金属护栏对洛阳地震台地电阻率干扰定量分析

自2018年12月起,因洛阳地震台测区内安装金属护栏,该台地电阻率出现异常变化。为正确评估此次影响,结合洛阳地震台电测深曲线、岩性资料建立了三维水平层状结构模型,利用有限元法计算了测区内金属护栏对洛阳地震台地电阻率观测的影响。同时,建立典型“H”型电性结构模型,分析了不同属性的金属导线对地电阻率观测的影响。结果显示：①金属护栏是洛阳地震台此次地电阻率年变异常的主要影响因素。当位于测区内影响系数为负的区域时,金属护栏引起地电阻率的趋势性上升;当位于影响系数为正的区域时,金属护栏引起地电阻率的趋势性下降。②不同属性的金属导线对地电阻率观测的影响不同。导线与测道夹角减小、导线长度增加、导线电阻率减小以及导线横截面积增加等均会导致干扰源对地电阻率年变影响作用增强。     

宽线地震技术在辽河盆地西部凹陷八一水库区域勘探的应用

宽线地震技术是一种地震勘探方法，它采用的是一种特殊的三维观测系统，特别适合在一些障碍区内施工。本文介绍的这项技术主要包括：研制出新型的水中钻井平台，解决了水中激发问题；精心试验，掌握了不同类型检波器之间的相位差别；采取一些特殊的处理方法，解决了新老资料在采集方法和资料品质上的差异。综合应用这些技术有效地填补了以往勘探地震剖面上的资料空白。     

Calculating complex‐valued P‐wave first‐arrival traveltimes in attenuative vertical transversely isotropic media with an irregular surface

The complex‐valued first‐arrival traveltime can be used to describe the properties of both velocity and attenuation as seismic waves propagate in attenuative elastic media. The real part of the complex‐valued traveltime corresponds to phase arrival and the imaginary part is associated with the amplitude decay due to energy absorption. The eikonal equation for attenuative vertical transversely isotropic media discretized with rectangular grids has been proven effective and precise to calculate the complex‐valued traveltime, but less accurate and efficient for irregular models. By using the perturbation method, the complex‐valued eikonal equation can be decomposed into two real‐valued equations, namely the zeroth‐ and first‐order traveltime governing equations. Here, we first present the topography‐dependent zeroth‐ and first‐order governing equations for attenuative VTI media, which are obtained by using the coordinate transformation from the Cartesian coordinates to the curvilinear coordinates. Then, we apply the Lax–Friedrichs sweeping method for solving the topography‐dependent traveltime governing equations in order to approximate the viscosity solutions, namely the real and imaginary parts of the complex‐valued traveltime. Several numerical tests demonstrate that the proposed scheme is efficient and accurate in calculating the complex‐valued P‐wave first‐arrival traveltime in attenuative VTI media with an irregular surface.     

Wave energy transmission system concepts for linear generator arrays

Wave energy is a renewable source, which has so far not been exploited widely. Many of the various schemes in the past consist of large mechanical structures, often located near the sea surface. This article presents a range of systems with point absorbers on the surface and linear generators placed on the seabed, converting the wave motion into electrical power. Electrical power components are combined in different ways to obtain solutions suitable for various conditions. Different topologies for the electrical system transmitting power to the grid are discussed. Qualitative case studies are used to exemplify system options and connection schemes.     

Hydrodynamic forces on a partly buried cylinder exposed to combined waves and current

The present study extends the investigations of the hydrodynamic forces on a cylinder, laid on, or partly buried in the bed. They were determined by measuring the pressure distribution on the cylinder surface in the case of steady current, waves and coexisting flow. The pressure distribution around the cylinder was measured by using pressure transducers, which were replaced in the cylinder. Force coefficients were obtained for the ranges of Re=0.8×10⁴–1.5×10⁴, for steady current, low KC numbers (KC<5) for wave alone case and, for current-to-wave velocity RATIO=0, 3, 6 and infinity (current) for coexisting flow. The forces were also determined for the various burial-depth-to-diameter ratios between 0 and 0.7 values of the cylinder.     

