穿越活断层铰链式衬砌隧道减震措施动力响应研究   总被引：2，自引：1，他引：1       下载免费PDF全文

姬云平 《地震工程学报》2021,43(4):909-919

鉴于穿越地震活动带逆断层的铁路山岭隧道易受逆断层滑动的影响,且目前铁路隧道穿越多条活动性断层可供借鉴经验较少的现状。文章采用数值分析方法,对活动逆断层错动下的铰链式衬砌隧道在地震荷载作用下围岩加固方式、超挖设计结构的动力响应进行对比分析。结果表明逆断层错动时,对浅部地层变形的影响范围大于深部,但最大附加变形出现在深部断层面附近,且错距越大其最大附加变形值越大,断层活动对隧道结构安全影响较为显著。注浆加固并不改变衬砌在地震中的震动频谱特性,宜采用施作单层衬砌预留修复空间的设计方案。对于是否超挖设计的两种工况下,衬砌位移变化规律一致,衬砌的震动频谱特性一致。经过监控量测发现支护压应力在埋设2个月左右后趋于稳定。所得结论可为今后类似工程结构设计与施工提供参考。  相似文献   

中国地壳运动观测网络基准站重力场变化的海潮负荷信号改正问题   总被引：7，自引：0，他引：7  

孙和平  周江存 《地球科学进展》2002,17(1):39-43

利用最新的全球海潮模型（Csr3．0，Fes95．2，Tpxo2和Csr4．0）和原有的Schwiderski海潮模型以及中国近海海潮数据和标准地球模型负荷格林函数，采用直接褶积积分方法研究了中国地壳运动观测网络25个基准站重力固体潮观测中的海潮负荷效应问题，计算了 8个主要潮汐波的负荷振幅和相位，构制了北京和上海等10个台站重力负荷随时间变化函数。  相似文献   

Magma transfer processes at persistently active volcanoes: insights from gravity observations     

Corinne A. Locke  Hazel Rymer  John Cassidy 《Journal of Volcanology and Geothermal Research》2003,127(1-2):73-86

Magma transfer processes at persistently active volcanoes are distinguished by the large magma flux required to sustain the prodigious quantities of heat and gas emitted at the surface. Although the resulting degassed magma has been conjectured to accumulate either deep within the volcanic edifice or in the upper levels of the sub-edifice system, no direct evidence for such active accumulation has been reported. Temporal gravity data are unique in being able to quantify mass changes and have been successfully used to model shallow magma movements on different temporal scales, but have not generally been applied to the investigation of postulated long-term accumulation of magma at greater spatial scales within volcanic systems. Here, we model the critical data acquisition parameters required to detect mass flux at volcanoes, we review existing data from a number of volcanoes that exemplify the measurement of shallow mass changes and present new data from Poas and Telica volcanoes. We show that if a substantial proportion of degassed magma lodges within the sub-edifice region, it would result in measurable annual to decadal gravity increases occurring over spatial scales of tens of kilometres and propose that existing microgravity data from Sakurajima and, possibly, Etna volcanoes could be interpreted in these terms. Furthermore, such repeat microgravity data could be used to determine whether the accumulation rate is in equilibrium with the rate of production of degassed magma as calculated from the surface gas flux and hence identify the build-up of gas-rich magma at depth that may be significant in terms of eruption potential. We also argue that large magma bodies, both molten and frozen, modelled beneath volcanoes from seismic and gravity data, could represent endogenous or cryptic intrusions of degassed magma based on order of magnitude calculations using present-day emission rates and typical volcano lifetimes.  相似文献   

汶川大地震前后GPS观测的精密单历元解得到的震区地壳运动          下载免费PDF全文

顾国华  孟国杰  方颖 《地震学报》2011,33(3):319-326

利用BERNESE软件的单历元观测值双差定位功能,获取了接近2008年5月12日汶川Ms8.0大地震震中5个GPS观测站(PIXI,CHDU,JYAN,NEIJ和LUZH站)震前的短临位移过程及震后短时间的位移.通过拟合和对比分析,讨论了单历元解的精度.计算结果表明,以YANC站为固定站,LUZH站震前5月9日N(南北...  相似文献   

