中国东西部地区震后形变有效松弛时间研究
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摘要
顾及脆性转换带上的断层蠕动及其深部黏滞流对震后地表位移的影响,对5次大地震的震后垂直位移进行了最小二乘反演,并估计了有效松弛时间。反演结果表明,中国东、西部地震的有效松弛时间差异很大,其中唐山地震的有效松弛时间最长(10.3年),邢台地震次之(4.4年),而西部通海、炉霍、共和等3次地震的有效松弛时间则仅为2年多。究其原因,可能主要是由于中国东部和西部地区上地壳厚度不同以及下地壳、上地幔黏滞系数的差异所致。
The post-seismic deformation,observed by precise leveling,of Ms7.2 Xingtai earthquake in 1966,Ms7.8 Tangshan earthquake in 1976,Ms7.8 Tonghai earthquake in 1970,Ms7.6 Luhuo earthquake in 1973 and Ms7.0 Gonghe earthquake in 1990 each shows typical characteristics of decaying exponential.Considering both the effects of fault creep on the brittle creeping fault zone(BCFZ) and viscous flow below BCFZ,we estimate the effective relaxation time of the five great earthquakes with least-square method.The inversion results show that the difference of relaxation time between eastern and western China is very significant.The effective relaxation time of Tangshan earthquake is the longest(10.3 years),and the time of Xingtai earthquake is the second longest(4.4 years),while the effective relaxation time of Tonghai,Luhuo and Gonghe earthquake are about 2 years only.The significant difference may be caused by different upper crustal depth and viscosity of lower crust and upper mantle between eastern and western China.
The post-seismic deformation,observed by precise leveling,of Ms7.2 Xingtai earthquake in 1966,Ms7.8 Tangshan earthquake in 1976,Ms7.8 Tonghai earthquake in 1970,Ms7.6 Luhuo earthquake in 1973 and Ms7.0 Gonghe earthquake in 1990 each shows typical characteristics of decaying exponential.Considering both the effects of fault creep on the brittle creeping fault zone(BCFZ) and viscous flow below BCFZ,we estimate the effective relaxation time of the five great earthquakes with least-square method.The inversion results show that the difference of relaxation time between eastern and western China is very significant.The effective relaxation time of Tangshan earthquake is the longest(10.3 years),and the time of Xingtai earthquake is the second longest(4.4 years),while the effective relaxation time of Tonghai,Luhuo and Gonghe earthquake are about 2 years only.The significant difference may be caused by different upper crustal depth and viscosity of lower crust and upper mantle between eastern and western China.
引文
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10马宗晋,等.1966—1976中国九大地震[M].北京:地震出版社,1982.(Ma Zhongjin,et al.Nine great earth-quakes occured between 1966 and 1976 in China[M].Bei-jing:Seismological Press,1982)
11 Perfettini H and Avouac J P.Postseismic relaxation drivenby brittle creep:A possible mechanism to reconcile geodet-ic measurements and the decay rate of aftershocks,applica-tion to the Chi-Chi earthquake,Taiwan[J].J GeophysRes.,2004,109,B02304,doi:10.1029/2003JB002488.
12 Perfettini H,Avouac J P and Ruegg J C.Geodetic dis-placements and aftershocks following the 2001 Mw=8.4Peru earthquake:Implication for the mechanics of theearthquake cycle along subduction zones[J].J GeophysRes.,2005,110,B09404,doi:10.1029/2004JB003522.
13 Okada Y.Surface deformation due to shear and tensilefaults in a half-space[J].Bull.Seism.Soc.Amer.,1985,75:1 135-1 154.
2王庆良,等.由1990年共和7.0级地震震后垂直形变求得的地球接介质有效弛豫时间和黏滞系数[J].地震学报,1997,19(5):480-486.(Wang Qingliang,et al.Ef-fective relaxation time and viscosity of theearth inferred fromthe postseismic vertical deformations of the 1990 Ms=7.0Gonghe earthquake[J].Acta Seismologia Sinica,1997,19(5):480-486)
3 Savage J C,Svarc J L and Yu S B.Postseismic relaxationand transient creep[J].J Geophys Res.,2005,110,B11402,doi:10.1029/2005JB003687.
4 Savage J C,Svarc J L and Yu S B.Postseismic relaxationand aftershocks[J].J Geophys Res.,2007,112,B06406,doi:10.1029/2006JB004584.
5 Savage J C and Yu S B.Postearthquake relaxation and after-shock accumulation linearly related after the 2003 M6.5Chengkung,Taiwan,and the 2004 M6.0 Parkfield,Califor-nia,earthquakes[J].Bull Seism Soc Amer.,2007,97(5):1 632-1 645,doi:10.1785/0120070069.
6 Ya Ju Hsu,et al.Rapid afterslip following the 1999 Chi-Chi,Taiwan earthquake[J].Geophysical Research Letters,2002,29(16),10.1029/2002GL014967.
7 Yu Shui-Beih,et al.GPS measurement of postseismic de-formation following the 1999 Chi-Chi,Taiwan,earthquake[J].J Geophys Res.,2003,108(B11):2520,doi:10.1029/2003JB002396.
8孙荀英,刘激扬,王仁.1976年唐山地震震时和震后变形的模拟[J].地球物理学报,1994,37(1):45-55.(Sun Xunying,Liu Jiyang and Wang Ren.The simulation ofcoseismic and postseismic crustal deformation due to Tangs-han earthquake in 1976[J].Chinese Journal Geophysics,1994,37(1):45-55)
9国家地震局.中国大地形变测量成果表[M].北京:测绘出版社,1984.(China Earthquake Administration.Geo-detic displacement measurement reports of China[M].Bei-jing:Surveying and Mapping Press,1984)
10马宗晋,等.1966—1976中国九大地震[M].北京:地震出版社,1982.(Ma Zhongjin,et al.Nine great earth-quakes occured between 1966 and 1976 in China[M].Bei-jing:Seismological Press,1982)
11 Perfettini H and Avouac J P.Postseismic relaxation drivenby brittle creep:A possible mechanism to reconcile geodet-ic measurements and the decay rate of aftershocks,applica-tion to the Chi-Chi earthquake,Taiwan[J].J GeophysRes.,2004,109,B02304,doi:10.1029/2003JB002488.
12 Perfettini H,Avouac J P and Ruegg J C.Geodetic dis-placements and aftershocks following the 2001 Mw=8.4Peru earthquake:Implication for the mechanics of theearthquake cycle along subduction zones[J].J GeophysRes.,2005,110,B09404,doi:10.1029/2004JB003522.
13 Okada Y.Surface deformation due to shear and tensilefaults in a half-space[J].Bull.Seism.Soc.Amer.,1985,75:1 135-1 154.
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