Seismology(inChinese),1981,3(4):335—350.
[5] 张禹慎,马石庄.全球地震面波相速度变化及其大地构造学意义.地球物理学报,1997,40(2):181—192.ZHANGYuShen,MAShiZhuang.Globalsurfacewavephasevelocityvariationsandtheirtectonicimplications.ChineseJ.Geophys.(ActaGeophysicaSinica),1997,40(2):181—192.
[6] 滕吉文,胡家富,张中杰.中国西北地区岩石层瑞利波三维速度结构与沉积盆地.地球物理学报,1995,38(6):737—749.TENGJiWen,HUJiaFu,ZHANGZhongJie.The3DstructureofRayleighwaveandsedimentarybasinsintheNorthwestChina,ChineseJ.Geophys.(ActaGeophysicaSinica),1995,38(6):737—749.
[7] 周 兵,朱介寿,秦建业.青藏高原及邻近区域S波三维速度结构.地球物理学报,1991,34(4):426—441.ZHOUBin,ZHUJieShou,CHUNKinYipThreedimensionalshearvelocitystructurebeneathQinghaiXizangplateauanditsadjacentarea.ChineseJ.Geophys.(ActaGeophysicaSinica),1991,34(4):426—441.
[8] 宋仲和,安昌强,陈国英等.中国西部三维速度结构及其各向异性.地球物理学报,1991,34(6):694—707.SONGZhongHe,ANChangQiang,CHENGuoYing,etal.Studyon3DvelocitystructureandanisotropybeneaththeWestChinafromtheLovewavedispersion.ChineseJ.Geophys.(ActaGeophysicaSinica),1991,34(6):694—707.
[9] 宋仲和,陈国英,安昌强等.中国大陆及其海域地壳-上地幔三维速度结构,中国科学(B),1993,23(2):180—188SONGZhongHe,CHENGuoYing,ANChangQiang,etal.The3DstructureofcrustandmantleinContinentalChinaandadjacentseas.ScienceinChina(B)(inChinese),1993,23(2):180—188.
[10] 宋仲和,陈国英,安昌强等.中国东部及其相邻海域S波三维速度结构.地球物理学报,1992,35(3):316—329.SONGZhongHe,CHENGuoYing,ANChangQiang,etal.The3DshearwavevelocitystructurebeneaththeEasternChinaanditsadjacentseas.ChineseJ .Geophys.(ActaGeophysicaSinica),1992,35(3):316—329.
[11] 徐果明,李光品,王善恩等.用瑞利面波资料反演中国大陆东部地壳上地幔横波速度的三维构造.地球物理学报,2000,43(3):366—375.XUGuoMing,LIGuangPin,WANGShanEn,etal.The3DstructureofshearwavesinthecrustandmantleofeastcontinentalChinainvertedbyRayleighwavedata.ChineseJ .Geophys.,2000,43(3):366—375.
[12] 郑月军,黄忠贤,刘福田等.中国东部海域地壳-上地幔瑞利波速度结构的研究.地球物理学报,2000,43(4):480—487.ZHENGYueJun,HUANGZhongXian,LIUFuTian,etal.RayleighwavevelocityandstructureofthecrustanduppermantlebeneaththeseasineasternChina.ChineseJ.Geophys.,2000,43(4):480—487.
[13] BruneJ,DormanJ .Seismicwavesandearth’sstructureintheCanadianShield.Bull.Seism.Soc.Am.,1963.43:167—210.
[14] SantoT .LateralvariationofRayleighwavedispersioncharacter.PartⅡ:Eurasia.PureandAppliedGeophys.,1965,62:67—75.
[15] ToksozMN ,AndersonDL .Phasevelocitiesoflong periodsurfacewavesandstructureoftheuppermantle,l,GreatcircleLoveandRayleighwavedata.J .Geophys.Res.,1966,71:1649—1658.
[16] WickensAJ.VariationsinlithosphericthicknessinCanada.Can.J .EarthSci.,1971,8:1154—1162.
