渭河断裂深、中、浅和近地表显示   总被引：3，自引：0，他引：3  

冯希杰  李晓妮  任隽  师亚芹  戴王强  王夫运  苗康运  韩恒悦 《地震地质》2008,30(1):264-272

渭河断裂是渭河盆地一条重要的隐伏断裂,对渭河盆地的形成和发展乃至盆地内的地震活动都具有一定的控制作用。文中基于横跨渭河断裂的深地震反射、浅层地震反射、钻孔勘探和槽探等勘探方法取得的探测结果,从深部、中部、浅部以及近地表4个深度,给出了渭河断裂的呈现特点,即最深切割层位、不同深度的产状变化、错距大小、断裂的最新活动时代和活动期次等  相似文献   

路堑边坡开挖对邻近既有隧道影响研究   总被引：5，自引：2，他引：3  

赵东平  王明年  贾玲利 《岩土力学》2009,30(5):1399-1402

设计中的承德迎宾大道路堑边坡邻近既有京承铁路21号隧道,边坡开挖后会对既有隧道产生不利影响。根据现场试验取得的围岩及隧道衬砌的力学参数,对边坡开挖进行了静力学和动力学数值分析,研究了路堑边坡可开挖的最大范围及爆破振动对隧道的影响。结果表明：当路堑二级边坡坡脚距离隧道中心线距离大于等于30 m时,边坡开挖后隧道衬砌内力虽有增加,但仍可保证结构安全。进行边坡爆破开挖时,如考虑3倍的安全系数,当京承铁路21号隧道衬砌振速小于1.5 cm/s时,隧道衬砌内产生的动拉应力小于衬砌极限抗拉强度,可按此控制指标进行现场监测。  相似文献   

西宁城市活动断裂地表特征初步研究   总被引：13，自引：2，他引：11  

李智敏  田勤俭  高占武  陈立泽 《地震》2005,25(4):119-126

在详细的野外地质调查基础上, 通过开挖探槽剖面揭露了断层的基本性质, 初步展示了西宁市北川河东岸断裂、 南川河断裂和湟水河断裂的地表特征。 结合前人的阶地测定年代结果初步判断, 北川河东岸断裂错断相当于湟水河Ⅱ至Ⅲ级阶地, Ⅱ级阶地形成不晚于0.05 Ma, Ⅲ级阶地形成不晚于0.12 Ma, 说明该断裂是晚更新世活动断裂; 南川河断裂错断相当于湟水河Ⅳ、 Ⅴ级阶地, Ⅳ级阶地形成不晚于0.54 Ma, Ⅴ级阶地形成不晚于0.78 Ma, 说明该断裂是早中更新世活动断裂; 湟水河断裂错断其Ⅱ、 Ⅲ级阶地砾石层, 说明该断裂是晚更新世活动断裂。 这些断裂规模小、 活动性弱, 可能为盖层断裂。  相似文献   

Petrogenesis of Volcanic Rocks from Saipan and Rota, Mariana Islands, and Implications for the Evolution of Nascent Island Arcs   总被引：2，自引：0，他引：2  

Reagan  Mark K.; Hanan  Barry B.; Heizler  Matthew T.; Hartman  Brian S.; Hickey-Vargas  Rosemary 《Journal of Petrology》2008,49(3):441-464

An ⁴⁰Ar/³⁹Ar age of 45·1 Ma determined for lavas fromnorthern Saipan confirms that these high-silica rhyolites eruptedduring the ‘proto-arc’ stage of volcanism in theIzu–Bonin–Mariana system, which is characterizedelsewhere by eruption of boninitic lavas. Incompatible traceelement concentrations and Sr, Hf, Nd, and Pb isotope ratiosfor these rhyolites are transitional between those of c. 48Ma boninitic lavas and post-38 Ma ‘first-arc’ andesitesand dacites from Saipan and Rota that have typical subduction-relatedcompositions. These transitional compositions are modeled bycrystal fractionation of parental tholeiitic basalt combinedwith assimilation of young boninitic crust. A second stage ofRayleigh fractionation in the upper crust is required by SiO₂concentrations that exceed 77 wt % and near-zero compatibleelement concentrations. First-arc magma compositions are consistentwith fractionation of basalt and assimilation of crust similarin composition to the first-arc magmas themselves. The mantlesources of the proto-arc and first-arc lavas from Saipan andRota are similar to those of Philippine back-arc basin basaltsbased on Nd and Hf isotopic compositions. The Pb isotope compositionsof these lavas are between those of Pacific sea-floor basaltsand Jurassic and younger cherty and clay-rich sediments. Thiscontrasts with the boninitic proto-arc volcanic rocks from Guamand Deep Sea Drilling Project Sites 458 and 459 that have Pbisotope compositions similar to Pacific basin basalts and volcaniclasticsediments. The preferred explanation for the difference in thenature of proto-arc volcanism between Saipan and other fore-arclocations is that the crust ceased extending 3–4 Myr earlierbeneath Saipan. This was caused by a change from mantle upwelling,fore-arc extension, and shallow melting to an environment dominatedby more normal mantle wedge convection, stable crust, and deepermelting. KEY WORDS: rhyolite; andesite; Mariana arc; isotope ratios; trace elements  相似文献   

Behavior of Vertical Pressure Imposed on the Bottom of a Trench     

Young-Suk Song  Meng-Leang Bov  Won-Pyo Hong 《Marine Georesources & Geotechnology》2016,34(8):703-711

