analyzing the variation characteristics of stress field in hetao seismic belt using focal mechanism data

doi:10.3969/j.issn.0253-4967.2015.04.008

Abstract

Abstract:

Based on analysis of background of geological tectonic movement and strong earthquake activity, we first obtained the focal mechanism solutions using amplitude ratio and CAP method, then determined the characteristic of average stress field of the study area by inversion of the stress field. On this basis, we selected the source mechanism consistency parameter as the inspection index to obtain the latest changes of stress field in Hetao seismic zone based on its temporal and spatial analysis. Two methods were used in the stress field inversion for comparison and analysis, which are average stress axis tensor and LSIB(Linear stress inversion bootstrap, LSIB). According to the geological tectonic movement and focal mechanism solutions of M_S≥4.0 earthquakes from 1970, we judge that the stress field evolution process of Hetao seismic belt is controlled jointly by vertical difference movement and horizontal shear movement, resulting in that the normal fault and strike-slip fault mechanisms are dominating.Taking into account the station layout of the study area, and in order to ensure the accuracy of calculation, we calculated 224 earthquakes focal mechanism solutions by using amplitude ratio and CAP method, including 164 earthquakes with 2.8≤M_L<3.5, 42 earthquakes with 3.5≤M_L<4.0, and 18 earthquakes with M_L≥4.0; The statistical results on type of focal mechanisms show that, there are 142 strike-slip earthquakes(63.4%), 50 normal fault earthquakes(22.3%)and 32 thrust fault earthquakes(14.3%). In this study period(from 2001 to 2012), most earthquakes had a strike-slip mechanism in Hetao seismic belt, this is one of the inherent characteristics of the stress field.The result of average stress axis tensor and LSIB shows that, the azimuth of maximum compressional stress is 47°～52°, direction is NE-SW; The azimuth of minimum compressional stress is 313°～322°, direction is NW-SE; This indicates that, the stress field characteristics of Hetao seismic belt and its sub-block are not completely consistent. Linhe Basin exhibits coordinated stress field characteristics with Hetao seismic belt, but Hubao Basin exhibits regional differences, direction of compressive stress has clockwise deflection in Baotou area, and the compressive stress direction is NEE. This heteropical character of stress field is also confirmed by horizontal projection distribution of stress axis of historical strong earthquakes and recent moderate and small earthquakes. Since 2003, the temporal sequence curve of consistency parameter of Hetao seismic belt had a downward trend, this change was caused by focal mechanism consistency parameter of Linhe to Wuhai area, which indicates that this structural position is possible to be a priority area for stress accumulation and accelerated release in future.

Key words: Hetao seismic belt, focal mechanism solutions, stress field inversion, consistency parameter

摘要：

从地质构造运动和1970年以来M_S≥4.0地震的震源机制资料分析认为, 垂直差异性和水平剪切运动共同控制河套地震带的应力场, 使其表现出左旋剪切并具有较多的正走滑型断层机制解。根据平均力轴张量计算和自助线性反演结果, 河套地震带的最大主压应力方位为47°～52°, 作用方向NE-SW; 最小主压应力方位313°～322°, 作用方向NW-SE。平均力轴张量计算结果显示, 所辖次级块体的应力场特征并不完全一致, 临河盆地的应力场与河套地震带相协调, 呼包盆地的应力场表现出区域性差异, 压应力方向在包头地区出现顺时针偏转, 作用方向NEE; 这种非均匀性的应力场分布特征可通过历史中强地震和近期中小地震的应力轴水平投影分布图像得到证实。2003年以来, 河套地震带的震源机制一致性参数的时序曲线趋势下降, 这种有序变化更多地是由临河至乌海地区的震源机制一致性引起的, 表明该构造部位有可能成为未来应力高度积累和加速释放的优先场所。

关键词: 河套地震带, 震源机制解, 应力场反演, 一致性参数

CLC Number:

P315.72⁺7

HAN Xiao-ming, LIU Fang, ZHANG Wen-tao, LI Juan, HOU Di. analyzing the variation characteristics of stress field in hetao seismic belt using focal mechanism data[J]. SEISMOLOGY AND GEOLOGY, 2015, 37(4): 1030-1042.

