On the impact of wind on the development of wave field during storm Britta     

Xiaoli Guo Larsén  Jianting Du  Rodolfo Bolaños  Søren Larsen 《Ocean Dynamics》2017,67(11):1407-1427

The observation of extreme waves at FINO 1 during storm Britta on the 1st November 2006 has initiated a series of research studies regarding the mechanisms behind. The roles of stability and the presence of the open cell structures have been previously investigated but not conclusive. To improve our understanding of these processes, which are essential for a good forecast of similarly important events offshore, this study revisits the development of storm Britta using an atmospheric and wave coupled modeling system, wind and wave measurements from ten stations across the North Sea, cloud images and Synthetic Aperture Radar (SAR) data. It is found here that a standard state-of-the-art model is capable of capturing the important characteristics of a major storm like Britta, including the storm path, storm peak wind speed, the open cells, and peak significant wave height (H _s ) for open sea. It was also demonstrated that the impact of the open cells has negligible contribution to the development of extreme H _s observed at FINO 1. At the same time, stability alone is not sufficient in explaining the development of extreme H _s . The controlling conditions for the development of Britta extreme H _s observed at FINO 1 are the persistent strong winds and a long and undisturbed fetch over a long period.  相似文献   

近场强震动记录基线校正方法的振动台实验研究     

卢滔  胡国瑞  何福  郭迅  霍敬妍 《震灾防御技术》2017,12(3):625-634

为了获取近场永久位移,通常采用基线校正方法,对近场加速度记录进行基线校正并积分得到永久位移值,但这一结果主观性较强,其可靠性也往往缺乏验证。为了解决这一问题,本文提出了一种能产生包含永久位移振动过程的振动台实验方案,采用振动台加滑动机构的方法,模拟记录到永久位移台站测点的真实振动情况;在实验中分别采用加速度计、摄影测量方法分别直接得到加速度和位移时程,对加速度时程进行基线校正并积分得到位移时程,将其与直接获得的位移时程进行对比,以验证采用基线校正方法的有效性。实验结果表明,在实验室条件下采用现有的基线校正方法校正后,通过积分能得到可以接受的位移时程。  相似文献   

Analysis and application of the response characteristics of DLL and LWD resistivity in horizontal well     

Song Hu  Jun Li  Hong-Bo Guo  Chang-Xue Wang 《应用地球物理》2017,14(3):351-362

There exist different response characteristics in the resistivity measurements of dual laterolog (DLL) and logging while drilling (LWD) electromagnetic wave propagation logging in highly deviated and horizontal wells due to the difference in their measuring principles. In this study, we first use the integral equation method simulated the response characteristics of LWD resistivity and use the three dimensional finite element method (3D-FEM) simulated the response characteristics of DLL resistivity in horizontal wells, and then analyzed the response differences between the DLL and LWD resistivity. The comparative analysis indicated that the response differences may be caused by different factors such as differences in the angle of instrument inclination, anisotropy, formation interface, and mud intrusion. In the interface, the curves of the LWD resistivity become sharp with increases in the deviation while those of the DLL resistivity gradually become smooth. Both curves are affected by the anisotropy although the effect on DLL resistivity is lower than the LWD resistivity. These differences aid in providing a reasonable explanation in the horizontal well. However, this can also simultaneously lead to false results. At the end of the study, we explain the effects of the differences in the interpretation of the horizontal well based on the results and actual data analysis.  相似文献   

Study on the simulation of acoustic logging measurements in horizontal and deviated wells     

He Liu  Bing Wang  Guo Tao  Kuo Zhang  Wen-Zheng Yue 《应用地球物理》2017,14(3):337-350

The conventional acoustic logging interpretation method, which is based on vertical wells that penetrate isotropic formations, is not suitable for horizontal and deviated wells penetrating anisotropic formations. This unsuitability is because during horizontal and deviated well drilling, cuttings will splash on the well wall or fall into the borehole bottom and form a thin bed of cuttings. In addition, the high velocity layers at different depths and intrinsic anisotropy may affect acoustic logging measurements. In this study, we examine how these factors affect the acoustic wave slowness measured in horizontal and deviated wells that are surrounded by an anisotropic medium using numerical simulation. We use the staggered-grid finite difference method in time domain (FDTD) combined with hybrid-PML. First, we acquire the acoustic slowness using a simulated array logging system, and then, we analyze how various factors affect acoustic slowness measurements and the differences between the effects of these factors. The factors considered are high-velocity layers, thin beds of cuttings, dipping angle, formation thickness, and anisotropy. The simulation results show that these factors affect acoustic wave slowness measurements differently. We observe that when the wavelength is much smaller than the distance between the borehole wall and high velocity layer, the true slowness of the formation could be acquired. When the wavelengths are of the same order (i.e., in the near-field scenarios), the geometrical acoustics theory is no longer applicable. Furthermore, when a thin bed of cuttings exists at the bottom of the borehole, Fermat's principle is still applicable, and true slowness can be acquired. In anisotropic formations, the measured slowness changes with increments in the dipping angle. Finally, for a measurement system with specific spacing, the slowness of a thin target layer can be acquired when the distance covered by the logging tool is sufficiently long. Based on systematical simulations with different dipping angles and anisotropy in homogenous TI media, slowness estimation charts are established to quantitatively determine the slowness at any dipping angle and for any value of the anisotropic ratio. Synthetic examples with different acoustic logging tools and different elastic parameters demonstrate that the acoustic slowness estimation method can be conveniently applied to horizontal and deviated wells in TI formations with high accuracy.  相似文献   

