龙门山断裂带地壳密度结构

doi:10.3969/j.issn.0253-4967.2012.01.004

摘要/Abstract

摘要：

研究龙门山及邻区地壳密度结构对于认识该地区地震活动性具有重要意义。根据龙门山及邻区(100°～105°E,28°～33°N)的布格重力异常资料,选取了跨越龙门山断裂带的6条重力测线,在深地震测深资料约束下,使用Geosoft软件分别反演出了龙门山地区地下的沉积层、康拉德界面和莫霍面的深度分布。研究结果表明:龙门山断裂带两侧的地壳结构明显不同,西面高原地区沉积层较薄,大部分为基岩出露;而东边盆地沉积层明显较厚,多在6km以上。莫霍面和康拉德面在两侧均相对平缓,康拉德面从东部的大约24km增加到青藏高原山区的35km左右;莫霍面深度从东部盆地的大约42km增加到西部青藏高原的67km左右。龙门山断裂带整体表现为一条近SN向的陡变重力梯度带,并在其地壳内各界面均发生错断,莫霍面和康拉德面错断距离分别达6～7km和3～5km。该区地壳的这种陡变和不均匀性是导致地震活动性强烈的主要原因之一。

关键词: 汶川地震, 龙门山断裂带, 重力反演, 地壳密度结构, 莫霍面

Abstract:

It is of importance to study the crustal density structure of Longmenshan Fault zone for understanding the seismicity of this area. Using commercial software of Geosoft, gravity inversion for 6 lines of Bouguer gravity anomaly data was carried out under the constraint of deep seismic sounding (DSS) data obtained in the last two decades. The depth and distribution of sediments, crustal thickness and Conrad discontinuity of Longmenshan tectonic zone and its adjacent area(100°～105°E, 28°～33°N)are obtained. The inverted results indicate that the crustal density structure of the Longmenshan Fault zone is obviously different between the two sides. The sedimentary layer in western plateau is thinner and base rocks outcrop almost in most parts; while the thickness of sedimentary layer in eastern Sichuan Basin is much larger, in most parts, it is larger than 6km. The Conrad and Moho discontinuities are relatively smooth in both sides of the fault and the depths of them increase gradually from the eastern 24km and 42km to 35km and 67km under Tibetan Plateau, respectively. The whole fault of Longmenshan displays as a SN-direction gravity gradient zone, with each of its interfaces in the crust under the faults being offset. The displacements of the Conrad and Moho discontinuities are 6～7km and 3～5km, respectively. The sharp change in crustal thickness is maybe one of the causes of strong earthquakes in this area.

Key words: Wenchuan earthquake, Longmenshan Fault zone, crustal density structure, gravity inversion, Moho discontinuity

中图分类号:

P315.2

唐新功, 尤双双, 胡文宝, 严良俊. 龙门山断裂带地壳密度结构[J]. 地震地质, 2012, 34(1): 28-38.

TANG Xin-gong, YOU Shuang-shuang, HU Wen-bao, YAN Liang-jun. THE CRUSTAL DENSITY STRUCTURE UNDERNEATH LONGMENSHAN FAULT ZONE[J]. SEISMOLOGY AND GEOLOGY, 2012, 34(1): 28-38.

