鄂尔多斯块体周缘地区近期地震活动性与汶川地震应力触发作用的关系
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摘要
采用β统计对汶川地震前后鄂尔多斯块体周缘地区的地震活动率进行了空间扫描分析,并采用JiChen的震源破裂模型计算了汶川地震产生的库仑破裂应力变化,以研究鄂尔多斯块体周缘地区近期地震活动性与汶川地震应力触发作用的关系。结果发现,鄂尔多斯块体西南缘弧形断裂束的南东段与南缘渭河盆地的地震活动率在汶川地震后提高显著,其他区域的地震活动率没有明显提高,库仑破裂应力计算得到两个区域的应力变化范围分别为0.005～0.02 MPa和0.001～0.01 MPa,表明汶川地震有可能触发了这两个区域的地震活动。鄂尔多斯块体东缘的山西断陷带处于库仑破裂应力计算的应力增加区,应力变化范围为0～0.012 MPa,2009年3月以来发生的4次ML4.5～5.2级强有感至微破坏地震有可能被汶川地震所延迟触发。b值、地震能量释放率与空间相关距离SCL等地震活动性参数随时间变化扫描结果显示,该区域可能处于不断趋近高应力累积的状态,其未来大震有可能提前发生。西缘地区为应力减小区,其目前的地震活动处于正常水平状态。
In order to investigate the seismicity possibly triggered by the Wenchuan earthquake,we analyzed the spatially-scanned variation of the seismicity rates in the peripheral areas of the Ordos block prior to and after the Wenchuan earthquake using the β statistics,and calculated the Coulomb stress changes,using the rupture model of Ji(2008).The result shows that the seismicity rate increased obviously both on the southeastern segment of the arcuate fault bundle on the southwestern border and in the Weihe down-faulted basin zone on the south border of the Ordos block,which corresponds to the calculated Coulomb stress change values of 0.0050.02 MPa and 0.0010.01 MPa respectively,suggesting that the seismicity of the two areas may have been triggered by the Wenchuan earthquake.The Shanxi down-faulted lenovo basin zone in the eastern margin of the Ordos block is located in the area of increasing stress with the change value of 00.012 MPa.Four felt earthquakes with magnitudes of ML 4.55.2 have occurred there since the March of 2009,which were possibly delay triggered by the Wenchuan earthquake.The results from the temporal variation of the seismicity parameters of b value,from earthquake energy release rate and SCL show that this region probably tends to accumulate high stress.The future large earthquake may occur in advance than expected.While the stress in the western margin has been decreasing since the Wenchuan earthquake,and the present seismicity level keeps in a normal state.
In order to investigate the seismicity possibly triggered by the Wenchuan earthquake,we analyzed the spatially-scanned variation of the seismicity rates in the peripheral areas of the Ordos block prior to and after the Wenchuan earthquake using the β statistics,and calculated the Coulomb stress changes,using the rupture model of Ji(2008).The result shows that the seismicity rate increased obviously both on the southeastern segment of the arcuate fault bundle on the southwestern border and in the Weihe down-faulted basin zone on the south border of the Ordos block,which corresponds to the calculated Coulomb stress change values of 0.0050.02 MPa and 0.0010.01 MPa respectively,suggesting that the seismicity of the two areas may have been triggered by the Wenchuan earthquake.The Shanxi down-faulted lenovo basin zone in the eastern margin of the Ordos block is located in the area of increasing stress with the change value of 00.012 MPa.Four felt earthquakes with magnitudes of ML 4.55.2 have occurred there since the March of 2009,which were possibly delay triggered by the Wenchuan earthquake.The results from the temporal variation of the seismicity parameters of b value,from earthquake energy release rate and SCL show that this region probably tends to accumulate high stress.The future large earthquake may occur in advance than expected.While the stress in the western margin has been decreasing since the Wenchuan earthquake,and the present seismicity level keeps in a normal state.
引文
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[6]Wan Y G,Shen Z K,Sheng S Z,et al.The influence of 2008Wenchuan earthquake on surrounding faults[J].Acta Seis-mologica Sinica,2009,31(2):128-139(in Chinese).
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[9]Wu X P,Huang Y,Hu J F,et al.Complete Coulombfailurestress changes produced by the Wenchuan Sichuan,Ms8.0earthquake and its strong aftershock swarms[J].Journal ofSeismological Research,2008,31(4):317-323(in Chinese).
