強地震動的觀測和數(shù)據(jù)處理

1、Engineering Seismology (2)Ground Motion Instrumentation and Data Processing1地震動的觀測(observation of GM)可以提供定量的數(shù)據(jù)可以測量地震破壞作用的全過程，能夠分別研究并測量導(dǎo)致建筑物破壞的各種因素不但為地震烈度和工程抗震措施提供定量數(shù)據(jù)和理論依據(jù)，同時又檢驗從抗震研究實踐中總結(jié)出來的認識、理論和辦法是否符合實際，從而加深人們對于抗震客觀規(guī)律的認識，成為不斷推動地震工程研究發(fā)展的重要手段。 2 Observation of strong motion is more difficult than th

2、e 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 teleseis

3、ms 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 str

4、ong 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 shaking.

5、 In the 1990s, the situation changed somewhat with improvements in digital recording technology.3如果沒有強震觀測及其所取得的科學(xué)資料，就談不上現(xiàn)代地震工程學(xué)的發(fā)展。地震工程之所以能成為一間定量的科學(xué)是和強震觀測的成果分不開的。 根據(jù)測量得到的地震加速度記錄，計算了大量的反應(yīng)譜曲線，獲得了“平均反應(yīng)譜”或“標準反應(yīng)譜”，使反應(yīng)譜分析得以真正應(yīng)用于工程設(shè)計。地震動特征的統(tǒng)計分析和結(jié)構(gòu)抗震理論的發(fā)展。例如，從震源參數(shù)、傳播介質(zhì)的性質(zhì)演算地震動，隨機合成地震動時程，從彈性反應(yīng)譜到非彈性反應(yīng)譜，烈度定量標準

6、及其觀測儀器的建立，以及場地條件對地震動的影響，地震時地基與結(jié)構(gòu)的相互作用等研究，都是在取得了強震觀測記錄的基礎(chǔ)上發(fā)展起來的。 4The 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 stimula

7、ted 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 inst

8、rument 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 records we

9、re obtained from the March 10, 1933 Long Beach, California earthquake. 5強震儀的原理絕對靜止參考系擺（pendulum）的原理6CDMG-SMIP instrument cabinet, nearest house slightly damaged.7強震儀主要由五個系統(tǒng)構(gòu)成拾振系統(tǒng)，直接測量地震動的裝置，通常稱為拾振器或擺。根據(jù)其所記錄的物理量不同可進一步分為位移計(擺)、速度計 (擺)和加速度計 (擺)。通常一點要采用一個測量豎向運動的拾振器、二個測量相互垂直的水平向運動的拾振器。 8記錄系統(tǒng)，機械、光、電流計、模擬磁

10、帶、數(shù)字磁帶和固態(tài)存儲； 觸發(fā)-起動控制系統(tǒng)，節(jié)省存儲空間等；預(yù)存儲系統(tǒng)，避免“丟頭”、節(jié)省存儲空間；時標系統(tǒng)，以便各分量、相鄰各點地震動的比較、分析，相對時標系統(tǒng)（晶振）或絕對時標系統(tǒng)（GPS時間信號）； 電源系統(tǒng)，一旦強震發(fā)生造成正常供電系統(tǒng)的破壞和失靈，要保證整套儀器驅(qū)動運轉(zhuǎn)、線路控制、以及時標和光源正常工作。9 Timing systems were not used in many of the early analog accelerographs, but they became more important as the analysis became more sophist

11、icated. 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 beyond

12、 what is possible using only the traditional high-gain seismic networks. 10強震觀測儀通常記錄的物理量（1）通過對加速度記錄積分求速度和位移，實際是計算加速度曲線（第二次積分是速度曲線），比起從位移曲線微分兩次獲得加速度的精度高；（2）因為記錄強震，而強震又比較罕見，所以要求強震儀具有一定的堅固性和較好的穩(wěn)定性，而加速度儀更容易實現(xiàn)；（3）加速度直接與力相關(guān)，比較其它物理量更受工程部門歡迎。11Instrumentation臺網(wǎng)的合理布局：應(yīng)設(shè)置強度高、頻度大的地震區(qū)；根據(jù)歷史和現(xiàn)今的地震活動性和地質(zhì)構(gòu)造情況臺陣的設(shè)計儀

13、器的正確設(shè)置：確保儀器的可靠性和精度要求臺網(wǎng)維護管理技術(shù)措施,確保儀器參數(shù)精度、儀器正常運行等。 12Golden 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 as well

