基于强震记录估算同震位移的研究进展及方法

通过对强震加速度记录估算同震位移技术自20世纪40年代以来国内外研究成果的总结,系统地阐述了通过近断层加速度记录计算同震位移的相关理论、方法的发展历程和成就。首先简述了基于强震记录估算同震位移的意义和普遍存在的漂移现象,然后总结了从模拟记录到数字记录两个阶段计算同震位移所取得的成果,接着归纳了为解决漂移现象所采取的3种基于时程拟合的方法和2种基于小波分析的方法,最后对基于数字强震仪记录估算同震位移的未来研究进行了展望。     

System identification and damage evaluation of degrading hysteresis of reinforced concrete frames

In this study, signal processing approaches and nonlinear identification are used to measure seismic responses of reinforced concrete (RC) structures using the shaking table test. To analyze structural nonlinearity, an equivalent linear system with time‐varying model parameters, singular spectrum analysis to elucidate residual deformation, and wavelet packet transformation analysis to yield the energy distribution among components are adopted to detect the nonlinearity. Then, damage feature extraction is conducted using both the Holder exponent and the Level‐1 detail of the discrete wavelet component. Finally, the modified Bouc‐Wen hysteretic model and the system identification process are employed to the shaking table test data to evaluate the physical parameters, including the stiffness degradation, the strength deterioration and the pinching hysteresis. Finally, the identified stiffness and strength degradation functions from the test data of RC frames in relation to the degree of ground shaking, damage index and the identified nonlinear features are discussed. Based on the proposed method, both signal‐based and model‐based identifications, the relationship between the damage occurrence and severity of structural damage can be identified. Copyright © 2010 John Wiley & Sons, Ltd.     

A wavelet based method for estimating the damping ratio in statnamic pile load tests

A wavelet based method is proposed to evaluate the time-dependent damping ratio in statnamic load tests by the continuous wavelet transform and half-power bandwidth method. The displacement along the pile during a statnamic test is described by a linear shape function, although the pile is assumed to be a single degree of freedom system (SDOF). The damping ratio is calculated by the half-power bandwidth method from the time–frequency spectra of continuous wavelet transform for the statnamic pile load test. A numerical simulation and two field statnamic tests were analyzed to verify the applicability of the proposed method, and the outcomes were compared with the results obtained using the unloading point method (UPM) and a method in literature. The damping ratio obtained with the proposed method is satisfactory and provides an additional interpretation measure for statnamic load tests.     

青藏公路沥青路面下土体温度的小波分析

青藏公路多年冻土区监测断面所获得的土体温度时间序列,只在时间域中分析会忽略频域中所含的重要信息．为了揭示多年冻土区路基下土体温度随时间变化的频谱特征,运用小波变换法对自然地面下和沥青路面下温度变化的频谱特征和趋势进行分析．结果表明：2m、6m深度处温度变化均存在12月、6月和3月的周期成分及1—2月的短周期成分,其中以...     

珠海小规模溪流水温与气温关系研究

使用最小二乘曲线拟合法、相关分析和互相关分析法,对中山大学珠海校区滨海水循环综合试验基地监测的2006年8月~2009年6月溪流水温、水位及气温数据进行分析,发现小规模溪流水温-气温可以用线性模型和logistic模型较好拟合,水温波动相对气温存在2.0h位相延迟,水温-气温相关程度与水位值呈负相关关系;使用Morlet小波滤波、功率谱分析及小波方差计算等方法对水温与气温的日周期、半日周期及季节性周期成分进行研究,探讨其周期大小以及周期成分能量等问题。     

淮河干流径流量长期变化趋势及周期分析

基于淮河干流鲁台子站1951～2008年径流量资料,采用最小二乘法、PIII曲线法和小波分析方法系统分析鲁台子站径流量的变化特征。结果表明:汛期径流量占全年径流总量的64%,年际变化最大相差4.7倍;从线性趋势来看,年径流量减少速率为0.68×108m3/a,其中汛期径流量减少速率为0.24×108m3/a,非汛期径流量减少速率为0.44×108m3/a,汛期径流量丰枯变化跟全年径流量相似程度高,非汛期径流量的年际波动较平稳;三种小波母函数对年径流序列周期分析结果略有差异,Mexcian hat小波检测结果偏宏观,Morlet小波和cmor2-1小波检测兼顾微观周期,cmor2-1小波更加准确全面反映径流周期变化,综合分析得出鲁台子年径流序列2年左右的主周期和8年左右的次周期。     

基于改进Morlet小波的MP算法在地震频谱分析中的应用

对地震信号的时频分析,Morlet小波是在时频联合域内具有最好分辨率的解析小波.介绍了基于Morlet小波的匹配追踪算法的原理,在此基础上改进了时频原子库,并增加了参数k来调节Morlet小波的带宽.对比了基于Morlet小波的匹配追踪(MP)算法与传统STFT时频分析方法,理论模型表明,该算法具有更高的时频分辨率;对...     

连续小波变换在面波压制中的应用

由于原始地震反射数据含有大量噪声,因此地震数据的降噪处理是十分重要的,而面波的压制是陆上地震资料降噪处理的主要问题之一。这里根据共炮点记录中面波与反射波主要能量在时间～尺度域的分布不同,以及面波的频率特性等特点,提出了一种基于时间～尺度域的面波衰减方法。将该方法用于实际炮集资料的处理,并与常用的F-K滤波方法进行对比,结果表明,该方法在衰减面波干扰的同时,能更好地保护反射波,并且对于信噪比较低的浅层反射信号能够取得较好的效果。     

平稳小波变换在地震反射资料中面波压制的应用

提高地震信号的分辨率是地震勘探要解决的一项主要任务,而提高地震信号的信噪比是提高地震信号分辨率的先决条件。要提高地震资料的信噪比,需要去除地震资料中的相干噪声和随机噪声。本文介绍了平稳小波变换结合阈值压制面波干扰的方法,通过实际地震记录的处理证实了该方法的有效性。     

Lithospheric Structure in the North China Craton Constrained from Gravity Field Model(EGM 2008)

A detailed knowledge of the thickness of the lithosphere in the North China craton(NCC) is important for understanding the significant tectonic reactivation of the craton in Mesozoic and Ce-nozoic.We achieve this goal by applying the newly proposed continuous wavelet transform theory to the Gravity Field Model(EGM 2008) data in the region.Distinct structural variations are identified in the scalogram image of profile Alxa-Datong(大同)-Qingdao(青岛)-Yellow Sea(profile ABC),trans-versing the main units of NCC,whi...