Structure of Crust and Upper Mantle in Tianshui-Wudu Strong Earthquake Region of North-South Tectonic Belt
-
摘要: 利用两条相互垂直的高分辨地震折射/宽角反射剖面和相应的非纵观测的多个扇形剖面取得的人工地震资料, 研究天水和武都8级大震区的地壳和上地幔顶部结构和构造.二维剖面结果显示, 地壳沿垂向可分为上地壳和下地壳两大层.上地壳中部存在低速层, 层内介质速度比背景值低0.3~0.5km/s.莫霍面深度大约为46~48km.NE向的天水-武都剖面下地壳速度在横向上变化剧烈, NW向的成县-武山剖面, 在礼县以西, Moho面和C界面有被上涌物质改造过的迹象.三维速度成像显示, 在105°E附近, 从7至11km的深度范围内, 存在一条近NS向的断裂带, 在该带的两侧速度结构有明显的差异, 西侧为低速异常, 而东侧为高速异常, 这一近NS向的断裂带与二维剖面的下地壳深断裂在位置上很接近.该地区的几个8级大震均发生在105°E附近, 并且呈一近NS条带.Abstract: The structure of crust and upper mantle in Tianshui-Wudu strong earthquake region is studied by using DSS data from two cross high resolution refraction /wide angle reflection profiles and corresponding fan profiles.The 2-D result shows that the crust can be vertically divided into two layers: upper crust and lower crust.There exists a low velocity layer in the upper crust with velocity difference of 0.3-0.5 km/s.The depth of Moho is about 46-48 km.There is a strong lateral variation in the lower crust along the NE Tianshui-Wudu profile.And along the NW Chengxian-Wushan profile, there are some evidences showing that the Moho and C discontinuities are changed by substances from the deep layer.The 3-D result shows that there is a fault with near NS strike at the depth of 7-11 km near 105°E.The velocities at the two sides of this fault are quite different: low velocity at the west side and high velocity at the east side.This NS fault is very close to the deep fault of 2-D profile.All the large earthquakes occurred near 105°E and formed a NS belt.
-
图 1 研究区地形和剖面位置及地震分布
Fig. 1. Topography of study area, positions of profiles and earthquake distribution
图 2 成县-武山人工地震剖面地震记录截面(SP9)
Fig. 2. Record section of Chengxian-Wushan DSS profile from SP9
图 3 天水-武都剖面(PF-1)SP6炮点射线追踪和走时对比
Fig. 3. Ray tracing and travel time comparison of Tianshui-Wudu DSS profile (PF-1) from SP6
图 4 天水-武都剖面(Pf-1)二维地壳速度结构
Fig. 4. 2-D velocity structure of Tianshui-Wudu DSS pro-file (Pf-1)
图 5 成县-武山剖面(PF-2)二维地壳速度结构
Fig. 5. 2-D velocity structure of Chengxian-Wushan DSS profile (PF-2)
图 6 炮点SP8 (天水-武都测线接收) 扇形地震记录截面
Fig. 6. Fan record section of SP8 observed along Tianshui-Wudu DSS profile
-
[1] Cui, Z. Z., Lu, D. Y., Chen, J. P., et al., 1987. The deepstructural and tectonic features of the crust in Panxi ar-ea. Chinese J. Geophys., 30 (6): 566-580 (in Chinesewith English abstract). http://en.cnki.com.cn/Article_en/CJFDTOTAL-DQWX198706003.htm [2] Li, S. L., Wu, N. Y., Song, Z. L., et al., 1997. Si multaneousinversion of velocity distribution and interface posi-tions. Acta Seismologica Sinica, 19 (4): 383-392 (inChinese with