Effect of varying normal stress on stability and dynamic motion of a spring-slider system with rate- and state-dependent friction          下载免费PDF全文

Changrong He  Teng-fong Wong 《地震科学（英文版）》2014,27(6):577-587

Incorporating rate and state friction laws, stability of linearly stable (i.e., with stiffness greater than the critical value) spring-slider systems subjected to triggering perturbations was analyzed under variable normal stress condition, and comparison was made between our results and that of fixed normal stress cases revealed in previous studies. For systems associated with the slip law, the critical magnitude of rate steps for triggering unstable slips are found to have a similar pattern to the fixed normal stress case, and the critical velocity steps scale with a/(b - a) when k = k_cr for both cases. The rate-step boundaries for the variable normal stress cases are revealed to be lower than the fixed normal stress case by 7 %–16 % for a relatively large α = 0.56 with (b - a)/a ranging from 0.25 to 1, indicating easier triggering under the variable normal stress condition with rate steps. The difference between fixed and variable normal stress cases decreases when the α value is smaller. In the same slip-law-type systems, critical displacements to trigger instability are revealed to be little affected by the variable normal stress condition. When k ≥ k_cr(V_*), a spring-slider system with the slowness law is much more stable than with the slip law, suggesting that the slowness law fits experimental data better when a single state variable is adopted. In stick-slip motions, the variable normal stress case has larger stress drops than the constant normal stress case. The variable normal stress has little effect on the range of slip velocity in systems associated with the slowness law, whereas systems associated with the slip law have a slowest slip velocity immensely smaller than the fixed normal stress case, by ~10 orders of magnitude.  相似文献   

An improved rheology model for the description of the rate-dependent cyclic behavior of high damping rubber bearings     

《Soil Dynamics and Earthquake Engineering》2015

An improved rheology model, inspired from explicit experiments is conceived to represent rate-dependent cyclic shear behavior of high damping rubber bearings at subzero and room temperatures. Total stress has been decomposed into nonlinear rate independent elasto-plastic stress, nonlinear elastic stress and nonlinear visco-elasto-plastic overstress branches. To represent nonlinear viscosity behavior, ‘overstress branch’ has been generalized by putting linear elastic spring in parallel to nonlinear elasto-plastic model, placed in series with nonlinear dashpot. Constitutive relations for model elements have been designated for respective fundamental phenomenon observed in constant strain rate experiments. An optimum calculation approach is developed to determine a unique set of overstress parameters capable not only of representing constant strain rate cyclic tests but also sinusoidal tests with variable input strain rates. Essential abilities of the proposed model and adequacy of estimated parameters have been confirmed by comparing numerical simulation results with experiments conducted at −30 °C, −10 °C and 23 °C.  相似文献   

Influence of interaction between small asperities on various types of slow earthquakes in a 3-D simulation for a subduction plate boundary   总被引：3，自引：1，他引：2  

Keisuke Ariyoshi  Takane Hori  Jean-Paul Ampuero  Yoshiyuki Kaneda  Toru Matsuzawa  Ryota Hino  Akira Hasegawa 《Gondwana Research》2009,16(3-4):534-544

Recently, the occurrence of slow earthquakes such as low-frequency earthquakes and very low-frequency earthquakes have been recognized at depths of about 30 km in southwest Japan and Cascadia. These slow earthquakes occur sometimes in isolation and sometimes break into chain-reaction, producing tremor that migrates at a speed of about 5–15 km/day and suggesting a strong interaction among nearby small asperities. In this study, we formulate a 3-D subduction plate boundary model with two types of small asperities chained along the trench at the depth of 30 km. Our simulation succeeds in representing various types of slow earthquakes including low-frequency earthquakes and rapid slip velocity in the same asperity, and indicates that interaction between asperities may cause the very low-frequency earthquakes. Our simulation also shows chain reaction along trench with propagation speed that can be made consistent with observations by adjusting model parameters, which suggests that the interactions also explain the observed migration of slow earthquakes.  相似文献   

2014年鲁甸M_S6.5地震形变高频信息异常与前兆机理浅析     

龚丽文  刘琦  张治广  武善艺  陈丽娟 《地震》2019,39(1):101-113

地震前兆异常的识别和提取一直是地震预报研究的重要任务, 也是地震预报事业发展的瓶颈。 结合鲁甸地震的研究成果, 利用S变换和超限率等方法, 提取定点形变高频异常, 总结鲁甸地震前兆高频异常形态特征, 分析异常台站空间分布规律, 剖析高频异常形成的前兆机理。 研究发现, 高频异常主要表现为信号周期在数分钟至数小时的信号成分, 频带较宽, 丛集性好, 与曲线的突跳、 毛刺或阶跃对应较好, 震前4~5 d开始出现, 震后2~3 d衰减消失; 其台站分布较分散, 主要沿NW—SE方向分布, 与区域应力场方向和发震断层走向趋于一致, 且均分布在构造块体边界; 可能是对不同速率的构造块体在震前发生的滑移和瞬间错动的记录, 它的形成与台站附近地壳介质的稳定性有关。  相似文献   

Estimation of Longshore Sediment Transport Rate for a Typical Pocket Beach Along West Coast of India     