燕山运动的“绪动”——燕山事件   总被引：10，自引：0，他引：10  

张宏仁  张永康  蔡向民  渠洪杰  李海龙  王猛 《地质学报》2013,87(12):1779-1790

燕山运动是中生代期间发生在中国东部的一次最重要构造变动,它打破了华北克拉通数亿年的稳定格局,形成了一系列北东向深大断裂,并引发了剧烈的岩浆活动。然而,由于褶皱变形不显著,构造运动的主要不整合面难以确定,所以对燕山运动的起始时间和形成机制长期以来存在较大争议。本文通过对燕山运动概念历史的考证、北京西山和平原区地层序列的对比,结合华北地区其他晚中生代盆地的发展演化过程,认为燕山运动的起始时间应为中侏罗世含煤碎屑岩沉积之后、同造山砾岩形成之前。该运动所产生的深大断裂成为中国东部的构造骨架,成为而后大量岩浆上升的通道。根据构造变形的特点,结合材料力学的原理,认为燕山运动是中国东部遭受来自外部快速打击的后果,是以脆性变形为主的构造运动,并将该快速打击事件定义为燕山运动的“绪动”或“燕山事件”。  相似文献   

Description of littoral,alongshore sediment movement from empirical eigen‐function analysis     

D. J. Clarke  I. G. Eliot 《Australian Journal of Earth Sciences》2013,60(3-4):327-341

Measurements of 18 closely spaced beach profiles spanning Warilla Beach, N.S.W., over a 5‐year period have been examined for alongshore exchanges in beachface configuration. Horizontal slices of beach corresponding with berm, upper swash, upper and lower intertidal zones were examined by empirical orthogonal function (EOF) analysis. The first four EOF's for each of the four slices contain over 90% of the total variance for each slice. In each instance the first eigen‐function mode represents the onshore‐offshore component of beach response, and accounts for 50 to 60% of the variance. Subsequent modes describe alongshore exchange of sediment associated with large, standing, cellular water circulations of the embayment. Sediment shunts along each horizontal slice are determined by identification of nodal points in the eigen‐functions. These represent pivotal points through which sediment is transferred. The patterns of exchange vary considerably from slice to slice, reflecting change in the dominant beach processes from swash processes in the top of the beach to wave, tidal and current processes on the lower beach slope. Despite their disparity, similar periodicities are determined for the sediment exchanges in each slice. The amplitude spectra of the time series associated with each eigen‐function indicate that the exchanges take place at 24, 12 and 6 monthly periods.  相似文献   

Seismicity of Victoria to 1980     

Gary Gibson  Vaughan Wesson  Russell Cuthbertson 《Australian Journal of Earth Sciences》2013,60(3-4):341-356

Since 1976 a number of analogue and digital seismographs, which record high frequency seismic waves in the range 4 to 20 Hz, have been installed in Victoria. These enable the detection and location of microearthquakes with Richter magnitude Ml down to less than zero. Because there are many more smaller than larger earthquakes, about 250 events are now being located in Victoria each year, compared with about 25 per year between 1960 and 1975, and an average of two per year between 1840 and 1959. Despite an uneven statewide seismograph coverage, the new instruments and new lithospheric models have led to substantial improvements in earthquake location accuracy. All Victorian earthquakes with reliable depth determinations have been found to lie within the crust, most at a depth of less than 18 km. Some very small but shallow microearthquakes have been felt or heard. The isoseismal map for such an event (of magnitude Ml 1.3) which occurred at Preston during July 1976, is given.

The greater range of magnitudes now recorded permits more reliable estimates of seismicity. On average, the recurrence of earthquakes in Victoria is represented by: log₁₀ (P) = 0.92M_L —2.40, where P is the return period of an earthquake with magnitude greater than M_l in an area of 100 km square. It is suggested that attenuation of seismic wave amplitudes with distance is quite high in Victoria.  相似文献   

Toward space-time buffering for spatiotemporal proximity analysis of movement data     

Hui Yuan  Qingquan Li  Shih-Lung Shaw  William H. K. Lam 《International journal of geographical information science》2018,32(6):1211-1246

