海洋物探技术在海南岛西南陆架灾害地质调查中的应用

随着勘探技术的发展和海洋油气勘探开发工作的不断进行,对海底尤其是陆架地区灾害地质情况调查势在必行。本文介绍了以海南岛西南陆架区域为研究区,利用海洋物探技术对海底灾害地质做的调查和研究。     

海洋天然气水合物的地球物理探测高新技术

海洋天然气水合物是一种潜在的巨大能源,在资源环境、灾害方面处于非常重要的地位。发展海洋天然气水合物的地球物理探测高新技术一蕴藏量估算技术、深水区高分辩率地震技术、井中地球物理技术、海洋电滋法探测技术,准确了解天然气水合物的分布与蕴藏量,对我国海洋天然气水合物产业的建立具有关键作用。     

英国海洋科技战略计划及其特点分析

引言 英国作为全球主要的海洋国家之一,近年来密集推出了若干重要的海洋战略和研究计划,数量仅次于美国.本文对英国近年来主要的海洋研究战略、计划和项目进行梳理后发现几个特点,即：十分重视海洋研究国家层面的顶层设计;未来海洋研究,十分注重海洋研究基础设施的建设;未来将重点关注海洋酸化、海洋可再生能源开发和海岸带灾害的研究.     

我国海洋地球物理探测技术发展现状及展望

海洋地球物理场是一个四维的动态复杂变化系统,涉及多物理场、多界面和多尺度问题,受内外因素的共同制约.基于海洋地球物理场特征,海洋地球物理探测是揭示地球内部构造与性质的重要技术手段.通过回顾国内外海洋科学研究历史以及海洋地球物理探测技术的发展历程,对我国海洋地球物理探测技术发展进行了分析,现今的技术发展受科技进步驱动,反映国家与时代发展的需求.探讨了技术发展与需求之间的关系,依据各种地球物理探测手段及其探测平台的特点,提出了以下技术展望:优化传统的海洋地球物理勘探技术;加速并完善多样式探测平台的建设和科学载荷的研究;构建"空-天-海-潜"海洋地球物理立体探测体系;海洋地球物理探测技术与"大数据"和"人工智能"等技术深度融合.     

海洋地球物理在国家安全领域的应用

要建设海洋强国,首先要“知海、懂海”.只有认识海洋,才能从战略上部署好海洋,才能因势利导,走向海洋,开发海洋.海洋地球物理有着极为重要的作用,特别是海防和海洋地质灾害预警这些关系到国家安全的领域更是意义重大.通过对海洋地球物理环境的“全局、精细、实时”监控,及早发现,及时预警,达到维护国家安全的目的.和平时期,唤醒全民...     

国外灾害行为研究:缘起、议题和发现

20世纪40年代末50年代初以来,国外灾害行为研究在结构功能主义灾害认识、致灾因子灾害认识和灾害社会生成认识下不断丰富、发展和深化,相关研究对于理解灾害社会影响、推动灾害研究发展和促进社会防灾减灾工作做出了重要贡献。文章在回顾灾害行为研究的缘起与发展基础上,主要梳理国外民众层面灾害研究行为研究的主要议题、研究内容和结论;指出面对我国灾害多、分布广、损失重的社会现实,研究灾害行为模式、特点及其社会心理机制之于我国而言同样具有广阔的背景基础和深远的理论与实际意义。     

海洋观测数据质量控制技术研究现状及展望

海洋观测数据的质量控制是建立高质量海洋科学数据库的基础,对于推动海洋及多学科交叉研究、预测预报、灾害预警等具有重要意义.随着各种自动化观测平台(仪器)的出现,海洋调查从近海逐渐拓展到开放大洋,海洋科学已进入大数据时代.目前,国内外对如何获得高质量的现场观测数据越来越重视.然而,由于获取数据手段多样、数据质量千差万别、数据错情类型繁多等因素,使得如何高效和精准地发现这些质量问题并对其进行质量控制是一个难点,也是数据处理中的核心技术.本文系统总结了海洋观测数据(温度、盐度、溶解氧等)质量控制的研究现状与最新进展,对比了国内外不同机构质量控制的差异,分析了现已取得的成果及存在的问题,探讨了开展质量控制性能评估的可能性,并就未来的发展方向提出了一些建议.     

