Present tectonic stress field in the Circum-Ordos region deduced from composite focal mechanism method
-
摘要: 利用2007年8月1日至2013年7月21日发生在鄂尔多斯块体周缘的8499个地震的49844个P波初动符号资料,应用综合震源机制解法获得了鄂尔多斯块体周缘0.25°×0.25°的精细地壳应力场,所得应力场结果基本上覆盖了整个鄂尔多斯周缘地区.研究结果表明鄂尔多斯周缘地壳应力场具有以下特征: (1)在环绕鄂尔多斯周缘的银川—吉兰泰断陷带、河套断陷带、岱海断陷带、山西断陷带和渭河断陷带内,综合震源机制解结果以正断层型为主,且综合震源机制解节面走向大体与控制断陷带边界的主要断裂走向相一致,与鄂尔多斯周缘断陷带现今的拉张状态相一致.(2)在鄂尔多斯西南缘,综合震源机制解类型主要为逆冲、逆冲走滑和走滑型,反映了鄂尔多斯块体在西南缘受到青藏高原北东向挤压作用.鄂尔多斯西南缘的应力场的主压应力方向在远处为东向,源自于青藏高原向东北挤压作用,靠近鄂尔多斯块体表现为北东—南西向.(3)P轴方位在局部地区变化较大,但总体呈现规律性变化.P轴方位在鄂尔多斯块体西缘,从南向北,主压应力轴方位更加偏北;在其北缘,由西向东,主压应力轴方位更加偏东.在其南缘和东缘,主压应力轴方位变化不大,大体上平行于控制各断陷带主要断裂走向.P轴倾角在西南缘为近水平,在其周缘各盆地内P轴倾角近直立.(4)T轴方位总体表现为北西—南东向;在鄂尔多斯周缘各断陷带内,T轴走向大体与控制断陷带主要断裂走向以及断陷盆地走向相垂直.(5)鄂尔多斯块体在其西南角受到来自青藏高原的北东向挤压和其东北角深部物质上涌形成的北西—南东向拉张力联合作用,上述作用使得鄂尔多斯块体周缘地区除西南区为挤压区外,其余区域均为剪切拉张区,与先前研究认为鄂尔多斯周缘地区处于引张应力场作用相符合,较好地解释了环鄂尔多斯周缘的断陷盆地构造,亦符合鄂尔多斯块体东西两侧的右旋剪切拉张带以及南北两侧的左旋剪切拉张带的认识.Abstract: With more and more densely seismic stations deployed, a large number of P wave first motion data are observed, which provides us an opportunity to further study the tectonic stress field. In this paper, by using the 49844 P wave first motion polarity data from 8499 earthquakes, which occurred in and around the Ordos block from August 1, 2007 to July 21, 2013, we obtained the precise and detailed stress field in the study area. The composite focal mechanism method was used in this study. By fitting the focal mechanism radiation pattern with P wave polarity data from a large number of earthquakes, this method can obtain the composite focal mechanism in specific grid, and P, B, T axes can be regarded as the principal stress axes of the tectonic stress field. The grid search method is used to fit the focal mechanism radiation pattern, the focal mechanism which has the minimum contradictory ratio was regarded as the optimal solution. The inconsistent ratio is the ratio of the number of P wave first motion polarity which is inconsistent with the focal mechanism and the total number of P wave first motion polarity data, which is weighted by the distance of the earthquake epicenter to the grid point.The study results show that the stress field has the following characteristics: First, in the rift zone of the Yinchuan-Jilantai, Hetao, Daihai, Shanxi, and Weihe around the Ordos block, the main types of composite focal mechanism are normal types, and the strike of the nodal planes is consistent with the strike of the main fault which controls the boundary of the rift zone, that is, in accord with the extension regime in the rift zone around the Ordos block. Second, the main types of the composite focal mechanism are thrust, thrust-strike-slip and strike-slip types in the southwest boundary of the Ordos block, which reflects that the Ordos block is subjected to the northeastward squeezing of the Qinghai-Tibetan plateau. The principal compressive stress direction is eastward in the distance from the southwest boundary of Ordos block, that may derived from the northeastward squeezing of the Qinghai-Tibetan plateau, the principal compressive stress direction turns to NE-SW direction when near the Ordos block. Third, the P-axis azimuth shows generally regular changes except in some local areas. From south to north, the P-axis azimuth becomes more to the north direction in the west boundary of the Ordos block. From west to east, the P-axis turns more to the east direction in the north boundary of the Ordos block. In the south and east boundary of the Ordos block, the P-axis azimuth has small change and is parallel to the main fault's strike which controls the boundary of the rift zone. The dip angle of the P-axis is nearly horizontal in the southwest boundary of the Ordos block, and nearly vertical in the basins around the Ordos block. Fourth, the T-axis azimuth is NW-SE overall. The T-axis is generally perpendicular to the strike of the main fault which controls the boundary of the rift zone and the strike of the basin in the basins around