Preliminary study on aftershock decay rate of the 2013 Ms7.0 Lushan earthquake     

Zhe Jia  Weiwen Chen  Risheng Chu 《地震学报(英文版)》2013,(3):185-190

We obtained a catalog of early aftershocks of the 2013 Lushan earthquake by examining waveform from a nearby station MDS which is 30.2 km far away from the epicenter, and then we analyzed the relation between aftershock rate and time. We used time-window ratio method to identify aftershocks from continuous waveform data and compare the result with the catalog provided by China Earthquake Networks Center （CENC）. As expected, a significant amount of earthquakes is missing in CENC catalog in the 24 h after the main shock. Moreover, we observed a steady seismicity rate of aftershocks nearly in the first 10,000 s before an obvious power-law decay of aftershock activity. We consider this distinct early stage which does not fit the Omori law with a constant p （p - 1） value as early aftershock deficiency （EAD）, as proposed by previous studies. Our study suggests that the main shock rupture process is different from aftershocks＇ processes, and EAD can vary in different cases as compared to earthquakes of strike-slip mechanism in California.  相似文献   

基于应力变化的余震预测研究综述     

贾若  蒋海昆 《中国地震》2013,29(3):293-305

本文综述了近期基于应力变化的余震预测研究进展。从静态库仑应力触发角度对余震活动进行研究主要有两方面内容:一是集中于对主震触发余震机制的讨论;二是通过库仑应力变化分布区域与实际余震空间分布区域进行定性对比分析,并认为库仑应力变化为正的区域有利于余震的发生,而这正是余震活动与应力变化高度相关的重要证据。基于应力变化的余震预测研究的一项重要内容是建立在速率-状态依从摩擦定律基础之上的余震活动率研究,即将余震活动作为一系列独立的成核事件,从断层滑动触发地震的角度出发,结合静态库仑应力计算得到余震活动率,进而得到余震数量。余震活动是与断层面上的剪切应力变化相关联的,余震活动率受应力扰动幅度、应力加载速率、断层基本物理特性及背景地震活动率等的影响。考虑到“余震激发余震”的特点,ETAS 模型与静态库仑应力变化相结合的研究方法提供了一条统计学与物理学方法(应力变化)相结合、能更完整地刻画余震活动特征的可能途径。  相似文献   

基于择优的块体模型解算南北地震带中南段主要断层滑动速率   总被引：1，自引：1，他引：0  

闫伟  武艳强  牛安福  李晓帆  张凌空  吉平 《中国地震》2013,29(1):81-90

利用1999 ～2007期GPS速度场数据,通过块体模型择优得到了南北地震带中南段主要块体边界带变形的适用模型,并给出了块体边界主要断层的滑动速率.结果表明,龙门山断裂带宝兴-汶川段张压速率较小,为0.5 ～ 1.8mm·a-1;汶川-茂县压性相对显著,速率达1.8～3.8mm·a-1;鲜水河断裂带张压及走滑速率存在一定的空间差异性特征,即炉霍以北张性滑动速率(8.1mm·a-1)比左旋走滑速率(4.8mm·a-1)大,炉霍-道孚段张压速率与走滑速率基本相同,道孚-康定段呈现出左旋走滑速率减小、张性速率增大的变化趋势,康定-石棉段表现出较明显的左旋走滑性质;小江断裂带走滑速率明显大于张压速率;红河断裂带空间分段性较为明显,北西段滑动量较小,但存在一定的张压分量(景东段速率4.7 mm·a-1),南东段(个旧以西)以走滑为主(速率4.5mm·a-1).  相似文献   

OSL chronology of Quaternary terraced deposits outcropping between Mt. Etna volcano and the Catania Plain (Sicily,southern Italy)     

《Physics and Chemistry of the Earth》2013

In this paper we tested the applicability of the Optically Stimulated Luminescence (OSL) technique through Single-Aliquot Regenerative-dose (SAR) protocol, on single grain quartz extracted from alluvial–coastal sediments. Five samples were collected from deposits belonging to a flight of seven orders of coastal–alluvial terraces outcropping in the area between Mt. Etna volcano and the Catania Plain (Sicily, southern Italy), at the front of the Sicilian fold and thrust system. After various performance tests, we obtained OSL ages ranging between 240 ± 12 and 80 ± 4 ka, consistent with the normal evolutionary model of a terraced sequence, moving from the highest to the lowest elevation. Obtained data allowed us to determine a mean uplift rate of 1.2 mm/year during the last 240 ka, mostly related to regional uplift processes coupled with sea-level changes. Moreover, terraces belonging to the two highest orders are folded, forming a large anticline. According to our results, the frontal thrust of the Sicilian chain was active between 236 and 197 ka ago, even though seismological and geodetic data suggest current activity to the back.  相似文献   