韩晓明, 刘芳, 张文韬, 李娟, 侯迪. 基于震源机制资料分析河套地震带的应力场变化特征[J]. 地震地质, 2015, 37(4): 1030-1042.

References

曹刚. 2001. 内蒙古地震研究［M］. 北京: 地震出版社.
CAO Gang. 2001. Earthquake Research in Inner Mongolia ［M］. Seismological Press, Beijing(in Chinese).
陈顒. 1978. 用震源机制一致性作为描述地震活动性的新参数［J］. 地球物理学报, 21(2): 146—159.
CHEN Yong. 1978. Consistency of focal mechanism as a new parameter in describing seismic activity ［J］. Acta Geophysica Sinica, 21(2): 146—159(in Chinese).
陈运泰, 顾浩鼎. 2008. 震源理论基础(上册)［M］. 北京: 地震出版社.
CHEN Yun-tai, GU Hao-ding. 2008. Fundamentals of Seismic Source Theory, Part 1 ［M］. Seismological Press, Beijing(in Chinese).
程万正, 阮祥, 张永久. 2006. 川滇次级地块震源机制解类型及一致性参数［J］. 地震学报, 28(6): 561—573.
CHENG Wan-zheng, RUAN Xiang, ZHANG Yong-jiu. 2006. Types of focal mechanism solutions and parameter consistency of the sub-blocks in Sichuan and Yunnan Provinces ［J］. Acta Geophysica Sinica, 28(6): 561—573(in Chinese).
邓起东, 冉勇康, 杨晓平, 等. 2007. 中国活动构造图(1:400万)［Z］. 北京: 地震出版社.
DENG Qi-dong, RAN Yong-kang, YANG Xiao-ping, et al. 2007. Map of China Active Faults(1:4 000 000)［Z］. Seismological Press, Beijing(in Chinese).
邓起东, 尤惠川. 1985. 鄂尔多斯周缘断陷盆地带的构造活动特征及其形成机制［A］. 见: 国家地震局地质研究所编. 现代地壳运动研究(1). 北京: 地震出版社.
DENG Qi-dong, YOU Hui-chuan. 1985. Mechanism and structure activity of Ordos Basin ［A］. In: Institute of Geology, CEA(ed). Study on the Modern Crustal Movement(1). Seismological Press, Beijing(in Chinese).
刁桂苓, 王海涛, 高国英, 等. 2005. 伽师强震系列应力场的转向过程［J］. 地球物理学报, 48(5): 1062—1068.
DIAO Gui-ling, WANG Hai-tao, GAO Guo-ying, et al. 2005. A deflection process for stress field of the Jiashi strong earthquake sequence ［J］. Chinese J Geophys, 48(5): 1062—1068(in Chinese).
刁桂苓, 于利明, 宁杰远, 等. 1992.1989年大同震群的破裂特征［J］. 地球物理学报, 36(3): 360—368.
DIAO Gui-ling, YU Li-ming, NING Jie-yuan, et al. 1992. Fracture characteristic of the 1989 Datong earthquake swarm ［J］. Chinese J Geophys, 36(3): 360—368(in Chinese).
范俊喜, 马瑾, 刁桂苓. 2003. 由小震震源机制解得到的鄂尔多斯周边构造应力场［J］. 地震地质, 25(1): 88—99.
FAN Jun-xi, MA Jin, DIAO Gui-ling. 2003. Contemporary tectonic stress field around the Ordos fault block inferred from earthquake focal mechanism ［J］. Seismology And Geology, 25(1): 88—99(in Chinese).
国家地震局"鄂尔多斯周缘活动断裂系"课题组. 1988. 鄂尔多斯周缘活动断裂系［M］. 北京: 地震出版社. 39—76.
The Research Group on "Active Fault System around Ordos Massif". 1988. Active Fault System around Ordos Massif ［M］. Seismological Press, Beijing. 39—76(in Chinese).
粱尚鸿, 李幼铭, 束沛镒, 等. 1984. 利用区域地震台网P、 S波振幅比资料测定小震震源参数［J］. 地球物理学报, 27(3): 249—257.
LIANG Shang-hong, LI You-ming, SHU Pei-yi, et al. 1984. On the determining of source parameters of small earthquakes by using amplitude ratios of P and S from regional network observations ［J］. Chinese J Geophys, 27(3): 249—257(in Chinese).
马瑾, Sherman S I, 郭彦双. 2012. 地震前亚失稳应力状态的识别: 以5°拐折断层变形温度场演化的实验为例［J］. 中国科学(D辑), 42(5): 633—645. doi: 10.1007/s11430-012-4423-2.
