地形对地震动的影响规律研究
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摘要
基于四川自贡西山公园台站实测的汶川地震波以及大型振动台试验数据,研究了地形对16种地震动强度参数和反应谱的影响规律,并详细分析了自贡西山公园场址内地表峰值加速度的变化规律。结果表明,在EW方向,高程仅对PGD、SMA、VSI、HI、V_RMS具有一定的影响;在NS方向,高程对PGD、V_RMS、SMA、SED、A_RMS、VSI、HI的作用可以忽略;在UD方向,SMV、PGD、V_RMS、SMV、ASI、VSI、HI的大小几乎不受高程的影响;斜坡场地反应谱幅值在短周期部分(T≤1s)随着高程的增加而增加,长周期部分(T>1s)反应谱幅值几乎不发生变化,局部地形对加速度响应的影响程度大于高程。
The influence of topography on ground motion intensity parameters,response spectrum,and peak ground acceleration(PGA)were studied.This study used measured data of the Wenchuan earthquake from large-scale shaking table tests and the monitoring stations in the Xishan Park,Zigong,Sichuan province,China.The results show that the peak ground acceleration at6# and 7#,which are at higher altitudes,are larger than those at the other stations;the peak ground acceleration at 1#,which is at the lowest altitude,is the smallest of all the monitoring stations.This demonstrates that local outstanding landscapes can amplify seismic waves.Comparing the correlation coefficient of the fitting functions of the peak intensity parameters shows that the sequence of correlation between the amplification coefficient and the fitted curve is PGD >SMV > PGA > PGV > EDA >SMA.With respect to the 10 types of comprehensive intensity parameters,the sequence is V_RMS>SED >Ia> ASI >Ic> HI >VSI >CAV > A_RMS> D_RMS.This study's results show that the curves between the amplification coefficient and height of the 16 intensity parameters are highly correlated.In the EW direction,the height does not affect PGD,SMA,VSI,and HI,while V_RMS decreases slightly at the center of the slope;the other intensity parameters increase with an increase in height.In the EW direction,the height has no influence on PGD,V_RMS,SMA,SED,A_RMS,VSI,and HI,but the other parameters increase with an increase in height.In the UD direction,the height has no influence on SMV,PGD,V_RMS,SMV,ASI,VSI,and HI,while A_RMS decreases at the center of the slope;the other intensity parameters increase with an increase in height.With an increase in the relative height,the amplification coefficients in the three directions show a noticeable increase.The maximum among the PGAamplification coefficients in the EW direction is 1.768(recorded at the 6#monitoring station);the maximum value in the NS direction is 1.717(recorded at the 7# monitoring station);the maximum value in the UD direction is 1.341(recorded at the 6# monitoring station).It is evident that the maximum values of the PGAamplification coefficient are similar in the horizontal directions,and that the values in the horizontal directions are larger than those in the vertical direction.Ignoring the effect of local topography,the amplitude of the response spectrum increases with an increase in height for a short period,decreases in height for the section with period T ≤1s,and the T >1speriod is not affected by the height.In the horizontal direction,the response in the short section,whose period T ≤1s,is highly affected by height,and the response in the long section,whose period T > 1sis negligible.In the vertical direction,the amplification effect of height on the response spectrum decreases with an increase in the period.However,when the period is larger than T > 1s,the effect of height on the response spectrum can be ignored.The ground motion is amplified by the local foveate topography,and the height also affects the ground motion.However,the influence of the local topography is larger than the height.This study increases our understanding of the effect of topography on ground motion.
The influence of topography on ground motion intensity parameters,response spectrum,and peak ground acceleration(PGA)were studied.This study used measured data of the Wenchuan earthquake from large-scale shaking table tests and the monitoring stations in the Xishan Park,Zigong,Sichuan province,China.The results show that the peak ground acceleration at6# and 7#,which are at higher altitudes,are larger than those at the other stations;the peak ground acceleration at 1#,which is at the lowest altitude,is the smallest of all the monitoring stations.This demonstrates that local outstanding landscapes can amplify seismic waves.Comparing the correlation coefficient of the fitting functions of the peak intensity parameters shows that the sequence of correlation between the amplification coefficient and the fitted curve is PGD >SMV > PGA > PGV > EDA >SMA.With respect to the 10 types of comprehensive intensity parameters,the sequence is V_RMS>SED >Ia> ASI >Ic> HI >VSI >CAV > A_RMS> D_RMS.This study's results show that the curves between the amplification coefficient and height of the 16 intensity parameters are highly correlated.In the EW direction,the height does not affect PGD,SMA,VSI,and HI,while V_RMS decreases slightly at the center of the slope;the other intensity parameters increase with an increase in height.In the EW direction,the height has no influence on PGD,V_RMS,SMA,SED,A_RMS,VSI,and HI,but the other parameters increase with an increase in height.In the UD direction,the height has no influence on SMV,PGD,V_RMS,SMV,ASI,VSI,and HI,while A_RMS decreases at the center of the slope;the other intensity parameters increase with an increase in height.With an increase in the relative height,the amplification coefficients in the three directions show a noticeable increase.The maximum among the PGAamplification coefficients in the EW direction is 1.768(recorded at the 6#monitoring station);the maximum value in the NS direction is 1.717(recorded at the 7# monitoring station);the maximum value in the UD direction is 1.341(recorded at the 6# monitoring station).It is evident that the maximum values of the PGAamplification coefficient are similar in the horizontal directions,and that the values in the horizontal directions are larger than those in the vertical direction.Ignoring the effect of local topography,the amplitude of the response spectrum increases with an increase in height for a short period,decreases in height for the section with period T ≤1s,and the T >1speriod is not affected by the height.In the horizontal direction,the response in the short section,whose period T ≤1s,is highly affected by height,and the response in the long section,whose period T > 1sis negligible.In the vertical direction,the amplification effect of height on the response spectrum decreases with an increase in the period.However,when the period is larger than T > 1s,the effect of height on the response spectrum can be ignored.The ground motion is amplified by the local foveate topography,and the height also affects the ground motion.However,the influence of the local topography is larger than the height.This study increases our understanding of the effect of topography on ground motion.