V. Noujas  R. S Kankara  K. Rasheed 《Marine Geodesy》2018,41(2):201-216

Estimation of Longshore Sediment Transport Rate (LSTR) in the littoral zone is essential for managing and developing any coastal zone. Numerical models are powerful tool to understand and investigate various processes responsible for LSTR in a systematic manner since direct measurement of LSTR is a difficult task. A one dimensional LITDRIFT model was implemented along the Vengurla coast for estimation of LSTR and to analyze the sensitivity of each input parameters towards the computation of LSTR. Major input parameters required for the estimation of LSTR are nearshore wave climate, bathymetry, and sediment characteristics. The nearshore wave data at a depth of 15 m were collected using wave rider buoy in 2015 is used in the present study. Field observations were carried out to survey the regional bathymetry and sediment characteristics. Annual net LSTR along Vengurala coast is relatively less and varies from ?7778 to ?9015 m³ with an average of ?8511 m³. The net direction of LSTR is towards south and gross LSTR is 1.18 × 10⁵ m³/year. The LSTR reveals more sensitivity to coastline orientation and wave direction. A 1° changes in coastline angle and wave direction causes approximately 3000 m³/month difference in LSTR. Moreover, wave height, wave period, and bed roughness has an important role for controlling LSTR. The model results help to identify the role of each parameter contributing towards LSTR estimation and a similar model approach can be applied to other coasts for estimating LSTR in an accurate way.  相似文献   

攀西地区活断层研究(英文)     

唐荣昌  黄祖智 《地震研究》1988,(5)

本文根据攀西地区活断层长期滑动速率及历史上最大地震震级上限,把攀西地区的活断层划分为A、B、C三级,并对区内几条主要活断层的近代活动特征进行了较全面的研究。指出第四纪断裂活动沿断裂带在空间上和时间上是有明显的分段性和不均匀性,断裂上的位移是以一种地震构造上的脉冲形式出现的,地震与晚更新世、全新世和现代断裂活动在空间上和成因上有密切的联系。  相似文献   

水污染的导电性和激电性与污染浓度变化关系的几个实验结果   总被引：15，自引：0，他引：15       下载免费PDF全文

李金铭  张春贺  肖顺 《地球物理学报》1999,42(3):428-434

为了解用电阻率法、电磁法和激发极化法监测地下水污染的可能性,给出了在水样和含水砂样中,加入了不同浓度的无机污染物和有机污染物时,样品电阻率、极化率、半衰时和偏离度等导电性和激电性参数与浓度变化关系的几个实验观测结果．水样中的观测结果表明,除个别有机污染样品的电阻率随浓度增加有所增大外,其余所有无机污染和有机污染样品的电阻率均随浓度的增加而减小．含水砂样中的观测结果表明,不同污染成分样品的电阻率和极化率,均随孔隙液浓度的增加而减小,但对反应样品激电时间特性的参数而言,则有半衰时随浓度增加而减小,偏离度随浓度增加而增大的规律．同时指出,用电阻率法、电磁法和激发激化法监测地下水污染是十分困难的．  相似文献   

精密测距测速系统的研究与应用     

张飞鹏 《天文学进展》1999,17(1):33-43

精密测距测速系统（ＰＲＡＲＥ）是由德国发展的双频双程微波卫星跟踪系统,其空间部分搭载在欧洲航天局（ＥＳＡ）的第二颗资源遥感卫星ＥＲＳ－２上并正常运行至今,该系统具有全天候,全自动,台站便于流动,数据多等特点,其高精度的跟踪信息可用于ＥＲＳ－２的定轨以主某些大地测量与地球物理参数的确定,其双频特性可用于电离层方面的研究,另外,ＰＲＡＲＥ还可用于精确的时钟同步,详细介绍了ＰＲＡＲＥ的发展,构成,测量原  相似文献   

Significance of an In Vivo Genotoxicity Test for Surface Waters Is Increased when the Physiological Characteristics of the Test Organism (Bivalvia: Mollusca) Are Taken into Account?     

M. Kramer  I. Hübner 《洁净——土壤、空气、水》2000,28(2):83-91

The alkaline filter elution assay using the gills of the freshwater clam species Corbicula fluminea detects breaks in single‐stranded DNA and is thus a good method for determining the genotoxic potential of surface waters. In attempting to standardize the procedure, a wide range of factors which could have an influence on the uptake of genotoxic substances by the exposed clams were studied. The most important parameters of the static exposure in relation to the rate of filtration by the animals turned out to be the temperature, the volume of the water, and the exposure time. Differences in body size and in the amount of suspended particles in surface waters did not play a significant role. The results demonstrate that the in vivo test system can be quite sensitive and its results reproducible when the relevant species‐specific characteristics of the test organisms are brought into consideration, even if the test organism belongs to a biologically more advanced group. A clear dose‐response relationship to the reference substances 4‐nitroquinoline‐1‐oxide (NQO) and N‐methyl‐N‐nitro‐N‐nitrosoguanidine (MNNG) can be observed even after a short exposure time of between four and twenty hours. No genotoxic effects were observed when using this method on surface waters from the area of Cologne (including water from the Rhine River and within the protection zone 2 of the Cologne waterworks).  相似文献   

结合置信度的多通道星载SAR在轨舰船低虚警快速检测     

郑儒楠  仇晓兰 《遥感学报》2022,26(3):516-527

舰船目标快速检测是星载合成孔径雷达的重要应用之一,也是SAR星上处理首先发展的应用方向.目前SAR舰船快速检测普遍使用的图像恒虚警(CFAR)检测方法中,低虚警一直是研究的重点,多通道SAR中舰船目标存在多通道虚假目标,进一步增加了虚警剔除的难度.为此,本文提出了一种基于置信度计算和SVM判别的低虚警CFAR(Cons...  相似文献