参考文献

陈九辉,刘启元,李顺成,等.2009.汶川M_S 8.0地震余震序列重新定位及其地震构造研究［J］.地球物理学报,52(2): 390-397.
CHEN Jiu-hui,LIU Qi-yuan,LI Shun-cheng,et al.2009.Seismotectonic study by relocation of the Wenchuan M_S 8.0 earthquake sequence［J］.Chinese J Geophys,52(2): 390-397(in Chinese).
郭飚,刘启元,陈九辉,等.2009.川西龙门山及邻区地壳上地幔远震P波层析成像［J］.地球物理学报,52(2): 346-355.
GUO Biao,LIU Qi-yuan,CHEN Jiu-hui,et al.2009.Teleseismic P wave tomography of the crust and upper mantle in Longmenshan area,west China［J］.Chinese J Geophys,52(2): 346-355(in Chinese).
冯锐.1985.中国地壳厚度及上地幔密度分布(三维重力反演结果)［J］.地震学报,7(2): 143-157.
FENG Rui.1985.Crustal thickness and densities in the upper mantle beneath China: The resolution of three dimensional gravity inversion［J］.Acta Seismologica Sinica,7(2): 143-157(in Chinese).
冯锐,郑书真,黄桂芳,等.1989.华北地区重力场与沉积层构造［J］.地球物理学报,32(4): 385-398.
FENG Rui,ZHENG Shu-zhen,HUANG Gui-fang,et al.1989.Gravity field and structure of the sedimentary layer in North China［J］.Chinese J Geophys,32(4): 385-398(in Chinese).
雷建设,赵大鹏,苏金蓉,等.2009.龙门山断裂带地壳精细结构与汶川地震发震机理［J］.地球物理学报,52(2): 339-345.
LEI Jian-she,ZHAO Da-peng,SU Jin-rong,et al.2009.Fine seismic structure under the Longmenshan Fault zone and the mechanism of the large Wenchuan earthquake［J］.Chinese J Geophys,52(2): 339-345(in Chinese).
刘启元,李昱,陈九辉,等.2009.汶川M_S 8.0地震: 地壳上地幔S波速度结构的初步研究［J］.地球物理学报,52(2): 309-319.
LIU Qi-yuan,LI Yu,CHEN Jiu-hui, et al.2009.Wenchuan M_S8.0 earthquake: Preliminary study of the S-wave velocity structure of the crust and upper mantle［J］.Chinese J Geophys,52(2): 309-319(in Chinese).
单新建,屈春燕,宋小刚,等.2009.汶川M_S 8.0地震InSAR同震形变场［J］.地球物理学报,52(2): 496-504.
SHAN Xin-jian,QU Chuan-yan,SONG Xiao-gang,et al.2009.Coseismic surface deformation caused by the Wenchuan M_S 8.0 earthquake from InSAR data analysis［J］.Chinese J Geophys,52(2): 496-504(in Chinese).
唐新功,陈永顺,唐哲.2006.应用布格重力异常研究郯庐断裂构造［J］.地震学报,28(6): 603-610.
TANG Xin-gong,CHEN Yong-shun,TANG Zhe.2006.Bouguer gravity study of middle section of Tanlu Fault［J］.Acta Seismologica Sinica,19(6): 650-657.
滕吉文,曾融生,严艳芬,等.2002.东亚大陆及周边海域Moho界面深度分布和基本构造格局［J］.中国科学(D辑),5(46): 428-446.
TENG Ji-wen,ZENG Rong-sheng,YAN Ya-fen,et al.2002.Depth distribution of Moho and tectonic framework in eastern Asian continent and its adjacent ocean areas［J］.Science in China(Ser D),5(46): 428-446(in Chinese).
王绪本,余年,朱迎堂,等.2008.龙门山逆冲构造带大地电磁测深初步成果［J］.成都理工大学学报(自然科学版),35(4): 992-304.
WANG Xu-ben,YU Nian,ZHU Ying-tang,et al.2008.The preliminary magnetotelluric results in Longmenshan reverse structure zone［J］.Journal of Chengdu University of Science and Technology(Science and Technology Edition),35(4): 992-304(in Chinese).
王有学,Mooney W D,韩国花,等.2005.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,48(1): 98-106.
WANG You-xue,Mooney W D,HAN Guo-hua,et al.2005.Crustal P wave velocity structure from Altyn Tagh to Longmen Mountains along the Taiwan-Altay geoscience transect［J］.Chinese J Geophys,48(1): 98-106(in Chinese).
吴建平,黄媛,张天中,等.2009.汶川M_S 8.0级地震余震分布及周边区域P波三维速度结构研究［J］.地球物理学报,52(2): 320-328.
WU Jian-ping,HUANG Yuan,ZHANG Tian-zhong,et al.2009.Aftershock distribution of the M_S 8.0 Wenchuan earthquake and three-dimensional P wave velocity structure in and around source region［J］.Chinese J Geophys,52(2): 320-328(in Chinese).
胥颐,黄润秋,李志伟,等.2009.龙门山构造带及汶川震源区的S波速度结构［J］.地球物理学报,52(2): 329-338.
XU Yi,HUANG Run-qiu,LI Zhi-wei,et al.2009.S wave velocity structure of the Longmen Shan and Wenchuan earthquake area［J］.Chinese J Geophys,52(2): 329-338(in Chinese).
赵国泽,陈小斌,肖骑彬,等.2009.汶川M_S 8.0级地震成因三 "层次"分析: 基于深部电性结构［J］.地球物理学报,52(2): 553-563.
ZHAO Guo-ze,CHEN Xiao-bin,XIAO Qi-bin,et al.2009.Generation mechanism of Wenchuan strong earthquake of M_S 8.0 inferred from EM measurement in three levels［J］.Chinese J Geophys,52(2): 553-563(in Chinese).
张季生,高锐,曾令森,等.2009.龙门山及邻区重、磁异常特征及与地震关系的研究［J］.地球物理学报,52(2): 572-578.
ZHANG Ji-sheng,GAO Rui,ZENG Ling-sen,et al.2009.Relationship between characteristics of gravity and magnetic anomalies and the earthquakes in Longmenshan range and adjacent area［J］.Chinese J Geophys,52(2): 572-578(in Chinese).
张培震,徐锡伟,闻学泽,等.2008.2008年汶川8.0级地震发震断裂的滑动速率、复发周期和构造成因［J］.地球物理学报,51(4): 1066-1073.
ZHANG Pei-zhen,XU Xi-wei,WEN Xue-ze,et al.2008.Slip rates and recurrence intervals of the Longmenshan active fault zone and tectonic implications for the mechanism of the May 12 Wenchuan earthquake,Sichuan,China［J］.Chinese J Geophys,51(4): 1066-1073(in Chinese).
曾融生,孙为国,毛桐恩,等.1995.中国大陆莫霍界面深度图［J］.地震学报,17(3): 322-327.
ZENG Rong-sheng,SUN Wei-guo,MAO Tong-en,et al.1995.The Moho depth of Chinese Mainland［J］.Acta Seismologica Sinica,17(3): 322-327(in Chinese).
朱介寿.2008.汶川地震的岩石圈深部结构与动力学背景［J］.成都理工大学学报(自然科学版),35(4): 348-356.
ZHU Jie-shou.2008.The deep lithospheric structure of Wenchuan earthquake and its geodynamic implications［J］.Journal of Chengdu University of Science and Technology(Science and Technology Edition),35(4): 348-356(in Chinese).