引文
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[11]徐锡伟,闻学泽,叶建青,等.汶川MS8.0地震地表破裂带及其发震构造[J].地震地质,2008,30(3):597-629.XU X W,WEN X Z,YE J Q,et al.The MS8.0Wenchuan Earthquake Surface Ruptures and its Seismogenic Structure[J].Chinese Journal of Geophysics,2008,30(3):597-629.(in Chinese)
[12]陈力波,郑凯锋,栗怀广,等.概率性地震需求分析中地震动强度指标的比较与选择[J].地震工程与工程振动,2012,32(6):23-31.CHEN L B,ZHENG K F,LI H G,et al.Comparison and Selection of Ground Motion Intensity Measures in Probabilistic Seismic Demand Analysis[J].Journal of Earthquake Engineering and Engineering Vibration,2012,32(6):23-31.(in Chinese)
[2]Boore D M.A Note on the Effect of Simple Topography on Seismic SH Waves[J].Bull Seism Soc Am,1972,62(1):275-284.
[3]Trifunac M D,D E Hudson.Analysis of the Pacoima Dam Accelerogram:San Fernando,California,Earthquake of 1971[J].Bull Seism Soc Am,1971,61(5):1393-1411.
[4]李大虎,梁明剑,黎小刚,等.2011年四川炉霍MS5.3地震加速度记录的时频分析与能量计算[J].西北地震学报,2012,34(4):335-342.LI D H,LIANG M J,LI X G,et al.Time-frequency Analysis and Energy Calculation for Acceleration Records of Luhuo MS5.3Earthquake in Sichuan Province in 2011[J].Northwestern Seismological Journal,2012,34(4):335-342.(in Chinese)
[5]赵雯佳,徐平,林向东,等.2011年10月12日北京市石景山区ML2.1地震近场加速度记录初步分析[J].地震工程学报,2013,35(1):183-189.ZHAO W J,XU P,Lin X D,et al.Near-field Acceleration Records and Preliminary Analysis of ML2.1Shijingshan District Earthquake on Oct.12,2011,Beijing[J].China Earthquake Engineering Journal,2013,35(1):183-189.(in Chinese)
[6]Lawrence L Davis,Lewisr West.Observed Effects of Topography on Ground Motion[J].Bull Seism Soc Am,1973,63(1):283-298.
[7]B E Tucker,J L King,D Hatzfeld,et al.Observations of Hard-rock Site Effects[J].Bull Seism Soc Am,1984,74(1):121-136.
[8]田秀丰,李佐唐,徐钦,等.甘肃岷县漳县6.6级地震强震动观测记录与初步分析[J].地震工程学报,2013,35(3):497-502.TIAN X F,LI Z T,XU Q,et al.The Strong Motion Records and Preliminary Analysis for Minxian-zhangxian M6.6Earthquake in Gansu Province[J].China Earthquake Engineering Journal,2013,35(3):497-502.(in Chinese)
[9]邓起东.关于四川汶川8.0级地震的思考[J].地震地质,2008,30(4):811-827.ZHENG D Q.Some Thoughts on the MS8.0 Wenchuan,Sichuan Earthquake[J].Seismology and Geology,2008,30(4):811-827.(in Chinese)
[10]王海云,谢礼立.自贡市西山公园地形对地震动的影响[J].地球物理学报,2010,53(7):1631-1638.WANG H Y,XIE L L.Effects of Topography on Ground Motion in the Xishan Park,Zigong City[J].Chinese J Geophys,2010,53(7):1631-1638.(in Chinese)
[11]徐锡伟,闻学泽,叶建青,等.汶川MS8.0地震地表破裂带及其发震构造[J].地震地质,2008,30(3):597-629.XU X W,WEN X Z,YE J Q,et al.The MS8.0Wenchuan Earthquake Surface Ruptures and its Seismogenic Structure[J].Chinese Journal of Geophysics,2008,30(3):597-629.(in Chinese)
[12]陈力波,郑凯锋,栗怀广,等.概率性地震需求分析中地震动强度指标的比较与选择[J].地震工程与工程振动,2012,32(6):23-31.CHEN L B,ZHENG K F,LI H G,et al.Comparison and Selection of Ground Motion Intensity Measures in Probabilistic Seismic Demand Analysis[J].Journal of Earthquake Engineering and Engineering Vibration,2012,32(6):23-31.(in Chinese)
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