MA Jin, Sherman S I, GUO Yan-shuang. 2012. Identification of meta-instable stress state based on experimental study of evolution of the temperature field during stick-slip instability on a 5°bending fault ［J］. Science in China(Ser D), 42(5): 633—645(in Chinese).
盛书中, 万永革, 黄骥超, 等. 2015. 应用综合震源机制解法推断鄂尔多斯块体周缘现今地壳应力场的初步结构［J］. 地球物理学报, 58(2): 436—452. doi: 10.6038/cjg20150208.
SHENG Shu-zhong, WAN Yong-ge, HUANG Ji-chao, et al. 2015. Present tectonic stress field in the cricum-Ordos region deduced from composite focal mechanism method ［J］. Chinese J Geophys, 58(2): 436—452(in Chinese).
万永革. 2011. 中国现代构造应力场［J］. 世界地震译丛, (3): 18—29.
WAN Yong-ge. 2011. Contemporary tectonic stress field in China ［J］. Translated World Seismology, (3): 18—29(in Chinese).
谢富仁, 崔效锋, 赵建涛, 等. 2004. 中国大陆及邻区现代应力场分区特征［J］. 地球物理学报, 47(4): 654—662.
XIE Fu-ren, CUI Xiao-feng, ZHAO Jian-tao, et al. 2004. Regional division of the recent tectonic stress field in China and adjacent area ［J］. Chinese J Geophys, 47(4): 654—662(in Chinese).
谢富仁, 张红艳, 崔效锋, 等. 2011. 中国大陆现代构造应力场与强震活动［J］. 国际地震动态, (1): 4—12.
XIE Fu-ren, ZHANG Hong-yan, CUI Xiao-feng, et al. 2011. The modern tectonic stress field and strong earthquakes in China ［J］. Recent Developments in World Seismology, (1): 4—12(in Chinese).
徐纪人, 赵志新, 石川有三. 2008. 中国大陆地壳应力场与构造运动区域特征研究［J］. 地球物理学报, 51(3): 770—781.
XU Ji-ren, ZHAO Zhi-xin, ISHIKAWA Y. 2008. Regional characteristics of crustal stress field and tectonic motions in and around Chinese mainland ［J］. Chinese J Geophys, 51(3): 770—781(in Chinese).
许忠淮. 1997. 岩石层应力场(讲座)［J］. 地震地磁观测与研究, 18(1): 18—37.
XU Zhong-huai. 1997. Lithosphere stress field(lecture)［J］. Seismological and Geomagnetic Observation and Research, 18(1): 18—37(in Chinese).
钟继茂, 程万正. 2006. 由多个地震震源机制解求川滇地区平均应力场方向［J］. 地震学报, 28(4): 337—346.
ZHONG Ji-mao, CHENG Wan-zheng. 2006. Determination of directions of the mean stress field in Sichuan-Yunnan region from a number of focal mechanism solutions ［J］. Acta Geophysica Sinica, 28(4): 337—346.
Gephart J W, Forsyth D W. 1984. An improved method for determining the regional stress tensor using earthquake focal mechanism data: Application to the San Fernando earthquake sequnence ［J］. J Geophys Res, 89: 9305—9320.
Giardini D, Dziewonski A M, Woodhouse J H. 1985. Centroid-moment tensor solutions for 113 large earthquakes in 1977-1980 ［J］. Phys Earth Planet Inter, 40(4): 259—272.
Michael A J. 1984. Determination of stress from slip data: Faults and folds ［J］. J Geophys Res, 89: 11517—11526.
Zhu L P, Helmberger D V. 1996. Advancement in source estimation techniques using broadband regional seismograms ［J］. Bull Seism Soc Amer, 86(5): 1634—1641.
Zhu L P, Rivera L A. 2002. A note on the dynamic and static displacements from a point source in multilayered media ［J］. Geophys J Int, 148(3): 619—627.

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