the Ordos block. Fifth, under the NE pushing force from the Qinghai-Tibetan plateau and the NW-SE extension caused by the uplifting of the deep substance, the regions around the Ordos block are shear zones with extensional components, except for the compressional region in the southwest of Ordos-block; these results are consistent with the previous studies which suggest that the Circum-Ordos block is in extensional stress field, also better explain the fault basins surrounding the Ordos block, also accord with the formation of right-lateral shear zones with extension components in its western and eastern boundary and left-lateral shear zones with extensional components in its southern and northern boundary. Overall, we obtained the stress field around the Ordos block, and its general characteristics are consistent with the results of previous study, our results are more consistent with the basin structure around the Ordos block. In this study we focus on the general characteristics of our results. In the further study, we will pay more attention on the inconsistency of our study with the previous study, try to find out the reason and give a reasonable explanation; and pay more attention on the phenomenon of sudden changes in the direction of the stress axis, try to find whether it caused by the inhomogeneity of stress field, or the complex geological structure, or other reasons.
-
Key words:
- Stress field /
- Composite focal mechanism /
- P wave first motion polarity /
- Ordos block
-
-
[1] Aki K. 1966. Earthquake generating stress in Japan for the years 1961 to 1963 obtained by smoothing the first motion radiation patterns. Bull. Earthq. Res. Inst., 44(2): 447-471.
[2] An M J, Li F Q. 1998. Current tectonic stress field of Shanxi garben system. Acta Seismologica Sinica (in Chinese), 20(5): 461-465.
[3] Bu Y F, Zhang Y S, Wan Y G, et al. 2013. The tectonic stress field in Southeastern area of Gansu province deduced from P wave polarity data. China Earthquake Engineering Journal (in Chinese), 35(1): 160-165.
[4] Chen A L, Zhao S L, Lu D H, et al. 1981. The characteristics of tectonic stress field and its relations to seismicity in Xiji-Haiyuan-Guyuan region. Northwestern Seismological Journal (in Chinese), 3(2): 31-38.
[5] Chen X B, Zang S X, Liu Y G, et al. Horizontal movement of Ordos block and the interaction of Ordos block and adjacent blocks. Journal of the Graduate School of the Chinese Academy of Sciences (in Chinese), 22(3): 309-314.
[6] Chen X D, Lin C Y, Zhang X O, et al. 1997. Deformation features of mantle xenoliths from Quaternary basalts in Datong, Shanxi province and their rheological implications. Seismology and Geology (in Chinese), 19(4): 313-320.
[7] Chen X D, Shi L B, Lin C Y. 2001. A research on Quaternary volcanism in north China. Seismology and Geology (in Chinese), 23(4): 564-573.
[8] Cheng E L, Li G F, Chen H C. 1982. On the direction of the maximum compressive principal stress before and after the 1976 Songpan-Pingwu earthquake (M=7.2) of the Sichuan province. Acta Seismologica Sinica (in Chinese), 4(2): 136-148.
[9] Cheng E L, Zhang M F. 1990. Modern NW-NNW tension stress field of rift valley series in Shanxi province. Northwestern Seismological Journal (in Chinese), 12(4): 20-25.
[10] Deng Q D, Wang K L, Wang Y P, et al. 1973. On the tendency of seismicity and their geological set-up of the seismic belt of Shanxi garben. Scientia Gaologica Sinica (in Chinese), (1): 37-47.
[11] Deng Q D, You H C. 1985. Mechanism and structural activity of Ordos basin. //Study on the Modern Crustal Movement (1) (in Chinese). Beijing: Seismological Press, 58-78.
[12] Deng Q D, Cheng S P, Min W, et al. 1999. Discussion on Cenozoic tectonics and dynamics of Ordos block. Journal of Geomechanics (in Chinese), 5(3): 13-21.
[13] Du X X, Shao H C. 1999. Modern tectonic stress field in the Chinese mainland inverted from focal mechanism solutions. Acta Seismologica Sinica (in Chinese), 21(4): 354-360.