14、 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.13Array layout臺陣

15、設(shè)計，根據(jù)具體的觀測內(nèi)容，給出能提供完整資料的儀器布設(shè)方案,包括確定臺陣的類型和規(guī)模，給出儀器的最優(yōu)布設(shè)方案，臺陣的設(shè)置方法，提出對儀器性能、儀器安設(shè)和維護管理技術(shù)的具體要求等。地震動觀測臺陣，震源機制臺陣、傳播效應(yīng)(衰減）臺陣、局部場地效應(yīng)臺陣以及特殊地震動臺陣等。結(jié)構(gòu)反應(yīng)臺陣，房屋結(jié)構(gòu)(工業(yè)與民用)地震反應(yīng)臺陣、地基-結(jié)構(gòu)系統(tǒng)地震反應(yīng)臺陣、橋梁、水壩、高爐、水塔、煙囪、核反應(yīng)堆等結(jié)構(gòu)地震反應(yīng)臺陣等，了解各類典型結(jié)構(gòu)在強烈地震作用下的反應(yīng)特征和破壞規(guī)律，確定結(jié)構(gòu)在地震作用下的反應(yīng)和導(dǎo)致破壞的數(shù)學(xué)物理模式。 140204060100200300400500600700m0(m)Observat

16、ionStation 2Xiangtang site effect arrayGraniteSoilGraniteObservationStation 3ObservationStation 116m32m47m Structural array of CSBs Disaster Prevention BuildingGroundMeasuring PointBasement15許多國家和地區(qū)強震觀測臺網(wǎng)規(guī)模迅速擴大（1）美國全國 5000臺以上 USGS臺網(wǎng)約1000臺，加州 4000臺以上 TriNet，實時監(jiān)測臺80臺，撥號臺100臺（2）日本全國5000臺以上， 臺站間距25km K-

17、net 有線遙測強震臺網(wǎng) 1000臺 1999年臺灣地震后，增設(shè) 2000臺的新計劃（3）臺灣 1500臺以上（數(shù)字強震儀） 集集大地震獲取記錄1萬條以上（4）伊朗 1000臺以上；墨西哥 430臺（1995）16其它有強地震觀測的國家（地區(qū)）阿根廷、加拿大、智利、印度、意大利、希臘、新西蘭、尼加拉瓜、秘魯、波多黎各、 （前）蘇、委內(nèi)瑞拉、（前）南等 In 2000, there were between 10,000-20,000 strong motion instruments operating worldwide. Most seismically active countries

18、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 networks operated by the US Geological Survey and other organizations. Networks

19、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 have produced over 2500 recordings. Unfortunately, it is still possible for large e

20、arthquakes 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). 17我國的強震觀測182002-2007年投入數(shù)億元大規(guī)模擴建我國數(shù)字強震臺網(wǎng) 初步計劃，增設(shè)2000臺強震儀，其中自由場固定臺1160個，使8個國家一級重點監(jiān)視區(qū)達到每600km2一臺強震儀(臺距約25 km)，13個二級重點監(jiān)視區(qū)達到每1800km2一臺強震儀(臺距約

21、42 km)。另在首都圈設(shè)310臺自由場固定臺，速報烈度，臺站密度達到每50km2一臺強震儀(臺距約7 km)。還包括12個專門的密集臺陣和200臺流動觀測儀器。 19一級強震監(jiān)控區(qū)（8個）20二級強震監(jiān)控區(qū)（13個）21太陽能電池220VGPS天線三分量加速度計固態(tài)強震記錄儀調(diào)制解調(diào)器電話線避雷器強震遙測中心地震動便攜計算機UPS電源電 源避雷器數(shù)字強震臺站框圖22強地震動數(shù)據(jù)處理(Data process)我國強震觀測數(shù)據(jù)中心設(shè)在工程力學(xué)所，積累了愈20000條強震記錄，其中我國記錄的amax20gal的強震數(shù)據(jù)約2000條，amax50gal的545條, amax100gal的206條,

22、 amax200gal的59條, amax500gal的8條，其中大部分是強余震記錄，強震主震記錄僅有數(shù)十條。 23 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

23、 the 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

24、(1997), 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 motio

25、n data 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 for

26、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 (.k-net.bosai.go.jp/ and .kik.bosai.go.jp/, respectively). The content of the European data is also ava

27、ilable on line (.isesd.cv.ic.ac.uk/esd/frameset.htm, Ambraseys et al, 2001) 24美國西部的強震記錄M6場地震級0R1010R3030R100100R300300R總計S1M452182110249377M51916492249308M61210960219211M70690015S2M41545155210236M51245155219233M6015149219185M700719080S3M42310570090M51310570080M6410570071M700420042S4M4460466671723167

28、2M5217404660723135676186571663902M72033763013225數(shù)字化零線（base line）調(diào)整 ，零線校正 ，Butterworth數(shù)字濾波器作雙向濾波，截止頻率可通過事前噪聲記錄與地震記錄的傅立葉譜分析確定。對位移時程用最小二乘法調(diào)整零線以消除線性趨勢。 26Significant accelerograms recorded on film formats are eventually 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