山东长岛震群震源机制解一致性参数时空演化特征
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摘要
借助山东数字地震台网记录到的长岛海域的中小地震波形资料,采用P波初动求取小震震源机制解的方法对研究区内293个ML≥2.0地震进行震源机制反演,并根据震源机制解的资料对长岛地区进行应力张量反演,计算各节点震源机制解一致性参数的时空演化,进而分析长岛地区的应力状态以及震源机制一致性参数的时空演化特征。结果表明:(1)研究区地震震源以走滑型为主,正断型次之,逆断型最少,初步判断发震断层为SE走向的高角度的走滑断层,主要表现为水平运动。(2)通过反演得到研究区区域平均应力场主压应力方向为101.4°,倾角29.1°;中等应力方向为280.8°,倾角60.8°;主张应力方向为11.3°,倾角0.3°,应力张量方差为0.085。(3)震源机制一致性参数的时空分布与中等地震活动有一定的关系,具体表现为:在中强地震发生前,震源机制和应力场一致,震源区附近的构造应力场的作用增强,此时震源机制一致性参数处于较低水平。空间上,研究区震源机制一致性参数整体上呈现出中间低两边高的特点,所有ML≥4.0地震都发生在极低值区或者高值区向低值区变化的过渡带上。
This paper applies the P-wave initial motion to invert the focal mechanisms of 293 earthquakes with ML≥2.0 in the Changdao area,Shandong Province.According to focal mechanism solutions,the stress tensor of Changdao was retrieved to calculate the spatial-temporal evolution of the focal mechanism consistency parameter of each node.We then analyzed the stress condition in the study area and the spatial-temporal characteristics of the consistency parameters.Our results showed that(1)The type of earthquake source was strike-slip type>normal faultingtype>thrust faulting type,and we judged that the seismogenic fault stretches along the SE and exhibits nearly vertical strike-slip movement,which mainly showed horizontal motion.(2)The inversion showed that the azimuth and plunge of the principal compressive stress axis were 101.4°and 29.1°,respectively;280.8°and 60.8°,respectively,for the middle compressive stress axis;and 11.3°and 0.3°,respectively,for the tensile stress axis.The stress tensor variance was 0.085.(3)There was a certain correlation between the time-space distribution of focal mechanism consistency parameters and the seismicity of moderate-strong earthquakes.Before the occurrence of a moderate-strong earthquake,the focal mechanism consistency parameters were relatively low,and the tectonic stress field near the earthquake source zones increased.In general,the focal mechanism consistency parameters of the study area exhibited low values in central part and high values on both edges,and all ML≥4.0 earthquakes occurred in areas with extremely low values and in the transitional areas from high values to low values.
This paper applies the P-wave initial motion to invert the focal mechanisms of 293 earthquakes with ML≥2.0 in the Changdao area,Shandong Province.According to focal mechanism solutions,the stress tensor of Changdao was retrieved to calculate the spatial-temporal evolution of the focal mechanism consistency parameter of each node.We then analyzed the stress condition in the study area and the spatial-temporal characteristics of the consistency parameters.Our results showed that(1)The type of earthquake source was strike-slip type>normal faultingtype>thrust faulting type,and we judged that the seismogenic fault stretches along the SE and exhibits nearly vertical strike-slip movement,which mainly showed horizontal motion.(2)The inversion showed that the azimuth and plunge of the principal compressive stress axis were 101.4°and 29.1°,respectively;280.8°and 60.8°,respectively,for the middle compressive stress axis;and 11.3°and 0.3°,respectively,for the tensile stress axis.The stress tensor variance was 0.085.(3)There was a certain correlation between the time-space distribution of focal mechanism consistency parameters and the seismicity of moderate-strong earthquakes.Before the occurrence of a moderate-strong earthquake,the focal mechanism consistency parameters were relatively low,and the tectonic stress field near the earthquake source zones increased.In general,the focal mechanism consistency parameters of the study area exhibited low values in central part and high values on both edges,and all ML≥4.0 earthquakes occurred in areas with extremely low values and in the transitional areas from high values to low values.
引文
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[8]曹凤娟,张博,杨牧萍,等.营口—海城地区震群的震源机制一致性特征[J].地震工程学报,2016,38(1):4-11.CAO Fengjuan,ZHANG Bo,YANG Muping,et al.Focal Mechanism Consistency Features of Earthquake Swarms in Yingkou—Haicheng Area[J].China Earthquake Engineering Journal,2016,38(1):4-11.