[17] SchwabF ,KnopoffL .Fastsurfacewaveandfreemodecomputation.In:BoltAed.MethodsinComputationalPhysics.NewYork:AcademicPress,1972.11,87—180.
[18] DziewonskiAM ,HalesAL .Numericalanalysisofdispersedseismicwaves,Seismology:Surfacewavesandearthoscillations.In:BoltAed.MethodsinComputationalPhysics.NewYork:AcademicPress,1972,11,39—86.
[19] BraileLW ,KellerGR .FinestructureofthecrustinferredfromlinearinversionofRayleighWavedispersion.Bull.Seis.Soc.Am.,1975,65:71—83.
[20] GodlewskiMJ,WestGF .Rayleigh wavedispersionovertheCanadianshield.Bull.Seismol.Soc.Am.,1977,67:771—779.
[21] KovachRL .Seismicsurfacewavesandcrustalanduppermantlestructure.ReviewsofGeophysicsandSpacePhysics.1978,16:1—13.
[22] FengCC ,Teng,T.L.Three dimensionalcrustanduppermantlestructureoftheEurasianContinent.J.Geophys.Res.,1983,88:2261—2273.
[23] NakanishiI.,AndersonD .L .WorldwidedistributionofgroupvelocityofmantleRayleighwavesasdeterminedbysphericalharmonicinversion.Bull.Seismol.Soc.Am.,1982,72:1185—1194.
[24] NatafH C ,NakanishiI.,AndersonD .L .Measurementsofmantlewavevelocitiesandinversionforlateralheterogeneityandanisotropy,3,inversion.J.Geophys.Res.,1986,91:7261—7307.
[25] ZhangYS ,TanimotoT.Ridges,hotspots,andtheirinterpretationasobservedinseismicvelocitymaps.Nature,1992,355:45—49.
[26] ZhangYS ,TanimotoT .High resolutionglobaluppermantlestructureandplatetectonics.J.Geophys.Res.,1993,98:9793—9823.
[27] Zhang,YS ,LayT .Globalsurfacewavephasevelocityvariations.J .Geophys.Res.,1996,101:8415—8436.
[28] Ekstr¨omGJ ,TrompJE ,LarsonWF .Measurementsandglobalmodelsofsurfacewavepropagation.J.Geophys.Res.,1997,102:8137—8158.
[29] WuF ,LevshinA .SurfacewavetomographyofEastAsia.Phys.EarthPlanet.Inter.,1994,84:59—78.
[30] RitzwollerMH ,LevshinAL .Eurasiansurfacewavetomography:Groupvelocities.J .Geophys.Res.,1998,83:4839—4878.
[31] NakamuraY ,ShibutaniT .3DshearwavevelocitystructureintheuppermantlebeneaththePhilippineSea.EarthPlanetsSpace,1998,50:939—952.
[32] VdovinO ,RialJA ,LevshinAL ,etal.Group velocitytomographyofSouthAmericaandsurroundingOceans.Geophys.J.Inter.,1999,136:324—340.
[33] NoletG .Partitionedwaveforminversionandtwo dimensionalstructureunderthenetworkofAutonomouslyRecordingseismographs.J .Geophys.Res.,1990,95:8499—8512.
[34] NoletG .Partitionedwaveforminversionandtwo dimensionalstructureundertheNARSarray.J.Geophys.Res.,1990,95:8513—8526.
[35] SniederR ,NoletG .LinearizedscatteringofsurfacewavesonasphericalEarth.J.Geophys.,1987,61:55—63.
[36] SniederR .Large scalewaveforminversionsofsurfacewavesforlateralheterogeneity,2,ApplicationtosurfacewavesinEuropeandtheMediterranean.J .Geophys.Res.,1988,93:12067—12080.
[37] HackerBR ,GnosE ,BacherLR ,etal.HotanddrycrustalxenolithsfromTibet.Science,2000,287:2463—2466.
