下扬子地壳P波速度结构:符离集-奉贤地震测深剖面再解释
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摘要
利用适于地壳速度结构重建的有限差分反演技术和RayInvr技术,解释了下扬子地区符离集-奉贤地震测深剖面密集的宽角反射/折射地震资料,重建研究区地壳上地幔顶部P波速度结构.该剖面速度模型在纵向上大致可分上地壳、中地壳和下地壳三部分,横向上可划分为6个块体.研究区速度分布符合稳定地台的速度结构特征.上地壳总厚度10.5～13.0km,速度横向变化剧烈,底部速度可达到6.2km·s-1.中地壳下部及下地壳上部速度分布横向不均匀性显著.中地壳上部和下部、下地壳及上地幔顶部的P波速度值度值分别在5.9～6.2,6.3～6.4,6.6～7.0和8.06～8.30km·s-1左右.莫霍界面深度为30～36km.郯庐断裂带域两侧中上地壳速度结构明显不同,而下地壳未见明显的速度异常和界面形态异常显示.推测郯庐断裂嘉山段在中生代曾经切割整个地壳,后由于造山带伸展及壳内均衡作用等,使得断裂特征在弹性中上地壳中得以保留,而在粘塑性下地壳中的断裂迹象则逐渐消失.镇江附近5级以上地震与延伸至下地壳的深大断裂有关,其地震成因可能是来自岩石圈的能量容易沿深大断裂传输至中上地壳,在构造有利的位置积聚,最终诱发地震.
引文
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29Christensen N,Mooney W D.Seismic velocity structure and composition of the continental crust:A global view.J Geophys Res,1995,100:9761—9788
30陈棋福,陈颙,陈凌,等.全球地震灾害预测.科学通报,1999,44(1):21—25
2陈沪生.下扬子地区HQ-13线的综合地球物理调查及其地质意义.石油与天然气地质,1988,9(3):211—222
3陈沪生,周雪清,李道琪,等.中国东部灵壁-奉贤(HQ-13)地学断面图1︰1000000说明书.北京:地质出版社,1992
4张四维,张锁喜,唐荣余,等.下杨子地区符离集-奉贤地震测深资料解释.地球物理学报,1988,31(6):637—648
5杨宝俊,穆石敏,金旭,等.中国满洲里-绥芬河地学断面地球物理综合研究.地球物理学报,1996,39(6):772—782
6Zhang Z J,Li Y K,Liu D Y,et al.Velocity and anisotropy structure of the crust in the Dabieshan orogenic belt from wide-angle seismic data.Phys Earth Planet Int,2000,122(1-2):115—131
7Zhang Z J,Badal J,Li Y K,et al.Crust–upper mantle seismic velocity structure across Southeastern China.Tectonophysics,2005,395(1-2):137—157
8Vidale J E.Finite-difference travel time calculation.Bull Seism Soc Am,1988,78:2062—2076
9Vidale J E.Finite-difference calculations of travel times in three dimensions.Geophysics,1990,55:521—526
10Hole J A.Nonlinear high-resolution three-dimensional seismic travel-time tomography.J Geophys Res,1992,97:6553—6562
11Ammon C J,Vidale J E.Tomography without rays.Bull Seism Soc Am,1993,83:509—528
12Zelt C A,Smith R B.Seismic travel time inversion for2-D crustal velocity structure.Geophys J Int,1992,108:16—34
13Zelt C A,Forsyth D A.Modeling wide-angle seismic data for crustal structure:Southeastern Grenville Province.J Geophys Res,1994,99:11687—11704
14王椿镛,张先康,丁志峰,等.大别造山带上部地壳结构的有限差分层析成像.地球物理学报,1997,40(4):495—501
15Zelt C A,Barton P J.Three-dimensional seismic refraction tomography:A comparison of two methods applied to data from the Faeroe Basin.J Geophys Res,1998,103:7187—7210
16The DOBREfraction’99Working Group.In:Grad M,Gryn’D,et al.“DOBREfraction’99”-velocity model of the crust and upper mantle beneath the Donbas Foldbelt(East Ukraaine).Tectonophysics,2003,371:81—110
17白志明,王椿镛.云南遮放-宾川和孟连-马龙宽角地震剖面层析成像研究.地球物理学报.2004,47(2):257—267
18Bai Z M,Zhang Z J,Badal J.Crust–upper mantle P-wave velocity structure in Yunnan,Southeastern China,from wide-angle seismic data.Geophys J Int,2006(待发)
19马杏垣.中国岩石圈动力学地图集.1989,4
20Weng S J,Chen H S,Zhou X Q,et al.Deep seismic probing of continental crust in the Lower Yangtze region,eastern China.Tectonophysics,1990,173:297—305
21Inoue H,Fukao Y,Tanabe K,et al..Whole mantle P-wave travel time tomography.Phys Earth Planet Inter,1990,59:294—328
22刘昌铨,祝治平,李捍东,等.连云港-临沂-泗水测深剖面及临沂8.5级地震深部构造背景.地震,1983,3:172—183
23郑晔,滕吉文.随县-马鞍山地带地壳与上地幔结构及郯庐构造带南段的某些特征.地球物理学报,1989,32(6):648—659
24胡家富,苏有锦,朱雄关,等.云南的地壳S波速度与泊松比结构及其意义.中国科学,D辑:地球科学,2003,33(8):714—722
25张中杰,白志明,王椿镛,等.刘振宽.三江地区地壳结构及动力学意义:云南遮放-宾川地震/折射剖面的启示.中国科学,D辑:地球科学,35(4):314—319
26高锐.青藏高原地壳与上地幔地球物理调查成果综述(上).中国地质,1995,4:26—28
27Zhang Z J,Klemperer S L.West-east variation in crustal thickness in northern Lhasa block,central Tibet,from deep seismic sounding data.J Geophys Res,2005,110,doi:10.1029/2004JB003139
28Mooney W D,Braile L W.The seismic structure of the continental crust and upper mantle of North America.In:Bally A W,Palmer A R,eds.The Geology of North America,An Overview.Geological Society of America,Boulder,Colo,1989,39—52
29Christensen N,Mooney W D.Seismic velocity structure and composition of the continental crust:A global view.J Geophys Res,1995,100:9761—9788
30陈棋福,陈颙,陈凌,等.全球地震灾害预测.科学通报,1999,44(1):21—25
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