基于环境噪声及地震数据对斜坡地震动响应特征分析——以芦山仁加斜坡为例
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摘要
"4·20"芦山强震导致震区斜坡动力响应强烈,并诱发大量斜坡次生地质灾害。强震后余震频发,在发震断裂附近芦山双石峡谷下游出口,对仁加水电站进水口边坡地震动效应监测初步揭示,该斜坡中上部峰值加速度放大达3.4倍,斜坡放大效应明显,但各监测点场地效应需深入分析。因此,基于对该斜坡环境噪声测试与地震监测数据,采用水平与竖向谱比(H/V)和标准反应谱(SSR)对比分析。研究揭示,该斜坡参考点H/V谱比曲线放大系数约为1.1,场地放大效应微弱;斜坡上部监测点环境噪声揭示H/V与SSR谱比放大峰值频率约为13.0 Hz,放大系数为1.2～1.6。环境噪声与地震监测数据对比表明,其平均谱比曲线峰值频率特征接近,但后者谱比放大系数为1.6～2.6。综合研究表明,该斜坡场地地质结构较为单一,其动力效应主要受斜坡地形因素较强,斜坡中上部地形放大效应较明显。基于环境噪声与地震数据对比研究斜坡场地效应,两者在场地卓越频率上较一致,而放大系数后者明显强于前者。
"4·20" Lushan macroshock triggered off massive dynamic responses from slopes in shock-hit area and consequently induced a large number of secondary slope failures. In view of frequent aftershocks ensuing from the earthquake, field observation at the downstream exit of Lushan Shuangshi Gorge near the seismogenic fault was conducted to investigate the vibration effect of a slope at the water inlet of Renjia Hydropower Station. It was preliminarily revealed that the peak acceleration in the middle and upper part of the slope was up to 3.4 times, suggesting a significant amplification effect of the slope, but the site effect of each monitoring point was worthy of in-depth analysis. In this research, based on the environmental noise test and seismic monitoring data of the slope, it had performed a comparison analysis of Horizontal to Vertical Spectral Ratio(H/V) with Standard Response Spectral(SSR). The study found that the amplification factor of the H/V curve of the slope at a reference point was about 1.1, indicating a weak site amplification effect. By analyzing the ambient noise at monitoring points on the upper slope, it suggested that the peak frequency of H/V as well as SSR both were about 13.0 Hz, and the amplification coefficient was 1.2-1.6. In comparison with seismic monitoring data, ambient noise had a similar peak frequency characteristics of average spectral ratio curve, but seismic data had a amplification factor of spectral ratio 1.6-2.6. In point of comprehensive study, owing to a relatively single geological structure, the dynamic effect of the slope was mainly governed by strong topographic factors, with a considerable topographic amplification effect in the middle and upper part of the slope. By comparative study of slope site effect between environmental noise and seismic data, both had relatively consistent site predominant frequency, whereas the amplification factor of the latter was noticeably stronger than that of the former.
"4·20" Lushan macroshock triggered off massive dynamic responses from slopes in shock-hit area and consequently induced a large number of secondary slope failures. In view of frequent aftershocks ensuing from the earthquake, field observation at the downstream exit of Lushan Shuangshi Gorge near the seismogenic fault was conducted to investigate the vibration effect of a slope at the water inlet of Renjia Hydropower Station. It was preliminarily revealed that the peak acceleration in the middle and upper part of the slope was up to 3.4 times, suggesting a significant amplification effect of the slope, but the site effect of each monitoring point was worthy of in-depth analysis. In this research, based on the environmental noise test and seismic monitoring data of the slope, it had performed a comparison analysis of Horizontal to Vertical Spectral Ratio(H/V) with Standard Response Spectral(SSR). The study found that the amplification factor of the H/V curve of the slope at a reference point was about 1.1, indicating a weak site amplification effect. By analyzing the ambient noise at monitoring points on the upper slope, it suggested that the peak frequency of H/V as well as SSR both were about 13.0 Hz, and the amplification coefficient was 1.2-1.6. In comparison with seismic monitoring data, ambient noise had a similar peak frequency characteristics of average spectral ratio curve, but seismic data had a amplification factor of spectral ratio 1.6-2.6. In point of comprehensive study, owing to a relatively single geological structure, the dynamic effect of the slope was mainly governed by strong topographic factors, with a considerable topographic amplification effect in the middle and upper part of the slope. By comparative study of slope site effect between environmental noise and seismic data, both had relatively consistent site predominant frequency, whereas the amplification factor of the latter was noticeably stronger than that of the former.
引文
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[9] WATHELET M,JONGMANS D,OHRNBERGER M,et al.Array performances for ambient vibrations on a shallow structure and Consequences over Vs inversion[J].Journal of Seismology,2008,12(1):1-19.
