1976年唐山M_S7.8地震余震序列持续时间及对地震危险性分析的意义
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摘要
1976年7月28日唐山MS7.8大地震对唐山及其周边地区造成了重大的人员伤亡和财产损失.主震之后约15小时滦县又发生了MS7.1地震;同年11月15日宁河也发生了MS6.9地震.唐山MS7.8主震后的余震一直持续至今,使该区域至今保持了与主震前相比具有较高的地震活动性.如何估计余震的持续时间,并进一步将余震从主震目录中去除,一直是地震学中所关注的问题.该文通过对数线性回归和理论计算,从不同角度求取并讨论了1976年唐山MS7.8大地震的余震持续时间.结果表明,由对数线性回归计算得到的余震持续时间约为80a.而基于Dieterich的余震触发理论所得到的余震持续时间则与区域剪应力变化率有关.区域剪应力变化率可有几种不同方法求得:①根据剪应力变化率和静态应力降Δτe及地震回复周期tr之间的关系求取应力变化率,该方法所得到的余震持续时间约为70—100a;②Ziv和Rubin对Dieterich的方法进行了修正,给出了通过远场加载速率和断层宽度求取应力变化率,该方法得到的余震持续时间约为80a;③由背景场地震活动性求取远场剪应力速率,可以得到该地区二维分布式的余震持续时间,此方法得到的研究区域内余震持续时间为130—160a.综上,唐山地区余震持续时间约为70—140a,据此,该地区现今所发生的地震仍为MS7.8唐山地震所触发的余震.
The disastrous M S 7.8earthquake in Tangshan,China,on 28July 1976caused great damage and significant casualties.The mainshock was followed by two large aftershocks : the M S 7.1event to the northeast near Luanxian 15hafter the mainshock,and the M S 6.9event on 15November south-west of Tangshan near Ninghe.The aftershock sequence lasts to date,making regional seismic activity around the Tangshan main fault much higher than that of before the mainshock.It is always difficult to accurately determine the duration time of aftershock sequences and identify the aftershocks from main event catalog.In this study,by using theoretical inference and empirical relation,we tried to derive the time length of aftershock sequences of the M S 7.8Tangshan earthquake.The estimated aftershock duration from a log-log regression is about 120years according to the empirical Omori ’ s relation ( Toda et al ) .Based on Dietrich theory,it has been claimed that the aftershock duration is a function of remote shear stressing rate,normal stress acting on the fault plane,and fault frictional constitutive parameters ( Dieterich ) .In general,shear stressing rate could be estimated in three ways : ① Shear stressing rate could be written as a function of static stress drop and a mean earthquake recurrence time ( Dieterich ) . In this case,the time length of aftershock sequences is about 70 — 100years. However,the recurrence time inherits a great deal of uncertainty.② Ziv and Rubin derived a general function between shear stressing rate,fault slip speed and fault width with a consideration that aftershock duration does not scale with mainshock magnitude.Therefore,from Ziv ’ s consideration,the aftershock duration is about 80years.③ Shear stressing rate can also be described as a function of background seismicity rate ( Console et al ) .From this approach,a two-dimensional spatial distribution of the aftershock duration can be obtained,and the resultant time length of aftershock sequences is about 130 — 160years,which is much longer than that given by previous two approaches.The conclusive noting gives that,for the 1976 M S 7.8Tangshan earthquake,the triggered aftershocks would last at least 70years,implying that the current earthquakes which occurred in Tangshan region after the 1976mainshock are the aftershocks of the main event.