[14] Fan J X, Ma J, Diao G L. 2003. Contemporary tectonic stress field around the Ordos fault block inferred from earthquake focal mechanisms. Seismology and Geology (in Chinese), 25(1): 88-99.
[15] Fan T Y, Long C X, Yang Z Y, et al. 2012. Comprehensive modeling on the present crustal stress of China mainland with the viscoelastic spherical shell. Chinese J. Geophys. (in Chinese), 55(4): 1249-1260, doi:10.6038/j.issn.00015733.2012.04.020.
[16] Gao M X. 1979. Current tensile stress field in the block-faulting tectonic areas of North China. Seismology and Geology (in Chinese), 1(2): 1-12.
[17] He Z Q, Ye T L, Ding Z F. 2009. Surface wave tomography for the phase velocity in the northeastern part of North China. Chinese J. Geophys. (in Chinese), 52(5): 1233-1242, doi: 10.3969/j.issn.0001-5733.2009.05.012.
[18] Hu H M. 1987. The characteristic of recent tectonic activity in Shanxi graben system. Earthquake Research in China (in Chinese), 3(4): 67-73.
[19] Hu H M. 1989. The modern tectonic activity and regional stress field of the Ordos block and the graben system around it. Collected Works of Tectonic and Crustal Stress (in Chinese), 3: 60-68.
[20] Hua X W. 1980. Stress variations in the region around Beijing and Tianjin before and after the 1976 Tangshan earthquake. Acta Seismologica Sinica (in Chinese), 2(2): 130-146.
[21] Jiang C S, Wu Z L, Zhuang J C. 2013. ETAS model applied to the earthquake-sequence association (ESA) problem: the Tangshan sequence. Chinese J. Geophys. (in Chinese), 56(9): 2971-2981, doi: 10.6038/cj920130911.
[22] Jiang J L. 1991. Recent tectonic stress field in Shanxi province and its adjacent area. Northwestern Seismological Journal (in Chinese), 13(4): 85-88.
[23] Kan R J, Liu Z Y, Wang S J, et al. 1983. The temporal variation of the orientation of the mean stress axis both before and after the strong Longling earthquake. Chinese J. Geophys. (in Chinese), 26(6): 564-573.
[24] Li M L. 1985. The seismic activity and tectonic around Ordos block. Northwestern Seismological Journal (in Chinese),7(Suppl.): 1-9.
[25] Li M L, Zhao Z J. 1981. Focal mechanism and stress field of Ningxia region. Northwestern Seismological Journal (in Chinese), 3(4): 49-55.
[26] Li M L, Zhao Z J. 1986. Modern tectonic stress field and its relation with seismicities in Ningxia and its neighborhood. Journal of Seismological Research (in Chinese), 9(3): 299-314.
[27] Li Q Z. 1980. General features of the stress field in the crust of North China. Chinese J. Geophys. (in Chinese), 23(3): 376-388.
[28] Li Q Z, Wang Z G, Jia Y N, et al. 1973. Stress field obtained for two regions from weak earthquake data recorded at a single seismic station. Chinese J. Geophys. (in Chinese), 16(1): 49-61.
[29] Liang H Q, Yang Z X, Guo Q L. 1986. Characteristics of present tectonic stress field of Shanxi graben system. Earthquake (in Chinese), (1): 47-52.
[30] Liu W, Zhao X P, An W P, et al. 1993. The crustal stress field in Shanxi province. Earthquake Research in Shanxi (in Chinese), (3): 3-11.
[31] Liu W, Zhao X P, An W P. 1994. Characteristics of stress field in Taiyuan basin. Earthquake Research in Shanxi (in Chinese), (1): 18-24.
[32] Liu W, Meng Y Y, Wang Z L. 1995. Present tectogenesis and characteristics of crustal stress field in Datong basin. Earthquake Research in Shanxi (in Chinese), (1): 7-13.
[33] Liu W, An W P, Zhao X P. 1996. Recent tectonic movement and recent crust stress field in Yuncheng basin. Earthquake Research in Shanxi (in Chinese), (2): 9-13.
[34] Northrup C J, Royden L H, Burchfiel B C. 1995. Motion of the Pacific plate relative to Eurasia and its potential relation to Cenozoic extension along the eastern margin of Eurasia. Geology, 23(8): 719-722.
[35] Peltzer G, Tapponnier P, Zhang Z T, et al. 1985. Neogene and Quaternary faulting in and along the Qinling Shan. Nature, 317(6037): 500-505.
