黄河中下游活动断层分布及其对古河道变迁的影响     

李峰  张杰汉  卢巍  张攀  占伟伟  田勤俭 《震灾防御技术》2022,17(2):197-207

黄河流域是我国遭受地震灾害最为严重的流域,近年来探测工作对黄河中下游的活动断层有较多新认识,如构成北华北盆地与南华北盆地新构造分界的新乡-商丘断裂,新发现存在多个晚更新世活动段,具备发生中强级以上地震的可能,对识别沿黄河中下游的地震危险源、提高地震危险性认识有重要影响。本文通过总结近年来活动断层探测的最新进展,分析了沿黄河中下游地区的活动断层分布特征及其可能产生的灾害影响,并提出后续工作规划建议。  相似文献   

盘谷寺-新乡断裂第四纪活动性分段特征     

郁军建  张扬  孙印  张哲 《震灾防御技术》2022,17(2):261-268

盘谷寺-新乡断裂以柏山、高村为界,分为西、中、东3段,根据物探剖面、地质标准孔和地层剖面出露特征,各段活动性具有明显差异。其中西段最新活动时代为中更新世,具有向盆地迁移发育的特征;中段最新活动时代为晚更新世早期;东段活动性稍复杂,经历了正断-逆冲-正断的运动过程演变,其最新活动时代为晚更新世早期,且活动强度向两端减弱。高村所处的武陟隆起区推测为盘谷寺-新乡断裂中、东段的挤压阶区,断层位移在此处有亏损和衰减。  相似文献   

基于结构水文地质学的采掘诱发高势能突水溃砂主动防控     

隋旺华 《工程地质学报》2022,30(1):101-109

在谷德振先生“水文地质结构”学术思想指引下,本文提出建立结构水文地质学的设想,论述了其基础理论框架。从方法论角度将矿山水害防控分为被动防控和主动防控两种方法。以结构水文地质学指导煤矿高势能突水溃砂防控,分析了被动防控可能产生突水溃砂灾害的机理; 提出了主动地质工程防控的原理,包括地质材料性质改造、结构隔水性能重构、赋存水动力环境改造、减轻采掘诱发覆岩破坏等具体方法。抛砖引玉,以期催生符合中国矿山防治水实践需要的创新理论和方法。  相似文献   

Identification of functionally active aerobic methanotrophs and their methane oxidation potential in sediments from the Shenhu Area,South China Sea     

Jing Li  Chang-ling Liu  Neng-you Wu  Xiao-qing Xu  Gao-wei Hu  Yan-long Li  Qing-guo Meng 《China Geology》2022,5(2):285-292

Large amounts of gas hydrate are distributed in the northern slope of the South China Sea, which is a potential threat of methane leakage. Aerobic methane oxidation by methanotrophs, significant methane biotransformation that occurs in sediment surface and water column, can effectively reduce atmospheric emission of hydrate-decomposed methane. To identify active aerobic methanotrophs and their methane oxidation potential in sediments from the Shenhu Area in the South China Sea, multi-day enrichment incubations were conducted in this study. The results show that the methane oxidation rates in the studied sediments were 2.03–2.36 μmol/gdw/d, which were higher than those obtained by sediment incubations from other areas in marine ecosystems. Thus the authors suspect that the methane oxidation potential of methanotrophs was relatively higher in sediments from the Shenhu Area. After the incubations family Methylococcaea (type I methanotrophs) mainly consisted of genus Methylobacter and Methylococcaea_Other were predominant with an increased proportion of 70.3%, whereas Methylocaldum decreased simultaneously in the incubated sediments. Collectively, this study may help to gain a better understanding of the methane biotransformation in the Shenhu Area.©2022 China Geology Editorial Office.  相似文献   

