基于CORS的DInSAR大气延迟校正方法研究

针对利用GPS数据改正DInSAR大气延迟误差中存在CORS站点稀疏的问题,给出一种广义曲面拟合插值模型,并基于北京地区的GPS观测数据和SAR影像对比较了反距离加权插值模型（IDW）和曲面拟合插值模型（CSF）用于区域对流层延迟建模的精度,然后对SAR差分干涉图进行大气延迟校正。结果表明,曲面拟合模型比反距离加权模型更能反映区域单差对流层延迟特性,两次实验的插值精度分别达到了7.1和3.5 mm。采用CORS观测数据和曲面拟合内插模型,可有效削弱DInSAR中的大气延迟误差,提高DInSAR测量结果的精度。     

基于网络法时序InSAR大气误差校正方法研究

将大气相位延迟对干涉图的影响分为3个主要分量,分别采用网络法进行解算和消除。以西藏崩错地区为实验区,利用2007~2010年期间20景ENVISAT ASAR数据对该方法进行验证,并采用一维协方差函数分别对校正前后的大气延迟误差进行估计。结果显示,协方差函数中平均方差从原来的3.1 mm²降到0.6mm²,降低了80%;e-folding波长从原来的1.5 km减低到0.21 km,减低了86%,说明网络法可以有效地校正干涉图中的大气相位延迟误差。     

Failure time variation derived from R-S relation： the role of the static stress perturbation

In general, earthquake cycle related to earthquake faulting could include four major processes which could be described by(1) fault locking,(2) self-acceleration or nucleation(possible foreshocks),(3) coseismic slip, and(4) post-stress relaxation and afterslip. A sudden static stress change/perturbation in the surrounding crust can advance/ delay the fault instability or failure time and modify earthquake rates. Based on a simple one-dimensional spring-slider block model with the combination of rate-and-statedependent friction relation, in this study, we have approximately derived the simple analytical solutions of clock advance/delay of fault failures caused by a sudden static Coulomb stress change applied in the different temporal evolution periods during an earthquake faulting. The results have been used in the physics-based explanation of delayed characteristic earthquake in Parkfield region, California, in which the next characteristic earthquake of M 6.0 after 1966 occurred in 2004 instead of around 1988 according to its characteristic return period of 22 years. At the same time, the analytical solutions also indicate that the time advance/ delay in Coulomb stress change derived by the dislocation model has a certain limitation and fundamental flaw. Furthermore, we discussed the essential difference between rate- and state-variable constitutive(R–S) model and Coulomb stress model used commonly in current earthquake triggering study, and demonstrated that, in fact, the Coulomb stress model could be involved in the R–S model. The results, we have obtained in this study, could be used in the development of time-dependent fault interaction model and the probability calculation related to the time-dependent and renewal earthquake prediction model.     

2006年3月31日吉林乾安M5．0余震序列S波分裂研究

2006年03月31日20时23分,松原市乾安县与前郭县交界处的查干花乡附近（44°36′N,124°03′E）发生5．0级地震,是吉林省近40年来最大一次地震。利用流动台记录到的地震波形资料对乾安地震余震序列进行s波分裂研究。结果表明,S波快波偏振方向的优势取向为NNE,与乾安地震主震的最大主压应力方向偏差较大,与该区区域应力场方向不一致,表明这次地震与区域的构造变化和应力场调整有关。s波分裂时间延时大小受多种因素影响,与S波传播时经过的介质性质关系密切,慢波延迟时间在0．02～0．38S之间变化。     

地震预警信息发布时延分析

对地震预警信息发布时延作调研后认为,预警接收终端的发布时延小于1 s;广播、电视发布时延为几s;互联网发布（新媒体、手机APP、第三方平台推送）时效性受并发量影响,在千万级用户时发布时延是30～40 s。因此,应采用分区域分级发布策略,以提高发布时效。以汶川地震为例,针对社会公众发布预警信息的时效分析结果表明,在首台触发3～4 s内开始发布预警信息,震中20～50 km范围内95%以上的网民有1～7 s的预警时间,而破裂最大区域（北川）95%以上的网民将获得30 s以上的预警时间。     

测站气温与气压对GPS定位结果的影响

分别利用全球气压气温模型GPT和GPT2处理相同的连续观测站数据。对比两组测站位置估值（简称位置）发现,测站气压偏差所导致的先验天顶延迟偏差不能完全被延迟参数所吸收,导致测站垂向位置出现偏差,且偏差的大小与测站纬度及数据处理中所采用的数据权重有关。测站气温偏差对测站位置的影响可忽略不计,但GPS定位结果的内符合精度随着测站气温的升高而降低。     

Large‐scale real‐time hybrid simulation involving multiple experimental substructures and adaptive actuator delay compensation

Real‐time hybrid simulation provides a viable method to experimentally evaluate the performance of structural systems subjected to earthquakes. The structural system is divided into substructures, where part of the system is modeled by experimental substructures, whereas the remaining part is modeled analytically. The displacements in a real‐time hybrid simulation are imposed by servo‐hydraulic actuators to the experimental substructures. Actuator delay compensation has been shown by numerous researchers to vitally achieve reliable real‐time hybrid simulation results. Several studies have been performed on servo‐hydraulic actuator delay compensation involving single experimental substructure with single actuator. Research on real‐time hybrid simulation involving multiple experimental substructures, however, is limited. The effect of actuator delay during a real‐time hybrid simulation with multiple experimental substructures presents challenges. The restoring forces from experimental substructures may be coupled to two or more degrees of freedom (DOF) of the structural system, and the delay in each actuator must be adequately compensated. This paper first presents a stability analysis of actuator delay for real‐time hybrid simulation of a multiple‐DOF linear elastic structure to illustrate the effect of coupled DOFs on the stability of the simulation. An adaptive compensation method then proposed for the stable and accurate control of multiple actuators for a real‐time hybrid simulation. Real‐time hybrid simulation of a two‐story four‐bay steel moment‐resisting frame with large‐scale magneto‐rheological dampers in passive‐on mode subjected to the design basis earthquake is used to experimentally demonstrate the effectiveness of the compensation method in minimizing actuator delay in multiple experimental substructures. Copyright © 2011 John Wiley & Sons, Ltd.     

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