哈工大 地震工程课件 工程地震部分 第四章 强地震动的观测和数据处理.ppt

1、Engineering Seismology (2),Ground Motion Instrumentation and Data Processing,地震动的观测(observation of GM),可以提供定量的数据 可以测量地震破坏作用的全过程， 能够分别研究并测量导致建筑物破坏的各种因素 不但为地震烈度和工程抗震措施提供定量数据和理论依据，同时又检验从抗震研究实践中总结出来的认识、理论和办法是否符合实际，从而加深人们对于抗震客观规律的认识，成为不断推动地震工程研究发展的重要手段。,Observation of strong motion is more difficult than

2、 the observations in other fields of seismology due to the infrequency of large earthquakes and the difficulty of anticipating areas of strong shaking for instrumentation. Weak motions from an earthquake with magnitude greater than 6.0 can be recorded worldwide. Thus a seismologist who studies teles

3、eisms can record on the order of 100 earthquakes per year, for interpretations of earth structure or tectonics. Similarly, local networks are generally set to the most sensitive level possible to detect and locate the smallest earthquakes, which are much more abundant. A specialized instrument, the

4、strong motion accelerograph, was developed in the 1930s to record strong motion. A network of these specialized instruments must furthermore have the good fortune to be located close to the earthquake, and must be maintained, often for decades, in a state of readiness to record the rare strong shaki

5、ng. In the 1990s, the situation changed somewhat with improvements in digital recording technology.,如果没有强震观测及其所取得的科学资料，就谈不上现代地震工程学的发展。,地震工程之所以能成为一间定量的科学是和强震观测的成果分不开的。 根据测量得到的地震加速度记录，计算了大量的反应谱曲线，获得了“平均反应谱”或“标准反应谱”，使反应谱分析得以真正应用于工程设计。 地震动特征的统计分析和结构抗震理论的发展。例如，从震源参数、传播介质的性质演算地震动，随机合成地震动时程，从弹性反应谱到非弹性反应谱，烈

6、度定量标准及其观测仪器的建立，以及场地条件对地震动的影响，地震时地基与结构的相互作用等研究，都是在取得了强震观测记录的基础上发展起来的。,The founding father of the strong motion instrumentation program in the United States is John R. Freeman. After the Tokyo, Japan earthquake of 1923, and the Santa Barbara, California and Montreal, Quebec earthquakes of 1925, he sti

7、mulated important early interactions between U.S. and Japanese institutions on earthquake engineering and wrote the first significant book in the English language on earthquake engineering, Earthquake Damage and Earthquake Insurance (Freeman, 1932). He particularly recognized the urgent need for an

8、instrument to record the strong shaking during earthquakes, and the result of his lobbying efforts was that the Coast and Geodetic Survey was authorized to develop and install such instruments in 1932. Nine months after the first instruments were installed, the first significant strong motion record

9、s were obtained from the March 10, 1933 Long Beach, California earthquake.,强震仪的原理,绝对静止参考系,摆（pendulum）的原理,CDMG-SMIP instrument cabinet, nearest house slightly damaged.,强震仪主要由五个系统构成,拾振系统，直接测量地震动的装置，通常称为拾振器或摆。根据其所记录的物理量不同可进一步分为位移计(摆)、速度计 (摆)和加速度计 (摆)。通常一点要采用一个测量竖向运动的拾振器、二个测量相互垂直的水平向运动的拾振器。,记录系统，机械、光、电流

10、计、模拟磁带、数字磁带和固态存储； 触发-起动控制系统，节省存储空间等； 预存储系统，避免“丢头”、节省存储空间； 时标系统，以便各分量、相邻各点地震动的比较、分析，相对时标系统（晶振）或绝对时标系统（GPS时间信号）； 电源系统，一旦强震发生造成正常供电系统的破坏和失灵，要保证整套仪器驱动运转、线路控制、以及时标和光源正常工作。,Timing systems were not used in many of the early analog accelerographs, but they became more important as the analysis became more s

11、ophisticated. High-precision time, usually from satellite systems, is now essential with the digital accelerographs that provide records of aftershocks and other small events in large numbers. Precision time together with pre-event memory allow digital accelerographs to improve earthquake locations

12、beyond what is possible using only the traditional high-gain seismic networks.,强震观测仪通常记录的物理量,（1）通过对加速度记录积分求速度和位移，实际是计算加速度曲线（第二次积分是速度曲线），比起从位移曲线微分两次获得加速度的精度高； （2）因为记录强震，而强震又比较罕见，所以要求强震仪具有一定的坚固性和较好的稳定性，而加速度仪更容易实现； （3）加速度直接与力相关，比较其它物理量更受工程部门欢迎。,Instrumentation,台网的合理布局：应设置强度高、频度大的地震区；根据历史和现今的地震活动性和地质构造情

13、况 台阵的设计 仪器的正确设置：确保仪器的可靠性和精度要求 台网维护管理技术措施,确保仪器参数精度、仪器正常运行等。,Golden State Bank building on Ventura Blvd. in Sherman Oaks. This is a 13-story reinforced-concrete structure instrumented by the California Strong Motion Instrumentation Program. Its response was recorded in the 1971 San Fernando earthquake

