壳幔物质流变的底辟作用孕育大地震——卫星重力资料的证据
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摘要
根据2-180阶与2-360阶的数字全球模型恢复的卫星重力场数据,主要源于地下18～36km深处的密度变化,多数大地震的震源也正是位于该层段。因此卫星重力场资料对于地震研究有很大的意义。笔者详细分析了中国汶川、墨脱、仲巴、伽师和台湾等地的卫星重力资料(这些地区在近几十年来均发生过6级以上的大地震),惊奇地发现,在这些地区,卫星重力场的样式具有极大的相似性,它们表现在:(1)卫星重力场的正负异常值成对出现;(2)震中通常位于重力场峰值间的陡梯度带;(3)由低阶到高阶的重力场正异常的峰值增大而宽度变窄;(4)正、负峰值间的距离随所处的大地构造背景而变;(5)不同应力场壳幔物质底辟的样式不同,从地质上看,高密度壳幔物质的流变底辟作用,可以合理地解释这种独特的样式变化。文中提出高密度生长指数的概念,用以度量密度由深部到浅部的增加。岩石圈断裂带、深大断裂带及多层次滑脱层是壳幔高密度塑性物质底辟活动的优势通道。壳幔物质的非均质性反映了大陆板块构造动力学过程的复杂性。
Satellite gravity field data recovered by digital global models with 2-180 to 2-360 order are mainly originated from the density variation in the depth of 18-36 km,at which epicenters of most major structure earthquakes were located.Therefore,satellite gravity data can make great contribution to earthquake research.The author has made a detailed analysis of the satellite gravity data over Wenchuan,Motuo,Zhongba,Jiashi and Taiwan Areas in China,where earthquakes more than magnitude of 6 took place in recent several decades.It is surprising that the gravity field patterns over these areas are extremely similar,which is characterized by the following features:(1)Paired positive and negative anomaly.(2)Epicenters usually were located between the pairs where the gradient of gravity field was the steepest.(3)The value of positive peak increased and its width decreased at higher order field.(4)The distance between positive and negative peaks varies in different tectonic background.(5)Different styles of crust-mantle material diapirism in different stress fields.Geologically,rheological diapirism of high density crust-mantle material could be a reasonable explanation to this unique pattern.The proposed high density growth index is a measurement of increase in density from deep to shallow.The passageways of diapirism for high density crust-mantle plastic material may be formed by the crust faults or giant fault zones and detached strata.The heterogeneity of crust-mantle material reflects the complexity of dynamic processes in continental plate tectonics.
Satellite gravity field data recovered by digital global models with 2-180 to 2-360 order are mainly originated from the density variation in the depth of 18-36 km,at which epicenters of most major structure earthquakes were located.Therefore,satellite gravity data can make great contribution to earthquake research.The author has made a detailed analysis of the satellite gravity data over Wenchuan,Motuo,Zhongba,Jiashi and Taiwan Areas in China,where earthquakes more than magnitude of 6 took place in recent several decades.It is surprising that the gravity field patterns over these areas are extremely similar,which is characterized by the following features:(1)Paired positive and negative anomaly.(2)Epicenters usually were located between the pairs where the gradient of gravity field was the steepest.(3)The value of positive peak increased and its width decreased at higher order field.(4)The distance between positive and negative peaks varies in different tectonic background.(5)Different styles of crust-mantle material diapirism in different stress fields.Geologically,rheological diapirism of high density crust-mantle material could be a reasonable explanation to this unique pattern.The proposed high density growth index is a measurement of increase in density from deep to shallow.The passageways of diapirism for high density crust-mantle plastic material may be formed by the crust faults or giant fault zones and detached strata.The heterogeneity of crust-mantle material reflects the complexity of dynamic processes in continental plate tectonics.
引文
[1]Han L,Jia Z Y.Development status of satellite application technology in geoscience study[J].Progress in Geophysics,2008,23(3):922-928(in Chinese).
[2]Wang Z T,Li J C,Jiang WP,et al.Determination of Earth Gravity Model WHU-GM-05using gravity data[J].Chinese Journal of Geophysics,2008,51(5):1364-1371(in Chi-nese).