Spatiotemporal proximity analysis to determine spatiotemporal proximal paths is a critical step for many movement analysis methods. However, few effective methods have been developed in the literature for spatiotemporal proximity analysis of movement data. Therefore, this study proposes a space-time-integrated approach for spatiotemporal proximal analysis considering space and time dimensions simultaneously. The proposed approach is based on space-time buffering, which is a natural extension of conventional spatial buffering operation to space and time dimensions. Given a space-time path and spatial tolerance, space-time buffering constructs a space-time region by continuously generating spatial buffers for any location along the space-time path. The constructed space-time region can delimit all space-time locations whose spatial distances to the target trajectory are less than a given tolerance. Five space-time overlapping operations based on this space-time buffering are proposed to retrieve all spatiotemporal proximal trajectories to the target space-time path, in terms of different spatiotemporal proximity metrics of space-time paths, such as Fréchet distance and longest common subsequence. The proposed approach is extended to analyze space-time paths constrained in road networks. The compressed linear reference technique is adopted to implement the proposed approach for spatiotemporal proximity analysis in large movement datasets. A case study using real-world movement data verifies that the proposed approach can efficiently retrieve spatiotemporal proximal paths constrained in road networks from a large movement database, and has significant computational advantage over conventional space-time separated approaches.  相似文献   

琼东南盆地陵南低凸起深水钻井岩心的稀土元素地球化学特征及其意义   总被引：2，自引：0，他引：2  

孙志鹏  翟世奎  修淳  刘新宇  宗统  罗威  刘晓锋  陈奎  李娜 《海洋学报(英文版)》2014,33(12):81-95

A geochemical analysis of rare-earth elements(REEs) in 97 samples collected from the core of deep-water Well LS-A located at the Lingnan Low Uplift Area of the Qiongdongnan Basin is conducted, with the purpose of revealing the changes of sedimentary source and environment in the study region since Oligocene and evaluating the response of geochemical characteristics of REEs to the tectonic evolution. In the core samples, both ∑REE and ∑LREE(LREE is short for light-group REEs) fluctuate in a relatively wide range, while ∑HREE(HREE is short for heavy-group REEs) maintains a relatively stable level. With the stratigraphic chronology becoming newer, both ∑REE and ∑LREE show a gradually rising trend overall. The ∑REE of the core is relatively high from the bottom of Yacheng Formation(at a well depth of 4 207 m) to the top of Ledong Formation, and the REEs show partitioning characteristics of the enrichment of LREE, the stable content of HREE, and the negative anomaly of Eu to varying degrees. Overall the geochemical characteristics of REEs are relatively approximate to those of China's neritic sediments and loess, with significant "continental orientation". The ∑REE of the core is relatively low in the lower part of Yacheng Formation(at a well depth of 4 207–4 330 m), as shown by the REEs partitioning characteristics of the depletion of LREE, the relative enrichment of HREE, and the positive anomaly of Eu; the geochemical characteristics of REEs are approximate to those of oceanic crust and basalt overall, indicating that the provenance is primarily composed of volcanic eruption matters. As shown by the analyses based on sequence stratigraphy and mineralogy, the provenance in study region in the early Oligocene mainly resulted from the volcanic materials of the peripheral uplift areas; the continental margin materials from the north contributed only insignificantly; the provenance developed to a certain extent in the late Oligocene. Since the Miocene, the provenance has ceaselessly expanded from proximal to distal realm, embodying a characteristic of multi-source sedimentation. In the core strata with 31.5, 28.4, 25.5, 23, and 16 Ma from today, the geochemical parameters of REEs and Th/Sc ratio have significant saltation, embodying the tectonic movement events in the evolution of the Qiongdongnan Basin. In the tectonic evolution history of the South China Sea, the South China Sea Movement(34–25 Ma BP, early expansion of the South China Sea), Baiyun Movement(23 Ma BP), late expansion movement(23.5–16.5 Ma BP), expansion-settlement transition, and other important events are all clearly recorded by the geochemical characteristics of REEs in the core.  相似文献   

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王伟  杨少敏  谭凯  赵斌  黄勇  张彩红  王迪晋 《大地测量与地球动力学》2014,34(3):75-80

?????й??????????????1999~2013????й?????????????????2009~2013???GPS????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????1????????????????????????????????????????????????????????????й????????????????????????????????????????????????Σ?77°E?????????45×10^-9/a???????????Σ?86°E?????????10×10^-9/a;2)???????????????????????????????????????????????????????????????????50~60??×10^-9/a??????????????40~50??×10^-9/a????????GPS?????????????10~15??mm/a??????????????????;3)?????????????????????????????????38°N?????????????????????????????????????????????????????????к?????????????????????????????????????????????Σ??????????????10~20??×10^-9/a???????????????;4)??????????????????????????????????б??Σ???????????????????????????????????????????????????????????40×10^-9/a??5)????????????????λ???????????78°E??????????????30×10^-9/a??  相似文献