[1]	刘奕均, 杨光亮, 王嘉沛, 谈洪波, 周怀斌, 申重阳. 基于粒子群算法的四川长宁地区印支构造界面反演[J]. 地震地质, 2023, 45(1): 172-189.
[2]	宋冬梅, 王慧, 单新建, 王斌, 崔建勇. 基于最大切应变的震前GRACE重力异常信息提取方法[J]. 地震地质, 2022, 44(6): 1539-1556.
[3]	宋婷, 沈旭章, 梅秀苹, 焦煜媛, 李敏娟, 苏小芸, 季婉婧. 利用接收函数频率特征研究青藏高原东北缘地区的莫霍面性质[J]. 地震地质, 2022, 44(5): 1290-1312.
[4]	王晓山, 万永革. 汶川地震前震中周围地壳应力场及应力方向集中的特征[J]. 地震地质, 2022, 44(2): 363-377.
[5]	叶轶佳, 谭锡斌, 钱黎. 通过河流剪切力获取河道侵蚀速率和基岩可蚀系数——以龙门山为例[J]. 地震地质, 2022, 44(1): 115-129.
[6]	郭树松, 祝意青, 徐云马, 刘芳, 赵云峰, 张国庆, 朱辉. 汶川地震前失稳过程的重力场观测证据[J]. 地震地质, 2021, 43(6): 1368-1380.
[7]	汪健, 申重阳, 孙文科, 谈洪波, 胡敏章, 梁伟锋, 韩宇飞, 张新林, 吴桂桔, 王青华. 红河断裂带北、中段近期重力变化及深部变形[J]. 地震地质, 2021, 43(6): 1537-1562.
[8]	酆少英, 刘保金, 李倩, 袁洪克, 朱国军, 田一鸣, 王宏伟, 侯黎华, 邓小娟, 谭雅丽. 深地震反射剖面揭示的华北地块南缘地壳的精细结构[J]. 地震地质, 2020, 42(3): 581-594.
[9]	兰剑, 陈晓利. 2008年M_S8.0汶川地震诱发滑坡灾害在映秀地区的演化特征[J]. 地震地质, 2020, 42(1): 125-146.
[10]	朱传华, 单新建, 张国宏, 焦中虎, 张迎峰, 李彦川, 乔鑫. 汶川地震热异常与构造应力关联的数值模拟[J]. 地震地质, 2019, 41(6): 1497-1510.
[11]	宋冬梅, 向亮, 单新建, 尹京苑, 王斌, 崔建勇. 基于SVR模型的电离层TEC背景场构建方法[J]. 地震地质, 2019, 41(6): 1511-1528.
[12]	汤井田, 杨磊, 任政勇, 胡双贵, 徐志敏. 龙门山断裂带卫星重力场特征及其发震机制[J]. 地震地质, 2019, 41(5): 1136-1154.
[13]	马思远, 许冲, 王涛, 刘甲美. 应用2类Newmark简易模型进行2008年汶川地震滑坡评估[J]. 地震地质, 2019, 41(3): 774-788.
[14]	李振月, 万永革, 盛书中. 米亚罗断裂活动与汶川地震序列活动的关系[J]. 地震地质, 2019, 41(1): 72-83.
[15]	徐志萍, 王夫运, 姜磊, 赵延娜, 杨利普, 唐淋. 龙门山中南段地壳上地幔三维密度结构[J]. 地震地质, 2019, 41(1): 84-98.