[3]Zhou G F,Chen J P,Zhang J.Characters of crust-mantle construction and deep structure in Qinghai-Xizang(Tibet)Plateau[J].Earth Science—Journal of China University of Geosciences,1996,21(2):191-197(in Chinese).
[4]Zhou X H,Wang HB,Zhan J G.Study on upper layer geo-strophic circulation in China marginal sea by use of data of satellite gravity and satellite altimetry[J].Journal of Geodesy and Geodynamics,2008,28(4):83-88(in Chinese).
[5]Yuan X C.3Dlithospheric structure of Western China andits enlightenment on petroleumprospecting[J].Geology in Chi-na,2005,32(1):1-12(in Chinese).
[6]Fei Q.Characters of deep structure for Wenchuan Earth-quake[J].Chinese Journal of Engineering Geophysics,2008,15(4):387-395(in Chinese).
[7]Peng H,He YJ.An unsolved mystery on Tai wan tectonics[J].Geology of Shanghai,1989(30):33-47(in Chinese).
[8]Wang Y X,Mooney W D,Han G H,et al.Crustal P-wave velocity structure from Altay to Longmen Mountains along the Tai wan-Altay Geoscience Transect[J].Chinese Journal of Geophysics,2008,48(1):98-106(in Chinese).
[9]Guo Z,Gao X,Wang W M.Rupture process of South Tai-wan OffshoreMs7.2earthquake of Dec.26,2006[J].Chi-nese Journal of Geophysics,2008,51(4):1103-1113(in Chi-nese).
[10]Xu Z Q,Li H Q,Hou L W,et al.Uplift of the Longmen-Jinping Orogenic Belt along the eastern margin of the Qing-hai-Tibet Plateau:Large-scale detachment faulting and extru-sion mechanism[J].Geological Bulletin of China,2007,26(10):1262-1276(in Chinese).
[11]Tu H W,Wan X H,Gao K,et al.Research of the reason for variations of the earthquake fault characters andthe stress fieldin the Jiashi Region of Xinjiang from1977to2006[J].Progress in Geophysics,2008,23(4):1038-1044(in Chi-nese).
[1]韩露,贾正元.卫星应用技术在地学研究中的发展现状[J].地球物理学进展,2008,23(3):922-928.
[2]王正涛,李建成,姜卫平,等.基于GRACE卫星重力数据确定地球重力场模型WHU-GM-05[J].地球物理学报,2008,51(5):1364-1371.
[3]周国藩,陈建国,张健.青藏高原卫星重力场及所反映的壳幔结构和深部构造特征[J].地球科学——中国地质大学学报,1996,21(2):191-197.
[4]周旭华,王虎彪,詹金刚.联合卫星重力和卫星测高数据研究中国近海上层地转流[J].大地测量与地球动力学,2008,28(4):83-88.
[5]袁学诚.论中国西部岩石圈三维结构及其对寻找油气资源的启示[J].中国地质,2005,32(1):1-12.
[6]费琪.汶川大地震的深部构造特征[J].工程地球物理学报,2008,15(4):387-395.
[7]彭华,何越教.试论台湾构造之谜[J].上海地质,1989(30):33-47.
[8]王有学,Mooney WD,韩果花,等.台湾-阿尔泰地学断面阿尔金-龙门山剖面的地壳纵波速度结构[J].地球物理学报,2005,48(1):98-106.
[9]郭志,高星,王卫民.2006年12月26日台湾南部滨海Ms7.2级地震破裂过程研究[J].地球物理学报,2008,51(4):1103-1113.
[10]许志琴,李化启,侯立炜,等.青藏高原东缘龙门—锦屏造山带的崛起——大型拆离断层和挤出机制[J].地质通报,2007,26(10):1262-1276.
[11]屠泓为,万秀红,高歌,等.1977年至2006年新疆伽师地震断层性质及应力场变化原因初探[J].地球物理学进展,2008,23(4):1038-1044.