The disastrous M S 7.8earthquake in Tangshan,China,on 28July 1976caused great damage and significant casualties.The mainshock was followed by two large aftershocks : the M S 7.1event to the northeast near Luanxian 15hafter the mainshock,and the M S 6.9event on 15November south-west of Tangshan near Ninghe.The aftershock sequence lasts to date,making regional seismic activity around the Tangshan main fault much higher than that of before the mainshock.It is always difficult to accurately determine the duration time of aftershock sequences and identify the aftershocks from main event catalog.In this study,by using theoretical inference and empirical relation,we tried to derive the time length of aftershock sequences of the M S 7.8Tangshan earthquake.The estimated aftershock duration from a log-log regression is about 120years according to the empirical Omori ’ s relation ( Toda et al ) .Based on Dietrich theory,it has been claimed that the aftershock duration is a function of remote shear stressing rate,normal stress acting on the fault plane,and fault frictional constitutive parameters ( Dieterich ) .In general,shear stressing rate could be estimated in three ways : ① Shear stressing rate could be written as a function of static stress drop and a mean earthquake recurrence time ( Dieterich ) . In this case,the time length of aftershock sequences is about 70 — 100years. However,the recurrence time inherits a great deal of uncertainty.② Ziv and Rubin derived a general function between shear stressing rate,fault slip speed and fault width with a consideration that aftershock duration does not scale with mainshock magnitude.Therefore,from Ziv ’ s consideration,the aftershock duration is about 80years.③ Shear stressing rate can also be described as a function of background seismicity rate ( Console et al ) .From this approach,a two-dimensional spatial distribution of the aftershock duration can be obtained,and the resultant time length of aftershock sequences is about 130 — 160years,which is much longer than that given by previous two approaches.The conclusive noting gives that,for the 1976 M S 7.8Tangshan earthquake,the triggered aftershocks would last at least 70years,implying that the current earthquakes which occurred in Tangshan region after the 1976mainshock are the aftershocks of the main event.
引文
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邓起东,徐锡伟,于贵华.1994.中国大陆活动断裂的分区特征及其成因[G]∥中国活动断层研究.北京:地震出版社:1--14.
万永革,沈正康,刁桂苓,王福昌,胡新亮,盛书中.2008.利用小震分布和区域应力场确定大震断层面参数方法及其在唐山地震序列中的应用[J].地球物理学报,51(3):793--804.
尤惠川,徐锡伟,吴建平,何正勤.2002.唐山地震深浅构造关系研究[J].地震地质,24(4):571--582.
王绳祖,张宗淳.2001.地震时空影响域、复发间隔和有效孕震时间[J].中国地震,17(4):364--377.
Beeler N M.2004.Review of the physical basis of laboratory-derived relations for brittle failure and their implications forearthquake occurrence and earthquake nucleation[J].Pure Appl Geophys,161(9--10):1853--1876.
Belardinelli M E,Cocco M,Coutant O,Cotton F.1999.Redistribution of dynamic stress during coseismic ruptures:Evidence for fault interaction and earthquake triggering[J].J Geophys Res,104(B7):14925--14945.
Butler R,Stewart G S,Kanamori H.1979.The July 27,1976Tangshan,China earthquake:A complex sequence ofintraplate events[J].Bull Seism Soc Amer,69(1):207--220.
Chen K H,Nadeau R M,Rau R.2007.Towards a universal rule on the recurrence interval scaling of repeating earth-quakes?[J].Geophys Res Lett,34(16):L16308,doi:10.1029/2007GL030554.
Console R,Murru M,Catalli F.2006.Physical and stochastic models of earthquake clustering[J].Tectonophysics,417(1):141--153.
Cornell C A.1968.Engineering seismic risk analysis[J].Bull Seism Soc Amer,58(5):1583--1606.
Dieterich J H.1979.Modeling of rock friction 2.Simulation of preseismic slip[J].J Geophys Res,84(B5):2169--2175.
Dieterich J H.1981.Constitutive properties of faults with simulated gouge[J].Mechanical Behavior of Crustal Rocks,24:103--120.
Dieterich J H.1992.Earthquake nucleation on faults with rate and state-dependent strength[J].Tectonophysics,211(1--4):115--134.
Dieterich J H.1994.A constitutive law for rate of earthquake production and its application to earthquake clustering[J].J Geophys Res,99(B2):2601--2618.
Gomberg J,Beeler N M,Blanpied M L,Bodin P.1998.Earthquake triggering by transient and static deformations[J].J Geophys Res,103(B10):24411--24426.
Gross S,Bürgmann R.1998.Rate and state of background stress estimated from the aftershocks of the 1989LomaPrieta,California,earthquake[J].J Geophys Res,103(B3):4915--4927.
Gross S,Kisslinger C.1997.Estimating tectonic stress rate and state with Landers aftershocks[J].J Geophys Res,102(B4):7603--7612.
Harris R A,Simpson R W.1998.Suppression of large earthquakes by stress shadows:A comparison of Coulomb andrate-and-state failure[J].J Geophys Res,103(24):439--451.
