长周期地震动衰减关系研究的迫切性

通过对长周期震害及长周期地震动研究的历史进行回顾指出,目前,大多数反应谱的周期还不够长,反应谱所反映的谱形与距离、震级和场地条件的关系还很有限,长周期地震动的研究仍需要不断完善,未来的长周期地震动的研究应注重软土场地的大震远场效应。     

1996年11月9日南黄海地震的长周期地震动反应谱

利用ＮＣＤＳＮ上海佘山地震台的宽频带数字地震记录计算了１９９６年１１月９日南黄海６．１级地震的基岩地震动反应谱。与１９９０年２月１０日江苏太仓４．９级震的反应谱进行了比较，发现这次南黄海南震的长周期地震成分较为丰富。鉴于这次地震在上海市出现了长周期破坏的事例，指出了研究长周期地震动的必要性和紧迫性。     

北京盆地结构对长周期地震动反应谱的影响

建立了北京盆地含起伏地形的地下介质三维速度结构模型, 以有限差分方法对盆地内的3次地震动进行了数值模拟． 计算了地表加速度反应谱, 论证了反应谱的有效周期范围, 从而获得了盆地结构对长周期段反应谱的平均放大系数, 并对不同周期时反应谱的平均放大系数进行了分区, 为今后城市的合理规划和长周期建筑物的建设提供了抗震设防参考． 最后对反应谱平均放大系数与等效沉积物厚度之间的关系进行了回归, 得出了反应谱放大系数随沉积物厚度增大而增强, 以及随周期增大而减弱等结论．      

台湾集集地震近场地震动的上盘效应

1999年9月21日（当地时间）台湾集集7.6级地震是一个逆断层型地震．用回归分析法对台湾集集地震的加速度峰值数据进行分析，得出了这次地震的水平与垂直向的加速度峰值衰减关系．从残差分布上看，位于断层上盘和下盘上的加速度峰值与从衰减关系所得到的结果相比存在不同的系统偏差，断层上盘地表的加速度峰值较高，而下盘地表的加速度峰值较低．从这次地震的加速度峰值分布等值线图上也可以看出，加速度峰值的分布相对于断层呈现明显的不对称性，上盘衰减较慢而下盘衰减较快．在近断层强地面运动研究、地震危险性分析、设定地震研究与震害预测等工作中，应考虑可能地震的震源机制特点，以便使所用的衰减模型更能反映不同地震环境地区的地震动分布特征．      

合成地震动方法用于研究强地震动长周期特性的探讨

合成地震动一直是地震学研究中一个非常跃的领域。针对２长周期结构物抗震设计缺少宽频带强震记录的现状,利用“反射率法”和“围道积分法”等合成地震动方法对地震动长周期特性进行了探讨。结果表明：合成地震动方法是研究地震动长周特性的一个有效方法;在地震动长周期成份中,面波起着重要作用。因此长周期结构物的抗震设计必须考虑面波的影响。     

长周期地震动研究综述

本文对长周期地震动研究的主要方法,即经验统计方法和震源模型方法进行了总结,分析了它们的适用范围和存在的问题。对长周期地震动的研究趋势进行了分析。     

邢台地区长周期地震动特征初步分析

沉积平原中存在地表低速沉积层是长周期地震动产生的关键因素,而长周期地震动会对长周期建筑物造成严重威胁和震害。本文基于邢台地震的历史地震震源模型和含地表沉积层的地壳速度模型,采用离散波数有限元法,对邢台地区进行了长周期地震动的计算分析。研究表明,邢台平原地区在大震中会产生长周期地震波,邢台地震中反应谱峰值区域位于宁晋南,与极震区基本重合。震中距小于55km区域内的周期1.5—4s的放大系数谱超过了抗震设计规范谱,反应谱放大系数值在周期2s附近达到峰值。因此,邢台地区因存在地表软弱沉积层,该区抗震设防可能对长周期地震动估计不足,建议应予以特别考虑。     

Long-period of the 1999 ground motion characteristic Jiji （Chi-Chi）, Taiwan, mainshock and aftershocks