A series of model tests were performed to investigate the behavior of vertical pressure imposed on the bottom of a trench. The tests were conducted in two phases to generate soil arching due to soil deformation: (1) the backfilling phase and (2) the lowering-bottom phase. First, the backfilling phase was performed by filling sand into the trench, in which soil deformation was developed due to selfcompaction by the weight of the sand. The lowering-bottom phase was then conducted by lowering the bottom plate of the trench to induce additional soil deformation. The behavior of the vertical pressure acting on the bottom of the trench during the backfilling phase can simulate that of the vertical pressure imposed on the bottom of buried rigid pipes. The behaviors of buried flexible pipes could be observed during the lowering-bottom phase, in which both the minimum and the maximum vertical pressures could be obtained according to the induced soil deformation. A novel method for predicting the vertical pressures in each phase was proposed. The agreements between the predictions by the proposed method and the experimental results were demonstrated.  相似文献   

琉球沟弧盆系莫氏面深度的三维广义反演     

刘保华  李学伦 《海洋地质与第四纪地质》1997,17(1):53-58

本文利用三维广义反演技术对重力资料进行反演，计算出了琉球沟弧盆系地区的莫氏面深度。由于考虑了分辨率和方差之间的最佳折衷问题，反演结果不论是在精度上还是在分辨能力方面都有了明显改进。分析结果也表明，重力反演得到的莫氏面深度同李昭兴等人用地震折射波法得到的莫氏面深度有较大的差别。文中地产生这种差别的可能原因提出了自己的见解。  相似文献   

Super-deep CTD measurements in the Izu-Ogasawara trench and a comparison of geostrophic shears with direct measurements     

Keisuke Taira 《Journal of Oceanography》2006,62(5):753-758

CTD (Conductivity-Temperature-Depth) data at five stations across the Izu-Ogasawara Trench at 34°N were examined. Geostrophic velocity was in accordance with the directly measured currents. Above the trench floor, potential temperature increased at a rate of 0.6 m°C/1000 db from 8000 db to 9417 db, and salinity increased from 8300 db to the bottom. Potential density was almost constant at 7100–8700 db, and it increased to the bottom. Above the eastern and western flanks, inversion of potential density was indicated in the bottom layers with an increase of potential temperature and a decrease of salinity, suggesting geothermal heating and outflow of ground water.  相似文献   

马里亚纳海槽玄武岩岩石学   总被引：3，自引：0，他引：3  

陈穗田  张德玉 《海洋地质与第四纪地质》1991,(3)

马里亚纳海槽岩石学的研究表明本区岩石属基性的玄武岩,又细分为洋底玄武岩(OFB)和钙碱玄武岩(CAB)。微量元素相对球粒陨石标准化数值特征:除了Sc、Ti,V外,其它过渡元素都有亏损,Cr、Ni出现了明显负异常,Ti相对较富集,稀土元素(REE)表现富集型的型式;同位素测试结果,εNd(0)=6.9。可以认为这些玄武岩是上幔岩的局部熔融形成的岩浆沿着扩张中心喷溢到海底,而形成的新生洋壳。  相似文献   

马里亚纳海槽区岩芯中浮游有孔虫和CaCO_3溶解及其影响溶解的因素     

高建西  周希林  鞠晓华 《海洋科学进展》1993,(2)

本文从浮游有孔虫壳体保存,数量,分异度值,底栖类/浮游类比率和CaCO_3含量诸方面讨论马里亚纳海槽区岩芯中溶解及其影响溶解的因素。  相似文献   

Deep CTD Casts in the Challenger Deep,Mariana Trench   总被引：1，自引：0，他引：1  

Keisuke?TairaEmail author  Daigo?Yanagimoto  Shoji?Kitagawa 《Journal of Oceanography》2005,61(3):447-454

On 1 December 1992, CTD (conductivity-temperature-depth profiler) casts were made at three stations in a north-south section of the Challenger Deep to examine temperature and salinity profiles. The station in the Challenger Deep was located at 11°22.78′ N and 142°34.95′ E, and the CTD cast was made down to 11197 db or 10877 m, 7 m above the bottom by reeling out titanium cable of 10980 m length. The southern station was located at 11° 14.19′ N and 142°34.79′ E, 16.1 km from the central station, where water depth is 9012 m. CTD was lowered to 7014 db or 6872 m. The northern station was located at 11°31.47′ N and 142° 35.30′ E, 15.9 km from the central station, and CTD was lowered to 8536 db or 8336 m, 10 m above the bottom. Below the thermocline, potential temperature decreased monotonously down to 7300–7500 db beyond a sill depth between 5500 m and 6000 m, or between 5597 db and 6112 db, of the trench. Potential temperature increased from 7500 db to the bottom at a constant rate of 0.9 m°C/1000 db. Salinity increased down to 6020–6320 db, and then stayed almost constant down to around 9000 db. From 9500 db to the bottom, salinity increased up to 34.703 psu at 11197 db. Potential density referred to 8000 db increased monotonously down to about 6200 db, and it was almost constant from 6500 db to 9500 db. Potential density increased from 9500 db in accordance with the salinity increase. Geostrophic flows were calculated from the CTD data at three stations. Below an adopted reference level of 3000 db, the flow was westward in the north of Challenger Deep and eastward in the south, which suggests a cyclonic circulation over the Challenger Deep. Sound speed in Challenger Deep was estimated from the CTD data, and a relation among readout depth of the sonic depth recorder, true depth, and pressure was examined.  相似文献