[10]Hua W,Chen J L,Li Z X,et al.Stress triggering and theaftershock distribution of the WenchuanM8.0 earthquake[J].Earthquake,2009,29(1):33-39(in Chinese).
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[13]Gomberg J,Bodin P,Reasenberg P A.Observing earth-quakes triggered in the near field by dynamic deformations[J].Bull SeismSoc Am,2003,93(1):118-138.
[14]Ji C.Preli minary result of the May 12,2008Mw7.9 SichuanEarthquake[EB/OL].http:∥www.geol.ucsd.edu/faculty/ji/big_earthquakes/2008/05/12/Sichuan.ht ml,2008.
[15]Okada Y.Internal deformation due to shear and tensile faultsin a half-space[J].Bull Seism Soc Am,1992,82(2):1018-1040.
[16]Harris R A.Introduction to special section:Stress triggers,stress shadows,and i mplications for seismic hazard[J].JGeophys Res,1998,103:24347-24358.
[17]Wiemer S,Wyss M.Mapping the frequency-magnitude dis-tribution in asperities:Ani mprovedtechnique to calculate re-currence ti mes[J].J Geophy Res,1997,102(B7):15115-15128.
[18]Wyss M,Schorlemmer D,Wiemer S.Mapping asperities bymini ma of local recurrence ti me:San Jacinto-Elsinore faultzones[J].J Geophy Res,2000,105(B4):7829-7844.
[19]Tyupkin Y S,Giovambattista R D.Correlation length as anindicator of critical point behavior prior to a large earthquake[J].Earth Planet Sci Lett,2005,230:85-96.
[20]Frohlich C,Davis S D.Single-link cluster analysis as a meth-od to evaluate spatial and temporal properties of earthquakes[J].Geophys J Inter,1990,100:19-32.
[21]Z ller G,Hainzl S,Kurths J.Observation of growing corre-lation length as an indicator for critical point prior to largeearthquakes[J].J Geophys Res,2001,106:2167-2175.
[22]Lei X L,Satoh T.Indicators of critical point behavior priorto rockfailure inferred frompre-failure damage[J].Tectono-physics,2007,431:97-111.
[23]Yi G X,Wen X Z,Fan J,et al.Assessing current faultingbehaviours and seismic risk of the Anninghe-Aemuhe faultzone fromseismicity parameters[J].Acta Seismologica Sini-ca,2004,26(30):294-303(in Chinese).
[24]Xie C D,Zhu Y Q,Lei X L,et al.Multiple sesi micity pa-rameters to investigate critical behavior prior to Wenchuanearthquake and spatial properties for the decay of aftershocks[J].Acta Seismologica Sinica,2010,32(5)(in press)(in Chi-nese).
[25]Scholz C H.The frequency-magnitude relation of microfrac-turingin rock andits relation to earthquakes[J].Bull SeismSoc Am,1968,58:399-415.
[26]Urbancic TI,Trifu CI,Long J M,et al.Space-ti me corre-lations ofbvalues with stress release[J].Pure Appl Geo-phys,1992,139:449-462.
[27]ncel A O,Wyss M.The major asperities of the 1999Mw=7.4 Izmit earthquake defined by the microseismicity of thetwo decades before it[J].Geophys J Int,2000,143:501-506.
[28]Zuniga F R,Wyss M.Most andleast-likelylocations of largeto great earthquakes along the Pacific coast of Mexico esti-mated fromlocal recurrence ti mes based onb-values[J].BullSeismSoc Am,2001,91(6):1717-1728.
[29]Wyss M,Matsumura S.Most likely location of large earth-quakes in the Kanto and Tokai areas,Japan,based onthelo-cal recurrence ti mes[J].Physics of the Earth and PlanetaryInteriors,2002,131:173-184.
[30]Lei X L,Nishizawa O,Kusunose K.Band-li mited heteroge-neous fractal structure of earthquakes and acoustic emissionevents[J].Geophys J Inter,1993,115:79-84.
[31]Lei X L,Masudaa K,Nishizawa O,et al.Detailed analysisof acoustic emission activity during catastrophic fracture offaults in rock[J].J Structural Geology,2004,26:247-258.
[32]Xu X W,Deng Q D,Dong RS,et al.Study on strong earth-quake activity and risk areasin the Shanxi graben system[J].Seismology and Geology,1992,14(4):305-316(in Chi-nese).
[6]万永革,沈正康,盛书中,等.2008年汶川大地震对周围断层的影响[J].地震学报,2009,31(2):128-139.
