强地震动的观测和数据处理

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Observation of strong motion is more difficult than 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 teleseisms 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 strong motion accelerograph, was developed in the 1930’s 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. In the 1990’s, the situation changed somewhat with improvements in digital recording technology.
• 记录系统，机械、光、电流计、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。
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。
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Xiangtang site effect array
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）
Measuring Point
Basement
Ground
Structural array of CSB’s Disaster Prevention Building
Observation Station 1 0 20 Granite 16m 32m Granite 60 (m) 0 100 200 300 400 500 600 47m 700 m Soil Observation Station 2 Observation Station 3
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。
Baidu Nhomakorabea
Golden State Bank building on Ventura Blvd. in Sherman Oaks. This is a 13-story reinforcedconcrete structure instrumented by the California Strong Motion Instrumentation Program. Its response was recorded in the 1971 San Fernando earthquake as well as the 1994 Northridge earthquake. In the north-south direction, the lateral-forceresisting 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 westernmost shear wall.
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。
Array layout
• 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。
• 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 stimulated 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 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 records were obtained from the March 10, 1933 Long Beach, California earthquake.
Engineering Seismology (2)
Ground Motion Instrumentation and Data Processing
地震动的观测(observation of GM)
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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。
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 strong 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 strongmotion networks are Japan and Taiwan. The United States has 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 have 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).
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。