A process-based model for sediment transport under various wave and current conditions

The purpose of this study is to investigate the capability of a newly developed process-based model for sediment transport under a wide variety of wave and current conditions.The model is based on the first-order boundary layer equation and the sediment advection-diffusion equation.In particular,a modified low Reynolds number k-e model is coupled to provide the turbulence closure.Detailed model verifications have been performed by simulating a number of laboratory experiments,covering a considerable range of hydrodynamic conditions such as sinusoidal waves,asymmetric waves and wave-current interactions.The model provides satisfactory numerical results which agree well with the measured results,including the time-averaged/dependent sediment concentration profiles and sediment flux profiles,as well as the time series of concentration at given elevations.The observed influences of wave orbital velocity amplitude,wave period and sediment grain size are correctly reproduced,indicating that the fundamental physical mechanisms of those processes are properly represented in the model.It is revealed that the present model is capable of predicting sediment transport under a wide range of wave and current conditions,and can be used to further study the morphodynamic processes in real coastal regions.     

“核冬天”理论及气溶胶的短波吸收作用

本文扼要回顾了国外关于核爆炸对人类生命、自然环境及气候影响的研究;介绍了近几年关于“核冬天”研究的新成果。通过沙暴尘埃对短波辐射吸收强度的分析,讨论了浓密气溶胶的天气气候效应。     

波阻抗反演技术在三维地震勘探煤层解释中的应用

通过测井约束波阻抗反演技术,不仅提高地震资料纵向、横向分辨率,也提高了对复杂煤层及煤层宏观结构解释精度.利用该技术可对煤层厚度及结构进行定量解释,较好地完成了勘探中的任务要求.该技术可应用于煤田类似任务要求的勘探工作中.     

Filling the gap: A 60 ky record of mixed carbonate-siliciclastic turbidite deposition from the Great Barrier Reef

Late Pleistocene to Holocene margin sedimentation on the Great Barrier Reef, a mixed carbonate-siliciclastic margin, has been explained by a transgressive shedding model. This model has challenged widely accepted sequence stratigraphic models in terms of the timing and type of sediment (i.e. carbonate vs. siliciclastic) deposited during sea-level oscillations. However, this model documents only hemipelagic sedimentation and the contribution of coarse-grained turbidite deposition, and the role of submarine canyons in this process, remain elusive on this archetypal margin. Here we present a new model of turbidite deposition for the last 60 ky in the north-eastern Australia margin. Using high-resolution bathymetry, 58 new and existing radiometric ages, and the composition of 81 turbidites from 15 piston cores, we found that the spatial and temporal variation of turbidites is controlled by the relationship between sea-level change and the variable physiography along the margin. Siliciclastic and mixed carbonate-siliciclastic turbidites were linked to canyons indenting the shelf-break and the well-developed shelf-edge reef barriers that stored sediment behind them. Turbidite deposition was sustained while the sea-level position allowed the connection and sediment bypassing through the inter-reef passages and canyons. Carbonate turbidites dominated in regions with more open conditions at the outer-shelf and where slope-confined canyons dominated or where canyons are generally less abundant. The turn-on and maintenance of carbonate production during sea-level fluctuations also influenced the timing of carbonate turbidite deposition. We show that a fundamental understanding of the variable physiography inherent to mixed carbonate-siliciclastic margins is essential to accurately interpret deep-water, coarse-grained deposition within a sequence stratigraphic context.     

Effects of interannual salinity variability on the barrier layer in the western-central equatorial Pacific: A diagnostic analysis from Argo

ABSTRACT In this paper, interannual variations in the barrier layer thickness （BLT） are analyzed using Argo three-dimensional temperature and salinity data, with a locus on the effects of interannually varying salinity on the evolution of the El Nifio Southern Oscillation （ENSO）. The interannually varying BLT exhibits a zonal seesaw pattern across the equatorial Pacific during ENSO cycles. This phenomenon has been attributed to two different physical processes. During E1 Nifio （La Nifia）, the barrier layer （BL） is anomalously thin （thick） west of about 160°E, and thick （thin） to the east. In the western equatorial Pacific （the western part： 130°-160°E）, interannual variations of the BLT indicate a lead of one year relative to those of the ENSO onset. The interannual variations of the BLT can be largely attributed to the interannual temperature variability, through its dominant effect on the isothermal layer depth （ILD）. However, in the central equatorial Pacific （the eastern part： 160~E- 170~W）, interannual variations of the BL almost synchronously vary with ENSO, with a lead of about two months relative to those of the local SST. In this region, the interannual variations of the BL are significantly affected by the interannually varying salinity, mainly through its modulation effect on the mixed layer depth （MLD）. As evaluated by a onedimensional boundary layer ocean model, the BL around the dateline induced by interannual salinity anomalies can significantly affect the temperature fields in the upper ocean, indicating a positive feedback that acts to enhance ENSO.