青藏高原东北缘黄河黑山峡出口段阶地特征与断层活动   总被引：7，自引：1，他引：6  

郭进京杜东菊  韩文峰柴寿喜 《工程地质学报》2004,12(4):367-372

青藏高原东北缘黄河黑山峡出口地段夜明山 -长流水沟一带 ,黄河的河流阶地发育和保存的较好。阶地的形成不仅记录了青藏高原北部第四纪以来地壳的 7次隆升过程的特点 ,而且阶地的空间展布及其特征反映了断层F8(7) 和F2 0 1活动的特点。详细的观测研究表明F8(7) 以南发育并保存有 7级阶地 ,而F8(7) 和F2 0 1之间及F2 0 1以北仅保存有 5级阶地。所有的阶地都为基座阶地。其中Ⅰ和Ⅱ级阶地前缘在区内连续展布 ,横跨断层F8(7) 两侧的Ⅲ级阶地前缘仍保持连续 ,但阶地宽度陡然变宽 ,Ⅳ级阶地前缘即Ⅲ级阶地后缘左旋位移 15 0m左右。横跨断层F2 0 1两侧 ,Ⅱ级阶地宽度由 2 0 0m急剧变宽为 710m ,Ⅱ级以上阶地前缘左旋位移均在 4 0 0m左右。断层F8(7) 和F2 0 1两侧阶地宽度的变化和阶地前缘的左旋位移记录了断层F8(7) 和F2 0 1第四纪晚期活动的时空规律 ,为断层的活动性评价提供了良好的依据  相似文献   

Mesozooplankton biomass and grazing responses to Cyclone Opal, a subtropical mesoscale eddy     

Michael R. Landry  Moira Decima  Melinda P. Simmons  Cecelia C.S. Hannides  Emy Daniels 《Deep Sea Research Part II: Topical Studies in Oceanography》2008,55(10-13):1378

As part of E-Flux III cruise studies in March 2005, plankton net collections were made to assess the effects of a cyclonic cold-core eddy (Cyclone Opal) on the biomass and grazing of mesozooplankton. Mesozooplankton biomass in the central region of Cyclone Opal, an area of uplifted nutricline and a subsurface diatom bloom, averaged 0.80±0.24 and 1.51±0.59 g DW m⁻², for day and night tows, respectively. These biomass estimates were about 80% higher than control (OUT) stations, with increases more or less proportionately distributed among size classes from 0.2 to >5 mm. Though elevated relative to surrounding waters south of the Hawaiian Islands (Hawai’i lee), total biomass and size distribution in Cyclone Opal were almost exactly the same as contemporary measurements made at Stn. ALOHA, 100 km north of the islands, by the HOT (Hawaii Ocean Time-series) Program. Mesozooplankton biomass and community composition at the OUT stations were also similar to ALOHA values from 1994 to 1996, preceding a recent decadal increase. These comparisons may therefore provide insight into production characteristics or biomass gradients associated with decadal changes at Stn. ALOHA. Gut fluorescence estimates were higher in Opal than in ambient waters, translating to grazing impacts of 0.11±0.02 d⁻¹ (IN) versus 0.03±0.01 d⁻¹ (OUT). Over the depth-integrated euphotic zone, mesozooplankton accounted for 30% of the combined grazing losses of phytoplankton to micro- and meso-herbivores in Opal, as compared to 13% at control stations. Estimates of active export flux by migrating zooplankton averaged 0.81 mmol C m⁻² d⁻¹ in Cyclone Opal and 0.37 mmol C m⁻² d⁻¹ at OUT stations, 53% and 24%, respectively, of the carbon export measured by passive sediment traps. Migrants also exported 0.18 mmol N m⁻² d⁻¹ (117% of trap N flux) in Cyclone Opal compared to 0.08 mmol N m⁻² d⁻¹ (51% of trap flux) at control stations. Overall, the food-web importance of mesozooplankton increased in Cyclone Opal both in absolute and relative terms. Diel migrants provided evidence for enhanced export flux in the eddy that was missed by sediment trap and ²³⁴Th techniques, and migrant-mediated flux was the major export term in the observed bloom-perturbation response and N mass balance of the eddy.  相似文献   

The critical scale of fluctuation for active lateral forces in spatially variable undrained clays     