从海洋碳汇前沿理论到海洋负排放中国方案

海洋是地球上最大的活跃碳库,对调节气候变化发挥着无可替代的作用.文章从全球气候变化的视角,厘清"蓝碳""海洋碳汇""海洋负排放"等概念的科学内涵和实用意义,回顾我国在海洋生物储碳过程机制方面的科学成就及其对该领域国际发展趋势的影响,展望我国领衔海洋负排放国际大科学计划、积极参与全球治理、支撑碳中和战略的前景.     

海洋沉积作用与浅层地层学学术讨论会在青岛召开

我国对海洋地质科学的研究是从五十年代末开始,从无到有、从小到大逐步发展起来的。目前,不仅对我国各海区及其沿岸地带进行了调查研究,同时还开展了深海远洋的调查。研究的深度、广度和精度也日益提高,为了进一步交流海洋沉积作用(包括海岸沉积过程)、海底、海岸浅层地层学的研究成果以及新技术方     

重大灾害链及其防御

重大自然灾害及其灾害链是当今世界科学难题,本文通过国内外具体实例,介绍了重大灾害链及其巨大危害,讨论了灾害链的类型、成因、演变及其预测和防御,并着重强调加强灾害链研究的紧迫性和必要性.     

On the synchronism in the events within the core and on the surface of the earth: the changes in the organic world and in the polarity of the geomagnetic field in the phanerozoic

The data on geomagnetic reversals are compared with the changes in the organic world and with the lower-mantle plumes. The times of the formation of plumes and the times of their appearance on the Earth’s surface relate to the intervals characterized by the different frequencies of geomagnetic reversals, i.e., there is no interrelation between the formation of plumes and the frequency of the changes in the geomagnetic field polarity. At the same time, a certain synchronism is observed between the frequency of the geomagnetic reversals and the boundaries of the biostratigraphic ages, i.e., the changes in the organic world in the long-period range. A hypothesis is proposed, which explains the change in the sign of the geomagnetic field by the combined effect of the irregular rotation of the internal core relative to the mantle and the changes in the slope angle of the axis of the Earth’s rotation, which, in turn, results in synchronous events on the Earth’s surface: the rates of changes in the organic world.     

Anomalies in the secular variations in the main geomagnetic field in the context of the hierarchic dipole model

The developed dynamic model of the main geomagnetic field (MGF) includes the sources of three levels, which have existed and continuously changed during the 100-year period. The spatial-temporal dynamics of the secular variations in MGF has been considered based on this model. It has been indicated that, at different times, the formation of anomalies (located in similar regions) depended on the total dynamics of different combinations of sources, including a change in the parameters of the dipoles of the secondorder smallness. Anomalies generated by the dynamics of the dipoles of the third-order smallness do not evidently manifest themselves in the total secular variations but are responsible for the specific shapes of isodynamic lines. Based on the stability and continuity of the constructed model, the conclusion is made that long-living turbulent flows of different scales can exist in the liquid core.     

Changes in sediment transport in the Kuye River in the Loess Plateau in China

In this paper, the changes in sediment transport over 51 years from 1955 to 2006 in the Kuye River in the Loess Plateau in China are assessed. Key factors affecting sediment yield and sediment transport, such as precipitation depth, discharge, and human activities are studied. To investigate the changes in sediment yield in this watershed, a trend analysis on sediment concentration, precipitation depth, and discharge is conducted. Precipitation depths at 2 Climate Stations （CSs）, as well as discharge and sediment transport at 3 Gauging Stations （GSs） are used to assess the features of sediment transport in the Kuye River. The rtmoff modulus （defined as the annual average discharge per unit area, L/（s·km^2）） and the sediment transport modulus （defined as the annual suspended sediment transport per unit area, t/（yr km^2）） are introduced in this study to assess the changes in runoff and sediment yield for this watershed. The results show that the highest average monthly discharge during the study period in the Kuye River is 66.23 m^3/s in August with an average monthly sediment concentration of 88.9 kg/m^3. However, the highest average monthly sediment concentration during the study period in the Kuye River is 125.34 kg/m^3 and occurs in July, which has an average discharge of 42.6 m^3/s that is much less than the average monthly discharge in August. It is found that both the runoff modulus and sediment transport modulus at Wenjiachuan GS on the Kuye River has a clear downward trend. During the summer season from July to August, the sediment transport modulus at Wenjiachuan GS is much higher than those at Toudaoguai and Longmen GSs on the Yellow River. The easily erodible loess in the Kuye River watershed and the sparse vegetation are responsible for the extremely high sediment yield from the Kuye River watershed. The analyses of the grain size distribution of suspended load in the Kuye River are presented. The average monthly median grain size of suspended load in the Kuye River is largest in February and then decreases until June. In July, the average monthly median grain size of suspended load approaches another peak and decreases until September. Then, the median grain size of suspended load starts to increase until February of the following year. However, the average monthly median grain size of suspended load in the Yellow River at Toudaoguai and Longmen GSs is the smallest between early summer and late fall The median grain size in the Yellow River starts to increase in November and approaches the largest size in January.     

