【作者】 刘陶钧；

【导师】 陶夏新；

【作者基本信息】 哈尔滨工业大学 ， 结构工程， 2009， 硕士

【摘要】 地震动衰减规律表达地震震源、传播途径和场地条件三方面因素对地震动特征的影响,用于推算工程场地的地震动,广泛应用于地震动区划图的编制,地震安全性评价,大多是根据强地震动观测数据统计拟合的经验性关系。本文借助基于地震学的方法,探讨缺乏强地震动观测数据的国家和地区建立衰减关系的方法,重点解决区域性参数的估计这一主要难点。总体思路是收集小地震观测数据,这在许多国家或地区已经积累了一定的数量,以据此计算的富氏谱的外包络线为目标,借助遗传算法反演三、五个关键的区域震源、衰减参数,依其建立区域地震动衰减关系。通过与观测数据及相应地区的经验性衰减关系的对比,考察结果的可靠性。从NSMP数据库中选取了加利福尼亚地区16个基岩台站在50次震级小于5.0的小地震中得到的68条观测记录(每条记录包括两个水平向)。计算的富氏谱显示了很强的振荡起伏,不是光滑的曲线,即使是震级、距离相近的记录,得出的富氏谱也有较大的差别。为了避免反演不稳定,采用富氏谱2~25Hz频段的外包络线为目标函数。借助遗传算法,先后反演了震源参数应力降??、衰减参数品质因子Q ? Q0 f ?中的Q0和? ,以及这三个参数和几何衰减模型中的两个分段点。这五个参数都是与区域地壳结构和介质特性密切相关的,不同地区会有差别,对地震动的衰减有控制作用。反演结果,与加州以前发表的区域参数研究成果大体上相符。基于地震学的随机合成方法,借助平稳随机振动理论、Parseval定理估计均方根加速度a rms,进而推算地震动加速度峰值。采用本文反演的参数,建立了区域地震动衰减关系。与本文使用的小震数据比较,符合得比较好,分组比较显示随着震级的增加,有差别增大的趋势。与美国最近发表的NGA项目成果的五条衰减关系比较,小震符合得好,随震级增大,差别越来越大;近场符合得相对好些,随距离增大,差别也越来越大。说明本文探讨的方法是有前途的,进一步的研究中要注意补充中-远场的数据。更多还原

【Abstract】 Ground motion attenuation relation describes the effect of earthquake source, wave propagation path and local site condition on the motion, can applied to estimate ground motion for seismic design, and is widely adopted in seismic zonation, site seismic hazard assessment. Most of the relations are empirical from statistical fit of observed data. The approach to develop a ground motion attenuation relation in a country or region with no enough observed data is deal with by means of seismological method in this paper, and mainly on the estimation of regional parameters.Some observed data in small earthquake is adopted, since they are usually available in many countries or regions. Total 68 records from 50 small events with magnitude less than 5.0 at 16 rock site stations, each has two horizontal components, are collected from NSMP (National Strong Motion Project) data bank.The calculated Fourier spectra from the data are taken as object of the inversion of three or five key parameters in regional source and attenuation, by Generic Algorithm. The regional ground motion attenuation is developed on this basis, and compared with the observed data and the empirical relation in the region, to demonstrate the result reliability. To guarantee the stability of the inversion, the envelopes of the Fourier spectra in range of 2-25 Hz are taken as the object function. The regional stress drop (source parameter), Q0 and ? in regional quality factor (damping attenuation parameter), and these three with another two parameters in geometric attenuation, are inversed respectively. These five parameters are all closely related with the structure and medium of the regional crust, and must be different in different regions. They control the rate of ground motion attenuation. The result is in the range of the parameter values published in regional parameter study in California.The seismological method with random synthesis, estimates mean square root acceleration a rms by Parseval theorem, and then the peak acceleration. The regional ground motion attenuation is developed by adopting the inversed parameter values. The result is consistent with the data adopted in this paper, and detail comparison in groups shows that the difference at larger magnitude is getting larger. From the comparison with the five attenuation relations published recently by the project NGA (Next Generation Attenuation), one can find that the result of this paper is close to NGA result at small magnitude range, and is getting different as magnitude increasing; is relatively good at near distance, and getting different as distance increasing. The fact illustrates that the approach deal with in this paper is promising, and more moderate to far data must be supplied in further study.更多还原