English abstract). http://www.onacademic.com/detail/journal_1000034536375210_0be9.html [3] Li, S. L., Zhang, X. K., Zhang, C. K., et al., 2002. Apreli mi-nary study on the crustal velocity structure of Maqin-Lanzhou-Jingbian by means of deep seismic soundingprofile. Chinese J. Geophys., 45 (2): 210-217 (in Chi-nese with English abstract). http://www.onacademic.com/detail/journal_1000039123943910_5597.html [4] Liu, J. H., Liu, F. T., Wu, H., et al., 1989. Three di men-tional velocity i mages of the crust and upper mantle be-neath north-south zone in China. Chinese J. Geophys., 32 (2): 143-152 (in Chinese with English abstract). [5] Ma, Z. J., Zheng, D. L., 1981. Central axis tectonic belt inChina-Mongolia continent and its seismic activities. Earthquake Research, 4 (4): 421-436 (in Chinese withEnglish abstract). [6] Mo, X. X., Zhao, Z. D., Deng, J. F., et al., 2007. Migration ofthe Tibetan enozoic potassic volcanismandits transitionto eastern basaltic province: I mplications for crustal andmantle flow. Geoscience, 21 (2): 255-264 (in Chinesewith English abstract). http://www.researchgate.net/publication/284543166_Migration_of_the_Tibetan_Cenozoic_potassic_volcanism_and_its_transition_to_eastern_basaltic_province_Implications_for_crustal_and_mantle_flow [7] Um, J., Thurber, C. H., 1987. Afast algorithmfor two-pointseismic ray tracing. Bull. Seism. Soc. Am., 77 (3): 972-986. doi: 10.1785/BSSA0770030972 [8] Wang, J., Li, J. P., 2002. Clinopyroxenes fromCenozoic kam-afugites in Lixian County, West Qinling. Acta Petrolog-ica et Mineralogica, 21 (3): 251-264 (in Chinese withEnglish abstract). http://en.cnki.com.cn/Article_en/CJFDTOTAL-YSKW200203006.htm [9] Xiong, S. B., Teng, J. W., Yin, Z. X., et al., 1986. Explosion seismological study on crust/upper mantle structures ofcentral axis region in Panxi tectonic belt. Chinese J. Geophys., 32 (3): 235-245 (in Chinese with Englishabstract). [10] Xu, X. W., Yu, G. H., Ma, W. T., et al., 2003. Recent tec-tonic motion pattern of central axis tectonic belt inChina continent andits dynamic meaning. Earth Science Frontiers, 10 (Suppl. ): 160-167 (in Chinese with Eng-lish abstract). [11] Yu, X. H., Mo, X. X., Su, S. G., et al., 2003. Discovery andsignificance of Cenozoic volcanic carbonatite in Lixian, Gansu Province. Acta Petrologica Sinica, 19 (1): 105-112 (in Chinese with English abstract). http://en.cnki.com.cn/Article_en/CJFDTOTAL-YSXB200301010.htm [12] Yu, X. H., Zhang, C. F., 1998. Sr-Nd isotope and trace ele-ments geochemical features of the Cenozoic volcanicrocks from West Qinling, Gansu Province. Earth Sci-ence Frontiers, 5 (4): 