Trends in the characteristics of the annual and semiannual variations observed in the radio wave absorption in the lower ionosphere

The continuous increase in concentration of greenhouse gases in the atmosphere is expected to cool higher levels of the atmosphere. There is some direct and indirect experimental evidence of long-term trends in temperature and other parameters in the mesosphere and lower thermosphere (MLT). Here we look for long-term trends in the annual and semiannual variations of the radio wave absorption in the lower ionosphere, which corresponds to the MLT region heights. Data from central and southeastern Europe are used. A consistent tendency to a positive trend in the amplitude of the semiannual wave appears to be observed. The reality of a similar tendency in the amplitude of the annual wave is questionable in the sense that the trend in the amplitude of the annual wave is probably induced by the trend in the yearly average values of absorption. The phases of both the annual and semiannual waves display a forward tendency, i.e. shift to an earlier time in the year. A tentative interpretation of these results in terms of changes of the seasonal variation of temperature and wind at MLT heights does not contradict the trends observed in those parameters.     

The changes in the electric conductivity of the lithosphere in the source region of the strongest Olyutora earthquake in the Koryak highlands

The results of the magnetotelluric (MT) soundings before and after an earthquake are analyzed. The interpretation is based on the longitudinal and transverse MT curves (along and across the strike of the main tectonic elements, respectively). The MT curves are distorted by the ρ- and coast effect. The distortions due to the coast effect are estimated by the testing three-dimensional (3D) model. It is established that the coast effect distortion at the periods up to 1000 s is small and can be disregarded. The divergence of the longitudinal and transverse MT curves, which points to the presence of the deep faults, is thoroughly studied. The inversion of the MTsounding curves is carried out by the REBOCC program of the numerical two-dimensional modeling. This program implements the procedures of elimination of the ρ-effect and the joint inversion of the longitudinal and transverse MT sounding curves. The obtained geoelectrical cross sections provide an insight into the structure of electrical conductivity of the lithosphere before and after the earthquake. The more intense variations in the electric conductivity are observed in the zone of the deep faults. These variations are related to the changes in the porosity and saturation of the rocks by the highly mineralized fluids.     

Site response in the Qionghai Basin in the Wenchuan earthquake

Amplification effects of soil site response can significantly impact ground motions, and must be considered in the seismic fortification of buildings/structures to prevent or mitigate this potential seismic hazard. Utilizing acceleration time histories from the main shock of the Wenchuan earthquake recorded at four stations (i.e., one on bedrock and three on soil) in the Qionghai Basin, the site responses from three soil sites are studied by using the traditional spectral ratio method. The bedrock site is selected as a reference site. This study found that peak ground accelerations (PGAs) on the soil sites are much larger than on bedrock, with EW, NS and UD components of 3.96–6.58, 6.27–10.98, and 3.17–6.66 times those of the bedrock site, respectively. The amplification effects of the soil sites on ground motions in the frequency range of 0.1 Hz to 10 Hz are significant, depending on the thickness of the soil layer and the frequency content of the site. A significant amplification occurs with high frequency components of ground motion at shallow soil sites, and low and high frequency components of ground motion at intermediate soil sites.     

浙江省北部及邻区中强地震前地倾斜异常特征及其预测意义

解释并讨论了湖州和宁波台１９９３年以来的地倾斜资料,总结了震前有异常显示的６次地震。发现：①异常在现场记录资料中均有显示,异常形态的识别对预报地震有重要的意义;②能观测到异常全过程的倾斜仪与震中的距离基本符合式ｌｇＤｊ＝０．３０３（ＭＳ＋１．６）给出的监测能力半径,大于这个半径的台有时也能观测到异常,但多为短临异常。如果震前记录到异常的全过程,则利用单台资料可能对地震三要素进行预测。     

