Modal response analysis of multi‐support structures using a random vibration approach

A formulation is developed for modal response analysis of multi‐support structures using a random vibration approach. The spectral moments of the structural response are rigorously decomposed into contributions from spectral moments of uncoupled modal responses. An advantage of the proposed formulation is that the total dynamic response can be obtained on the basis of mode by mode uncoupled analyses. The contributions to the total response from modal responses under individual support ground motions and under cross‐correlated pairs of support ground motions can be recognized explicitly. The application and performance of the formulation is illustrated by means of an example using a well‐established coherency spectrum model and widely known power spectra models, such as white noise and Kanai–Tajimi. The first three spectral moments of displacement, shear, and bending moment responses are computed, showing that the formulation produces the same results as the exact solution. Copyright © 2015 John Wiley & Sons, Ltd.     

Framework of aftershock fragility assessment–case studies: older California reinforced concrete building frames

Current seismic design codes and damage estimation tools neglect the influence of successive events on structures. However, recent earthquakes have demonstrated that structures damaged during an initial event (mainshock) are more vulnerable to severe damage and collapse during a subsequent event (aftershock). This increased vulnerability to damage translates to increased likelihood of loss of use, property, and life. Thus, a reliable risk assessment tool is required that characterizes the risk of the undamaged structure subjected to an initial event and the risk of the damaged structure under subsequent events. In this paper, a framework for development of aftershock fragilities is presented; these aftershock fragilities define the likelihood that a building damaged during a mainshock will exhibit a given damage state following one or more aftershocks. Thus, the framework provides a method for characterizing the risk associated with damage accumulation in the structure. The framework includes the following: (i) creation of a numerical model of the structure; (ii) characterization of building damage states; (iii) generation of a suite of mainshock–aftershocks; (iv) mainshock–aftershock analyses; and (v) development of aftershock fragility curves using probabilistic aftershock demand models, defined as a linear regression of aftershock demand–intensity pairs in a logarithmic space, and damage‐state prediction models. The framework is not limited to a specific structure type but requires numerical models defining structural response and linking structural response with damage. In the current study, non‐ductile RC frames (low‐rise, mid‐rise, and high‐rise) are selected as case studies for the application of the framework. Copyright © 2015 John Wiley & Sons, Ltd.     

松辽盆地北部反转构造的几何特征、变形机制及其地震地质意义——以大安-德都断裂为例

松辽盆地北部发育的中-新生代反转构造代表着盆地继伸展裂陷阶段、热冷却拗陷阶段之后的第3个构造演化阶段。系统收集了布设在覆盖大安-德都断裂及其附近的14个3维地震工区,30条区域地震反射大剖面,在此基础上准确追踪解释了T06、T1、T11、T2、T3、T4、T5等7个地震反射层位。同时基于52口钻孔的资料对重点反射层的地质年代进行了重新厘定,分析了不同时期断层展布特征及分布规律,重点就松辽盆地中新生代反转构造的几何学形态、变形特征与机制进行了研究。研究结果认为,该反转构造为大安-德都断裂在中生代末期和新生代早期的主要变形模式,符合"逆断层-褶皱"构造的几何形态和变形机制。松辽盆地内部的构造变形主要集中在该构造反转带上。此外,重点选择了2条典型剖面开展了野外实验性浅层人工地震勘探。根据勘探结果并结合该地区第四纪地层厚度分析认为,广泛发育在背斜顶部且断错T06界面的小断裂可能代表了大安-德都断裂强变形带的最新活动性,勘探剖面揭示的上断点断错最年轻地层为中更新统,并据此初步判定该断裂最新活动时代可能为中更新世。此外,综合人工地震勘探结果、现代地震活动性和震源机制解研究结果认为,大安-德都断裂的"逆断层-褶皱"构造反转带最新的活动已明显影响到了近地表的反射层,清楚断错了早-中更新世地层,控制着断裂附近中强地震的发生,是松辽盆地内部或整个东北地区重要和典型的发震构造之一。     

雪峰造山带北段地质构造特征——以慈利—安化走廊剖面为例

以慈利—安化走廊带为例, 对雪峰造山带北段西部地质构造特征进行了调查研究。研究表明, 雪峰造山带在廊带上可分为北部武陵断弯褶皱带和南部雪峰基底拆离带。武陵断弯褶皱带内主要发育北东东—东西向褶皱和同走向逆断裂, 另有少量北东向和北北西向右行平移断裂、北东东—东西向正断裂; 雪峰基底拆离带发育东西—北东向褶皱和同走向逆断裂、正断裂以及少量北东向平移断裂。武陵断弯褶皱带变形主要受控于板溪群底界面向北的滑脱及其导生的逆冲; 雪峰基底拆离带变形主要受控于切穿冷家溪群褶皱基底的断裂拆离与逆冲, 拆离与逆冲的方向总体由南向北, 但南缘总体逆冲方向指向南, 从而组成背冲构造样式。上述褶皱和断裂形成于武陵运动、加里东运动、印支运动、早燕山运动等挤压事件, 白垩纪伸展事件, 古近纪中晚期区域北东—北北东向挤压以及古近纪末—新近纪初北西向挤压等构造事件, 其中以加里东运动和印支运动形成的褶皱和同走向逆断裂最为重要。雪峰造山带北段与中段—南段一样具背冲构造样式, 但受加里东期近南北向挤压的区域大地构造背景影响, 北段逆冲、增厚和抬升作用的强度与幅度更大。      

