自贡市西山公园地形对地震动的影响
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摘要
不规则地形和土层对地震动的影响较大,建(构)筑物选址及其抗震设防必须考虑地形和土层场地的放大效应,以避免或减轻其震害.利用自贡地形台阵记录的汶川地震(M_s8.0)的主震加速度时程,基于传统谱比法分别研究了地形和土层场地对地震动的放大效应.结果表明:(1)地形场地在低频的放大效应不明显,最大仅为1.24;在高频的放大效应较显著,在1～10 Hz频带,山顶的放大效应最大,EW、NS和UD地震动的最大放大效应分别为4.15、3.61和2.41,对应频率分别为5.72 Hz、6.46 Hz和7.44 Hz;在10～20 Hz频带,靠近山顶的山脊上某个地震动分量的放大效应最大,7#台站EW、5#台站NS和7#台站UD地震动的最大放大效应分别为9.10、5.56和2.52,对应频率分别为16.97 Hz、16.91 Hz和17.91 Hz.(2)地形场地的最大放大效应随高度有增加的趋势,且在0.1～10 Hz频带随高度增加的趋势更加明显.(3)土层场地水平向地震动在2 Hz以上开始明显放大,竖向地震动在4 Hz以上开始明显放大;EW、NS和UD地震动的最大放大效应分别为13.4、12.168和6.0,对应频率分别为6.94 Hz、7.55 Hz和10.8 Hz.(4)土层场地与地形场地的最大放大效应相比较,前者显著大于后者,对于水平向地震动,前者至少是后者的3倍以上;对于竖向地震动,前者至少是后者的2.5倍以上.(5)无论是地形场地还是土层场地,地震动的最大放大效应均有水平向大于竖向的特征.
Effects of both soil layer and irregular topography on ground motion are relatively serious, their amplification effects on ground motion must be considered in site selection and seismic fortification of buildings to prevent or mitigate seismic hazard of buildings.Utilizing acceleration time histories of the Wenchuan earthquake's mainshock recorded by Zigong topographic array located in Xishan park, Zigong city, the amplification effects of both soil and site topography on ground motions are analyzed and studied by traditional spectral ratio method. The results are as follows.(1) The amplification effect of topography at low frequency is not obvious, and the maximal amplification factor is 1.24.And the amplification effect of topography at high frequency is significant.In the frequency range from 1 Hz to 10 Hz, the amplification factor of hilltop is maximal, the maximal amplification factors of EW, NS and UD ground motions on hilltop are 4.15, 3.61 and 2.41 respectively, the corresponding frequencies are 5.72 Hz, 6.46 Hz and 7.44 Hz respectively.In the frequency range from 10 Hz to 20 Hz, the amplification factor of some components of ground motions on ridges in the vicinity of hilltop is maximal, the maximal amplification factors of EW (7 # ) , NS (5 # ) and UD (7 # ) ground motions of ridges in the vicinity of hilltop are 9.10, 5.56 and 2.52 respectively, corresponding frequencies are 16.97 Hz, 16.91 Hz and 17.91 Hz respectively.(2) The maximal topographic amplification factors of ground motions tend to increase with elevation of the hill, and the trend in frequency range from 0.1 Hz to 10 Hz is more obvious.(3) The amplification effect of horizontal ground motion at soil sites is obvious when frequency is more than 2 Hz, and that of vertical ground motion is obvious when frequency is more than 4 Hz.The maximal amplification factors of EW, NS and UD ground motions of soil site are 13.4, 12.168 and 6.0 respectively, corresponding frequencies are 6.94 Hz, 7.55 Hz and 10.8 Hz respectively.(4) The maximal amplification factors of soil site are more than ones of topographic sites.For horizontal ground motions, the former is 3 times the latter at lowest.For vertical ground motions, the former is 2.5 times the latter at lowest.(5) For both topographic site and soil site, the maximal amplification factors of horizontal ground motions are more than the ones of vertical ground motions.
