1999年岫岩地震序列研究
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摘要
用相对定位法对1999年11月29日辽宁省岫岩地区5.4级地震序列的前震、主震和余震进行了重新定位。结果是该序列的主震震源位置为40.538°N,123.026°E,深度为6.958km;重新定位的前震震中分布长短轴差别不大,分布在长轴约1.38km,短轴约1.23km,深度为6～11km的震源范围内,其中4级以上前震明显沿NW向分布,主震位于前震震中NW向分布的东南端;重新定位的余震明显沿NW走向分布,长轴约3.26km,短轴约0.79km,深度为5～12km,余震分布范围比前震分布范围大,主要是后期余震活动向SE向发展的结果。分析表明,1999年岫岩地震序列主要沿NW向分布,这个方向与1975年海城地震序列的NW向分布一致,与海城7.3级主震和岫岩5.4级主震震源机制解NW走向节面一致,也与海城 岫岩震区活动构造方向和岫岩主震的等震线长轴方向一致。并认为岫岩5.4级主震可能被前震触发,这为主破裂成核过程提供了一次实例。
The foreshocks, mainshock and aftershocks of the 1999 Xiuyan earthquake sequence have been relocated using a relative location method. The results show that: mainshock is located at the 40.538°N, 123.026°E, and the focal depth is 6.958 km; the difference between the long axis and short one of the epicenter distribution of foreshocks relocated is small, the long axis is about 1.38 km, the short one is about 1.23 km and the depth is between 6～11 km. The epicenter distribution of M_L≥4.0 foreshocks is mainly NW orientation, and mainshock is located at the southeastern end of NW direction. The distribution of aftershocks relocated is nearly NW orientation, the long axis is 3.26 km, the short one is 0.79 km, and the depth is 6～12 km. The NW distribution of the 1999 Xiuyan earthquake sequence is consistent with that of the 1975 Haicheng sequence, it is generally identical to NW strike of nodal plane of focal mechanism of Haicheng and Xiuyan earthquakes, and is correlated to the NW faulting of the epicenter area, and authors consider that it is possible that the occurrence of the Xiuyan mainshock is triggered by foreshock action. It gives one example of the earthquake nucleation process.
The foreshocks, mainshock and aftershocks of the 1999 Xiuyan earthquake sequence have been relocated using a relative location method. The results show that: mainshock is located at the 40.538°N, 123.026°E, and the focal depth is 6.958 km; the difference between the long axis and short one of the epicenter distribution of foreshocks relocated is small, the long axis is about 1.38 km, the short one is about 1.23 km and the depth is between 6～11 km. The epicenter distribution of M_L≥4.0 foreshocks is mainly NW orientation, and mainshock is located at the southeastern end of NW direction. The distribution of aftershocks relocated is nearly NW orientation, the long axis is 3.26 km, the short one is 0.79 km, and the depth is 6～12 km. The NW distribution of the 1999 Xiuyan earthquake sequence is consistent with that of the 1975 Haicheng sequence, it is generally identical to NW strike of nodal plane of focal mechanism of Haicheng and Xiuyan earthquakes, and is correlated to the NW faulting of the epicenter area, and authors consider that it is possible that the occurrence of the Xiuyan mainshock is triggered by foreshock action. It gives one example of the earthquake nucleation process.
引文
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[2] Lupeiling.Foreshocksequence,theimpendingpredictionandseismicityofthe1999Xiuyanearthquake,Liaoningprovince,china[A].AmericanGeohysicalUnion.The2000WesternPacificGeophysicsMeeting(Abstract)[C].TokyoJapenJune,2000.27 30.
[3] 高景春,胡斌,张从珍,等.用相对定位法精细测定张北地震序列的时空参数[J].华北地震科学,1999,17(1):42 46.
[4] 郑秀芬,丁晗,张宏志,等.张北尚义地震序列的空间分布和构造活动性初探[J].地震地磁观测与研究,1998,19(6):25 29.
[5] 周仕勇,许忠淮.主地震定位法分析以及1997年新疆伽师强震群高精度定位[J].地震学报,1999,21(3):258 265.
[6] 杨智娴,陈运泰,张宏志,等.张北 尚义地震序列的重新定位和发震构造[J].地震学报,2002,24(4):366 377.
[7] 佟晓辉,蒋秀琴,吴小兵,等.辽宁省遥测数字地震台网建设特色及在岫岩 海城地震中的应用[J].地震地磁观测与研究,2001,22(2):10 18.
[8] 王安东,谷光裕,黄河,等.1999年11月29日和2000年1月12日辽宁省海城 岫岩5.4和5.1级地震[A].陈棋福,郑大林,高荣胜,等.中国震例[C].(1997～1999年),北京:地震出版社,2003.405 412.
[9] 张萍,蒋秀琴.岫岩地震序列的震源机制解及应力场特征[J].地震地磁观测与研究,2000,22(2):76 83.
[10] OhnakaM.Criticalsizeofthenucleationzoneofearthquakeruptureinferredfromimmediateforeshockactivity[J].JPhysicsEarth,1993,41:45 56.
[11] DouglasAD,BorezaGC,EllsworthWL.Foreshocksequenceofthe1992Landers,California,earthquakeanditsimplicationsfortheearthquakenucleation[J].JGeophysRes,1995,100(B7):9865 9880.
[12] DouglasAD,BorezaGC,EllsworthWL.DetaildobservationsofCaliforniaforeshocksequence:Implicationsfortheearthquakeinitiationprocess[J].JGeophysRes,1996,101(B10):22371 22392.
[13] EllsworthWL,BerozaGC.ObservationoftheSeismicnucleationphaseintheRidgecrest,California,earthquakesequence[J].GeophysResLett,1998,25(3):401 404.
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