[9]高朝军,张志鹏,夏爱国.2012年新疆新源、和静交界MS6.6地震前后震源机制解一致性参数变化特征[J].地震工程学报,2016,38(1):19-25.GAO Chaojun,ZHANG Zhipeng,XIA Aiguo.Variation Characteristics of Consistency Parameter of Focal Mechanisms before and after the 2012Xinyuan—Hejing MS6.6Earthquake[J].China Earthquake Engineering Journal,2016,38(1):19-25.
[10]苏笃声.长岛地区分维结构变化与区域地震活动关系及短临前兆特征[J].地震研究,1993,16(1):33-40.SU Dusheng.Relationship between the Fractal Structure Variation in Changdao Area and the Areal Seismicity and Short Term and Impending Precursor Feature[J].Journal of Seismological Research,1993,16(1):33-40.
[11]程万正,阮祥,张永久.川滇次级地块震源机制解类型与一致性参数[J].地震学报,2006,28(6):561-573.CHENG Wanzheng,RUAN Xiang,ZHANG Yongjiu.Types of Focal Mechanism Solutions and Parameter Consistency of the Sub Blocks in Sichuan and Yunnan Provinces[J].Acta Seismologica Sinica,2006,28(6):561-573.
[12]泽仁志玛,刁桂苓,李志雄等.千岛岛弧2006年MW8.3地震前震源机制解的一致性变化[J].地震学报,2009,31(4):467-470.ZEREN Zhima,DIAO Guiling,LI Zhixiong,et al.Variation of Focal Mechanism Consistency before 2006Kuril Islands Arc MW9.3 Earthquake[J].Acta Seismologica Sinica,2009,31(4):467-470.
[13]付虹,王绍晋,李丽,等.滇中地区震源机制一致性参数时空分布与强震活动[J].地震研究,2011,34(2):113-118.FU Hong,WANG Shaojin,LI Li,et al.Spatial-Temporal Distribution of the Parameters of the Focal Mechanism and Strong Seismicity in Centeal Yunnan[J].Journal of Seismological Research,2011,34(2):113-118.
[14]张致伟,张永久,程万正,等.汶川8.0级地震序列的小震震源机制及应力场特征[J].地震研究,2010,33(1):43-49.ZHANG Zhiwei,ZHANG Yongjiu,CHENG Wanzheng,et al.Focal Mechanism and Stress Field of Small Earthquakes of the MS8.0 Wenchuan Earthquake Sequence[J].Journal of Seismological Research,2010,33(1):43-49.
[15] ANGELIER J.Determination of the Mean Principal Directions of Stresses for a Given Fault Population[J].Tectonophysics,1979,56(3-4):T17-T26.
[16]MICHAEL A J.Determination of Stress from Slip Data:Faults and Folds[J].Journal of Geophysical Research:Solid Earth,1984,89(B13):11517-11526.
[17]MICHAEL A J.Use of Focal Mechanisms to Determine Stress:A Control Study[J].Journal of Geophysical Research:Solid Earth,1987,92(B1):357-368.
[18] ZHAO L,LUO Y,LIU T Y,et al.Earthquake Focal Mechanisms in Yunnan and Their Inference on the Regional Stress Field[J].Bulletin of the Seismological Society of America,2013,103(4):2498-2507.
[19] LU Z,WYSS M,PULPAN H.Details of Stress Directions in the Alaska Subduction Zone from Fault Plane Solutions[J].Journal of Geophysical Research:Solid Earth,1997,102(B3):5385-5402.
[2] ELLSWORTH W L,XU Z H.Determination of the Stress Tensor from Focal Mechanism Data[J].EOS Trans AGU,1980,61:11-17.
[3] GEPHART J W,FORSYTH D W.An Improved Method for Determining the Regional Stress Tensor Using Earthquake Focal Mechanism Data:Application to the San Fernando Earthquake Sequence[J].Journal of Geophysical Research:Solid Earth,1984,89(B11):9305-9320.
[4]刁桂苓,赵英萍,啜永清,等.大同晚期强余震前震源机制解的一致性特征[J].内陆地震,2004,18(3):202-206.DIAO Guiling,ZHAO Yingping,CHUAI Yongqing,et al.Coherence Characteristics of Focal Mechanism Solutions of Laterperiod Strong Aftershocks[J].Inland Earthquake,2004,18(3):202-206.
[5]黄显良,刘泽民,郁建芳,等.2014年安徽金寨ML3.9震群序列震源一致性研究[J].地震学报,2015,37(6):916-924.HUANG Xianliang,LIU Zemin,YU Jianfang,et al.Consistency Parameters of Focal Mechanism for the ML3.9Jinzhai,Anhui,Earthquake Swarm in 2014[J].Acta Seismologica Sinica,2015,37(6):916-924.