Effects of both soil layer and irregular topography on ground motion are relatively serious, their amplification effects on ground motion must be considered in site selection and seismic fortification of buildings to prevent or mitigate seismic hazard of buildings.Utilizing acceleration time histories of the Wenchuan earthquake's mainshock recorded by Zigong topographic array located in Xishan park, Zigong city, the amplification effects of both soil and site topography on ground motions are analyzed and studied by traditional spectral ratio method. The results are as follows.(1) The amplification effect of topography at low frequency is not obvious, and the maximal amplification factor is 1.24.And the amplification effect of topography at high frequency is significant.In the frequency range from 1 Hz to 10 Hz, the amplification factor of hilltop is maximal, the maximal amplification factors of EW, NS and UD ground motions on hilltop are 4.15, 3.61 and 2.41 respectively, the corresponding frequencies are 5.72 Hz, 6.46 Hz and 7.44 Hz respectively.In the frequency range from 10 Hz to 20 Hz, the amplification factor of some components of ground motions on ridges in the vicinity of hilltop is maximal, the maximal amplification factors of EW (7 # ) , NS (5 # ) and UD (7 # ) ground motions of ridges in the vicinity of hilltop are 9.10, 5.56 and 2.52 respectively, corresponding frequencies are 16.97 Hz, 16.91 Hz and 17.91 Hz respectively.(2) The maximal topographic amplification factors of ground motions tend to increase with elevation of the hill, and the trend in frequency range from 0.1 Hz to 10 Hz is more obvious.(3) The amplification effect of horizontal ground motion at soil sites is obvious when frequency is more than 2 Hz, and that of vertical ground motion is obvious when frequency is more than 4 Hz.The maximal amplification factors of EW, NS and UD ground motions of soil site are 13.4, 12.168 and 6.0 respectively, corresponding frequencies are 6.94 Hz, 7.55 Hz and 10.8 Hz respectively.(4) The maximal amplification factors of soil site are more than ones of topographic sites.For horizontal ground motions, the former is 3 times the latter at lowest.For vertical ground motions, the former is 2.5 times the latter at lowest.(5) For both topographic site and soil site, the maximal amplification factors of horizontal ground motions are more than the ones of vertical ground motions.
引文
[1] 王钟琦,谢君斐,石兆吉.地震工程地质导论.北京:地震出版社,1983 Wang Z Q,Xie J F,Shi Z J.Introduction of Earthquake Engineering Geology(in Chinese).Beijing:Seismological Press,1983
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[5] Celebi M.Topographical and geological amplification-case studies and engineering implications.Structural Safety,1991,10:199～217
[6] Faccioli E.Seismic amplification in the presence of geological and topographic irregularities.Proceedings of the Second International Conference on Recent Advances in Geotechnical Earthquake Engineering and Soil Dynamics,St.Louis,Missouri,1991,2:1779～1797
[7] Finn W D L.Geotechnical engineering aspects of microzonation.Proceedings of 4~(th)international conference on microzonation,Earthquake Engineering Research Institute,Stanford University,Palo Alto,California,1991,1:199～ 259
[8] Bard P-Y.Effects of surface geology on ground motion:recent results and remaining issues.In:Duma Editor.Proceedings of 10~(th)European Conference on Earthquake Engineering,Vienna,Austria,1995． 305～323
[9] Borcherdt R D.Effects of local geology on ground motion near San Francisco Bay.Bull.Seism.Soc.Am.,1970,60:29～61
[10] Andrews D J.Objective determination of source parameters and similarity of earthquakes of different size.In:Das S,Boatwright J,Scholz C H Eds.Earthquake Source Mechanics.American Geophysical Union,Washington,D.C.,1986． 259～268
[11] Hartzell S H,Carver D L,King K W.Initial investigation of site and topographic effects at Robinwood Ridge,California.Bull.Seism.Soc.Am.,1994,84(5) :1336～1349