This paper investigates long-period ground motion characteristic of the 1999 Jiji （Chi-Chi）, Taiwan, mainshock and aftershocks on the basis of lots of high quality digital strong motion records. The study attaches the importance to the variation of strength of the long-period ground motion with the magnitude, distance, and site condition. In the meantime, the near-fault long-period ground motion characteristic is analyzed. The result shows that the shape of the long-period response spectrum is mainly controlled by site condition and magnitude （the spectrum of class D＋E is wider than that of class B＋C, and the spectrum of larger magnitude is wider than that of smaller magni- tude）, and the effect of fault distance on the shape is not evident. And near-fault long-period ground motion characteristic depends on fault activity apparently, that is to say, the long-term ground motion in the hanger is stronger than that in the footwall, and the long-term ground motion in the north is stronger than that in the south.     

Long-period ground motion characteristic of the 1999 Jiji (Chi-Chi),Taiwan,main-shock and aftershocks

Introduction The study of attenuation relations for long-period ground motion is to meet the requirement of economy development. During the earthquakes such as the June 16, 1964 Niigata, Japan, M=7.5 earthquake, the March 24, 1977 Romania M=7.3 earthquake, the March 29, 1970 Gediz, Turkey, M=7.1 earthquake, the May 26, 1983 M=7.7 earthquake in the middle Japanese Sea, the September 19, 1985 Mexico M=8.1 earthquake, the September 16, 1994 M=7.3 earthquake in Tai- wan Strait, and the No…     

1999年台湾集集大地震的地表断层破裂特征

野外考察结果表明 ,1999年 9月 2 1日台湾集集大地震是由车笼埔断层发生逆冲作用造成的。地震产生的地表破裂长约 80km ,具有明显的挤压逆断层特征 ,其活动方式为具左旋性质的逆倾滑动。实测逆冲断层以 30°～ 50°的角向西北逆冲而上。断层的垂直位移量 ,南段约 2～ 3m ,北段约 3～ 8m ;断层的水平位移量 ,南段 0～ 3m ,北段 3～ 5m ;垂直断层的水平缩短量 ,南段 2～ 3m ,北段 3～ 6m。从台湾西部麓山带的地质构造剖面分析 ,地震震源恰好位于台湾西部麓山带中生代基底与其上的沉积盖层的界面的深度 ,而西部麓山带第三纪地层和其下的基底的分离面为一滑动面 (decolle ment)。在菲律宾海板块的挤压作用下 ,沿该区中生代基底之上滑动面的错动导致了地震的发生     

Effects of the hanging wall and footwall on peak acceleration during the Jiji (Chi-Chi), Taiwan Province, earthquake

Introduction In the study of ground motion attenuation model the considered parameters are generally sim-plified as ground motion parameters (acceleration, velocity, displacement, response spectrum, dura-tion, etc), earthquake magnitude, distance and site condition. As the accumulation of ground motion records, it was found that the characteristic of ground motion attenuation in tectonicly compressional region was different from that in tectonicly tensional region and the peak ground accelerat…     

921台湾集集地震近断层强震记录的基线校正

分析了 92 1台湾集集地震近断层强震记录基线偏移的原因 ,指出强震仪的倾斜是导致近断层强震记录基线偏移的主要原因 ,并提出了相应的基线校正方法 ,比较好地消除了近断层强震记录的基线偏移。根据作者的研究 ,原始记录经基线初始化之后 ,基线偏移对反应谱在工程界最感兴趣的0 .1～ 6s周期范围内的影响是很小的 ,对PGA的影响也很小 ,但对PGV ,PGD和永久位移 (D -last)的影响则相当大。因此 ,对近断层强震记录进行基线校正具有重要的意义。文中所提出的基线校正方法 ,可应用于对 1999年土耳其地震及 92 1台湾集集地震余震产生的近断层强震记录和其他近断层强震记录的基线校正     

设计地震动反应谱长周期区段确定方法的探讨

本文比较了GB50011-2010《建筑抗震设计规范》中的地震影响曲线和GB18306-20《中国地震动参数区划图》中使用的设计地震动反应谱,并参考实际工程场地的地震动反应谱,探讨了长周期结构工程地震安全性评价工作中的设计地震动反应谱长周期区段的确定方法。     

