2008年汶川地震震源区横波分裂的变化特征
摘要
对2008年汶川地震序列的横波分裂的时空变化现象进行了研究.通过在横波窗内S波质点运动图的分析,从地震余震区附近台站的近场地震记录中提取了S波分裂的快波偏振方向和快慢波之间的时间延迟.龙门山断裂附近7个台站的S波分裂的结果显示了快波偏振方向的空间分布特征,断裂带东南侧(四川盆地一侧)台站的快波偏振方向总体为北东方向,而在断裂西北侧高原内部的PWU(平武台)则为近东西方向.观测到了快慢波之间到时差的趋势性变化,靠近余震带南端的L5501台的到时差在主震后持续减小,北端PWU台的到时差比主震前明显增大.横波分裂现象主要由台站下方岩层中随应力场方向排列的微裂隙控制,结果显示了主震和余震过程中区域应力场的变化,汶川地震余震活动带南部的应力在主震和余震中得到了释放,地壳应力场在余震带北部集中,导致了PWU台在主震后介质各向异性强度的增强.
引文
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2Crampin S.Calculable fluid-rock interactions.J Geol Soc,1999,156:501—514
3刘堃,张中杰,胡家富,等.中国陆区S波分裂的频带相关性及其意义.中国科学D辑:地球科学,2001,31(2):155—161
4Zhang Z J,Teng J W,Badal J,et al.Construction of regional and local seismic anisotropic structures from wide-angle seismic data:crustal deformation in the southeast of China.J Seismol,2008,doi:10.1007/s10950-008-9124-0
5Crampin S,Volti T,Stefansson R.A successfully stress-forecast earthquake.Geophys J Int,1999,138:F1—F5
6Gao Y,Wang P D,Zheng S H,et al.Temporal changes in shear-wave splitting at an isolated swarm of small earthquakes in1992near Dongfang,Hainan Island,southern China.Geophys J Int,1998,135(1):102—112
7Gao Y,Crampin S.Temporal variations of shear-wave splitting in field and laboratory in China.J Appl Geophys,2003,54:279—287
8Booth D C,Crampin S.Shear-wave polarizations on a curved wavefront at an isotropic free-surface.Geophys J Royal Astron Soc,1985,83:31—45
9Menke W,Brandsdottir B,Jakobsdottir S,et al.Seismic anisotropy in the crust at the mid-Atlantic plate boundary in south-west Ice-land.Geophys J Int,1994,119:783—790
10Chen T C,Booth D C,Crampin S.Shear-wave polarizations near the North Anatolian fault—Ⅲ.Observations of temporal changes.Geophys J Royal Astron Soc,1987,91:287—311
11Liu Y,Crampin S,Main I.Shear-wave anisotropy:spatial and temporal variations in time delays at Parkfield,Central California.Geo-phys J Int,1997,130:771—785
12Peacock S,Crampin S,Booth D C,et al.Shear-wave splitting in the Anza seismic gap,Southern California:temporal variations as possible precursors.J Geophys Res,1988,93:3339—3356
13Silver P G,Chan W W.Shear wave splitting and subcontinental deformation.J Geophys Res,1991,96:16429—16454
14Shih X R,Meyer R P,Schneider J F.An automated,analytical method to determine shear-wave anisotropy.Tectonophysics,1989,165:271—278
15Volti T,Crampin S.A four-year study of shear-wave splitting in Iceland:1.Background and preliminary analysis,in New insights into structural interpretation and modeling.Geol Soc Lond Spec Publ,2003,212:117—133
2Crampin S.Calculable fluid-rock interactions.J Geol Soc,1999,156:501—514
3刘堃,张中杰,胡家富,等.中国陆区S波分裂的频带相关性及其意义.中国科学D辑:地球科学,2001,31(2):155—161
4Zhang Z J,Teng J W,Badal J,et al.Construction of regional and local seismic anisotropic structures from wide-angle seismic data:crustal deformation in the southeast of China.J Seismol,2008,doi:10.1007/s10950-008-9124-0
5Crampin S,Volti T,Stefansson R.A successfully stress-forecast earthquake.Geophys J Int,1999,138:F1—F5
6Gao Y,Wang P D,Zheng S H,et al.Temporal changes in shear-wave splitting at an isolated swarm of small earthquakes in1992near Dongfang,Hainan Island,southern China.Geophys J Int,1998,135(1):102—112
7Gao Y,Crampin S.Temporal variations of shear-wave splitting in field and laboratory in China.J Appl Geophys,2003,54:279—287
8Booth D C,Crampin S.Shear-wave polarizations on a curved wavefront at an isotropic free-surface.Geophys J Royal Astron Soc,1985,83:31—45
9Menke W,Brandsdottir B,Jakobsdottir S,et al.Seismic anisotropy in the crust at the mid-Atlantic plate boundary in south-west Ice-land.Geophys J Int,1994,119:783—790
10Chen T C,Booth D C,Crampin S.Shear-wave polarizations near the North Anatolian fault—Ⅲ.Observations of temporal changes.Geophys J Royal Astron Soc,1987,91:287—311
11Liu Y,Crampin S,Main I.Shear-wave anisotropy:spatial and temporal variations in time delays at Parkfield,Central California.Geo-phys J Int,1997,130:771—785
12Peacock S,Crampin S,Booth D C,et al.Shear-wave splitting in the Anza seismic gap,Southern California:temporal variations as possible precursors.J Geophys Res,1988,93:3339—3356
13Silver P G,Chan W W.Shear wave splitting and subcontinental deformation.J Geophys Res,1991,96:16429—16454
14Shih X R,Meyer R P,Schneider J F.An automated,analytical method to determine shear-wave anisotropy.Tectonophysics,1989,165:271—278
15Volti T,Crampin S.A four-year study of shear-wave splitting in Iceland:1.Background and preliminary analysis,in New insights into structural interpretation and modeling.Geol Soc Lond Spec Publ,2003,212:117—133
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