Helmstetter A,Shaw B E.2009.Afterslip and aftershocks in the rate-and-state friction law[J].J Geophys Res,114:B01308.doi:10.1029/2007JB005077.
Huang B,Yeh Y T.1997.The fault ruptures of the 1976Tangshan earthquake sequence inferred from coseismic crustaldeformation[J].Bull Seism Soc Amer,87(4):1046--1057.
King G C P,Stein R S,Lin J.1994.Static stress changes and the triggering of earthquakes[J].Bull Seism Soc Amer,84(3):935--953.
Knopoff L.1958.Energy release in earthquakes[J].Geophys J,1(1):44--52.
Kramer S L.1996.Geotechnical Earthquake Engineering[M].Singapore:Pearson Education Inc:106--138.
Marone C.1998.Laboratory-derived friction laws and their application to seismic faulting[J].Ann Rev Earth Planet Sci,26(1):643--696.
Parsons T,Velasco A A.2009.On near-source earthquake triggering[J].J Geophys Res,114:B10307.doi:10.1029/2008JB006277,doi:10.1029/2008JB006277.
Rice J R,Gu J C.1983.Earthquake aftereffects and triggered seismic phenomena[J].Pure Appl Geophys,121(2):187--219.
Robinson R,Zhou S.2005.Stress interactions within the Tangshan,China,earthquake sequence of 1976[J].Bull SeismSoc Amer,95(6):2501--2505.
Ruina A.1983.Slip instability and state variable friction laws[J].J Geophys Res,88(10):359--370.
Scholz C H.1998.Earthquakes and friction laws[J].Nature,391:37--42.
Shen Z,Zhao C,Yin A,Li Y,Jackson D D,Fang P,Dong D.2000.Contemporary crustal deformation in east Asiaconstrained by Global Positioning System Measurements[J].J Geophys Res,105(B3):5721--5734.
Stein S,Liu M.2009.Long aftershock sequences within continents and implications for earthquake hazard assessment[J].Nature,462(5):87--89.
Toda S,Stein R S,Reasenberga P A,Dieterich J H,Yoshida A.1998.Stress transferred by the 1995 MW=6.9Kobe,Japan,shock:Effect on aftershocks and future earthquake probabilities[J].J Geophys Res,103(24):543--565.
Wang Q,Zhang P Z,Freymueller J T,Bilham R,Larson K M,Lai X,You X,Niu Z J,Wu J C,Li Y X,Liu J N,YangZ Q,Chen Q Z.2001.Present-day crustal deformation in China constrained by Global Positioning System Measure-ments[J].Science,294(5542):574--577.
Ziv A,Rubin A M.2003.Implications of rate-and-state friction for properties of aftershock sequence:Quasi-staticinherently discrete simulations[J].J Geophys Res,108(B1):2051.
邓起东,徐锡伟,于贵华.1994.中国大陆活动断裂的分区特征及其成因[G]∥中国活动断层研究.北京:地震出版社:1--14.
万永革,沈正康,刁桂苓,王福昌,胡新亮,盛书中.2008.利用小震分布和区域应力场确定大震断层面参数方法及其在唐山地震序列中的应用[J].地球物理学报,51(3):793--804.
尤惠川,徐锡伟,吴建平,何正勤.2002.唐山地震深浅构造关系研究[J].地震地质,24(4):571--582.
王绳祖,张宗淳.2001.地震时空影响域、复发间隔和有效孕震时间[J].中国地震,17(4):364--377.
Beeler N M.2004.Review of the physical basis of laboratory-derived relations for brittle failure and their implications forearthquake occurrence and earthquake nucleation[J].Pure Appl Geophys,161(9--10):1853--1876.
Belardinelli M E,Cocco M,Coutant O,Cotton F.1999.Redistribution of dynamic stress during coseismic ruptures:Evidence for fault interaction and earthquake triggering[J].J Geophys Res,104(B7):14925--14945.
Butler R,Stewart G S,Kanamori H.1979.The July 27,1976Tangshan,China earthquake:A complex sequence ofintraplate events[J].Bull Seism Soc Amer,69(1):207--220.
Chen K H,Nadeau R M,Rau R.2007.Towards a universal rule on the recurrence interval scaling of repeating earth-quakes?[J].Geophys Res Lett,34(16):L16308,doi:10.1029/2007GL030554.