14、 as well as the 1994 Northridge earthquake. In the north-south direction, the lateral-force-resisting system consists of shear walls at either end of the building, while in the east-west direction, a moment frame resists lateral force. Cracking can be observed in the western-most shear wall.,Array l

15、ayout,台阵设计，根据具体的观测内容，给出能提供完整资料的仪器布设方案,包括确定台阵的类型和规模，给出仪器的最优布设方案，台阵的设置方法，提出对仪器性能、仪器安设和维护管理技术的具体要求等。 地震动观测台阵，震源机制台阵、传播效应(衰减）台阵、局部场地效应台阵以及特殊地震动台阵等。 结构反应台阵，房屋结构(工业与民用)地震反应台阵、地基-结构系统地震反应台阵、桥梁、水坝、高炉、水塔、烟囱、核反应堆等结构地震反应台阵等，了解各类典型结构在强烈地震作用下的反应特征和破坏规律，确定结构在地震作用下的反应和导致破坏的数学物理模式。,许多国家和地区强震观测台网规模迅速扩大,（1）美国全国 5000台

16、以上 USGS台网约1000台，加州 4000台以上 TriNet，实时监测台80台，拨号台100台 （2）日本全国5000台以上， 台站间距25km K-net 有线遥测强震台网 1000台 1999年台湾地震后，增设 2000台的新计划 （3）台湾 1500台以上（数字强震仪） 集集大地震获取记录1万条以上 （4）伊朗 1000台以上；墨西哥 430台（1995）,其它有强地震观测的国家（地区）,阿根廷、加拿大、智利、印度、意大利、希腊、新西兰、尼加拉瓜、秘鲁、波多黎各、 （前）苏、委内瑞拉、（前）南等 In 2000, there were between 10,000-20,000 s

17、trong motion instruments operating worldwide. Most seismically active countries have at least a few accelerographs in operation. Industrial nations with high seismic hazards have extensive programs. Countries with the most extensive strong-motion networks are Japan and Taiwan. The United States has

18、networks operated by the US Geological Survey and other organizations. Networks in other countries that have produced data from major earthquakes in recent years are in Mexico and Turkey. Ambraseys (1997) estimated that there are 2000 strong motion instruments operating in Europe, and that these hav

19、e produced over 2500 recordings. Unfortunately, it is still possible for large earthquakes to occur in populated regions of the world but not be recorded by any local strong motion instruments (e.g. Gujarat, India, January 26, 2001, Mw = 7.6).,我国的强震观测,2002-2007年投入数亿元大规模扩建我国数字强震台网,初步计划，增设2000台强震仪，其中自

20、由场固定台1160个，使8个国家一级重点监视区达到每600km2一台强震仪(台距约25 km)，13个二级重点监视区达到每1800km2一台强震仪(台距约42 km)。另在首都圈设310台自由场固定台，速报烈度，台站密度达到每50km2一台强震仪(台距约7 km)。还包括12个专门的密集台阵和200台流动观测仪器。,一级强震监控区（8个）,二级强震监控区（13个）,强地震动数据处理(Data process),我国强震观测数据中心设在工程力学所，积累了愈20000条强震记录，其中我国记录的amax20gal的强震数据约2000条，amax50gal的545条, amax100gal的206条,

21、 amax200gal的59条, amax500gal的8条，其中大部分是强余震记录，强震主震记录仅有数十条。,With so many different organizations operating strong motion accelerograph networks, a single global system of access to strong motion data has never been completely achieved. Various systems for data recovery have been put in place. Perhaps th

22、e most thorough for the late 1900.s was the World Data Center, which sought to compile and reproduce various tapes or computer disks. Seekins et al. (1992) prepared a CD-ROM with much of the data gathered in North America through 1986. Other CD-ROM data sets have been prepared by Alcantara et al (19

23、97), Cousins (1998), Ambraseys et al (2000), Lee (2001), and Celebi et al (2001). Distribution over the Internet also began in the late 1990s. In 2000, many strong motion programs operated active web sites for data distribution. A particularly useful U. S. program for distribution of strong motion d

24、ata was the one established by SCEC for southern California data, and expanded with support from COSMOS to other data sets. The database could be accessed through the World Wide Web operated by the Southern California Earthquake Center (http:/smdb.crustal ) or the Consortium of Organizations

25、 for Strong Motion Observation Systems (). Data from large and small earthquakes recorded on the extensive Kyoshin Net and Kiban-Kyoshin Net in Japan could be accessed through their excellent web sites (http:/www.k-net.bosai.go.jp/ and http:/www.kik.bosai.go.jp/, respectively).

26、 The content of the European data is also available on line (http:/www.isesd.cv.ic.ac.uk/esd/frameset.htm, Ambraseys et al, 2001),美国西部的强震记录,数字化 零线（base line）调整 ， 零线校正 ，Butterworth数字滤波器作双向滤波，截止频率可通过事前噪声记录与地震记录的傅立叶谱分析确定。对位移时程用最小二乘法调整零线以消除线性趋势。,Significant accelerograms recorded on film formats are eve

27、ntually digitized and distributed. A great deal of effort has been devoted to this process because of the importance of accurate information for earthquake resistant design. Although the instruments record acceleration, estimates of the ground velocity and displacement are also important for both engineering and geophysical research. Thus numerical integration of the records is important. The challenge in doing