基于国普数据的芦山县地震应急基础数据更新及其应用研究     

申源  蔡晓燕  张莹  郭红梅 《震灾防御技术》2017,12(4):893-901

通过研究地理国情普查数据和四川省芦山县地震应急基础数据库的数据类型、数据结构及二者间的关系,完成了地理国情普查数据向芦山县地震应急基础数据的转换与更新;并以芦山地震为例,利用城镇地震应急快速评估系统验证了更新后数据的可靠性。  相似文献   

多因素控制的城镇地震灾害应急处置模型研究     

郭红梅  张莹  陈维锋  尹文刚  鲁长江 《震灾防御技术》2017,12(4):882-892

随着城镇化水平的快速提高,地震灾害高风险暴露城镇数量将不断增加,震后有效的应急处置尤为重要。而当前城镇的地震应急处置主要依据平时制定的地震应急预案开展,缺乏针对性与可操作性。本文以提升城镇地震灾害应急处置能力为目的,总结以往城镇地震应急处置案例,提炼城镇地震灾害应急处置流程,结合城镇特殊的社会经济、自然地理等特点,在分析影响地震灾害应急处置关键因素的基础上,按地震烈度的不同,研究构建了具有区域特征且操作性较强的城镇地震灾害应急处置模型,为城镇地震应急处置的科学化、规范化提供了参考。  相似文献   

Altitudinal effect of soil <Emphasis Type="Italic">n</Emphasis>-alkane <Emphasis Type="Italic">δ</Emphasis>D values on the eastern Tibetan Plateau and their increasing isotopic fractionation with altitude     

Yan Bai  ChiHao Chen  XiaoMin Fang  XiaoMing Liu  HaiChao Guo 《中国科学:地球科学(英文版)》2017,60(9):1664-1673

Stable isotope paleoaltimetry has provided unprecedented insights into the topographic histories of many of the world’s highest mountain ranges. However, on the Tibetan Plateau (TP), stable isotopes from paleosols generally yield much higher paleoaltitudes than those based on fossils. It is therefore essential when attempting to interpret accurately this region’s paleoaltitudes that the empirical calibrations of local stable isotopes and the relations between them are established. Additionally, it is vital that careful estimations be made when estimate how different isotopes sourced from different areas may have been influenced by different controls. We present here 29 hydrogen isotopic values for leaf wax-derived n-alkanes (i.e., _δD_wax values, and abundance-weighted average δD values of C₂₉ and C₃₁) in surface soils, as well as the δD values of soil water (δD_sw) samples (totaling 22) from Mount Longmen (LM), on the eastern TP (altitude ~0.8–4.0 km above sea level (asl), a region climatically affected by the East Asian Monsoon (EAM). We compared our results with published data from Mount Gongga (GG). In addition, 47 river water samples, 55 spring water samples, and the daily and monthly summer precipitation records (from May to October, 2015) from two precipitation observation stations were collected along the GG transect for δD analysis. LM soil _δD_wax values showed regional differences and responded strongly to altitude, varying from?160‰ to?219‰, with an altitudinal lapse rate (ALR) of?18‰ km^?1 (R ²=0.83; p<0.0001; n=29). These _δD_wax values appeared more enriched than those from the GG transect by ~40‰. We found that both the climate and moisture sources led to the differences observed in soil _δD_wax values between the LM and GG transects. We found that, as a general rule, ε _wax/rw, ε _wax/p and ε _wax/sw values (i.e., the isotopic fractionation of _δD_wax corresponding to δD_rw, δD_p and δD_sw) increased with increasing altitude along both the LM and GG transects (up to 34‰and 50‰, respectively). Basing its research on a comparative study of _δD_wax, δD_p, δD_rw(δD_springw) and δD_sw, this paper discusses the effects of moisture recycling, glacier-fed meltwater, relative humidity (RH), evapotranspiration (ET), vegetation cover, latitude, topography and/or other factors on ε _wax/p values. Clearly, if ε _wax-p values at higher altitudes are calculated using smaller ε _wax-p values from lower altitudes, the calculated paleowaterδD_p values are going to be more depleted than the actual δD values, and any paleoaltitude would therefore be overestimated.  相似文献   

