川滇地区重力场特征及其与区域强震的关系
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摘要
本文利用最新超高阶重力场模型EIGEN-6C2、全球DEM模型topo_15.1.img和地壳模型CRUST1.0等数据,研究了川滇地区的不同类型的静态重力场(自由空气重力异常、布格重力异常和剩余均衡重力异常)分布特征,探讨了区域强震与静态重力场之间的关系.整体上看,川滇地区自由空气重力异常FA与地形镜像关系明显,说明地形效应对重力场影响较大;由于扣除了地形效应,区域布格重力异常格呈现西北低、东南高的特征,总体反映了川滇地区地壳厚度变化的基本格局,并在此之上,叠加了各种强度不等的局部异常;利用Parker方法正演了Moho起伏引起的地表重力变化,将其从区域布格重力异常中扣除,得到反映地表密度分布的剩余重力异常.通过对比2000年以来发生的区域大震震源机制与不同静态重力场分布特征可知,逆冲/正断型地震(如汶川地震、芦山地震)往往发生在静态重力异常的高梯度带上,而走滑型地震(如玉树地震、鲁甸地震)发生在重力异常变化较为平稳的区域,这可能与断裂的性质及其所处构造环境有关.
Using the newly ultrahigh order gravity field model EIGEN-6C2,the global DEM model topo_15.1.img and the crust model CRUST1.0,we calculate three kinds of static gravity fields(Free-air gravity anomaly,Bouguer anomaly and residue gravity anomaly)of Sichuan-Yunnan region,and study the relationship between these gravity fields and regional earthquakes.As a whole,the Free-air gravity anomaly has a clear mirror-image relation with regional topography,which means that the regional topography has a big effect on Free-air gravity anomaly.By subtracting the topography gravity effect from Free-air gravity anomaly,we get the Bouguer anomaly of Sichuan-Yunnan region,which presents a characteristic of the lower northwest higher southeast;And the Bouguer anomaly basically reflect the crustal thickness changes of SichuanYunnan region,which be superposed of the intensity of various range of local anomalies.Based on the Parker method we calculate the gravity effect of regional Moho discontinuity,by subtracting it from regional Bouguer anomaly,we get the residue gravity anomaly, which can reflect the density difference of crust in Sichuan-Yunnan region.By comparing the patterns of these gravity fields with the earthquakes source mechanism which occurred after the year 2000,we found that,the thrust or normal type of earthquakes are likely to break on the high gradient zone of three kinds of static gravity fields,and the strike-slip type of earthquakes are likely to break on the smooth and steady area static of gravity fields,which may be concerned with the nature of the faults and the structural setting of the crust.
Using the newly ultrahigh order gravity field model EIGEN-6C2,the global DEM model topo_15.1.img and the crust model CRUST1.0,we calculate three kinds of static gravity fields(Free-air gravity anomaly,Bouguer anomaly and residue gravity anomaly)of Sichuan-Yunnan region,and study the relationship between these gravity fields and regional earthquakes.As a whole,the Free-air gravity anomaly has a clear mirror-image relation with regional topography,which means that the regional topography has a big effect on Free-air gravity anomaly.By subtracting the topography gravity effect from Free-air gravity anomaly,we get the Bouguer anomaly of Sichuan-Yunnan region,which presents a characteristic of the lower northwest higher southeast;And the Bouguer anomaly basically reflect the crustal thickness changes of SichuanYunnan region,which be superposed of the intensity of various range of local anomalies.Based on the Parker method we calculate the gravity effect of regional Moho discontinuity,by subtracting it from regional Bouguer anomaly,we get the residue gravity anomaly, which can reflect the density difference of crust in Sichuan-Yunnan region.By comparing the patterns of these gravity fields with the earthquakes source mechanism which occurred after the year 2000,we found that,the thrust or normal type of earthquakes are likely to break on the high gradient zone of three kinds of static gravity fields,and the strike-slip type of earthquakes are likely to break on the smooth and steady area static of gravity fields,which may be concerned with the nature of the faults and the structural setting of the crust.
