汶川地震强震动地面倾斜研究
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摘要
根据三分量强震动传感器水平摆和竖向摆对倾斜的动力响应差异,利用谱比法计算出汶川MS8.0地震中近断层强震动的断层法线方向和平行方向的同震地面倾斜.结果表明,本次地震中强震动观测台处地面倾斜一般小于1°,影响频段主要在0.1Hz以下,发生较大倾斜的台站主要在距地表破裂迹线30km以内,在100km之外或水平向加速度幅值均方根在200cm/s2以下时很少发生0.01°以上的同震地面倾斜.总体上看,上盘区域的倾斜值普遍小于下盘区域,法线方向倾斜值一般大于平行线方向倾斜值.位于前山断裂与中央断裂之间区域的绵竹清平台谱比较低但平缓且频带较宽,可能反应了该区域的运动特殊性,而汶川卧龙台则显示了上盘边缘区域地面倾斜较大.逆冲段与走滑段台站倾斜对比显示,地面倾斜可能受局部场地条件影响较大.
Based on the difference of dynamic response to tilts between horizontal pendulums and vertical pendulum,spectral ratio method was applied to estimate the coseismic surface tilts deduced from strong motion records of the Wenchuan earthquake.The result shows that the ground surface tilts are generally less than 1 degree and mainly appears within 30 km to fault rupture surface traces,while rarely discovered in the area outside 100 km or root-mean-squared horizontal peak accelerations are less than 200 cm/s2.The frequency band influenced by tilts is less than 0.1 Hz.In general,tilts in hanging wall is greater than that in footwall in near fault areas,and tilts in normal direction of fault is less than those in parallel direction.The spectral ratio of Qingping station located between central fault and front mount fault is relatively low and stable,which may imply ae special movement feature of the area.The tilts of Wolong station may be controlled by deformation transition from the hanging wall to laterally stationary area.Comparison of tilts between the stations at reverse and strike slip fault segments showed that the tilts may be influenced by local site condition.
Based on the difference of dynamic response to tilts between horizontal pendulums and vertical pendulum,spectral ratio method was applied to estimate the coseismic surface tilts deduced from strong motion records of the Wenchuan earthquake.The result shows that the ground surface tilts are generally less than 1 degree and mainly appears within 30 km to fault rupture surface traces,while rarely discovered in the area outside 100 km or root-mean-squared horizontal peak accelerations are less than 200 cm/s2.The frequency band influenced by tilts is less than 0.1 Hz.In general,tilts in hanging wall is greater than that in footwall in near fault areas,and tilts in normal direction of fault is less than those in parallel direction.The spectral ratio of Qingping station located between central fault and front mount fault is relatively low and stable,which may imply ae special movement feature of the area.The tilts of Wolong station may be controlled by deformation transition from the hanging wall to laterally stationary area.Comparison of tilts between the stations at reverse and strike slip fault segments showed that the tilts may be influenced by local site condition.
引文
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赵斌,吕品姬,陈志遥,李正媛,谭凯.2010.汶川MS8.0地震同震倾斜应变变化分析[J].大地测量与地球动力学,30(3):17--21.
Boore D M.2001.Effect of baseline corrections on displacements and response spectra for several recordings of the1999Chi-Chi,Taiwan,earthquake[J].Bull Seism Soc Amer,91(5):1199--1211.
Boore D M,Bommer J J.2005.Processing of strong-motion accelerograms:Needs,options and consequences[J].SoilDyn Earthq Eng,25(2):93--115.
Bouchon M,Aki K.1982.Strain,tilt,and rotation anssociated with strong ground motion in the vicinity of earthquakefaults[J].Bull Seism Soc Amer,72(5):1717--1738.
Chanerley A A,Alexander N A.2010.Obtaining estimates of the low-frequency‘fling’instrument tilts and displacementtimeseries using wavelet decomposition[J].Bull Earthq Eng,8(2):231--255.
Graizer V M.1989.On inertial seismometry[J].Izvestiya Earth Physics,25(1):26--29.
Graizer V M.1991.Inertial seismometry methods[J].Izvestiya Earth Physics,27(1):51--61.