[36] Shao H C, Su G. 1999. Analysis on the seismicity trend around the Ordos block. Northwestern Seismological Journal (in Chinese), 21(4): 395-398.
[37] Shen Z K, Jackson D D, Ge B X. 1996. Crustal deformation across and beyond the Los Angeles basin from geodetic measurements. J. Geophys. Res., 101(B12): 27957-27980.
[38] Shen Z K, Wang M, Gan W J, et al. 2003. Contemporary tectonic strain rate field of Chinese continent and its geodynamic implications. Earth Science Frontiers (China University of Geosciences, Beijing) (in Chinese), 10(Suppl.): 93-100.
[39] Sheng S Z, Wan Y G, Li H G, et al. 2013. Direction of tectonic stress in Nantong city deduced from composite focal mechanism method. Progress in Geophysics (in Chinese), 28(3): 1297-1303, doi: 10.6038/pg20130322.
[40] Su G. 1984. The research of regional seismicity using the moving-block as an unit (The Orduoce block and its seismicity). Northwestern Seismological Journal (in Chinese), 6(2): 1-9.
[41] Tapponnier P, Peltzer G, Le Dain A Y, et al. 1982. Propagating extrusion tectonics in Asia: New insights from simple experiments with plasticine. Geology, 10(12): 611-616.
[42] Tapponnier P, Peltzer G, Armijo R. 1986. On the mechanics of the collision between India and Asia. Geological Society, London, Special Publications, 19(1): 113-157.
[43] The Research Group on Active Fault System around Ordos Massif, SSB. 1988. Active Fault System Around Ordos Massif (in Chinese). Beijing: Seismological Press.
[44] Tian Z Y, Han P, Xu K D. 1992. The Mesozoic-Cenozoic East China rift system. Tectonophysics, 208(1-3): 341-363.
[45] Uyeda S, Kanamori H. 1979. Back-arc opening and the mode of subduction. J. Geophys. Res., 84(B3): 1049-1061.
[46] Wan Y G. 2010. Contemporary tectonic stress field in China. Earthq. Sci., 23(4): 377-386, doi: 10.1007/s11589-010-0735-5.
[47] Wan Y G, Wu Y M, Sheng S Z, et al. 2011. Priliminary result of Taiwan 3-D stress field from P wave polarity data. Chinese J. Geophys. (in Chinese), 54(11): 2809-2818, doi: 10.3969/j.issn.0001-5733.2011.11.011.
[48] Wang S Y, Xu Z H. 1985. Seismo-tectonic stress field in east China. Acta Seismologica Sinica (in Chinese), 7(1): 17-32.
[49] Wang S Y, Xu Z H, Yu Y X, et al. 1996. Inversion for the plate driving forces acting at the boundaries of China and its surroundings. Chinese J. Geophys. (in Chinese), 39(6): 764-771.
[50] Wessel P, Smith W H F. 1995. New version of the generic mapping tools. Eos, Transactions American Geophysical Union, 76(33): 329-329.
[51] Xie F R, Cui X F, Zhao J T, et al. 2004. Regional division of the recent tectonic stress field in China and adjacent areas. Chinese J. Geophys. (in Chinese), 47(4): 654-662, doi: 10.3321/j.issn:0001-5733.2004.04.016.
[52] Xie F R, Shu S B, Dou S Q, et al. 2000. Quaternary tectonic stress field in the region of Haiyuan-Liupanshan fault zone to Yinchuan fault-depression. Seismology and Geology (in Chinese), 22(2): 139-146.
[53] Xu J R, Zhao Z X. 2006. Regional characteristics of the lithospheric stress field and tectonic motions in China and its adjacent areas. Geology in China (in Chinese), 33(4): 782-792.
[54] Xu J R, Zhao Z X, Ishikawa Y. 2008. Regional characteristics of crustal stress field and tectonic motions in and around Chinese mainland. Chinese J. Geophys. (in Chinese), 51(3): 770-781, doi: 10.3321/j.issn:0001-5733.2008.03.018.
[55] Xu L M, Zhou L F, Zhang Y K, et al. 2006. Characteristics and tectonic setting of tectono-stress field of Ordos basin. Geotectonica et Metallogenia (in Chinese), 30(4): 455-462.
[56] Xu M J, Jiang Y J, Zhou C Y. 1996. Preliminary analysis for the space distribution of present stress field in Jiangsu and its adjacent area. Earthquake Research in China (in Chinese), 12(4): 383-388.