引文
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Frste C,Bruinsma S L,Flechtner F,et al.2012.A preliminary\supdate of the Direct approach GOCE Processing and a new\srelease of EIGEN-6C[C].//Presented at the AGU Fall\sMeeting 2012,San Francisco,USA,3-7 Dec,Abstract No.G31B-0923.
Fullea J,Fernàndez M,Zeyen H.2008.FA2BOUG-AFORTRAN 90code to compute Bouguer gravity anomalies from\sgridded free-air anomalies:Application to the AtlanticMediterranean transition zone[J].Computers&Geosciences,34(12):1665-1681.
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Laske G,Masters G,Ma Z T,et al.2013.Update on CRUST1.0-a1-degree global model of Earth’s crust[Z].Vienna:EGUgeneral assembly.
Li J C,Chen J Y,Ning J S,et al.2003.Global Gravity Field\sApproximation Theory and Determination of 2000 Quasi-Geoid\sof China(in Chinese)[M].Whuhan:Whuhan University\sPress.
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Ning J S.2002.The satellite gravity surveying technology and\sresearch of Earth’s gravity field[J].Journal of Geodesy and\sGeodynamics(in Chinese),22(1):1-5.
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Shen F,Royden L H,Burchfiel B C.2001.Large-scale crustal\sdeformation of the Tibetan Plateau[J].Journal of Geophysical\sResearch,106(B4):6793-6816.
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Sjberg L E,Bagherbandi M.2011.A method of estimating the\sMoho density contrast with a tentative application of EGM08and CRUST2.0[J].Acta Geophysica,59(3):502-525.
Smith W H F,Sandwell D T.1994.Bathymetric prediction from\sdense satellite altimetry and sparse shipboard bathymetry[J].Journal of Geophysical Research,99(B11):21803-21824.
Teng J W,Bai D H,Yang H,et al.2008.Deep processes and\sdynamic responses associated with the Wenchuan MS8.0earthquake\sof 2008[J].Chinese J.Geophys.(in Chinese),51(5):1385-1402.
Wang J,Li H,Shen C Y.2012.Precision analysis of gravity\sanomaly forward algorithm in the wave number domain[J].Journal of Southwest University of Science and Technology(in\sChinese),27(4):65-68.
Wang S X,Jiang F Y,Hao M,et al.2013.Investigation of features\sof present 3Dcrustal movement in eastern edge of Tibet plateau[J].Chinese J.Geophys.(in Chinese),56(10):3334-3345,doi:10.6038/cjg20131010.
Xu H Z.2001.Statellite gravity missions-new hotpoint in geodesy[J].Science of Surveying and Mapping(in Chinese),26(3):1-3.
Xu Z Q,Hou L W,Wang Z X,et al.1992.Orogenic Process of the\sSongpan-Ganzi Orogen in China[M].Beijing:The Geological\sPublishing House.
Xu Z Q,Yang J S,Jiang M.1999.Continental subduction and\suplifting of the orogenic belts at the margin of the QinghaiTibetan Plateau[J].Earth Science Frontiers(in Chinese),6(3):139-151.
Zhang Y Q,Li H L,Li J H.2010.Middle pleistocene extension\salong the eastern margin of xizang(Tibetan)plateau and its\sneotectonic significance[J].Geological Review(in Chinese),56(6):781-791.
Zhao D J,Zhang M L,Wang Q,et al.2014.Accuracy analyses of\sEIGEN-6C2geopotential model in China mainland[J].Journal\sof Geodesy and Geodynamics(in Chinese),34(5):21-24.
邓起东.2007.中国活动构造图[M].北京:地震出版社.
李建成,陈俊勇,宁津生,等.2003.地球重力场逼近理论与中国2000似大地水准面的确定[M].武汉:武汉大学出版社.
楼海,王椿镛.2005.川滇地区重力异常的小波分解与解释[J].地震学报,27(5):515-523.
宁津生.2002.卫星重力探测技术与地球重力场研究[J].大地测量与地球动力学,22(1):1-5.