Seismic response of steel structures with seesaw systems using viscoelastic dampers     

Jae‐Do Kang  Hiroshi Tagawa 《地震工程与结构动力学》2013,42(5):779-794

Vibration control systems are being used increasingly worldwide to provide enhanced seismic protection for new and retrofitted buildings. This paper presents a new vibration control system on the basis of a seesaw mechanism with viscoelastic dampers. The proposed vibration control system comprises three parts: brace, seesaw member, and viscoelastic dampers. In this system, only tensile force appears in bracing members. Consequently, the brace buckling problem is negligible, which enables the use of steel rods for bracing members. By introducing pre‐tension in rods, long steel rods are applicable as bracing between the seesaw members and the moment frame connections over some stories. Seesaw mechanisms can magnify the damper deformation according to the damper system configuration. In this paper, first, the magnification factor, that is, the ratio of the damper deformation to the story drift, is delivered, which includes the rod deformation. Results of a case study demonstrate that the magnification factor of the proposed system is greater than unity for some cases. Seismic response analysis is conducted for steel moment frames with the proposed vibration control system. Energy dissipation characteristics are examined using the time‐history response results of energy. The maximum story drift angle distributions and time‐history response results of displacement show that the proposed system can reduce the seismic response of the frames effectively. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

Analytical and experimental investigations on seismic performance of exterior beam–column subassemblages of existing RC‐framed building     

Saptarshi Sasmal  K. Ramanjaneyulu  Balthasar Novák  N. Lakshmanan 《地震工程与结构动力学》2013,42(12):1785-1805

Seismic performance of exterior beam–column subassemblages of reinforced concrete structure designed and detailed on the basis of the provisions of Eurocode and Indian Standards at different stages of their evolution is evaluated. Performance of the subassemblages designed and detailed according to the three different stages of codal evolution (gravity load design, ‘Nonductile’, and ‘Ductile’) is evaluated through analytical formulations and experimental investigations. In the ‘NonDuctile’ specimens, it has been observed that the shear distortion and degradation in stiffness and strength are significantly high. Performance of the ‘Ductile’ specimens based on Eurocode and Indian Standards is almost similar in terms of strength and stiffness degradation. Nevertheless, the specimen designed on the basis of Indian Standard shows higher energy dissipation at a given drift ratio. In the analytical study, shear and flexural failure of members of subassemblage and shear failure of the joint are considered as possible modes of failure of the beam–column subassemblage. For evaluating the shear strength of the joint region, a soften strut‐and‐tie model is used. Analytically obtained strengths based on the failure criteria of different components of the specimens have been first validated with experimental results and then used to determine the strength of the specimens. The investigation could indicate even the mode of failure at local level. It is utmost important to mention here that even the ductile specimens dissipate most of the energy through the development of damage in the joint region, which is neither desirable nor safe for the stability of whole structure. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

Reducing the non-axisymmetry of a planetary dynamo and an application to saturn     

D. J. Stevenson 《地球物理与天体物理流体动力学》2013,107(1-2):113-127

Abstract

If a conducting fluid shell is undergoing spin-axisymmetric differential rotation and overlies the dynamo generating region of a planet then it is capable of greatly reducing the non-spin-axisymmetric components of the generated field, provided the appropriate magnetic Reynolds number is large. The model, closely related to the electromagnetic skin effect, is quantified and applied to Saturn. The observed small dipole tilt (～ 1°) of Saturn's magnetic field can be explained because of the presence of a stably stratified conducting layer overlying the dynamo region. This layer is a predicted consequence of the thermal evolution, arises because of the limited solubility of helium in metallic hydrogen (Stevenson, 1980), and appears to be required by the Voyager infrared observations indicating depletion of helium from Saturn's atmosphere. The much larger dipole tilt angles of Jupiter and the Earth indicate the absence of any such stable, differentially rotating layer with a large magnetic Reynolds number.  相似文献   