[10] PANOU A A,THEODULIDIS N,HATZIDIMITRIOU P,et al.Ambient noise horizontal-to-vertical spectral ratio in site effects estimation and correlation with seismic damage distribution in urban environment:the case of the city of Thessaloniki (Northern Greece)[J].Soil Dynamics and Earthquake Engineering,2005,25(4):261-274.
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[12] TAYLOR S R,GERSTOFT P ,FEHLER M C.Estimating site amplification factors from ambient noise[J].Geophysical Research Letters,2009:36,L09303.
[13] BONNEFOY-CLAUDET S,BAIZE S,BONILLA L F,et al.Site effect evaluation in the basin of Santiago de Chile using ambient noise measurements[J].Geophysical Journal International,2009,176(3):925-937.
[14] CHATELAIN J L,GUILLIER B,CARA F,et al.Evaluation of the influence of experimental conditions on H/V results from ambient noise recordings[J].Bulletin of Earthquake Engineering,2008,6(1):33-74.
[15] MUCCIARELLI M.Reliability and applicability of nakamura’s technique using microtremors:an experimental approach[J].Journal of Earthquake Engineering,1998,2(4):625-638.
[16] ZHAO B,LUO YH,WANG YS,et al.Seismic response of steep slopes inferred from ambient noise and accelerometer recordings:The case of Dadu River valley,China[J].Engineering Geology,2019:1-24.
[17] ZASLAVSKY Y,SHAPIRA A,ARZI A A.Amplification effects from earthquakes and ambient noise in the Dead Sea rift (Israel)[J].Soil Dynamics & Earthquake Engineering,2000,20(1):187-207.
[18] HORIKE,M.ZHAO B,KAWASE H,Comparison of site response characteristics inferred from microtremors and earthquake shear waves[J].Bulletin of the Seismological Society of America,2001,91(6):1526-1536.
[19] RODRIGUEZ V H S.Applicability of the H/V spectral ratio of microtremors in assessing site effects on seismic motion[J].Earthquake Engineering and Structural Dynamics,2002,31:261-79.
[20] 张磊,王运生,罗永红.芦山地震仁家村斜坡地震动监测[J].山地学报,2015(3):339-347.[ZHANG Lei,WANG Yunsheng,LUO Yonghong.Monitoring result analysis of Renjia village slope ground shock response of Lushan earthquake in Sichuan,China[J].Mountain Research,2015(3):339-347]
[21] YAMANAKA H,MASAYUKI T,HIROSHI I,et al.Characteristics of long-period microtremors and their applicability in exploration of deep sedimentary layers[J].Bulletin of the Seismological Society of America ,1994,84(6):1831–1841.
[22] FIELD,EH ,JACOB K H .A comparison and test of various site-response estimation techniques,including three that are not reference-site dependent[J].Bulletin of the Seismological Society of America,1995,85(4):1127-1143.
[23] BORCHERDT R D.Effects of local geology on ground motion near San Francisco Bay.Bulletin of the Seismological Society of America[J] ,1970,60(1):29-61.
[24] JGJ/T97—2011,工程抗震术语标准[S].北京:中国建筑工业出版社,2011.[JGJ/T97-2011,Term Standard in Earthquake Engineering[S].Beijing:China Architeture & Buiding Press,2011]
[25] 罗永红.地震作用下复杂斜坡响应规律研究[D].成都:成都理工大学,2011.[LUO Yonghong.Study on complex slopes response law under earthquake action[D].Chengdu:Chengdu University of Technology,2011]
[26] HARTZELL S H,CARVER D L,KING K W.Initial investigation of site and topographic effects at Robinwood Ridge,California[J].Bulletin of the Seismological Society of America,1994,84(5):1336-1349.
[2] NOGUCHI S ,SASATANI T.Quantification of degree of nonlinear site response[C].14th World Conference on Earthquake Engineering,Beijing,China.2008.
[3] 刘塑宽,查小刚.唐山地震高烈度区场地条件对震害的影响[J].西北地震学报,1982,4(2):67-74.[LIU Sukuan,ZHA Xiaogang.The damage anomaly of 1976 Tangshan earthquake in high intensity region[J].Northwestern Seismological Journal,1982,4(2):67-74]
[4] 冀昆.基于H/V谱比法的场地特征研究[D].哈尔滨:中国地震局工程力学研究所,2014.[JI Kun .Estimation on site characteristic based on H/V spectral ratio method[D].Harbin:Institute of Engineering Mechanics,China Earthquake Administration,2014]
[5] BUECH F,DAVIES T R,PETTINGA J R.The little red hill seismic experimental study:Topographic effects on ground motion at a bedrock-dominated mountain edifice[J].Bulletin of the Seismological Society of America,2010,100(5A):2219-2229.
[6] DAVIS L L,WEST L R.Observed effects of topography on ground motion[J].Bulletin of the Seismological Society of America,1973,63(1):283-298.