[6]李丽,宋美琴,刘素珍,等.山西地区震源机制一致性参数时空特征分析[J].地震,2015,35(2):43-50.LI Li,SONG Meiqin,LIU Suzhen,et al.Spatial-Temporal Characteristics of the Consistency Parameter of Focal Mechanisms in Shanxi Area[J].Earthquake,2015,35(2):43-50.
[7]李金,周龙泉,龙海英,等.天山地震带(中国境内)震源机制一致性参数的时空特征[J].地震地质,2015,37(3):792-803.LI Jin,ZHOU Longquan,LONG Haiying,et al.Spatial-Temporal Characteristics of the Focal Mechanism Consistency Parameter in Tianshan(with in Chinese Territory)Seismic Zone[J].Seismology and Geology,2015,37(3):792-803.
[8]曹凤娟,张博,杨牧萍,等.营口—海城地区震群的震源机制一致性特征[J].地震工程学报,2016,38(1):4-11.CAO Fengjuan,ZHANG Bo,YANG Muping,et al.Focal Mechanism Consistency Features of Earthquake Swarms in Yingkou—Haicheng Area[J].China Earthquake Engineering Journal,2016,38(1):4-11.
[9]高朝军,张志鹏,夏爱国.2012年新疆新源、和静交界MS6.6地震前后震源机制解一致性参数变化特征[J].地震工程学报,2016,38(1):19-25.GAO Chaojun,ZHANG Zhipeng,XIA Aiguo.Variation Characteristics of Consistency Parameter of Focal Mechanisms before and after the 2012Xinyuan—Hejing MS6.6Earthquake[J].China Earthquake Engineering Journal,2016,38(1):19-25.
[10]苏笃声.长岛地区分维结构变化与区域地震活动关系及短临前兆特征[J].地震研究,1993,16(1):33-40.SU Dusheng.Relationship between the Fractal Structure Variation in Changdao Area and the Areal Seismicity and Short Term and Impending Precursor Feature[J].Journal of Seismological Research,1993,16(1):33-40.
[11]程万正,阮祥,张永久.川滇次级地块震源机制解类型与一致性参数[J].地震学报,2006,28(6):561-573.CHENG Wanzheng,RUAN Xiang,ZHANG Yongjiu.Types of Focal Mechanism Solutions and Parameter Consistency of the Sub Blocks in Sichuan and Yunnan Provinces[J].Acta Seismologica Sinica,2006,28(6):561-573.
[12]泽仁志玛,刁桂苓,李志雄等.千岛岛弧2006年MW8.3地震前震源机制解的一致性变化[J].地震学报,2009,31(4):467-470.ZEREN Zhima,DIAO Guiling,LI Zhixiong,et al.Variation of Focal Mechanism Consistency before 2006Kuril Islands Arc MW9.3 Earthquake[J].Acta Seismologica Sinica,2009,31(4):467-470.
[13]付虹,王绍晋,李丽,等.滇中地区震源机制一致性参数时空分布与强震活动[J].地震研究,2011,34(2):113-118.FU Hong,WANG Shaojin,LI Li,et al.Spatial-Temporal Distribution of the Parameters of the Focal Mechanism and Strong Seismicity in Centeal Yunnan[J].Journal of Seismological Research,2011,34(2):113-118.
[14]张致伟,张永久,程万正,等.汶川8.0级地震序列的小震震源机制及应力场特征[J].地震研究,2010,33(1):43-49.ZHANG Zhiwei,ZHANG Yongjiu,CHENG Wanzheng,et al.Focal Mechanism and Stress Field of Small Earthquakes of the MS8.0 Wenchuan Earthquake Sequence[J].Journal of Seismological Research,2010,33(1):43-49.
[15] ANGELIER J.Determination of the Mean Principal Directions of Stresses for a Given Fault Population[J].Tectonophysics,1979,56(3-4):T17-T26.
[16]MICHAEL A J.Determination of Stress from Slip Data:Faults and Folds[J].Journal of Geophysical Research:Solid Earth,1984,89(B13):11517-11526.
[17]MICHAEL A J.Use of Focal Mechanisms to Determine Stress:A Control Study[J].Journal of Geophysical Research:Solid Earth,1987,92(B1):357-368.
[18] ZHAO L,LUO Y,LIU T Y,et al.Earthquake Focal Mechanisms in Yunnan and Their Inference on the Regional Stress Field[J].Bulletin of the Seismological Society of America,2013,103(4):2498-2507.
[19] LU Z,WYSS M,PULPAN H.Details of Stress Directions in the Alaska Subduction Zone from Fault Plane Solutions[J].Journal of Geophysical Research:Solid Earth,1997,102(B3):5385-5402.