伽师强震群震源特征及震源机制力学成因分析
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摘要
应用改进的主地震相对定位法对 1 997年伽师强震群 3级以上地震进行了精确定位 ,根据较强地震的空间分布和震源机制解推断出伽师震群的发震构造为北北西向的雁行断裂 .根据伽师震群地震的 2 1 77个P波初动方向记录 ,计算了伽师震群的平均震源机制解 .基于Silver的震源模型 ,由震源谱推断了伽师震群主要地震的破裂方向 ,破裂尺度及应力降 .文中最后用右阶雁行断裂的数值模型计算了伽师震群的发震构造所产生的扰动应力场的空间分布图像 ,用其解释了序列地震震源机制的多样性和低应力降现象 ,并认为特定的雁行发震构造与强震的多发性有关 .
WTHT The Jiashi swarm earthquakes have been relocated using the "master event" method. On the basis of the high-precision relative locations and focal mechanisms of the swarm,we infer that a pair of echelon fault segments with NNW strike,right step and right lateral may exist in the swarm area. The average focal mechanism of the swarm area has been inversed from the spatial distribution of the polarities of 2177 P-wave initial motions in the Jaishi swarm. Based on the Silver's seismic source model,the main fracture characteristics of the swarm have been inferred from source spectra. According to the faulting model inferred mainly from the high-precision locations of the swarm earthquakes,we calculated the perturbing stress field generated by the echelon fault segments and explained some swarm source characteristics. WTHZHTH
WTHT The Jiashi swarm earthquakes have been relocated using the "master event" method. On the basis of the high-precision relative locations and focal mechanisms of the swarm,we infer that a pair of echelon fault segments with NNW strike,right step and right lateral may exist in the swarm area. The average focal mechanism of the swarm area has been inversed from the spatial distribution of the polarities of 2177 P-wave initial motions in the Jaishi swarm. Based on the Silver's seismic source model,the main fracture characteristics of the swarm have been inferred from source spectra. According to the faulting model inferred mainly from the high-precision locations of the swarm earthquakes,we calculated the perturbing stress field generated by the echelon fault segments and explained some swarm source characteristics. WTHZHTH
引文
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[2] 刘启元,陈九辉,李顺成等.新疆伽师强震群区三维地壳上地幔S波速度结构及其地震成因的探讨.地球物理学报,2000,43(3):356—365.LIUQiYuan,CHENJiuHui,LIShunCheng,etal.PassiveseismicexperimentinXingjiangJiashistrongearthquakeregionanddiscussiononitsseismicgenesis.ChineseJGeophys.,2000,43(3):356—365.
[3] Deichmann,N .andMariano.Rupturegeometryfromhigh precisionrelativehypocenterlocationsofmicroearthquakecluster.Geophys.J.Int.,1992,110,501—517.
[4] Bott,JacquelineD .J.andWongI.G .The1986CrestedButteearthquakeswarmanditsimplicationsforseismogenesisinCol orade.Bull.Seism.Soc.Am.,1995,85:1495—1500.
[5] 周仕勇,许忠淮,韩 京等.主地震定位法分析及1997年新疆伽师强震群高精度定位.地震学报,1999,21(3):258—265.ZHOUShiYing,XUZhongHuai,HANJing,etal.Analysisonthemastereventmethodandpreciselocationof1997JiashistrongearthquakeswarminwesternChina.ActaSeismologicaSinica(inChinese),1999,21(3):258—265.
[6] 傅承义,陈运泰,祁贵仲.地球物理学基础.北京:科学出版社,1985.FUChengYi,CHENYunTai,QIGuiZhong.Geophysics.Beijing:SciencePress,1985.
[7] Dziewonski,A .M .,Ekstrom,G .,Woodhouse,J.H .,andZwart,G .,Centroid momenttensorsolutionsforAprilJune1990.Phys.EarthPlanet.Inter.,1991,66:133—143.
[8] 许忠淮,汪素云,黄雨蕊等.由大量地震资料推断的我国大陆构造应力场.地球物理学报,1989,32(6):637—647XUZhongHuai,WANGSuYun,HUANGYuRui,etal.ThetectonicstressfieldofChinesecontinentdeducedfromagreatnumberofearthquakes.ChineseJGeophys.,1989,32(6):637—647.
[9] SilverP .Retrievalofsource extentparametersandtheinterpretationofcornerfrequency.Bull.Seism.Soc.Am,1983,73(6):1499—1511.
[10] ShiJ.,KimW .Y .andRichardsP .G .ThecornerfrequenciesandstressdropsofintraplateearthquakesinthenortheasternU niteStates.Bull.Seism.Soc.Am.,1998,88(2):531—542.
[11] SegallP .AndD .D .Pollard,MechanicsofDiscontinuousFaults.J.Geophys.Res.,1980,85(B8):4337—4350.
[12] WallaceR .E .andE .F .Roth.RatesandPatternsofProgressiveDeformation,inParkfieldCholame,CaliforniaEarthquakesofJuneAugust1966,U .S .G .S .,1967,Prof.Paper579,23—40
[13] ScholzC .H .Anexperimentalstudyofthefracturingprocessinbrittlerock.J .Geophys.Res.,1968,73:1447—1454.
[14] 刘琦亮.平面剪切断层系相互作用的研究[硕士论文].北京:中国地震局地球物理研究所,2000.LIUQiLiang.Studyonthedynamicinteractionofaplane shearcracksystem,[Masterthesis]Beijing:InstituteofGeo physics,ChinaSeismologicalBureau,2000.
[15] BelardinelliMariaElinaandMassimoCocco.Redistributionofdynamicstressduringcoseismicruptures:Evidenceforfaultin teractionandearthquaketriggering.J.Geophs.Res.,1999,104(B7):14925—14945.
[16] 林邦慧,李大鹏,白武明等.1988年澜沧—耿马地震的震源特征及其有限元模拟.地球物理学报,1994,37:621—632.LINBangHui,LIDaPeng,BAIWuMing,etal.CharactersoftheseismicsourceandFEMmodelingfor1988LanchangGengmaearthquake.ChineseJGeophys.,1994,37:621—632.
[17] Simpson,R .W .,andP .A .Reasemberg,EarthquakeinducedstaticstresschangesoncentralCaliforniafaults,U .S.Geol.Surv.Prof.Pap.,1994,1550F ,F55F89
[18] DengJ.,andL .R .Sykes.StressevolutioninsouthernCaliforniaandtriggeringofmoderate,small,andmicro sizeearth quakes.J.Geophys.Res.,1997,102(B11):24,411—24,433
[19] Bakun,W .H .Stewart,R .M .BufeC .G .,etal.ImplicationofseismicityforfailureofasectionoftheSanAndreasfault.Bull.Seism.Soc.Amer.,1980,70:185—201.
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