[9]吴小平,黄雍,胡家富,等.汶川Ms8.0巨震产生的完全库仑破裂应力变化及其强余震群[J].地震研究,2008,31(4):317-323.
[10]华卫,陈章立,李志雄,等.汶川8.0级地震触发与余震活动空间分布研究[J].地震,2009,29(1):33-39.
[11]国家地震局“鄂尔多斯周缘活动断裂系”课题组.鄂尔多斯周缘活动断裂系[M].北京:地震出版社,1988.
[23]易桂喜,闻学泽,范军,等.由地震活动参数分析安宁河—则木河断裂带的现今活动习性及地震危险[J].地震学报,2004,26(30):294-303.
[24]解朝娣,朱元清,Lei X L,等.用地震活动多参数扫描法探测汶川地震孕育的临界信息[J].地震学报,2010,32(5)(待刊).
[32]徐锡伟,邓起东,董瑞树,等.山西地堑系强震的活动规律和危险区段的研究[J].地震地质,1992,14(4):305-316.
[2]Papadopoulos G A.The Athens,Greece earthquake(Ms5.9)of 7 September 1999:An event triggered by the Izmit,Turkey,17 August 1999 earthquake[J]?Bull SeismSoc Am,2002,92(1):312-321.
[3]Prejean S G,Hill D P,Brodsky E E,et al.Remotely trig-gered seismicity onthe United States west coast followingtheM7.9 Denali fault earthquake[J].Bull Seism Soc Am,2004,94(6B):S348-S359.
[4]Husker A L,Brodsky E E.Seismicityin Idaho and Montanatriggered by the Denali Fault earthquake:A windowinto thegeologic context for seismic triggering[J].Bull Seism SocAm,2004,94(6B):S310-S316.
[5]Dreger D S,Kaverina A.Seismic remote sensing for theearthquake source process and near-source strong shaking:Acase study of the October 16,1999 Hector Mine earthquake[J].Geophys Res Lett,2000,27:1941-1944.
[6]Wan Y G,Shen Z K,Sheng S Z,et al.The influence of 2008Wenchuan earthquake on surrounding faults[J].Acta Seis-mologica Sinica,2009,31(2):128-139(in Chinese).
[7]Shan B,Xiong X,Zheng Y,et al.Stress changes on majorfaults caused byMw7.9 Wenchuan earthquake,May 12,2008[J].Sciencein China:Series D,2009,52(5):593-601.
[8]Xie C D,Zhu Y Q,Lei X L,et al.Pattern of stress changeandits effect on seismicity rate caused byMs8.0 Wenchuanearthquake[J].Science in China:Series D,2010,40(6):688-698,doi:10.1007/s11430-010-4025-9.
[9]Wu X P,Huang Y,Hu J F,et al.Complete Coulombfailurestress changes produced by the Wenchuan Sichuan,Ms8.0earthquake and its strong aftershock swarms[J].Journal ofSeismological Research,2008,31(4):317-323(in Chinese).
[10]Hua W,Chen J L,Li Z X,et al.Stress triggering and theaftershock distribution of the WenchuanM8.0 earthquake[J].Earthquake,2009,29(1):33-39(in Chinese).
[11]The Research Group on“Active Fault System Around OrdosBlock”,State Seismological Bureau.Active Fault System A-round Ordos Massif[M].Beijing:Seismological Press,1988(in Chinese).
[12]Mathews M V,Reasenberg P A.Statistical methods for in-vestigating quiescence and other temporal seismicity patterns[J].Pure Appl.Geophys,1988,126:357-72.
[13]Gomberg J,Bodin P,Reasenberg P A.Observing earth-quakes triggered in the near field by dynamic deformations[J].Bull SeismSoc Am,2003,93(1):118-138.
[14]Ji C.Preli minary result of the May 12,2008Mw7.9 SichuanEarthquake[EB/OL].http:∥www.geol.ucsd.edu/faculty/ji/big_earthquakes/2008/05/12/Sichuan.ht ml,2008.
[15]Okada Y.Internal deformation due to shear and tensile faultsin a half-space[J].Bull Seism Soc Am,1992,82(2):1018-1040.
[16]Harris R A.Introduction to special section:Stress triggers,stress shadows,and i mplications for seismic hazard[J].JGeophys Res,1998,103:24347-24358.
[17]Wiemer S,Wyss M.Mapping the frequency-magnitude dis-tribution in asperities:Ani mprovedtechnique to calculate re-currence ti mes[J].J Geophy Res,1997,102(B7):15115-15128.