[38] XuX ,O’ReilySY ,GriffinWL ,etal.ThenatureoftheCenozociclithosphereatNushan,easternChina.In:FlowerMFJ,etal.eds.AGUGeodynamicsSeries———MantleDynamicsandPlateInteractionsinEastAsia.Washington,D .C .:AmericanGeophysicalUnion,1998.27,167—196.
[39] SmithAD .ThegeodynamicsignificanceoftheDUPALanomalyinAsia.In:FlowerM .F .J.,etal.eds.AGUGeodynamicsSeries———MantleDynamicsandPlateInteractionsinEastAsia.Washington,D .C .:AmericanGeophysicalUnion,1998.27,89—106.
[40] MenziesMA ,XuYG .GeodynamicsofthenorthChinaCraton.In:FlowerM .F .J.,etal.eds.AGUGeodynamicsSeries———MantleDynamicsandPlateInteractionsinEastAsia.Washington,D .C .:AmericanGeophysicalUnion,1998.27,155—166.
[41] JaupartC ,MareschalJC .Thethermalstructureandthicknessofcontinentalroots.In:R .D .VanDerHilstandW .F .McDonougheds.Composition,DeepStructureandEvolutionofContinents.Amsterdam:ElsevierPress,1999.93—144.
[42] 金性春,周祖翼,汪品先编著.大洋钻探与中国地球科学.上海:同济大学出版社,1995.JINXingChun,ZHOUZuYi,WANGPinXian.OceanDrillingProgramandEarthScienceinChina.Shanghai:TongJiUniversityPress,1995.
[2] 朱介寿.全球地幔三维结构模型及动力学研究新进展.地球科学进展,1996,11(5):421—431.ZHUJieShou,Therecentdevelopmentofthree dimensionalmodelsandgeodynamicsoftheearth’smantle.AdvanceinEarthSciences(inChinese),1996,11(5):421—431.
[3] 刘福田,曲克信,吴 华等.中国大陆及其邻近地区的地震层析成像.地球物理学报,1989,32(3):281—291.LIUFuTian,QUKeXin,WUHua,etal.SeismictomographyoftheChineseContinentandadjacentregion.ChineseJ.Geophys.(ActaGeophysicaSinica),1989,32(3):281—291.
[4] 冯 锐,朱介寿,丁韫玉等.利用地震面波研究中国地壳结构.地震学报,1981,3(4):335—350.FENGRui,ZHUJieShou,DINGWenYu,etal.StudythecrustalstructureinChinabyusingtheseismicsurfacewave.ChineseJ.Seismology(inChinese),1981,3(4):335—350.
[5] 张禹慎,马石庄.全球地震面波相速度变化及其大地构造学意义.地球物理学报,1997,40(2):181—192.ZHANGYuShen,MAShiZhuang.Globalsurfacewavephasevelocityvariationsandtheirtectonicimplications.ChineseJ.Geophys.(ActaGeophysicaSinica),1997,40(2):181—192.
[6] 滕吉文,胡家富,张中杰.中国西北地区岩石层瑞利波三维速度结构与沉积盆地.地球物理学报,1995,38(6):737—749.TENGJiWen,HUJiaFu,ZHANGZhongJie.The3DstructureofRayleighwaveandsedimentarybasinsintheNorthwestChina,ChineseJ.Geophys.(ActaGeophysicaSinica),1995,38(6):737—749.
[7] 周 兵,朱介寿,秦建业.青藏高原及邻近区域S波三维速度结构.地球物理学报,1991,34(4):426—441.ZHOUBin,ZHUJieShou,CHUNKinYipThreedimensionalshearvelocitystructurebeneathQinghaiXizangplateauanditsadjacentarea.ChineseJ.Geophys.(ActaGeophysicaSinica),1991,34(4):426—441.
[8] 宋仲和,安昌强,陈国英等.中国西部三维速度结构及其各向异性.地球物理学报,1991,34(6):694—707.SONGZhongHe,ANChangQiang,CHENGuoYing,etal.Studyon3DvelocitystructureandanisotropybeneaththeWestChinafromtheLovewavedispersion.ChineseJ.Geophys.(ActaGeophysicaSinica),1991,34(6):694—707.
