川滇地区地震动衰减关系中震源谱与衰减参数反演的改进

发布时间：2018-05-15 19:00

本文选题：地震动衰减关系 + 测震数据　；参考：《哈尔滨工业大学》2015年硕士论文

【摘要】：地震动衰减关系是工程地震研究的一个重要课题,国内外学者一直很关注。和世界上大多数国家和地区一样,我国积累的强地震动观测数据相对经验性衰减关系的统计,尚不够充分。基于地震学的地震动衰减关系,借助地震学理论建立起来的计算点源引起的地表地震动傅里叶幅值谱计算公式,区域参数可以提供地震监测台网小地震测震数据反演,是一条可以指望发展方向,已经取得了引人注目的成果。为进一步深入研究基于地震学的地震动衰减关系,本文收集、整理了川滇地区4.5级及以上的共计1303条强地震动记录,通过图、表的直观分析,指出两地强地震动数据近场的少、大地震的少,PGA小的多、大的少,不足以统计经验性衰减关系,只宜用来对衰减关系做比较检验。本文以数字地震监测台网的小震记录为基础,矩震级均在3.5至4.5级之间,包括四川82次地震的147条记录,云南154次地震的863条记录,震级在3.6至4.3之间分布较均匀,距离在50km至300km之间分布亦比较均匀。文中反演采用微遗传算法,其本质是寻优搜索的过程。正演采用地震学中点源引起的地表一点地震动傅里叶幅值谱傅氏谱的计算式,其中不能直接测量、有待反演的参数,包括震源谱中的应力降Δσ、品质因子Q中的Q0和?以及几何衰减项的两个距离分段点1R和2R等五个参数。计算式估计的傅里叶幅值谱是光滑的曲线,实际记录经FFT获得的谱曲线在显现总体涨落起伏特征外还有剧烈振荡是一个矛盾的问题。从观测数据计算的傅里叶幅值谱中提取体现谱曲线总体走势、贴近平均谱幅值的光滑目标曲线对反演稳定性很重要。以前采用傅里叶幅值谱包络函数可以抑制剧烈振荡可能带来反演不稳定的问题,但是会在实质上提高谱幅值的总体水平,可能导致建立的衰减关系估计地震动偏高。本文探讨两种表达傅立叶幅值谱平均特征的曲线,滑动平均曲线和周期图曲线,通过光滑效果的比较,选取了滑动平均曲线作为反演的目标曲线。归纳区域已有研究成果,适当扩大,选定了上述五个参数可能的取值范围。以滑动平均得到的目标曲线构造反演的目标函数,得出两个地区各一组参数值。与采用幅值谱包络线为目标曲线反演的参数值相比,数值差别不是很大,会在一定程度上导致几何衰减略加快,非弹性衰减有所减慢,强烈地震近距离处估计的地震动幅值减小。据反演参数建立了川、滇两地的地震动PGA衰减关系,给出了衰减曲线和用二维表格给出的(部分)数值。与区域有限的实际观测数据比较,表明本文的PGA衰减结果都能通过观测数据丛,7级的估计更接近观测数据点。受非弹性衰减减慢的效应影响,几何衰减表现的地壳波导效应被明显削弱。与区域常用的PGA衰减关系比较,本文的结果总体居中。定量的误差项值总体偏大,随着距离增大,误差值有增大的趋势。本文的改进主要表现在对大地震地震动估计的改善上,四川7级地震的误差项均值大大减小,标准差也有所减小,云南7级的误差项标准差减小明显。与随机振动理论简化方法结果的比较,表明其简化会导致一定的低估,差别随震级的增加而增大,7级的差别可以达到两三倍。所采用的随机振动理论中谱矩和峰值因子均是建立在平稳随机过程基础上的,与地震动的强烈非平稳性相差很大,是低估的主要原因。最后,总结了本文的主要工作进展,也展望了有待进一步深入研究的三个问题。
[Abstract]:Seismic dynamic attenuation relationship is an important subject in engineering earthquake research, and scholars at home and abroad have been very concerned. Like most countries and regions in the world, statistics on the relative empirical attenuation relation of strong ground motion data accumulated in China are not sufficient. The calculation formula of the dynamic Fourier amplitude spectrum of the ground surface earthquake caused by the calculated point source is obtained. The regional parameters can provide the seismic data inversion of the seismic monitoring network with small earthquakes. It is a direction of development and has achieved remarkable results. A total of 1303 strong ground motion records of 4.5 and above in the Sichuan and Yunnan areas are recorded. Through the visual analysis of the chart and the table, it is pointed out that the near field of strong ground motion data in the two places is few, the large earthquakes are few, the PGA is small, and the large few are small enough to be used to compare the empirical attenuation relations. Based on seismic record, the moment magnitude is between 3.5 and 4.5 levels, including 147 records of 82 earthquakes in Sichuan, 863 records of 154 earthquakes in Yunnan, the distribution of the magnitude between 3.6 and 4.3 is more uniform and the distance between 50km and 300km is more uniform. The Fourier spectrum of a point ground motion caused by a point source in seismology is calculated, which can not be measured directly. The parameters to be retrieved, including the stress drop in the source spectrum, the Q0 in the quality factor Q and the five parameters of the two distance segments 1R and 2R of the geometric attenuation term, are calculated. A smooth curve, the actual recording of the spectral curves obtained by FFT is a contradictory problem in