[12] 徐锡伟,闻学泽,叶建青等.汶川M_s8． 0地震地表破裂带及其发震构造.地震地质,2008,30(3) :597～629 Xu X W,Wen X Z,Ye J Q,et al.The M_s8． 0 Wenchuan earthquake surface rupture and its seismogenic structure.Seismology and Geology(in Chinese),2008,30(3) :597～629
[13] 邓起东.关于四川汶川8． 0级地震的思考.地震地质,2008,30(4) :811～827 Deng Q D.Some thoughts on the Ms8． 0 Wenchuan,Sichuan earthquake.Seismology and Geology(in Chinese),2008,30(4) :811～827
[14] Field E H,Jacob K H.A comparison and test of various siteresponse estimation techniques,including three that are not reference-site dependent.Bull.Seism.Soc.Am.,1995,85(4) :1127～1143
[15] 杨秋梅.自贡市城市环境地质分区评价[硕士论文].成都:成都理工大学,2008 Yang Q M.The divisional evaluation of urban environmental geology[Master thesis](in Chinese).Chengdu:Chengdu University of Technology,2008
[16] 徐争强,杨秋梅,张成江等.论四川自贡市的城市地质环境.四川地质学报,2008,28(4) :313～315 Xu Z Q,Yang Q M,Zhang C J,et al.On urban geological environment in Zigong city.Acta Geologica Sichuan(in Chinese),2008,28(4) :313～315
[17] 杨涛,邓贵荣,何强.自贡地区第四系地层动力特性及地震反应分析.路基工程,2003,3～7 Yang T,Deng G R,He Q.Analysis of dynamic properties and seismic response of the Quaternary strata.Subgrade Engineering(in Chinese),2003,3～7
[2] 周锡元,王广军,苏经宇.场地·地基·设计地震.北京:地震出版社,1991 Zhou X Y,Wang G J,Su J Y.Site,Foundation,Design Earthquake(in Chinese).Beijing:Seismological Press,1991
[3] Geli L,Bard P Y,Jullien B.The effect of topography on earthquake ground motion:a review and new results.Bull.Seism.Soc.Am.1988,78:42～63
[4] Celebi M.Topographical and geological amplifications determined from strong-motion and aftershock records of the 3 March 1985 Chile earthquake.Bull.Seism.Soc.Am.1987,77(4) :1147～1167
[5] Celebi M.Topographical and geological amplification-case studies and engineering implications.Structural Safety,1991,10:199～217
[6] Faccioli E.Seismic amplification in the presence of geological and topographic irregularities.Proceedings of the Second International Conference on Recent Advances in Geotechnical Earthquake Engineering and Soil Dynamics,St.Louis,Missouri,1991,2:1779～1797
[7] Finn W D L.Geotechnical engineering aspects of microzonation.Proceedings of 4~(th)international conference on microzonation,Earthquake Engineering Research Institute,Stanford University,Palo Alto,California,1991,1:199～ 259
[8] Bard P-Y.Effects of surface geology on ground motion:recent results and remaining issues.In:Duma Editor.Proceedings of 10~(th)European Conference on Earthquake Engineering,Vienna,Austria,1995． 305～323
[9] Borcherdt R D.Effects of local geology on ground motion near San Francisco Bay.Bull.Seism.Soc.Am.,1970,60:29～61
[10] Andrews D J.Objective determination of source parameters and similarity of earthquakes of different size.In:Das S,Boatwright J,Scholz C H Eds.Earthquake Source Mechanics.American Geophysical Union,Washington,D.C.,1986． 259～268
[11] Hartzell S H,Carver D L,King K W.Initial investigation of site and topographic effects at Robinwood Ridge,California.Bull.Seism.Soc.Am.,1994,84(5) :1336～1349
[12] 徐锡伟,闻学泽,叶建青等.汶川M_s8． 0地震地表破裂带及其发震构造.地震地质,2008,30(3) :597～629 Xu X W,Wen X Z,Ye J Q,et al.The M_s8． 0 Wenchuan earthquake surface rupture and its seismogenic structure.Seismology and Geology(in Chinese),2008,30(3) :597～629
[13] 邓起东.关于四川汶川8． 0级地震的思考.地震地质,2008,30(4) :811～827 Deng Q D.Some thoughts on the Ms8． 0 Wenchuan,Sichuan earthquake.Seismology and Geology(in Chinese),2008,30(4) :811～827
[14] Field E H,Jacob K H.A comparison and test of various siteresponse estimation techniques,including three that are not reference-site dependent.Bull.Seism.Soc.Am.,1995,85(4) :1127～1143
[15] 杨秋梅.自贡市城市环境地质分区评价[硕士论文].成都:成都理工大学,2008 Yang Q M.The divisional evaluation of urban environmental geology[Master thesis](in Chinese).Chengdu:Chengdu University of Technology,2008
[16] 徐争强,杨秋梅,张成江等.论四川自贡市的城市地质环境.四川地质学报,2008,28(4) :313～315 Xu Z Q,Yang Q M,Zhang C J,et al.On urban geological environment in Zigong city.Acta Geologica Sichuan(in Chinese),2008,28(4) :313～315
[17] 杨涛,邓贵荣,何强.自贡地区第四系地层动力特性及地震反应分析.路基工程,2003,3～7 Yang T,Deng G R,He Q.Analysis of dynamic properties and seismic response of the Quaternary strata.Subgrade Engineering(in Chinese),2003,3～7
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