2004年阳江5．2级地震前地震视应变场的时空演变

利用阳江周边地区的地震资料研究了1999年至2004年该区地震视应变的分布和时空变化特征,结果表明,地震视应变的时空变化与阳江地震具有较好的对应关系,2001年在阳江5．2级地震前出现视应变异常区,并且地震视应变总体上逐年增加,逐渐靠近震中,地震就发生在地震视应变异常区附近。     

龙门山断裂带中北段大震复发特征与复发间隔估计

汶川MS8.0地震发生在青藏高原东缘著名的龙门山断裂带上,造成了从映秀、北川至南坝长约240km的同震地表破裂带．然而目前关于龙门山断裂带的大震复发特征研究较少．通过地震地质科学考察和断层断错地貌的差分GPS测量,发现第一级河流阶地、河床和河漫滩上的垂直断距大致相当,均代表汶川地震的位错,而第二级河流阶地上的累计位移大致是最新地震垂直位移的2倍．利用断错地貌、地震矩率和滑动速率3种方法,分别估算了龙门山断裂带大地震的复发间隔．结果表明:龙门山断裂带中北段可能发生与汶川大地震相当的地震,大震复发符合特征地震模型;大震复发间隔为3000——6000a．该结果可为龙门山断裂带的大震预测和地震危险性评价等研究提供重要的定量数据．      

2009年3月19日汤加地震快速矩张量解

2009年3月20日2点17分37秒(北京时间),在汤加群岛发生了Ms7.9地震.我们利用多年来发展的矩张量快速反演技术,通过反演全球台网的宽频带P波波形得到了这次地震的矩张量解,并确定了发震断层参数.     

Geodetic deformation vs. seismic strain deduced by historical earthquakes across the Alborz Mountains

Historical seismicity is used in order to map spatial distribution of seismic moment released by past earthquakes and to compare strain rate deduced from seismicity to those measured by geodetic GPS survey. Spatial analyses are performed on the seismicity of northern boundary of Central Iranian Block which coincides with the Alborz Mountains. This belt has been responsible for several catastrophic earthquakes in the past. In this study, the records of historical and instrumental earthquakes in the Alborz Mountains are used to calculate and plot geographical distribution of seismic moment released in time. A two-dimensional distribution function is proposed and used here to spread seismic moment along causative tectonic features. Using accumulated seismic moment, average slip rates across active faults are estimated for 32 sub-zones along the Alborz Mountains and western Kopet Dag. Seismic moment released by historical and recent earthquakes on this belt accounts for slip rate of 3–5 mm/year which is in good agreement with the geodetic vectors recently deduced from GPS survey in this region. The study also reveals geographical variations of slip rates along some 900 km length of this zone based on seismic history. The results are compared against finding from similar study in this region. Portions of Central and Eastern Alborz show lower seismic strain rate which could imply aseismic motion or overdue earthquakes. Completeness of historical earthquake catalogue and its reliability with regard to earthquake magnitudes, locations, and rupturing systems are among many plausible factors controlling the credibility of such results. Therefore, any conclusions derived from these results remain as reliable as the data and assumptions used for the analyses.     

Moment tensor inversion of explosive long period events recorded on Arenal volcano,Costa Rica,constrained by synthetic tests

In order to constrain the moment tensor solution of an explosive seismic event recorded on Arenal volcano, Costa Rica, we perform tests using synthetic data. These data are generated using a 3D model including the topography of the volcano and the best estimation of the velocity model available for Arenal. Solutions for (i) the moment tensor components, and (ii) the moment tensor plus single forces, are analyzed. When noisy data and mislocated sources are used in the inversion, spurious single forces are easily generated in the solution for the moment tensor components plus single forces. Forces also appear when the inversion is performed using an explosive event recorded on Arenal in 2005. Synthetic tests indicate that these forces might be spurious. However the mechanism is correctly retrieved by the inversion in both solutions. The ability to recover the explosive mechanism for the 2005 event combined with the interpretative aids from the synthetics tests will enable us to invert for the large variation in events observed on Arenal.     