[9] 宋仲和,陈国英,安昌强等.中国大陆及其海域地壳-上地幔三维速度结构,中国科学(B),1993,23(2):180—188SONGZhongHe,CHENGuoYing,ANChangQiang,etal.The3DstructureofcrustandmantleinContinentalChinaandadjacentseas.ScienceinChina(B)(inChinese),1993,23(2):180—188.
[10] 宋仲和,陈国英,安昌强等.中国东部及其相邻海域S波三维速度结构.地球物理学报,1992,35(3):316—329.SONGZhongHe,CHENGuoYing,ANChangQiang,etal.The3DshearwavevelocitystructurebeneaththeEasternChinaanditsadjacentseas.ChineseJ .Geophys.(ActaGeophysicaSinica),1992,35(3):316—329.
[11] 徐果明,李光品,王善恩等.用瑞利面波资料反演中国大陆东部地壳上地幔横波速度的三维构造.地球物理学报,2000,43(3):366—375.XUGuoMing,LIGuangPin,WANGShanEn,etal.The3DstructureofshearwavesinthecrustandmantleofeastcontinentalChinainvertedbyRayleighwavedata.ChineseJ .Geophys.,2000,43(3):366—375.
[12] 郑月军,黄忠贤,刘福田等.中国东部海域地壳-上地幔瑞利波速度结构的研究.地球物理学报,2000,43(4):480—487.ZHENGYueJun,HUANGZhongXian,LIUFuTian,etal.RayleighwavevelocityandstructureofthecrustanduppermantlebeneaththeseasineasternChina.ChineseJ.Geophys.,2000,43(4):480—487.
[13] BruneJ,DormanJ .Seismicwavesandearth’sstructureintheCanadianShield.Bull.Seism.Soc.Am.,1963.43:167—210.
[14] SantoT .LateralvariationofRayleighwavedispersioncharacter.PartⅡ:Eurasia.PureandAppliedGeophys.,1965,62:67—75.
[15] ToksozMN ,AndersonDL .Phasevelocitiesoflong periodsurfacewavesandstructureoftheuppermantle,l,GreatcircleLoveandRayleighwavedata.J .Geophys.Res.,1966,71:1649—1658.
[16] WickensAJ.VariationsinlithosphericthicknessinCanada.Can.J .EarthSci.,1971,8:1154—1162.
[17] SchwabF ,KnopoffL .Fastsurfacewaveandfreemodecomputation.In:BoltAed.MethodsinComputationalPhysics.NewYork:AcademicPress,1972.11,87—180.
[18] DziewonskiAM ,HalesAL .Numericalanalysisofdispersedseismicwaves,Seismology:Surfacewavesandearthoscillations.In:BoltAed.MethodsinComputationalPhysics.NewYork:AcademicPress,1972,11,39—86.
[19] BraileLW ,KellerGR .FinestructureofthecrustinferredfromlinearinversionofRayleighWavedispersion.Bull.Seis.Soc.Am.,1975,65:71—83.
[20] GodlewskiMJ,WestGF .Rayleigh wavedispersionovertheCanadianshield.Bull.Seismol.Soc.Am.,1977,67:771—779.
[21] KovachRL .Seismicsurfacewavesandcrustalanduppermantlestructure.ReviewsofGeophysicsandSpacePhysics.1978,16:1—13.
[22] FengCC ,Teng,T.L.Three dimensionalcrustanduppermantlestructureoftheEurasianContinent.J.Geophys.Res.,1983,88:2261—2273.
[23] NakanishiI.,AndersonD .L .WorldwidedistributionofgroupvelocityofmantleRayleighwavesasdeterminedbysphericalharmonicinversion.Bull.Seismol.Soc.Am.,1982,72:1185—1194.
[24] NatafH C ,NakanishiI.,AndersonD .L .Measurementsofmantlewavevelocitiesandinversionforlateralheterogeneityandanisotropy,3,inversion.J.Geophys.Res.,1986,91:7261—7307.