滕吉文,白登海,杨辉,等.2008.2008汶川Ms8.0地震发生的深层过程和动力学响应[J].地球物理学报,51(5):1385-1402.
汪健,李辉,申重阳.2012.波数域重力异常正演计算精度分析[J].西南科技大学学报,27(4):65-68.
王双绪,蒋锋云,郝明,等.2013.青藏高原东缘现今三维地壳运动特征研究[J].地球物理学报,56(10):3334-3345,doi:10.6038/cjg20131010.
许厚泽.2001.卫星重力研究:21世纪大地测量研究的新热点[J].测绘科学,26(3):1-3.
许志琴,侯立玮,王宗秀,等.1992.中国松潘-甘孜造山带的造山过程[M].北京:地质出版社.
许志琴,杨经绥,姜枚.1999.大陆俯冲作用及青藏高原周缘造山带的崛起[J].地学前缘,6(3):139-151.
张岳桥,李海龙,李建华.2010.青藏高原东缘中更新世伸展作用及其新构造意义[J].地质论评,56(6):781-791.
赵德军,张敏利,王强,等.2014.EIGEN-6C2重力场模型在中国大陆的精度分析[J].大地测量与地球动力学,34(5):21-24.
Block A E,Bell R E,Studinger M.2009.Antarctic crustal\sthickness from satellite gravity:Implications for the\sTransantarctic and Gamburtsev Subglacial Mountains[J].Earth\sand Planetary Science Letters,288(1-2):194-203.
Deng Q D.2007.Map of Active Tectonics in China(in Chinese)[M].Beijing:Seismological Press.
Frste C,Bruinsma S L,Flechtner F,et al.2012.A preliminary\supdate of the Direct approach GOCE Processing and a new\srelease of EIGEN-6C[C].//Presented at the AGU Fall\sMeeting 2012,San Francisco,USA,3-7 Dec,Abstract No.G31B-0923.
Fullea J,Fernàndez M,Zeyen H.2008.FA2BOUG-AFORTRAN 90code to compute Bouguer gravity anomalies from\sgridded free-air anomalies:Application to the AtlanticMediterranean transition zone[J].Computers&Geosciences,34(12):1665-1681.
Griffin W L,OReilly S Y.1987.Is the continental Moho the crustmantle boundary?[J].Geology,15(3):241-244.
Hofmann-Wellenhof B,Moritz H.2006.Physical Geodesy[M].Wien:Springer.
Laske G,Masters G,Ma Z T,et al.2013.Update on CRUST1.0-a1-degree global model of Earth’s crust[Z].Vienna:EGUgeneral assembly.
Li J C,Chen J Y,Ning J S,et al.2003.Global Gravity Field\sApproximation Theory and Determination of 2000 Quasi-Geoid\sof China(in Chinese)[M].Whuhan:Whuhan University\sPress.
Lou H,Wang C Y.2005.Wavelet analysis and interpretation of\sgravity data in Sichuan-Yunnan region,China[J].Acta\sSeismologica Sinica(in Chinese),27(5):515-523.
Ning J S.2002.The satellite gravity surveying technology and\sresearch of Earth’s gravity field[J].Journal of Geodesy and\sGeodynamics(in Chinese),22(1):1-5.
Oldenburg D W.1974.The inversion and interpretation of gravity\sanomalies[J].Geophysics,39(4):526-536.
Parker R L.1973.The rapid calculation of potential anomalies[J].Geophysical Journal Internationa,31(4):447-455.
Pavlis N K,Holmes S A,Kenyon S C,et al.2008.An earth\sgravitational model to degree 2160:EGM2008[R].2008General Assembly of the EGU General Assembly,13-18.
Sandwell D,Garcia E,Soofi K,et al.2013.Toward 1-mGal\saccuracy in global marine gravity from CryoSat-2,Envisat,and\sJason-1[J].The Leading Edge,32(8):892-899.
Shen F,Royden L H,Burchfiel B C.2001.Large-scale crustal\sdeformation of the Tibetan Plateau[J].Journal of Geophysical\sResearch,106(B4):6793-6816.