Console R,Murru M,Catalli F.2006.Physical and stochastic models of earthquake clustering[J].Tectonophysics,417(1):141--153.
Cornell C A.1968.Engineering seismic risk analysis[J].Bull Seism Soc Amer,58(5):1583--1606.
Dieterich J H.1979.Modeling of rock friction 2.Simulation of preseismic slip[J].J Geophys Res,84(B5):2169--2175.
Dieterich J H.1981.Constitutive properties of faults with simulated gouge[J].Mechanical Behavior of Crustal Rocks,24:103--120.
Dieterich J H.1992.Earthquake nucleation on faults with rate and state-dependent strength[J].Tectonophysics,211(1--4):115--134.
Dieterich J H.1994.A constitutive law for rate of earthquake production and its application to earthquake clustering[J].J Geophys Res,99(B2):2601--2618.
Gomberg J,Beeler N M,Blanpied M L,Bodin P.1998.Earthquake triggering by transient and static deformations[J].J Geophys Res,103(B10):24411--24426.
Gross S,Bürgmann R.1998.Rate and state of background stress estimated from the aftershocks of the 1989LomaPrieta,California,earthquake[J].J Geophys Res,103(B3):4915--4927.
Gross S,Kisslinger C.1997.Estimating tectonic stress rate and state with Landers aftershocks[J].J Geophys Res,102(B4):7603--7612.
Harris R A,Simpson R W.1998.Suppression of large earthquakes by stress shadows:A comparison of Coulomb andrate-and-state failure[J].J Geophys Res,103(24):439--451.
Helmstetter A,Shaw B E.2009.Afterslip and aftershocks in the rate-and-state friction law[J].J Geophys Res,114:B01308.doi:10.1029/2007JB005077.
Huang B,Yeh Y T.1997.The fault ruptures of the 1976Tangshan earthquake sequence inferred from coseismic crustaldeformation[J].Bull Seism Soc Amer,87(4):1046--1057.
King G C P,Stein R S,Lin J.1994.Static stress changes and the triggering of earthquakes[J].Bull Seism Soc Amer,84(3):935--953.
Knopoff L.1958.Energy release in earthquakes[J].Geophys J,1(1):44--52.
Kramer S L.1996.Geotechnical Earthquake Engineering[M].Singapore:Pearson Education Inc:106--138.
Marone C.1998.Laboratory-derived friction laws and their application to seismic faulting[J].Ann Rev Earth Planet Sci,26(1):643--696.
Parsons T,Velasco A A.2009.On near-source earthquake triggering[J].J Geophys Res,114:B10307.doi:10.1029/2008JB006277,doi:10.1029/2008JB006277.
Rice J R,Gu J C.1983.Earthquake aftereffects and triggered seismic phenomena[J].Pure Appl Geophys,121(2):187--219.
Robinson R,Zhou S.2005.Stress interactions within the Tangshan,China,earthquake sequence of 1976[J].Bull SeismSoc Amer,95(6):2501--2505.
Ruina A.1983.Slip instability and state variable friction laws[J].J Geophys Res,88(10):359--370.
Scholz C H.1998.Earthquakes and friction laws[J].Nature,391:37--42.
Shen Z,Zhao C,Yin A,Li Y,Jackson D D,Fang P,Dong D.2000.Contemporary crustal deformation in east Asiaconstrained by Global Positioning System Measurements[J].J Geophys Res,105(B3):5721--5734.
Stein S,Liu M.2009.Long aftershock sequences within continents and implications for earthquake hazard assessment[J].Nature,462(5):87--89.
Toda S,Stein R S,Reasenberga P A,Dieterich J H,Yoshida A.1998.Stress transferred by the 1995 MW=6.9Kobe,Japan,shock:Effect on aftershocks and future earthquake probabilities[J].J Geophys Res,103(24):543--565.
Wang Q,Zhang P Z,Freymueller J T,Bilham R,Larson K M,Lai X,You X,Niu Z J,Wu J C,Li Y X,Liu J N,YangZ Q,Chen Q Z.2001.Present-day crustal deformation in China constrained by Global Positioning System Measure-ments[J].Science,294(5542):574--577.
Ziv A,Rubin A M.2003.Implications of rate-and-state friction for properties of aftershock sequence:Quasi-staticinherently discrete simulations[J].J Geophys Res,108(B1):2051.
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