Prediction of the consumption rates for juvenile Atlantic salmon (Salmo salar L.) on the scale of habitat patches: Development of empirical models based on stomach contents     

Frédéric Burton  Daniel Boisclair 《Limnologica》2013,43(5):332-338

Rivers and streams are unstable environments in which estimation of energetic costs and benefits of habitat utilization are the daunting exercise. Empirical models of food consumption may be used to estimate energetic benefits based on abiotic and biotic conditions in patches of habitat. We performed thirty daily surveys of fish stomach contents to estimate the consumption rates for juvenile Atlantic salmon (Salmo salar) in a river. The data were used to assess whether variations of daily consumption rates existed within the river, and to develop empirical models that could predict fish consumption rates using abiotic and biotic conditions as independent variables. Daily consumption rates based on stomach content surveys in the field (range: 0.15–1.49 g dry/(100 g wet day)) varied significantly depending on habitat patch (500–1000 m²), summer period, and sampling year. Variables such as water temperature, numerical density of salmon, water depth and moon phase explained 83–93% of the variations in daily food consumption rates. Daily consumption rates tended to increase with water temperature and depth, and were also higher near a full moon. However, they tended to decrease with the numerical density of salmon. Our work suggests that empirical models based on independent variables that are relatively simple to estimate in the field may be developed to predict fish consumption rates in different habitat patches in a river.  相似文献   

中高山地区滑坡发育地形地貌因子敏感性研究          下载免费PDF全文

汪旭涛  谢昭宇  胡凯锋 《地震工程学报》2013,35(3):597-603

为分析海拔高度大于1 300m的中高山地区地形地貌因子对滑坡发育的敏感性程度,运用基于因子综合贡献率的敏感性分析方法,研究黔东北中高山地区坡面形态、地形坡度、相对高差三类影响因子对滑坡发育的影响程度.在各类影响因子对滑坡发育频数、面积及体积分量贡献率的基础上,利用顺序赋值法量化各分量贡献率的贡献指数,并以各分量贡献指数的几何平均数构建敏感性系数,定量分析三类地形地貌影响因子对中高山地区滑坡发育的敏感性.研究结果表明,阶梯形和凸形坡面形态的斜坡中后部为地貌演化堆积区,能提供较大重力势能,属滑坡发育的敏感性坡面形态因子;地形坡度在18°～22°之间的较陡坡和相对高差在40～80m之间的矮坡常分布于受地表水强烈冲刷的地带,在一定重力势能和强烈地下水共同作用下,极易诱发浅层小规模滑坡;地形坡度大于27°的极陡坡和相对高差大于120m的高坡由于具备较大重力势能,常诱发深层大规模滑坡.  相似文献   

2013年甘肃岷县漳县M_s6.6地震前地壳形变特征研究          下载免费PDF全文

马海萍  武艳强  杨立明  江在森  刘晓霞  张辉 《地震工程学报》2013,35(4):730-736

基于2013年岷县漳县M6.6地震震源区及其邻区1999年以来的GPS观测资料,通过应变率动态特征分析、多期次GPS剖面分析和基线变形速率的分析讨论了地震的震前变形特征.GPS速度场和块体应变率表明,汶川地震的发生导致了柴达木地块运动与变形状态发生明显调整,但由于西秦岭北缘等深大断裂的存在,岷-秦地块对其响应不明显;GPS连续应变率显示,在汶川地震引起的区域地壳变形调整过程中岷县漳县地震震源区附近的应变积累速率有减缓的迹象;GPS剖面显示,平行于岷县漳县主破裂带的运动分量对汶川地震响应显著,汶川震后表现为剪切变形速率的增强,而垂直于主破裂带的运动分量则对汶川地震响应不明显;震中周边GPS基线变形速率表明,基线伸缩变化率总体呈现NW向拉张、NE向压缩状态,且拉张量明显小于压缩量.上述地壳变形动态特征表明西秦岭北缘断裂及其附近地区的应变积累水平和断层闭锁程度可能处于较高水平,在岷县漳县地震前该区表现出局部“硬化”迹象.  相似文献