瞬变电磁法多匝重叠小回线装置实验研究

文中采用实验方法对瞬变电磁法多匝重叠小回线装置发射磁矩、关断时间、感应信号强度随发射线圈匝数及接收线圈匝数的变化分别进行了研究。对固定发射线圈匝数改变接收线圈匝数与固定接收线圈匝数改变发射线圈匝数这2种实验方式进行了对比,从而找出了更适合地质响应的发射与接收线圈的匝数。同时还分别采用线圈边长为0.5m×0.5m与1m×1m的线框进行了对比实验,通过分析发射磁矩、关断时间、感应信号强度随线圈边长、线圈匝数的变化,找到合理的重叠小回线装置。实验结果表明发射磁矩随线圈的边长与发射线圈匝数的增加而增加;关断时间随发射线圈匝数近乎呈正比增加,与接收线圈无关;感应信号强度与线圈匝数呈正比关系,但是相比之下,接收线圈匝数更占主导地位。     

隧道开挖对邻近地下管线的影响预测分析

隧道施工会引起周围土体移动,进而对邻近地下管线产生危害。采用Loganathan公式计算隧道开挖引起的管线平面处的土体竖向位移,对地下管线的受力模型进行简化,基于Winkler地基模型,推导出地下管线由于隧道开挖引起的弯矩和变形计算公式。通过相关算例的分析,与连续弹性解和Attwell解的计算结果进行了比较,研究结果表明,提出的方法可以很好地预估地下管线所受的弯矩。     

地震作用下预应力混凝土管桩运动响应三维数值分析

基于黏弹性人工边界,建立上部结构-桩-土的共同作用三维有限元模型,分析地震作用下预应力混凝土管桩的运动响应特性。分别针对预应力混凝土管桩的桩径、双层软硬土剪切波速比值、上覆土层厚度、上部结构荷载等影响因素进行数值计算。参数分析表明:在地震作用下,桩径的增大会导致桩身整体弯矩相应增加,特别是桩身土层分界面处增大明显;软硬土层剪切波速比及上覆土层厚度的增加,引起土层分界面处桩身峰值弯矩增加;固定桩头条件下,桩头与桩身软硬土层分界面处均会产生较大的运动弯矩;上部结构的惯性荷载对固定桩头的内力有着较大影响,对桩身深处段弯矩影响较小。本文研究结论可为预应力混凝土管桩抗震设计提供有益的理论参考。     

A comparative study of seismic provisions between International Building Code 2003 and Uniform Building Code 1997

This study focuses on the comparison of the Uniform Building Code （UBC） 1997 and International Building Code （IBC） 2003 in relation to the seismic design and analysis of special steel moment resisting frame buildings （SMRF）. This paper formulates a numerical study of a steel SMRF building, studied in four different situations, namely： as an office building in San Francisco; as an office building in Sacramento; as an essential facility in San Francisco, and as an essential facility in Sacramento. The analytical results of the model buildings are then compared and analyzed taking note of any significant differences. This case study explores variations in the results obtained using the two codes, particularly the design base shear and drift ratios as they relate to different locations and occupancy use. This study also proves that IBC 2003 is more stringent for the redundancy factor under design category E for the SMRF building, and drift limits for essential facilities.     

基于矩匹配算法的山区影像地形辐射校正方法研究

针对山区遥感影像地形辐射校正问题,应用现有模型(如C校正)进行地形辐射校正很难达到理想效果。引入矩匹配算法,利用DEM数据计算坡度、坡向等地形信息,以特定坡度和坡向数据为参考依据,对影像进行地形辐射校正。通过北京房山区SPOT5影像进行试验,表明该方法能在很大程度上消除地形阴影,更好地反映阴影区域的细节信息,同时光谱特性保真程度较好,原模糊的影像区域通过处理基本上达到有效识别地物的要求。