辽宁地区长周期地震动灾害预测及防灾对策

减轻长周期地震动灾害是城市防震减灾面临的新课题。本文在分析长周期地震动灾害产生条件的基础上,对辽宁地区的地震环境、长周期地震波的传播途径及地基条件作了分析,认为在下辽河平原及周边地区城市有产生长周期地震动灾害的可能,文章最后提出了防治和减轻长周期地震动灾害的对策。     

ANALYSIS ON THE CHARACTERISTICS OF DURATION AND PERIOD OF GROUND MOTION OF THE LUSHAN EARTHQUAKE BASED ON THE STATION RECORDS

Based on 60 records from the 20 stations within 100km to the epicenter of Lushan earthquake, the predominant period, period of peak response spectrum, duration of ground motion, and source duration are investigated. By the study, we conclude that within 100km to the epicenter, the scope of predominant period is 0.013~0. 275s in EW, NS and UD direction; the scope of period of peak response spectrum for 5% damping ratio is 0.03~0.65s; the scope of 90% ground motion durations is 5. 1~35. 9s; the scope of averaging source duration is 6.41 (EW), 6.05 (NS) and 5.47s (UD). Furthermore, based on the ground motion duration calculated by 20 stations dada, the predictive curve and equation of ground motion duration is regressed and compared with the recent equation of ground motion duration by Bommer (2009). We find that the ground motion durations of most stations are larger than predictively mean value by Bommer (2009), which means that the source effect of Lushan earthquake is relatively larger. Lastly, by the contour figure of ground motion duration and source duration, we conclude that the directivity character of duration is relatively apparent in NE direction. The relatively larger source duration and ground motion duration in NE direction indicate more energy release in the main shock of Lushan earthquake, which perhaps causes the relatively less aftershocks in this direction. The duration has no hanging wall effect, which perhaps results from the blind-reverse fault structure of Lushan earthquake.     

Source time functions of the 1999, Jiji (Chi-Chi) earthquake from GDSN long period waveform data using aftershocks as empirical Green''''s functions

IntroductionA large earthquake occurred in Jiji (Chi-Chi) town of Nantou County, Taiwan, China at 17h47min on September 20, 1999 (UTC). The origin time was determined to be 17h47min19s of September 20 UTC (1h47min19s of September 21, Beijing Time). The epicenter was determined to be longitude 120.80°E and latitude 23.86°N. It was reported that 2 333 people were killed, 10 002 people were injured, and thousands of houses collapsed which made more than 100 000 people homeless (Shin, e…     

Source time functions of the 1999, Jiji (Chi-Chi) earthquake from GDSN long period waveform data using aftershocks as empirical Green’s functions

A large earthquake (M _W=7.6) occurred in Jiji (Chi-Chi), Taiwan, China on September 20, 1999, and was followed by many moderate-size shocks in the following days. Two of the largest aftershocks with the magnitudes of M _W=6.1 and M _W=6.2, respectively, were used as empirical Green’s functions (EGFs) to obtain the source time functions (STFs) of the main shock from long-period waveform data of the Global Digital Seismograph Network (GDSN) including IRIS, GEOSCOPE and CDSN. For the M _W=6.1 aftershock of September 22, there were 97 pairs of phases clear enough from 78 recordings of 26 stations; for the M _W=6.2 aftershock of September 25, there were 81 pairs of phases clear enough from 72 recordings of 24 stations. For each station, 2 types of STFs were retrieved, which are called P-STF and S-STF due to being from P and S phases, respectively. Totally, 178 STF individuals were obtained for source-process analysis of the main shock. It was noticed that, in general, STFs from most of the stations had similarities except that those in special azimuths looked different or odd due to the mechanism difference between the main shock and the aftershocks; and in detail, the shapes of the STFs varied with azimuth. Both of them reflected the stability and reliability of the retrieved STFs. The comprehensive analysis of those STFs suggested that this event consisted of two sub-events, the total duration time was about 26 s, and on the average, the second event was about 7 s later than the first one, and the moment-rate amplitude of the first event was about 15% larger than that of the second one. Foundation item: State Natural Science Foundation of China (49904004) and IPGP of France. Contribution No. 02FE2007, Institute of Geophysics, China Seismological Bureau.