[7] 罗永红,王运生,王福海,等.青川县桅杆梁斜坡地震动响应监测研究[J].工程地质学报,2010,18(1):27-34.[LUO Yonghong,WANG Yunsheng,WANG Fuhai,et al.Monitoring of slope seismic response during aftershocks of Wenchuan earthquake in Qingchuan county[J].Journal of Engineering Geology,2010,18(1):27-34]
[8] 罗永红,王运生,何源,等.“4·20”芦山地震冷竹关地震动响应监测数据分析[J].成都理工大学学报(自然科学版),2013,40(3):232-241.[LUO Yonghong,WANG Yunsheng,HE Yuan,et al.Monitoring result analysis of Lengzhuguan slope ground shock response of Lushan earthquake of Sichuan,China[J].Journal of Chengdu University of Technology(Science & Technology Edition),2013,40(3):232-241]
[9] WATHELET M,JONGMANS D,OHRNBERGER M,et al.Array performances for ambient vibrations on a shallow structure and Consequences over Vs inversion[J].Journal of Seismology,2008,12(1):1-19.
[10] PANOU A A,THEODULIDIS N,HATZIDIMITRIOU P,et al.Ambient noise horizontal-to-vertical spectral ratio in site effects estimation and correlation with seismic damage distribution in urban environment:the case of the city of Thessaloniki (Northern Greece)[J].Soil Dynamics and Earthquake Engineering,2005,25(4):261-274.
[11] DEL G V,COCCIA S,WASOWSKI J,et al.Detection of directivity in seismic site response from microtremor spectral analysis[J].Natural Hazards and Earth System Sciences,2008,8(4):751-762.
[12] TAYLOR S R,GERSTOFT P ,FEHLER M C.Estimating site amplification factors from ambient noise[J].Geophysical Research Letters,2009:36,L09303.
[13] BONNEFOY-CLAUDET S,BAIZE S,BONILLA L F,et al.Site effect evaluation in the basin of Santiago de Chile using ambient noise measurements[J].Geophysical Journal International,2009,176(3):925-937.
[14] CHATELAIN J L,GUILLIER B,CARA F,et al.Evaluation of the influence of experimental conditions on H/V results from ambient noise recordings[J].Bulletin of Earthquake Engineering,2008,6(1):33-74.
[15] MUCCIARELLI M.Reliability and applicability of nakamura’s technique using microtremors:an experimental approach[J].Journal of Earthquake Engineering,1998,2(4):625-638.
[16] ZHAO B,LUO YH,WANG YS,et al.Seismic response of steep slopes inferred from ambient noise and accelerometer recordings:The case of Dadu River valley,China[J].Engineering Geology,2019:1-24.
[17] ZASLAVSKY Y,SHAPIRA A,ARZI A A.Amplification effects from earthquakes and ambient noise in the Dead Sea rift (Israel)[J].Soil Dynamics & Earthquake Engineering,2000,20(1):187-207.
[18] HORIKE,M.ZHAO B,KAWASE H,Comparison of site response characteristics inferred from microtremors and earthquake shear waves[J].Bulletin of the Seismological Society of America,2001,91(6):1526-1536.
[19] RODRIGUEZ V H S.Applicability of the H/V spectral ratio of microtremors in assessing site effects on seismic motion[J].Earthquake Engineering and Structural Dynamics,2002,31:261-79.
[20] 张磊,王运生,罗永红.芦山地震仁家村斜坡地震动监测[J].山地学报,2015(3):339-347.[ZHANG Lei,WANG Yunsheng,LUO Yonghong.Monitoring result analysis of Renjia village slope ground shock response of Lushan earthquake in Sichuan,China[J].Mountain Research,2015(3):339-347]
[21] YAMANAKA H,MASAYUKI T,HIROSHI I,et al.Characteristics of long-period microtremors and their applicability in exploration of deep sedimentary layers[J].Bulletin of the Seismological Society of America ,1994,84(6):1831–1841.
[22] FIELD,EH ,JACOB K H .A comparison and test of various site-response estimation techniques,including three that are not reference-site dependent[J].Bulletin of the Seismological Society of America,1995,85(4):1127-1143.
[23] BORCHERDT R D.Effects of local geology on ground motion near San Francisco Bay.Bulletin of the Seismological Society of America[J] ,1970,60(1):29-61.
[24] JGJ/T97—2011,工程抗震术语标准[S].北京:中国建筑工业出版社,2011.[JGJ/T97-2011,Term Standard in Earthquake Engineering[S].Beijing:China Architeture & Buiding Press,2011]
[25] 罗永红.地震作用下复杂斜坡响应规律研究[D].成都:成都理工大学,2011.[LUO Yonghong.Study on complex slopes response law under earthquake action[D].Chengdu:Chengdu University of Technology,2011]
[26] HARTZELL S H,CARVER D L,KING K W.Initial investigation of site and topographic effects at Robinwood Ridge,California[J].Bulletin of the Seismological Society of America,1994,84(5):1336-1349.