[18]Wyss M,Schorlemmer D,Wiemer S.Mapping asperities bymini ma of local recurrence ti me:San Jacinto-Elsinore faultzones[J].J Geophy Res,2000,105(B4):7829-7844.
[19]Tyupkin Y S,Giovambattista R D.Correlation length as anindicator of critical point behavior prior to a large earthquake[J].Earth Planet Sci Lett,2005,230:85-96.
[20]Frohlich C,Davis S D.Single-link cluster analysis as a meth-od to evaluate spatial and temporal properties of earthquakes[J].Geophys J Inter,1990,100:19-32.
[21]Z ller G,Hainzl S,Kurths J.Observation of growing corre-lation length as an indicator for critical point prior to largeearthquakes[J].J Geophys Res,2001,106:2167-2175.
[22]Lei X L,Satoh T.Indicators of critical point behavior priorto rockfailure inferred frompre-failure damage[J].Tectono-physics,2007,431:97-111.
[23]Yi G X,Wen X Z,Fan J,et al.Assessing current faultingbehaviours and seismic risk of the Anninghe-Aemuhe faultzone fromseismicity parameters[J].Acta Seismologica Sini-ca,2004,26(30):294-303(in Chinese).
[24]Xie C D,Zhu Y Q,Lei X L,et al.Multiple sesi micity pa-rameters to investigate critical behavior prior to Wenchuanearthquake and spatial properties for the decay of aftershocks[J].Acta Seismologica Sinica,2010,32(5)(in press)(in Chi-nese).
[25]Scholz C H.The frequency-magnitude relation of microfrac-turingin rock andits relation to earthquakes[J].Bull SeismSoc Am,1968,58:399-415.
[26]Urbancic TI,Trifu CI,Long J M,et al.Space-ti me corre-lations ofbvalues with stress release[J].Pure Appl Geo-phys,1992,139:449-462.
[27]ncel A O,Wyss M.The major asperities of the 1999Mw=7.4 Izmit earthquake defined by the microseismicity of thetwo decades before it[J].Geophys J Int,2000,143:501-506.
[28]Zuniga F R,Wyss M.Most andleast-likelylocations of largeto great earthquakes along the Pacific coast of Mexico esti-mated fromlocal recurrence ti mes based onb-values[J].BullSeismSoc Am,2001,91(6):1717-1728.
[29]Wyss M,Matsumura S.Most likely location of large earth-quakes in the Kanto and Tokai areas,Japan,based onthelo-cal recurrence ti mes[J].Physics of the Earth and PlanetaryInteriors,2002,131:173-184.
[30]Lei X L,Nishizawa O,Kusunose K.Band-li mited heteroge-neous fractal structure of earthquakes and acoustic emissionevents[J].Geophys J Inter,1993,115:79-84.
[31]Lei X L,Masudaa K,Nishizawa O,et al.Detailed analysisof acoustic emission activity during catastrophic fracture offaults in rock[J].J Structural Geology,2004,26:247-258.
[32]Xu X W,Deng Q D,Dong RS,et al.Study on strong earth-quake activity and risk areasin the Shanxi graben system[J].Seismology and Geology,1992,14(4):305-316(in Chi-nese).
[6]万永革,沈正康,盛书中,等.2008年汶川大地震对周围断层的影响[J].地震学报,2009,31(2):128-139.
[9]吴小平,黄雍,胡家富,等.汶川Ms8.0巨震产生的完全库仑破裂应力变化及其强余震群[J].地震研究,2008,31(4):317-323.
[10]华卫,陈章立,李志雄,等.汶川8.0级地震触发与余震活动空间分布研究[J].地震,2009,29(1):33-39.
[11]国家地震局“鄂尔多斯周缘活动断裂系”课题组.鄂尔多斯周缘活动断裂系[M].北京:地震出版社,1988.
[23]易桂喜,闻学泽,范军,等.由地震活动参数分析安宁河—则木河断裂带的现今活动习性及地震危险[J].地震学报,2004,26(30):294-303.
[24]解朝娣,朱元清,Lei X L,等.用地震活动多参数扫描法探测汶川地震孕育的临界信息[J].地震学报,2010,32(5)(待刊).
[32]徐锡伟,邓起东,董瑞树,等.山西地堑系强震的活动规律和危险区段的研究[J].地震地质,1992,14(4):305-316.
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