showing the fluctuation characteristics of the overall fluctuation. The general trend of the spectral curve is extracted from the Fourier amplitude spectrum calculated from the observed data. The smooth target curve close to the average spectral amplitude is very important for the inversion stability. Fu Li was used before. The spectral envelope function of the leaf amplitude can suppress the problem that the violent oscillation may bring the inversion instability, but it will substantially increase the overall level of the spectral amplitude, which may lead to the established attenuation relationship to estimate the ground motion. This paper discusses two kinds of curves, the sliding mean curve and the periodic graph, which express the Fu Liye amplitude spectrum. The sliding average curve is selected as the target curve of the inversion. The existing research results are summed up in the region. The range of the possible value of the above five parameters is selected. The target function of the target curve obtained by the sliding average is constructed, and the parameters of each group of two regions are obtained. Compared with the parameter values of the target curve, the numerical difference is not very large, and the geometric attenuation is slightly quicker, the inelastic attenuation is slowed down to some extent, and the seismic amplitude of the strong earthquake near the near distance is reduced. According to the inversion parameters, the seismic dynamic PGA attenuation relation of Sichuan and Yunnan provinces is established, and the attenuation curve and the two dimensional table are given. The (part) value given by the lattice is compared with the actual observed data from the limited area. It shows that the PGA attenuation results in this paper can all pass through the observation data cluster, and the estimation of the 7 level is closer to the observation data point. The effect of the inelastic attenuation reduction on the geometric attenuation performance of the crustal waveguide effect is obviously weakened. The relation to the PGA attenuation relationship commonly used in the region is compared. Compared with the overall results of this paper, the quantitative error value is generally large, and the error value increases with the increase of distance. The improvement of this paper is mainly shown in the improvement of the earthquake ground motion estimation. The mean value of the error term of the Sichuan 7 magnitude earthquake is greatly reduced, the standard deviation is also reduced, and the standard deviation of the error term of the 7 level is reduced obviously. Compared with the results of the random vibration theory, it is shown that the simplification results in a certain underestimation, the difference increases with the increase of the magnitude, and the difference of the 7 level can reach two or three times. The spectral moments and the peak factors in the random vibration theory are based on the stationary random Guo Chengji, and the difference from the strong non-stationary of the ground motion. At last, the main progress of this paper is summarized, and three problems that need further study are also looked forward to.

【学位授予单位】：哈尔滨工业大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：P315.9

【参考文献】