[2]Wang Z T,Li J C,Jiang WP,et al.Determination of Earth Gravity Model WHU-GM-05using gravity data[J].Chinese Journal of Geophysics,2008,51(5):1364-1371(in Chi-nese).
[3]Zhou G F,Chen J P,Zhang J.Characters of crust-mantle construction and deep structure in Qinghai-Xizang(Tibet)Plateau[J].Earth Science—Journal of China University of Geosciences,1996,21(2):191-197(in Chinese).
[4]Zhou X H,Wang HB,Zhan J G.Study on upper layer geo-strophic circulation in China marginal sea by use of data of satellite gravity and satellite altimetry[J].Journal of Geodesy and Geodynamics,2008,28(4):83-88(in Chinese).
[5]Yuan X C.3Dlithospheric structure of Western China andits enlightenment on petroleumprospecting[J].Geology in Chi-na,2005,32(1):1-12(in Chinese).
[6]Fei Q.Characters of deep structure for Wenchuan Earth-quake[J].Chinese Journal of Engineering Geophysics,2008,15(4):387-395(in Chinese).
[7]Peng H,He YJ.An unsolved mystery on Tai wan tectonics[J].Geology of Shanghai,1989(30):33-47(in Chinese).
[8]Wang Y X,Mooney W D,Han G H,et al.Crustal P-wave velocity structure from Altay to Longmen Mountains along the Tai wan-Altay Geoscience Transect[J].Chinese Journal of Geophysics,2008,48(1):98-106(in Chinese).
[9]Guo Z,Gao X,Wang W M.Rupture process of South Tai-wan OffshoreMs7.2earthquake of Dec.26,2006[J].Chi-nese Journal of Geophysics,2008,51(4):1103-1113(in Chi-nese).
[10]Xu Z Q,Li H Q,Hou L W,et al.Uplift of the Longmen-Jinping Orogenic Belt along the eastern margin of the Qing-hai-Tibet Plateau:Large-scale detachment faulting and extru-sion mechanism[J].Geological Bulletin of China,2007,26(10):1262-1276(in Chinese).
[11]Tu H W,Wan X H,Gao K,et al.Research of the reason for variations of the earthquake fault characters andthe stress fieldin the Jiashi Region of Xinjiang from1977to2006[J].Progress in Geophysics,2008,23(4):1038-1044(in Chi-nese).
[1]韩露,贾正元.卫星应用技术在地学研究中的发展现状[J].地球物理学进展,2008,23(3):922-928.
[2]王正涛,李建成,姜卫平,等.基于GRACE卫星重力数据确定地球重力场模型WHU-GM-05[J].地球物理学报,2008,51(5):1364-1371.
[3]周国藩,陈建国,张健.青藏高原卫星重力场及所反映的壳幔结构和深部构造特征[J].地球科学——中国地质大学学报,1996,21(2):191-197.
[4]周旭华,王虎彪,詹金刚.联合卫星重力和卫星测高数据研究中国近海上层地转流[J].大地测量与地球动力学,2008,28(4):83-88.
[5]袁学诚.论中国西部岩石圈三维结构及其对寻找油气资源的启示[J].中国地质,2005,32(1):1-12.
[6]费琪.汶川大地震的深部构造特征[J].工程地球物理学报,2008,15(4):387-395.
[7]彭华,何越教.试论台湾构造之谜[J].上海地质,1989(30):33-47.
[8]王有学,Mooney WD,韩果花,等.台湾-阿尔泰地学断面阿尔金-龙门山剖面的地壳纵波速度结构[J].地球物理学报,2005,48(1):98-106.
[9]郭志,高星,王卫民.2006年12月26日台湾南部滨海Ms7.2级地震破裂过程研究[J].地球物理学报,2008,51(4):1103-1113.
[10]许志琴,李化启,侯立炜,等.青藏高原东缘龙门—锦屏造山带的崛起——大型拆离断层和挤出机制[J].地质通报,2007,26(10):1262-1276.
[11]屠泓为,万秀红,高歌,等.1977年至2006年新疆伽师地震断层性质及应力场变化原因初探[J].地球物理学进展,2008,23(4):1038-1044.
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