张家口地区近年中小地震震源机制解及应力场反演
|
摘要
利用垂直向Pg和Sg波最大振幅比方法,计算得到张家口地区2007—2015年发生的中小地震震源机制解;通过系统聚类分析,研究震源机制分布特征与断裂活动的关系,并采用网格搜索法对张家口地区的现今地壳应力场进行反演,得到了较为精确的张家口地区的构造应力场。结果表明:主压应力轴的走向范围:211°～223°,即NE—SW向;主张应力轴的走向范围:323°～332°,即NNW—SSE向,P轴、T轴都近于水平;两组节面的走向分别为N18°E向和近EW向(N83°E),破裂以水平走滑为主。
Based on the maximum amplitude ratio of vertical Pg and Sg waves,the focal mechanism solutions of medium-small earthquakes in Zhangjiakou area from 2007 to 2015are obtained.According to systematic cluster analysis,the relationship between distribution characteristics of the focal mechanism and fault activity is discussed.In addition,grid search method is employed for inversing the crustal stress field in the Zhangjiakou area.Ultimately,the tectonic stress field in Zhangjiakou area is obtained accurately.The results show that the strike of the principal compressive stress is NE-SW,and ranges from 211to223 degrees.The strike of the principal tensional stress is NNW-SSE with a range of 323～232degrees,which indicates P and T axes are nearly horizontal.The joint strikes of the two groups are N18°E and N83°E respectively.The break mode is dominated by horizontal strike slip.
Based on the maximum amplitude ratio of vertical Pg and Sg waves,the focal mechanism solutions of medium-small earthquakes in Zhangjiakou area from 2007 to 2015are obtained.According to systematic cluster analysis,the relationship between distribution characteristics of the focal mechanism and fault activity is discussed.In addition,grid search method is employed for inversing the crustal stress field in the Zhangjiakou area.Ultimately,the tectonic stress field in Zhangjiakou area is obtained accurately.The results show that the strike of the principal compressive stress is NE-SW,and ranges from 211to223 degrees.The strike of the principal tensional stress is NNW-SSE with a range of 323～232degrees,which indicates P and T axes are nearly horizontal.The joint strikes of the two groups are N18°E and N83°E respectively.The break mode is dominated by horizontal strike slip.
引文
[1]梁尚鸿,李幼铭,束沛镒,等.利用区域地震台网Pg、Sg振幅比资料测定小震震源参数[J].地球物理学报;1984,27(3):247-257.
[2]胡新亮,刁桂苓,马瑾,等.利用数字地震记录的Pg、Sg振幅比资料测定小震震源机制解的可靠性分析[J].地震地质,2004,26(2):347-354.
[3]刁桂苓,于利民,李钦祖,等.震源机制解的系统聚类分析——以海城地震序列为例[J].中国地震,1992,8(3):86-92.
[4]龙海英,高国英,聂晓红,等.乌鲁木齐地区中小地震震源机制解及构造应力场[J].地震,2007,27(3):89-96.
[5]杨文远.张家口市及邻区地震地质基本特征及区域稳定性分析[J].河北地质学院学报,1989,12(4):385-395.
[6]宋津生,魏世英.张家口一宣化盆地地质构造与地震活动的初步分析[J].河北地质学院学报,1979,2(1):56-63.
[7]于新昌,靳雅敏.京西北地区的地震活动性[J].山西地震,1986,13(4):11-15.
[8] Gephart J W,Forsyth D W.AN improved method for determining the regional stress tensor usingfocal mechanism data:Application to the San Fernando earthquake sequence[J].J Geophys Res,1984,89(B11):9 305-9 320.
[9] Michael A J.Determination of stress from slip data:faults and folds[J].J Geophys Res,1984,89(B13):11 517-11 526.
[10]许忠淮,阎明,赵仲和.由多个小地震推断的华北地区构造应力场的方向[J].地震学报,1983,5(3):268-279.
[11]万永革.根据震源机制求解构造应力场的网格搜索法[J].国际地震动态,2012,(6):19.
[12] Wan Y G,Sheng S Z,Huang J C,et al.The Grid Search Algorithm of Tectonic Stress Tensor Based on Focal Mechanism Data and Its Application in the Boundary Zone of China,Vietnam and Laos[J].Journal of Earth Science,2016,27(5):777-785.
[13]万永革.联合采用定性和定量断层资料的应力张量反演方法及在乌鲁木齐地区的应用[J].地球物理学报,2015,58(9):3 144-3 156.
[14]李钦祖.华北地壳应力场的基本特征[J].地球物理学报,1980,23(4):376-388.
[2]胡新亮,刁桂苓,马瑾,等.利用数字地震记录的Pg、Sg振幅比资料测定小震震源机制解的可靠性分析[J].地震地质,2004,26(2):347-354.
[3]刁桂苓,于利民,李钦祖,等.震源机制解的系统聚类分析——以海城地震序列为例[J].中国地震,1992,8(3):86-92.
[4]龙海英,高国英,聂晓红,等.乌鲁木齐地区中小地震震源机制解及构造应力场[J].地震,2007,27(3):89-96.
[5]杨文远.张家口市及邻区地震地质基本特征及区域稳定性分析[J].河北地质学院学报,1989,12(4):385-395.
[6]宋津生,魏世英.张家口一宣化盆地地质构造与地震活动的初步分析[J].河北地质学院学报,1979,2(1):56-63.
[7]于新昌,靳雅敏.京西北地区的地震活动性[J].山西地震,1986,13(4):11-15.
[8] Gephart J W,Forsyth D W.AN improved method for determining the regional stress tensor usingfocal mechanism data:Application to the San Fernando earthquake sequence[J].J Geophys Res,1984,89(B11):9 305-9 320.
[9] Michael A J.Determination of stress from slip data:faults and folds[J].J Geophys Res,1984,89(B13):11 517-11 526.
[10]许忠淮,阎明,赵仲和.由多个小地震推断的华北地区构造应力场的方向[J].地震学报,1983,5(3):268-279.
[11]万永革.根据震源机制求解构造应力场的网格搜索法[J].国际地震动态,2012,(6):19.
[12] Wan Y G,Sheng S Z,Huang J C,et al.The Grid Search Algorithm of Tectonic Stress Tensor Based on Focal Mechanism Data and Its Application in the Boundary Zone of China,Vietnam and Laos[J].Journal of Earth Science,2016,27(5):777-785.
[13]万永革.联合采用定性和定量断层资料的应力张量反演方法及在乌鲁木齐地区的应用[J].地球物理学报,2015,58(9):3 144-3 156.
[14]李钦祖.华北地壳应力场的基本特征[J].地球物理学报,1980,23(4):376-388.