[57] Xu X W, Cheng G L, Ma X Y, et al. 1994. Rotation model and dynamics of blocks in North China and its adjacent areas. Earth Science-Journal of China University of Geosciences (in Chinese), 19(2): 129-138.
[58] Xu Z H, Liu Y F, Zhang Y Z, et al. 1979. On the characteristic of direction of the earthquake stress field around the Beijing area. Acta Seismologica Sinica (in Chinese), 1(2): 121-132.
[59] Xu Z H, Yan M, Zhao Z H. 1983. Evaluation of the direction of tectonic stress in North China from recorded data of a large number of small earthquakes. Acta Seismologica Sinica (in Chinese), 5(3): 268-279.
[60] Xu Z H, Wang S Y, Huang Y R, et al. 1987. Direction of mean stress axes in southwestern China deduced from microearthquake data. Chinese J. Geophys. (in Chinese), 30(5): 476-486.
[61] Xu Z H, Wang S Y, Huang Y R, et al. 1989. The tectonic stress field of Chinese continent deduced from a great number of earthquakes. Chinese J. Geophys. (in Chinese), 32(6): 636-647.
[62] Xu Z H, Wang S Y, Gao A J. 2000. Present-day tectonic movement in the northeastern margin of the Qinghai-Xizang (Tibetan) plateau as revealed by earthquake activity. Acta Seismologica Sinica (in Chinese), 22(5): 472-481.
[63] Xu Z H. 2001. A present-day tectonic stress map for eastern Asia region. Acta Seismologica Sinica (in Chinese), 23(5): 492-501.
[64] Xue H Y, Yan J Q. 1984. The contemporary crustal stress field around the Ordos block. Chinese J. Geophys. (in Chinese), 27(2): 144-152.
[65] Yan J Q, Shi Z L, Wang S Y, et al. 1979. Some features of the recent tectonic stress field of China and environs. Acta Seismologica Sinica (in Chinese), 1(1): 9-24.
[66] Zhang D N, Gao L S. 1989. Three dimensional numerical simulation of eastern Asian stress field. Earthquke Research in China (in Chinese), 5(4): 24-33.
[67] Zhang H, Liu X F, Zhao L Y. 2007. Characteristics analysis of the stress field in Gansu and its adjacent region with various focal mechanism solutions. South China Journal of Seismology (in Chinese), 27(2): 33-39.
[68] Zhang H, Gao Y, Shi Y T, et al. 2012. Tectonic stress analysis based on the crustal seismic anisotropy in the northeastern margin of Tibetan plateau. Chinese J. Geophys. (in Chinese), 55(1): 95-104, doi: 10.6038/j.issn.0001-5733.2012.01.009.
[69] Zhang J H, Li Y X, Guo L Q, et al. 2004. Study on present-day deformation and strain field in North China by use of GPS data. Journal of Geodesy and Geodynamics (in Chinese), 24(3): 40-46.
[70] Zhang X, Jiang Z S, Zhang X L, et al. 2002. A seismic negative dislocation inversion of recent horizontal crust movement in North China. Journal of Geodesy and Geodynamics (in Chinese), 22(3): 40-45.
[71] Zhang Y Q, Liao C Z, Shi W, et al. 2006. Neotectonic evolution of the peripheral zones of the Ordos basin and geodynamic setting. Geological Journal of China Universities (in Chinese), 12(3): 285-297.
[72] Zhao Z J, Liu X J. 1990. Seismic activity and local tectonic stress field in Ningxia and nearby regions. Seismology and Geology (in Chinese), 12(1): 31-46.
[73] Zhao Z J, Liu X J, Kang L Y. 2002. Features of focal-mechanism solutions in Ningxia and its neighboring region. Northwestern Seismological Journal (in Chinese), 24(2): 162-166,173.
[74] Zheng X F, Ouyang B, Zhang D N, et al. 2009. Technical system construction of Data Backup Centre for China Seismograph Network and the data support to researches on the Wenchuan earthquake. Chinese J. Geophys. (in Chinese), 52(5): 1412-1417, doi: 10.3969/j.issn.0001-5733.2009.05.031.
[75] Zhu S B, Shi Y L. 2006. Study on the cause of tectonic stress field of Chinese mainland and its adjacent area. Science in China Series D (Earth Science) (in Chinese), 36(12): 1077-1083.
[76] Zoback M L. 1992. First- and second-order patterns of stress in the lithosphere: the world stress map project. J. Geophys. Res., 97(B8): 11703-11728.
-
计量
- 文章访问数:
- PDF下载数:
- 施引文献: 0