直流电阻率法的深部结构分辨——三维模型的二维反演

利用三维有限差分方法进行深部三维结构的电阻率三维数值模拟,对计算得到的单极-单极和对称四极装置视电阻率剖面进行电阻率二维反演研究。结果显示:单极-单极装置在横向上只要三维异常体中心的水平间距不小于两者中心埋深之和,就可以基本将2个三维结构分辨出来;相同情况下,对称四极装置在横向上的分辨效果优于单极-单极装置;单极-单极装置在垂向上的分辨要优于对称四极装置。      

Kriging in the Presence of Locally Varying Anisotropy Using Non-Euclidean Distances

A stationary specification of anisotropy does not always capture the complexities of a geologic site. In this situation, the anisotropy can be varied locally. Directions of continuity and the range of the variogram can change depending on location within the domain being modeled. Kriging equations have been developed to use a local anisotropy specification within kriging neighborhoods; however, this approach does not account for variation in anisotropy within the kriging neighborhood. This paper presents an algorithm to determine the optimum path between points that results in the highest covariance in the presence of locally varying anisotropy. Using optimum paths increases covariance, results in lower estimation variance and leads to results that reflect important curvilinear structures. Although CPU intensive, the complex curvilinear structures of the kriged maps are important for process evaluation. Examples highlight the ability of this methodology to reproduce complex features that could not be generated with traditional kriging.     

马元铅锌矿含矿构造带特征及矿床成因讨论

陕西马元铅锌矿产于扬子板块北缘碑坝穹隆构造周缘灯影组上段。矿化受角砾状、裂隙状白云岩和放射状横向断裂组成的构造带控制。矿化强度与构造角砾岩发育程度和藻屑白云岩厚度成正相关。晚震旦世灯影期,通过基底断裂及裂隙通道产生的海水循环系统不断地萃取并吸收基底杂岩中的Pb、Zn等有用组份,运移到台坪相被藻类吸附,铅锌矿初步富集。灯影世末期,基底隆起产生灯影组容矿构造系统,同时形成构造热卤水活化、迁移吸附在藻屑白云岩中的铅锌等成份形成含矿热液,并在容矿构造带中充填富集成矿。     

The crust and upper mantle of the Sulu UHPM belt

All results from integrated geophysical investigations in the Sulu region are summarized in this paper, trying to reconstruct the Sulu UHPM processes. New seismic S-wave tomographic results suggest a velocity-abnormal zone occurs beneath the Sulu crust, revealing detailed upper mantle structures that high-velocity lumps within the abnormal zone are sequentially distributed beneath the bottom of the asthenosphere. These high-velocity lumps might represent delaminated eclogites or residuals of the subducted oceanic plate. Based on integrated interpretation of the geophysical data, we propose a working model for tectonic reconstruction of the Sulu UHPM processes, which can explain the crust and upper mantle structures of the area. The involved tectonic processes are related to north-eastward escaping of the Sulu terrane, subduction and delamination cycles of the Dabie-Sulu oceanic plate, and post-orogenic lithospheric thinning and magma underplating. The UHPM rocks are believed to have syn-subduction delaminated down to the bottom of the asthenosphere during 245-180 Ma, and the delamination process seemed smooth and nearly continuous without extensive violence.     

吉林省东部韧性剪切带特征及其与金银成矿关系

国内外贵金属与控矿构造研究表明,韧性剪切带,特别是发育在太古宙古老陆核花岗-绿岩地体中的韧性剪切带是最重要的控矿构造.文章列举夹皮沟韧性剪切带、小四平-南岔韧性剪切带、山门-叶赫韧性剪切带等实例对吉林省东部韧性剪切带的展布规律、基本特征及其控矿作用进行了详细论述,总结了韧性剪切带与金、银矿产的关系.     

江西彭山锡(铅锌)多金属矿田构造地质特征及成矿机理探讨

江西彭山锡 (铅锌 )多金属矿田位于长江中下游多金属成矿带中的九瑞地区。彭山隐伏钙碱性花岗岩体侵位为锡 (铅锌 )多金属矿的形成提供了热动力及成矿物质来源。自晋宁期形成的长期活动的基底深断裂和由彭山岩体底辟侵位形成的穹窿构造 ,以及由此派生的次级断裂带 ,诸如环形滑脱断裂、顶脱断裂和节理裂隙 ,都为含矿热液的运移和矿体就位提供了空间。形成彭山岩体 (DI >90 )的岩浆经历了较为充分的分异 ,在岩浆热液对流系统和地下水对流系统的双重作用下 ,含矿热液流体的成分随温度降低而改变 ,导致 6个阶段的成矿作用。各阶段的矿物组合随温度而变化 ,在空间上有一定的叠加 ,在萤石 -硅酸锡阶段 ,还发现了马来亚石。各类矿产在空间上的分布呈环状 ,即由岩体中心向外围依次出现内侧的高温As-Sn带、中间的Sn -Pb和Pb -Zn -Ag带和外围的低温萤石带。文中还以锡为例 ,详细讨论了锡在黑云母与热液流体之间的迁移及其矿化过程。