[25] ZhangYS ,TanimotoT.Ridges,hotspots,andtheirinterpretationasobservedinseismicvelocitymaps.Nature,1992,355:45—49.
[26] ZhangYS ,TanimotoT .High resolutionglobaluppermantlestructureandplatetectonics.J.Geophys.Res.,1993,98:9793—9823.
[27] Zhang,YS ,LayT .Globalsurfacewavephasevelocityvariations.J .Geophys.Res.,1996,101:8415—8436.
[28] Ekstr¨omGJ ,TrompJE ,LarsonWF .Measurementsandglobalmodelsofsurfacewavepropagation.J.Geophys.Res.,1997,102:8137—8158.
[29] WuF ,LevshinA .SurfacewavetomographyofEastAsia.Phys.EarthPlanet.Inter.,1994,84:59—78.
[30] RitzwollerMH ,LevshinAL .Eurasiansurfacewavetomography:Groupvelocities.J .Geophys.Res.,1998,83:4839—4878.
[31] NakamuraY ,ShibutaniT .3DshearwavevelocitystructureintheuppermantlebeneaththePhilippineSea.EarthPlanetsSpace,1998,50:939—952.
[32] VdovinO ,RialJA ,LevshinAL ,etal.Group velocitytomographyofSouthAmericaandsurroundingOceans.Geophys.J.Inter.,1999,136:324—340.
[33] NoletG .Partitionedwaveforminversionandtwo dimensionalstructureunderthenetworkofAutonomouslyRecordingseismographs.J .Geophys.Res.,1990,95:8499—8512.
[34] NoletG .Partitionedwaveforminversionandtwo dimensionalstructureundertheNARSarray.J.Geophys.Res.,1990,95:8513—8526.
[35] SniederR ,NoletG .LinearizedscatteringofsurfacewavesonasphericalEarth.J.Geophys.,1987,61:55—63.
[36] SniederR .Large scalewaveforminversionsofsurfacewavesforlateralheterogeneity,2,ApplicationtosurfacewavesinEuropeandtheMediterranean.J .Geophys.Res.,1988,93:12067—12080.
[37] HackerBR ,GnosE ,BacherLR ,etal.HotanddrycrustalxenolithsfromTibet.Science,2000,287:2463—2466.
[38] XuX ,O’ReilySY ,GriffinWL ,etal.ThenatureoftheCenozociclithosphereatNushan,easternChina.In:FlowerMFJ,etal.eds.AGUGeodynamicsSeries———MantleDynamicsandPlateInteractionsinEastAsia.Washington,D .C .:AmericanGeophysicalUnion,1998.27,167—196.
[39] SmithAD .ThegeodynamicsignificanceoftheDUPALanomalyinAsia.In:FlowerM .F .J.,etal.eds.AGUGeodynamicsSeries———MantleDynamicsandPlateInteractionsinEastAsia.Washington,D .C .:AmericanGeophysicalUnion,1998.27,89—106.
[40] MenziesMA ,XuYG .GeodynamicsofthenorthChinaCraton.In:FlowerM .F .J.,etal.eds.AGUGeodynamicsSeries———MantleDynamicsandPlateInteractionsinEastAsia.Washington,D .C .:AmericanGeophysicalUnion,1998.27,155—166.
[41] JaupartC ,MareschalJC .Thethermalstructureandthicknessofcontinentalroots.In:R .D .VanDerHilstandW .F .McDonougheds.Composition,DeepStructureandEvolutionofContinents.Amsterdam:ElsevierPress,1999.93—144.
[42] 金性春,周祖翼,汪品先编著.大洋钻探与中国地球科学.上海:同济大学出版社,1995.JINXingChun,ZHOUZuYi,WANGPinXian.OceanDrillingProgramandEarthScienceinChina.Shanghai:TongJiUniversityPress,1995.
版权所有：© 2023 中国地质图书馆 中国地质调查局地学文献中心