Graizer V M.2005.Effect of tilt on strong motion data processing[J].Soil Dyn Earthq Eng,25(3):197--204.
Graizer V M.2006.Tilts in strong ground motion[J].Bull Seism Soc Amer,96(6):2090--2102.
Graizer V M,Kalkan E.2009.Resoponse of pendulums to complex input ground motion[J].Soil Dyn Earthq Eng,28(8):621--631.
Graizer V M.2010.Strong motion recordings and residual displacement:What are we actually recording in strong motionseismology[J].Seism Res Lett,81(4):635--639.
Li X J,Zhou Z H,Yu H Y,Wen R Z,Lu D W,Huang M,Zhou Y N,Cu J W.2008.Strong motion observations andrecordings from the great Wenchuan earthquake[J].Earthq Eng Eng Vib,7(3):235--246.
Trifunac M D,Todorovska M I.2001.A note on the useable dynamic range of accelerographs recording translation[J].Soil Dyn Earthq Eng,21(4):275--286.
Wong H L,Trifunac M D.1977.Effect of cross-axis sensitivity and misalignment on response of mechanical-optical accelerograhps[J].Bull Seism Soc Amer,67(3):929--956.
卢寿德,李小军(主编).2008.汶川8.0级地震未校正加速度记录[M].北京:地震出版社:1--600.
徐锡伟,闻学泽,叶建青,马保起,陈杰,周荣军,何宏林,田勤俭,何玉林,王志才,孙昭民,冯希杰,于贵华,陈立春,陈桂华,于慎鄂,冉勇康,李细光,李陈侠,安艳芬.2008.汶川MS8.0地震地表破裂带及其发震构造[J].地震地质,30(3):894--926.
赵斌,吕品姬,陈志遥,李正媛,谭凯.2010.汶川MS8.0地震同震倾斜应变变化分析[J].大地测量与地球动力学,30(3):17--21.
Boore D M.2001.Effect of baseline corrections on displacements and response spectra for several recordings of the1999Chi-Chi,Taiwan,earthquake[J].Bull Seism Soc Amer,91(5):1199--1211.
Boore D M,Bommer J J.2005.Processing of strong-motion accelerograms:Needs,options and consequences[J].SoilDyn Earthq Eng,25(2):93--115.
Bouchon M,Aki K.1982.Strain,tilt,and rotation anssociated with strong ground motion in the vicinity of earthquakefaults[J].Bull Seism Soc Amer,72(5):1717--1738.
Chanerley A A,Alexander N A.2010.Obtaining estimates of the low-frequency‘fling’instrument tilts and displacementtimeseries using wavelet decomposition[J].Bull Earthq Eng,8(2):231--255.
Graizer V M.1989.On inertial seismometry[J].Izvestiya Earth Physics,25(1):26--29.
Graizer V M.1991.Inertial seismometry methods[J].Izvestiya Earth Physics,27(1):51--61.
Graizer V M.2005.Effect of tilt on strong motion data processing[J].Soil Dyn Earthq Eng,25(3):197--204.
Graizer V M.2006.Tilts in strong ground motion[J].Bull Seism Soc Amer,96(6):2090--2102.
Graizer V M,Kalkan E.2009.Resoponse of pendulums to complex input ground motion[J].Soil Dyn Earthq Eng,28(8):621--631.
Graizer V M.2010.Strong motion recordings and residual displacement:What are we actually recording in strong motionseismology[J].Seism Res Lett,81(4):635--639.
Li X J,Zhou Z H,Yu H Y,Wen R Z,Lu D W,Huang M,Zhou Y N,Cu J W.2008.Strong motion observations andrecordings from the great Wenchuan earthquake[J].Earthq Eng Eng Vib,7(3):235--246.
Trifunac M D,Todorovska M I.2001.A note on the useable dynamic range of accelerographs recording translation[J].Soil Dyn Earthq Eng,21(4):275--286.
Wong H L,Trifunac M D.1977.Effect of cross-axis sensitivity and misalignment on response of mechanical-optical accelerograhps[J].Bull Seism Soc Amer,67(3):929--956.
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