《Computers and Geotechnics》2014

This study addresses the phenomenon of the critical scale of fluctuation (SOF) for active lateral force (P_a) in undrained clay when there is a spatial variability in the clay. The phenomenon is significant under shear strength (τ_f) random fields but is insignificant under unit weight (γ) random fields. It is found that the phenomenon of the critical SOF is connected to the nature of the spatial averaging, which is “line averaging” under τ_f random fields and is “area averaging” under γ random fields. The former averaging effect (line) is significantly weaker than the latter (area), so the tendency for the critical slip plane to seek for a favorable location is stronger for the τ_f random field than for the γ random field. Hence, the phenomenon of the critical SOF is more pronounced under τ_f random fields than under γ random fields. The underlying mechanisms for the phenomenon of the critical SOF will be explored in this paper.  相似文献   

Intraplate geodynamics and magmatism in the evolution of the Central Asian Orogenic Belt     

《Journal of Asian Earth Sciences》2014

The Central Asian Orogenic Belt (CAOB) was produced as a consequence of the successive closure of the Paleoasian Ocean and the accretion of structures formed within it (island arcs, oceanic islands, and backarc basins) to the Siberian continent. The belt started developing in the latest Late Neoproterozoic, and this process terminated in the latest Permian in response to the collision of the Siberian and North China continents that resulted in closure of the Paleoasian ocean (Metcalfe, 2006; Li et al., 2014; Liu et al., 2009; Xiao et al., 2010; Didenko et al., 2010). Throughout the whole evolutionary history of this Orogenic Belt, a leading role in its evolution was played by convergent processes. Along with these processes, an important contribution to the evolution of the composition and structure of the crust in the belt was made by deep geodynamic processes related to the activity of mantle plumes.Indicator complexes of the activity of mantle plumes are identified, and their major distribution patterns in CAOB structures are determined. A number of epochs and areas of intraplate magmatism are distinguished, including the Neoproterozoic one (Rodinia breakup and the origin of alkaline rock belt in the marginal part of the Siberian craton); Neoproterozoic–Early Cambrian (origin of oceanic islands in the Paleoasian Ocean); Late Cambrian–Early Ordovician (origin of LIP within the region of Early Caledonian structures in CAOB); Middle Paleozoic (origin of LIP in the Altai–Sayan rift system); Late Paleozoic–Early Mesozoic (origin of the Tarim flood-basalt province, Central Asian rift system, and a number of related zonal magmatic areas); Late Mesozoic–Cenozoic (origin of continental volcanic areas in Central Asia).Geochemical and isotopic characteristics are determined for magmatic complexes that are indicator complexes for areas of intraplate magmatism of various age, and their major evolutionary trends are discussed. Available data indicate that mantle plumes practically did not cease to affect crustal growth and transformations in CAOB in relation to the migration of the Siberian continent throughout the whole time span when the belt was formed above a cluster of hotspots, which is compared with the African superplume.  相似文献   

西天山海西中期花岗岩的地质特征及其构造环境   总被引：1，自引：0，他引：1  

李伍平  姜常义  吴文奎  谢广成 《地球科学与环境学报》1995,(4)

海西中期花岗岩是西天山加里东褶皱带内规模最大的一次岩浆活动。本文从岩石学、矿物学、岩石化学和地球化学等方面对该期花岗岩的成因类型、岩浆起源和形成的构造环境进行了探讨，认为海西中期花岗岩以Ｉ型为主，Ｓ型次之，在空间上成对分布，花岗岩浆起源于地壳；海西中期花岗岩形成于活动大陆边缘岛孤环境．  相似文献   

DCMT活动光栅控制系统     

Li Huanxin  Li Zhigang  Zhang Jing 《时间频率学报》1995,(1)

ＤＣＭＴ活动光栅的控制系统是主测微器的主要部分，本控制系统操作灵活，它既能联机工作又能脱机工作，并具有自动报警和自动复位功能。主测微器承担测定天体和５个自准直像的位置，要比传统的活动光栅复杂得多．本设计的独特之处在于用分区、分时并配以光栏控制诸方法确定全部像的位置。保证了所有的观测在同一个系统之内．经一年来的实际观测证明，本系统精度优于０”．０３，达到了同类别微器的先进水平．  相似文献