闾阳－海城－东沟剖面深地震波动力学特征初探

本文利用国内外有关深地震波动力学特征的研究方法，结合现有原始资料的实际条件，对闾阳－海城－东沟深地震测深剖面某些地段的主要波组的动力学特征进行了定性或半定量的分析与研究。在频谱分析，速度振幅的计算与相对理论振幅的对比等方面，获得了一些有益信息。为进一步合理解释深地震测深资料提供依据。     

Source mechanism and source parameters of May 28, 1998 earthquake,Egypt

On May 28, 1998, a moderate size earthquake of mb 5.5 occurred offshore the northwestern part of Egypt (latitude 31.45°N and longitude 27.64°E). It was widely felt in the northern part of Egypt. Being the largest well-recorded event in the area for which seismic data from the global digital network are available, it provides an excellent opportunity to study the tectonic process and present day stress field occurring along the offshore Egyptian coast. The source parameters of this event are determined using three different techniques: modeling of surface wave spectral amplitudes, regional waveform inversion, and teleseismic body waveform inversion. The results show a high-angle reverse fault mechanism generally trending NNW–SSE. The P-axis trends ENE–WSW consistently with the prevailed compression stress along the southeastern Hellenic arc and southwestern part of the Cyprean arc. This unexpected mechanism is most probably related to a positive inversion of the NW trending offshore normal faults and confirms an extension of the back thrusting effects towards the African margin. The estimated focal depth ranges from 22 to 25 km, indicating a lower crustal origin earthquake owing to deep-seated tectonics. The source time function indicates a single source with rise time and total rupture duration of 2 and 5 s, respectively. The seismic moment (M _o) and the moment magnitude (M _w) determined by the three techniques are 1.03 × 10¹⁷ Nm, 5.28; 1.24 × 10¹⁷ Nm, 5.33; and 1.68 × 10¹⁷ Nm, 5.42; respectively. The calculated fault radius, stress drop, and the average dislocation assuming a circular fault model are 7.2 km, 0.63 Mpa, and 0.11 m, respectively.     

Stability and accuracy analysis of outer loop dynamics in real‐time pseudodynamic testing of SDOF systems

Real‐time pseudodynamic (PSD) testing is an experimental technique for evaluating the dynamic behaviour of a complex structure. During the test, when the targeted command displacements are not achieved by the test structure, or a delay in the measured restoring forces from the test structure exists, the reliability of the testing method is impaired. The stability and accuracy of real‐time PSD testing in the presence of amplitude error and a time delay in the restoring force is presented. Systems consisting of an elastic single degree of freedom (SDOF) structure with load‐rate independent and dependent restoring forces are considered. Bode plots are used to assess the effects of amplitude error and a time delay on the steady‐state accuracy of the system. A method called the pseudodelay technique is used to derive the exact solution to the delay differential equation for the critical time delay that causes instability of the system. The solution is expressed in terms of the test structure parameters (mass, damping, stiffness). An error in the restoring force amplitude is shown to degrade the accuracy of a real‐time PSD test but not destabilize the system, while a time delay can lead to instability. Example calculations are performed for determining the critical time delay, and numerical simulations with both a constant delay and variable delay in the restoring force are shown to agree well with the stability limit for the system based on the critical time delay solution. The simulation models are also used to investigate the effects of a time delay in the PSD test of an inelastic SDOF system. The effect of energy dissipation in an inelastic structure increases the limit for the critical time delay, due to the energy removed from the system by the energy dissipation. Copyright © 2007 John Wiley & Sons, Ltd.     

地震子波旁瓣对薄砂体识别的影响

我们研究中国西部某盆地一些气田时,发现地震子波旁瓣在很大程度上影响着薄砂体的识别和解释。该区目的层段H段地层中,辫状河流相薄砂岩储层与湖相泥岩成互层。在地震资料上,来自H段地层顶面的强波谷总跟随一个弱波峰(源于子波旁瓣),此弱波峰与薄砂体顶面反射波峰相互叠合,掩盖了砂体反射,造成了薄砂体识别和解释的困难。为此,我们设计了一套正演模型,利用不同频率的零相位雷克子波合成人工地震剖面,来研究砂体位置、频率与地震子波旁瓣效应的关系,以及振幅类属性与薄砂体关系。提出处于高位置的砂体反射形态清晰,易于识别解释;认为通过对比不同带通滤波处理后的地震资料,可很好辨别旁瓣效应和砂体反射;同时发现振幅类属性可作为薄砂体识别表征参数,可有效合理地描述砂体分布范围和特征。     

内蒙古地区2001年夏季气候特征及前兆信号分析

2001年夏季，内蒙古地区发生了继1999、2000年连续两年的干旱之后的较为严重的全区性干旱。通过分析2001年内蒙古地区夏季气候特征及预测信息，研究内蒙古夏季（1739－2000年中西部地区、1774－2000年东部地区）旱涝气候变化规律，探讨影响内蒙古地区夏季干旱前期信息的变化特征。结果表明，严重干旱年多发生在La Nina事件峰值年次次，环流特征为北半球极涡强度前冬弱后冬强，自上年5月至当年4月呈现出鄂霍次克海高压偏强副高偏弱，并持续3－7个月，继而转成鄂霍次克海高压偏弱副高偏强，并持续2－6个月，可将这些特征作为内蒙古地区夏季严重干旱的前兆信号。     

Galileo系统的频率和信号结构

根据近期公布的由Galileo信号任务组制订的Galileo频率和信号结构计划，列出了Galileo选用的频率和信号结构，包括数据周期，伪随机噪声码扩频的实施等，它考虑了和GPS系统的全兼容和相互共用问题，但对码序列选择、导航电文格式内容等方面尚未确定，有待今后进一步研究确定后公布。     

振幅处理技术在探地雷达资料处理中的应用

作者在文中简述了在自激自收（10天线距）的探地雷达资料处理中，振幅处理（振幅恢复、道内振幅平衡）和道间振幅均衡的方法原理。在实现编程后，应用于实际资料处理，用以增强雷达的深部弱信号，平衡道内的振幅能量和滤除干扰噪声，取得了良好的效果。     

714C天气雷达接收系统故障分析

本文对714C天气雷达接收系统可能发生的故障及原因进行分析，从而为检修接收系统的故障提供参考。     

数字地震台实时处理软件的研制

本软件作为对北京港震机电技术公司软件系统的一个补充，在中文Windows下研制，适用于数字地震台进行数字地震信号实时连续接收和处理。软件的研制充分考虑了台站应用的特点和需求，引入完整的软件工程学理念，采用了面向对象（OOP）的分析设计方法和软件组件技术（COM）。