青岛崂山M_L4.1地震序列应力降变化研究
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摘要
根据Andrews谱积分方法,采用近震源Brune圆盘模型,研究了2003年6月3日青岛崂山ML4.1地震序列破裂过程中应力降变化情况。结果表明,崂山序列主震静应力降为24MPa,动态应力降大约为静态应力降的2.2倍;崂山序列余震应力降普遍低于5MPa,约有80%的余震应力降小于1MPa,显示出与主震断层面有关的余震低应力降现象,这说明主震的破裂与余震破裂过程之间存在明显的差别。这种现象与崂山序列的弱强度衰减一致,表明此次序列的余震属于低能量破裂过程。计算结果显示:①由Andrews谱积分方法得到的小震应力降与震级大小存在一定的相关性;②小应力降事件的静态应力降和动态应力降的比值普遍小于1,未发现明显的应力降之比与Brune应力降之间的关系。
Based on the Andrews's spectra integral method,the near-source Brune model is employed to determine the source parameters,especially stress drop,of the June 5,2003 Laoshan ML=4.1 earthquake sequence in this paper.The result shows that,the static stress drop of the main shock is 24 MPa,and the dynamic stress drop is approximately 2.2 times greater than the static stress drop.The stress drops which are yield by aftershocks are generally lower than 5 MPa,and there are about 80 percent aftershock's stress drops smaller than 1 MPa,which can be treated as low-stress-drop events.These states imply that the low stress is relative to the fault plane,and the rupture process of the main shock is obviously different to that of aftershocks.The low stress phenomenon is consistent with the weakly attenuation of Laoshan sequence activity.It indicates that the aftershock sequence is a rupture procedure with low energy released.Additionally,the result also has shown that,first,stress drop derived from Andrews's method has relation to magnitude;second,the ratios of static to dynamic stress drops of events with low stress drops are generally smaller than 1,and they are independent of Brune stress drops.
Based on the Andrews's spectra integral method,the near-source Brune model is employed to determine the source parameters,especially stress drop,of the June 5,2003 Laoshan ML=4.1 earthquake sequence in this paper.The result shows that,the static stress drop of the main shock is 24 MPa,and the dynamic stress drop is approximately 2.2 times greater than the static stress drop.The stress drops which are yield by aftershocks are generally lower than 5 MPa,and there are about 80 percent aftershock's stress drops smaller than 1 MPa,which can be treated as low-stress-drop events.These states imply that the low stress is relative to the fault plane,and the rupture process of the main shock is obviously different to that of aftershocks.The low stress phenomenon is consistent with the weakly attenuation of Laoshan sequence activity.It indicates that the aftershock sequence is a rupture procedure with low energy released.Additionally,the result also has shown that,first,stress drop derived from Andrews's method has relation to magnitude;second,the ratios of static to dynamic stress drops of events with low stress drops are generally smaller than 1,and they are independent of Brune stress drops.
引文
陈学忠,许向彤,翟文杰.2005.1995年7月20日河北沙城ML4.1地震序列破裂过程中应力变化的研究[J].地震学报,27(3):276～281
李艳娥,陈学忠.2006.1999年11月20日岫岩5.4级地震序列震源参数测定及标度关系分析[J].地震,27(4):59～67
秦嘉政,钱晓东,蔡静观等.2001.武定6.5级地震序列的地震应力降研究[J].地震研究,24(1):17～22
王红霞,郭玉贵.2005.青岛马山-王哥庄断裂带构造活动性分析[J].地球物理进展,20(3):630～634
郑建常,张永仙,潘元生等.2006.青岛崂山地区环境应力与视应力变化分析[J].地震,26(3):123～130
郑治真,胡祚春,郭亚平等.1997.海城地震的前、余震波谱变化[J].地球物理学报,20(2):125～130
Andrews DJ.1991.Objective determination of source parameters and similarity of earthquakes of different size,1986.见:陈步云译.地震震源力学[M].北京:地震出版社,250～259
Brune J N.1970.Tectonic stress and the spectra of seismic shear waves from earthquakes[J].J Geophys Res,75(26):4997～5009
Brune J N.1971.Correction[J].J Geophys Res,76(20):5002
Gibowicz S J.1973.Stress drop and aftershocks[J].Bull SeismSoc Am,63(4):1433～1446
Grant T Lindley.1994.Source parameters of the23April1992Joshua Tree,California,earthquake,its largest foreshock,and aftershocks[J].Bull SeismSoc Am,84(4):1051～1057
Housner G W.1955.Properties of strong ground motion earthquakes[J].Bull SeismSoc Am,45(3):197～218
Keilis-Borok VI.1959.On estimation of the displacement in an earthquake source and of source dimensions[J].AnnGeofisica,12(2):205～2l4
Rogers G C,Ellis R M,Hasegawa HS.1980.The Mcnaughtonlake earthquake of May14,1978[J].Bull SeismSoc Am,70(5):1771～1786
Sammis C G.2001.Repeating earthquakes as low-stress-drop events at a border between locked and creeping fault patches[J].Bull SeismSoc Am,91(3):532～537
Savage J C,Wood M D.1971.The Relation Between Apparent Stress and Stress Drop[J].Bull Seism Soc Am,61(5):1381～1388
李艳娥,陈学忠.2006.1999年11月20日岫岩5.4级地震序列震源参数测定及标度关系分析[J].地震,27(4):59～67
秦嘉政,钱晓东,蔡静观等.2001.武定6.5级地震序列的地震应力降研究[J].地震研究,24(1):17～22
王红霞,郭玉贵.2005.青岛马山-王哥庄断裂带构造活动性分析[J].地球物理进展,20(3):630～634
郑建常,张永仙,潘元生等.2006.青岛崂山地区环境应力与视应力变化分析[J].地震,26(3):123～130
郑治真,胡祚春,郭亚平等.1997.海城地震的前、余震波谱变化[J].地球物理学报,20(2):125～130
Andrews DJ.1991.Objective determination of source parameters and similarity of earthquakes of different size,1986.见:陈步云译.地震震源力学[M].北京:地震出版社,250～259
Brune J N.1970.Tectonic stress and the spectra of seismic shear waves from earthquakes[J].J Geophys Res,75(26):4997～5009
Brune J N.1971.Correction[J].J Geophys Res,76(20):5002
Gibowicz S J.1973.Stress drop and aftershocks[J].Bull SeismSoc Am,63(4):1433～1446
Grant T Lindley.1994.Source parameters of the23April1992Joshua Tree,California,earthquake,its largest foreshock,and aftershocks[J].Bull SeismSoc Am,84(4):1051～1057
Housner G W.1955.Properties of strong ground motion earthquakes[J].Bull SeismSoc Am,45(3):197～218
Keilis-Borok VI.1959.On estimation of the displacement in an earthquake source and of source dimensions[J].AnnGeofisica,12(2):205～2l4
Rogers G C,Ellis R M,Hasegawa HS.1980.The Mcnaughtonlake earthquake of May14,1978[J].Bull SeismSoc Am,70(5):1771～1786
Sammis C G.2001.Repeating earthquakes as low-stress-drop events at a border between locked and creeping fault patches[J].Bull SeismSoc Am,91(3):532～537
Savage J C,Wood M D.1971.The Relation Between Apparent Stress and Stress Drop[J].Bull Seism Soc Am,61(5):1381～1388
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