Shin Y H,Xu H,Braitenberg C,et al.2007.Moho undulations\sbeneath Tibet from GRACE-integrated gravity data[J].Geophysical Journal International,170(3):971-985.
Sjberg L E,Bagherbandi M.2011.A method of estimating the\sMoho density contrast with a tentative application of EGM08and CRUST2.0[J].Acta Geophysica,59(3):502-525.
Smith W H F,Sandwell D T.1994.Bathymetric prediction from\sdense satellite altimetry and sparse shipboard bathymetry[J].Journal of Geophysical Research,99(B11):21803-21824.
Teng J W,Bai D H,Yang H,et al.2008.Deep processes and\sdynamic responses associated with the Wenchuan MS8.0earthquake\sof 2008[J].Chinese J.Geophys.(in Chinese),51(5):1385-1402.
Wang J,Li H,Shen C Y.2012.Precision analysis of gravity\sanomaly forward algorithm in the wave number domain[J].Journal of Southwest University of Science and Technology(in\sChinese),27(4):65-68.
Wang S X,Jiang F Y,Hao M,et al.2013.Investigation of features\sof present 3Dcrustal movement in eastern edge of Tibet plateau[J].Chinese J.Geophys.(in Chinese),56(10):3334-3345,doi:10.6038/cjg20131010.
Xu H Z.2001.Statellite gravity missions-new hotpoint in geodesy[J].Science of Surveying and Mapping(in Chinese),26(3):1-3.
Xu Z Q,Hou L W,Wang Z X,et al.1992.Orogenic Process of the\sSongpan-Ganzi Orogen in China[M].Beijing:The Geological\sPublishing House.
Xu Z Q,Yang J S,Jiang M.1999.Continental subduction and\suplifting of the orogenic belts at the margin of the QinghaiTibetan Plateau[J].Earth Science Frontiers(in Chinese),6(3):139-151.
Zhang Y Q,Li H L,Li J H.2010.Middle pleistocene extension\salong the eastern margin of xizang(Tibetan)plateau and its\sneotectonic significance[J].Geological Review(in Chinese),56(6):781-791.
Zhao D J,Zhang M L,Wang Q,et al.2014.Accuracy analyses of\sEIGEN-6C2geopotential model in China mainland[J].Journal\sof Geodesy and Geodynamics(in Chinese),34(5):21-24.
邓起东.2007.中国活动构造图[M].北京:地震出版社.
李建成,陈俊勇,宁津生,等.2003.地球重力场逼近理论与中国2000似大地水准面的确定[M].武汉:武汉大学出版社.
楼海,王椿镛.2005.川滇地区重力异常的小波分解与解释[J].地震学报,27(5):515-523.
宁津生.2002.卫星重力探测技术与地球重力场研究[J].大地测量与地球动力学,22(1):1-5.
滕吉文,白登海,杨辉,等.2008.2008汶川Ms8.0地震发生的深层过程和动力学响应[J].地球物理学报,51(5):1385-1402.
汪健,李辉,申重阳.2012.波数域重力异常正演计算精度分析[J].西南科技大学学报,27(4):65-68.
王双绪,蒋锋云,郝明,等.2013.青藏高原东缘现今三维地壳运动特征研究[J].地球物理学报,56(10):3334-3345,doi:10.6038/cjg20131010.
许厚泽.2001.卫星重力研究:21世纪大地测量研究的新热点[J].测绘科学,26(3):1-3.
许志琴,侯立玮,王宗秀,等.1992.中国松潘-甘孜造山带的造山过程[M].北京:地质出版社.
许志琴,杨经绥,姜枚.1999.大陆俯冲作用及青藏高原周缘造山带的崛起[J].地学前缘,6(3):139-151.
张岳桥,李海龙,李建华.2010.青藏高原东缘中更新世伸展作用及其新构造意义[J].地质论评,56(6):781-791.
赵德军,张敏利,王强,等.2014.EIGEN-6C2重力场模型在中国大陆的精度分析[J].大地测量与地球动力学,34(5):21-24.