大型双槽渡槽地震反应分析

为了得到比较精确的大型双槽渡槽结构的地震反应，根据渡槽结构复杂、影响动力因素较多等特点，采用8结点空间块体单元对渡槽槽身和槽墩进行有限元离散，分别用耦合自由度和多个弹簧单元分别模拟渡槽槽身横向拉杆、加劲肋和盆式橡胶支座，建立了大型双槽渡槽结构地层反应分析的有限元模型，计算了南水北调水利工程中的双洎河大型双槽渡槽的振动特性，并分别用反应谱法和时程分析法对该渡槽进行了地震反应分析，计算结果可为该渡槽的抗震设计提供参考。     

高维PP时间序列分析在地震预报中的应用

将投影寻踪(PP)与高维时间序列分析结合起来，建立了地震PP综合预测模型。并选取祁连山地区作研究区，做了未来三个月内最大震级的短期预测，经展望式检验，合格率(预测误差≤0．5或≤10％)≥80％。中根据实际需要提出建立一定震级门限(M≥4．0)的预测具有更好的效果。本预测模型还可增加自变量、维数和改变时间尺度，并运用到其他领域中。     

Weibull分布的信息熵在地震预报中的应用研究

根据统计分布与信息熵理论，定义了震级信息熵Hm和地震间隔时间信息熵Ht，并推导了它们的计算公式。通过时空扫描和计算，发现强震前1～3年Hm和Ht出现低值异常，与地震有较好的对应关系，可以作为一组中期或中短期预测指标。     

面波群速度频散计算中滤波的数值实验研究

面波群速度计算中容易出现长周期部分时间域分辨率低的问题，因此，如何提高时间域的分辨率很重要。本文将引入等误差滤波的方法就改进群速度计算中滤波效果进行数值试验。结果表明，采用等误差滤波能明显提高群速度长周期部分的分辨率，对准确地测定长周期部分的群速度有重要意义。     

睡莲类植物ITS nrDNA序列的分子系统发育分析

睡莲类植物是目前植物分子系统学与进化研究的一个重要类群。核基因组的ITS区是核核糖体（nrDNA)转录单位的一部分。测定和分析了5个属的7种睡莲类植物的核核糖体ITS序列，并与GenBank中提取的相关序列进行了组合分析，初步获得了睡莲类植物的2个ITS系统树，结果也支持现有分子系统学研究中有关金鱼藻处于较原始位置的观点。     

Changes in source parameters of foreshocks and aftershocks of the 2001 M_S=6.0 Yajiang, Sichuan, earthquake

Introduction An MS=6.0 earthquake occurred on February 23, 2001 in Yajiang county, Sichuan Province. The earthquake is located on the east of the southeast segment of the Litang-Dewu fault with strike of NW. Before the event, on February 14, an MS=5.0 earthquake took place nearly in the same place. In 1948 an MS=7.3 earthquake occurred on the northwestern segment of the Litang fault. The length of the surface rupture belt caused by the earthquake is 70 km, which extended from Litang to…     

Discussion on the feature of strong earthquake: Orderly distribution in time, space and intensity before the Western Kunlun Mountain Pass M=8.1 earthquake

Introduction The Western Kunlun Mountain Pass M=8.1 earthquake occurred on November 14, 2001 is the other M=8 earthquake occurred 50 years after Dangxiong, Tibet M=8.0 earthquake in Chinese mainland. The earthquake has caused the attention of the seismologists in the following aspects: 1) The fracture length is more than 400 km, which is far away from the estimated length by the statistic empirical function between the magnitude and the fracture length (WANG, et al, 2002); 2) The aftersh…     

Tensor time domain electromagnetic resistivity measurements at Ngatamariki geothermal field, New Zealand

Experimental measurements in the Ngatamariki geothermal field, North Island, New Zealand were made to test the applicability of the time domain electromagnetic method for detailed investigation of the resistivity structure within a geothermal field. Low-frequency square wave signals were transmitted through three grounded bipole current sources sited about 8 km from the measurement lines. Despite high levels of electrical noise, transient electric field vectors could be determined reliably for times between 0.02 and 3.3 s after each step in the source current. Instantaneous apparent resistivity tensors were then calculated. Apparent resistivity pseudosections along the two measurement lines show smooth variations of resistivity from site to site. Over most of the field the images consistently show a three-layer resistivity structure with a conductive middle layer (3–10 Ωm) representing the conductive upper part of the thermal reservoir. A deep-seated region of low resistivity in the northwest of the field may indicate a conductive structure at about 1 km associated with a deeper diorite intrusion. Measurements sited closer than about 100 m to drillholes appear to have been disturbed by metallic casing in the holes. A change in resistivity structure in the east of the field may indicate a major geological or hydrothermal boundary.     

Identification of soil degradation during earthquake excitations by Bayesian inference

A Bayesian inference approach is introduced to identify soil degradation behaviours at four downhole array sites. The approach of inference is based on a parametric time‐varying infinite impulse response filter model. The approach is shown to be adaptive to the changes of filter parameters and noise amplitudes. Four sites, including the Lotung (Taiwan), Chiba (Japan), Garner Valley (California), and Treasure Island (California) sites with downhole seismic arrays are analysed. Our results show two major types of soil degradation behaviour: the well‐known strain‐dependent softening, and reduction in stiffness that is not instantaneously recoverable. It is also found that both types of soil degradation are more pronounced in sandy soils than in clayey soils. The mechanism for the second type of soil degradation is not yet clear to the authors and suggested to be further studied. Copyright © 2003 John Wiley & Sons, Ltd.     

Predictive instantaneous optimal control of elastic structures during earthquakes

A predictive instantaneous optimal control (PIOC) algorithm is proposed for controlling the seismic responses of elastic structures. This algorithm compensates for the time delay that happens in practical control applications by predicting the structural response over a period that equals the time delay, and by substituting the predicted response in the instantaneous optimal control (IOC) algorithm. The unique feature of this proposed PIOC algorithm is that it is simple and at the same time compensates for the time delay very effectively. Numerical examples of single degree of freedom structures are presented to compare the performance of PIOC and IOC systems for various time delay magnitudes. Results show that a time delay always causes degradation of control efficiency, but PIOC can greatly reduce this degradation compared to IOC. The effects of the structure's natural periods and the choice of control gains on the degradation induced by the time delay are also analyzed. Results show that shorter natural periods and larger control gains are both more sensitive and more serious to the degradation of control efficiency. Finally, a practical application of PIOC is performed on a six‐story moment‐resisting steel frame. It is demonstrated that PIOC contributes significantly to maintain stability in multiple degree of freedom structures, and at the same time PIOC has a satisfactory control performance. Copyright © 2003 John Wiley & Sons, Ltd.