The subsistence patterns of the Shengedaliang site (~4,000 yr BP) revealed by stable carbon and nitrogen isotopes in northern Shaanxi,China     

XiangLong Chen  XiaoNing Guo  WeiLin Wang  SongMei Hu  MiaoMiao Yang  Yan Wu  YaoWu Hu 《中国科学:地球科学(英文版)》2017,60(2):268-276

In order to explore subsistence patterns in northern Shaanxi Province around 4,000 yr BP,28 human and 24 animal bones from the Shengedaliang site were sampled for stable carbon and nitrogen isotope ratio analysis.The results show that most people primarily subsisted on C_4 resources,e.g.millet and millet-related animal products,despite the fact that there was some intake of C_3 plants by some individuals.Stable nitrogen isotope values indicate that there were differences in meat consumption between individuals at the site.Pigs were mainly foddered with millet and millet byproducts,as well as some cattle,according to their highδ~(13)C values.However,most cattle and the sheep/goats consumed wild C_3 plants at Shengedaliang.Our above findings indicates that subsistence patterns in northern Shaanxi around 4,000 yr BP were characterized by millet farming,while the grassland animal husbandry,e.g.cattle and sheep/goats raising,displayed very little contribution to local economy.The intensive millet farming in northern Shaanxi provided enough food for population growth,ensured the accumulation of wealth,and consequently accelerated social differentiation and complexity.  相似文献   

Effects of fracture intersections on seismic dispersion: theoretical predictions versus numerical simulations          下载免费PDF全文

Junxin Guo  J. Germán Rubino  Stanislav Glubokovskikh  Boris Gurevich 《Geophysical Prospecting》2017,65(5):1264-1276

The detection and characterisation of domains of intersecting fractures are important goals in several disciplines of current interest, including exploration and production of unconventional reservoirs, nuclear waste storage, CO₂ sequestration, and groundwater hydrology, among others. The objective of this study is to propose a theoretical framework for quantifying the effects of fracture intersections on the frequency‐dependent elastic properties of fluid‐saturated porous and fractured rocks. Three characteristic frequency regimes for fluid pressure communication are identified. In the low‐frequency limit, fractures are in full pressure communication with the embedding porous matrix and with other fractures. Conversely, in the high‐frequency limit, fractures are hydraulically isolated from the matrix and from other fractures. At intermediate frequencies, fractures are hydraulically isolated from the matrix porosity but can be in hydraulic communication with each other, depending on whether fracture sets are intersecting. For each frequency regime, the effective stiffness coefficients are derived using the linear‐slip theory and anisotropic Gassmann equations. Explicit mathematical expressions for the two characteristic frequencies that separate the three frequency regimes are also determined. Theoretical predictions are then applied to two synthetic 2D samples, each containing two orthogonal fracture sets: one with and another without intersections. The resulting stiffness coefficients, Thomsen‐style anisotropy parameters, and the transition frequencies show good agreement with corresponding numerical simulations. The theoretical results are applicable not only to 2D but also to 3D fracture systems and are amenable to being employed in inversion schemes designed to characterise fracture systems.  相似文献   

锦州湾表层海水微塑料分布特征   总被引：2，自引：0，他引：2  

曲玲  张微微  王旭  郭洪发  陈元  李明浩  张守锋  赵骞  王菊英 《海洋学报》2021,43(2):98-104

海洋微塑料是全球关注的新兴环境问题,海湾由于特殊的地理环境特征,成为微塑料分布研究的热点区域。本研究以锦州湾为研究海域,于2017年10月布设了11个点位开展表层海水微塑料样品采集,在实验室采用湿式氧化法开展样品前处理,应用傅立叶变换显微红外光谱仪分析鉴定微塑料成分。研究结果表明,锦州湾表层水体微塑料平均丰度为(0.93±0.59)个/m3,微塑料数量占全部塑料样品的96.2%。微塑料的主要成分为聚丙烯和聚乙烯,分别占55.0%和23.5%;线状和片状塑料的比例最高,分别占41.7%和26.2%;白色、蓝色和半透明微塑料分别占35.1%、26.0%和21.4%。受水动力条件和陆域河流输入等影响,锦州湾表层水体中微塑料的空间分布整体呈现北部偏高,向南部递减的趋势。  相似文献