The electric field produced in the mantle by the dynamo in the core

A rigorous singular perturbation theory is developed to estimate the electric field E produced in the mantle M by the core dynamo when the electrical conductivity σ in M depends only on radius r, and when |r?_rln σ| ? 1 in most of M. It is assumed that σ has only one local minimum in M, either (a) at the Earth's surface ?V, or (b) at a radius b inside the mantle, or (c) at the core-mantle boundary ?K. In all three cases, the region where σ is no more than e times its minimum value constitutes a thin critical layer; in case (a), the radial electric field E_r ≈ 0 there, while in cases (b) and (c), E_r is very large there. Outside the critical layer, E_r ≈ 0 in all three cases. In no case is the tangential electric field E_S small, nearly toroidal, or nearly calculable from the magnetic vector potential A as ??_tA_S. The defects in Muth's (1979) argument which led him to contrary conclusions are identified. Benton (1979) cited Muth's work to argue that the core-fluid velocity u just below ?K can be estimated from measurements on ?V of the magnetic field B and its time derivative $\text{?}{}_{\mathrm{t}}\text{B}$. A simple model for westward drift is discussed which shows that Benton's conclusion is also wrong.In case (a), it is shown that knowledge of σ in M is unnecessary for estimating E_S on ?K with a relative error |r?_r 1nσ|^?1from measurements of E_S on ?V and knowledge of ?_tB in M (calculable from ?_tB on ?V if σ is small). Then, in case (a), u just below ?K can be estimated as $\text{?}\text{r}\text{×}\text{E}{}_{\mathrm{S}}\text{/B}{}_{\mathrm{r}}$. The method is impractical unless the contribution to E_S on ?V from ocean currents can be removed.The perturbation theory appropriate when σ in M is small is considered briefly; smallness of σ and of |r?_r ln σ|^?1 a independent questions. It is found that as σ → 0, B approaches the vacuum field in M but E does not; the explanation lies in the hydromagnetic approximation, which is certainly valid in M but fails as σ → 0. It is also found that the singular perturbation theory for |r?_r ln σ|^?1 is a useful tool in the perturbation calculations for σ when both σ and |r?_r ln σ|^?1 are small.     

Hydrological changes in the Ganges system in Bangladesh in the post-Farakka period

Abstract

The basin area of the Ganges River in Bangladesh is extremely dependent on a regular water supply from upstream to meet requirements for agriculture, fisheries, navigation, salinity control, and domestic and industrial sectors. In 1975, India commissioned a barrage on the Ganges River at Farakka to divert a significant portion of the dry season flow in order to make the Calcutta Port navigable. Statistical analyses of discharge and water level data have been carried out to determine if significant changes have occurred in the hydrology of the Ganges system in Bangladesh in the post-Farakka period. Siltation of the Gorai River (an offtake of the Ganges River) has also been examined using the stage-discharge relationship and regression analysis. The analyses show that the diversion has caused considerable hydrological changes in the Ganges system in Bangladesh. The water supply in the dry season has been reduced substantially, while siltation of the Gorai River has increased significantly.     

Methanogenesis in the sediment of the acidic Lake Caviahue in Argentina

The biogeochemistry of methane in the sediments of Lake Caviahue was examined by geochemical analysis, microbial activity assays and isotopic analysis. The pH in the water column was 2.6 and increased up to a pH of 6 in the deeper sediment pore waters. The carbon isotope composition of CH₄ was between − 65 and − 70‰ which is indicative for the biological origin of the methane. The enrichment factor ε increased from − 46‰ in the upper sediment column to more than − 80 in the deeper sediment section suggesting a transition from acetoclastic methanogenesis to CO₂ reduction with depth. In the most acidic surface layer of the sediment (pH < 4) methanogenesis is inhibited as suggested by a linear CH₄ concentration profile, activity assays and MPN analysis. The CH₄ activity assays and the CH₄ profile indicate that methanogenesis in the sediment of Lake Caviahue was active below 40 cm depth. At that depth the pH was above 4 and sulfate reduction was sulfate limited. Methane was diffusing with a flux of 0.9 mmol m^− 2 d^− 1 to the sediment surface where it was probably oxidized. Methanogenesis contributed little to the sediments carbon budget and had no significant impact on lake water quality. The high biomass content of the sediment, which was probably caused by the last eruption of Copahue Volcano, supported high rates of sulfate reduction which probably raised the pH and created favorable conditions for methanogens in deeper sediment layers.