319-328 (in Chinese with Eng-lish abstract). [13] Zhang, G. W., Cheng, S. Y., Guo, A. L., et al., 2004. Mian-lue paleo-suture on the southern margin of the centralorogenic systemin Qinling-Dabie—With a discussion ofthe assembly of the main part of the continent of China. Geological Bulletin of China, 23 (9-10): 846-853 (inChinese with English abstract). [14] Zhang, S. Q., Wu, L. J., Guo, J. M., et al., 1985. Interpreta-tion of data from Menyuan-Pingliang-Weinan deep seis-mic sounding profile, western China. Chinese J. Geo-phys., 28 (5): 460-472 (in Chinese with English ab-stract). http://en.cnki.com.cn/Article_en/CJFDTOTAL-DQWX198505002.htm [15] Zhou, J. C., Wu, Z. Y., 1989. Seismic tectonics of GansuProvince. In: Ma, X. Y., et al., ed., Lithospheric dy-namics atlas of China. China Cartographic PublishingHouse, Beijing (in Chinese). [16] 崔作舟, 卢德源, 陈纪平, 等, 1987. 攀西地区深部地壳结构与构造. 地球物理学报, 30 (6): 566-580. doi: 10.3321/j.issn:0001-5733.1987.06.003 [17] 李松林, 吴宁远, 宋占龙, 等, 1997. 速度分布和界面位置的联合反演. 地震学报, 19 (4): 383-392. https://www.cnki.com.cn/Article/CJFDTOTAL-DZXB704.005.htm [18] 李松林, 张先康, 张成科, 等, 2002. 玛沁-兰州-靖边地震测深剖面地壳速度结构的初步研究. 地球物理学报, 45 (2): 210-217. doi: 10.3321/j.issn:0001-5733.2002.02.007 [19] 刘建华, 刘福田, 吴华, 等, 1989. 中国南北带地壳和上地幔的三维速度图像. 地球物理学报, 32 (2): 143-152. doi: 10.3321/j.issn:0001-5733.1989.02.003 [20] 莫宣学, 赵志丹, 邓晋福, 等, 2007. 青藏新生代钾质火山活动的时空迁移及向东部玄武岩省的过渡: 壳幔深部物质流的暗示. 现代地质, 21 (2): 255-264. doi: 10.3969/j.issn.1000-8527.2007.02.010 [21] 马宗晋, 郑大林, 1981. 中蒙大陆中轴构造带及其地震活动. 地震研究, 4 (4): 421-436. https://www.cnki.com.cn/Article/CJFDTOTAL-DZYJ198104009.htm [22] 王建, 李建平, 2002. 西秦岭礼县地区新生代钾霞橄黄长岩系的单斜辉石. 岩石矿物学杂志, 21 (3): 251-264. doi: 10.3969/j.issn.1000-6524.2002.03.007 [23] 熊绍柏, 滕吉文, 尹周勋, 等, 1986. 攀西构造带轴部地区地壳与上地幔结构的爆炸地震研究. 地球物理学报, 39: 235-245. doi: 10.3321/j.issn:0001-5733.1986.03.004 [24] 徐锡伟, 于贵华, 马文涛, 等, 2003. 中国大陆中轴构造带地壳最新构造变动样式及其动力学内涵. 地学前缘, 10 (增刊): 160-167. https://www.cnki.com.cn/Article/CJFDTOTAL-DXQY2003S1022.htm [25] 喻学惠, 张春福, 1998. 甘肃西秦岭新生代碱性火山岩的Sr, Nd同位素及微量元素地球化学特征. 地学前缘, 5 (4): 319-328. doi: 10.3321/j.issn:1005-2321.1998.04.015 [26] 喻学惠, 莫宣学, 苏尚国, 等, 2003. 甘肃礼县新生代火山喷发碳酸岩的发现及意义. 岩石学报, 19 (1): 105-112. https://www.cnki.com.cn/Article/CJFDTOTAL-YSXB200301010.htm [27] 张国伟, 程顺有, 郭安林, 等, 2004. 秦岭-大别中央造山系南缘勉略古缝合带的再认识——兼论中国大陆主体的拼合. 地质通报, 23 (9-10): 846-853. https://www.cnki.com.cn/Article/CJFDTOTAL-ZQYD2004Z2004.htm [28] 张少泉, 武利均, 郭建明, 等, 1985. 中国西部地区门源-平凉-渭南地震测深剖面资料分析解释. 地球物理学报, 28 (5): 460-472. doi: 10.3321/j.issn:0001-5733.1985.05.003 [29] 邹谨敞, 吴增益, 1989. 甘肃地震构造. 见: 马杏垣等主编. 中国岩石圈动力学地图集. 北京: 中国地图出版社. -
下载:
点击查看大图
图(8)
计量
- 文章访问数: 3662
- HTML全文浏览量: 103
- PDF下载量: 72
- 被引次数: 0
