近60年来渤海海域波候变化及其与东亚环流的联系

研究海洋的波候变化是了解海洋动力过程对气候变迁响应的关键。渤海所处特殊的地理位置,使其波候在长期风场变化影响下存在阶段性变化特征。文章采用1950~2011年NCEP再分析资料中的渤海海域10 m风场资料,利用SWAN模式模拟逐月渤海波浪的有效波高、波向、波周期,分析该海区波候的变化特征。分析结果显示:1950~2011年期间渤海海域的有效波高呈现下降的趋势;波向角度均呈现上升的趋势,波周期相对平稳,略有上升;有效波高平均下降0.3 cm/a,波向角度平均增加0.12°/a。有效波高在1968年前后显现突变点,波向角度约在1960年突变,波周期在1965年左右出现突变点。渤海波候变化与海气振荡密切相关,是大尺度的大气环流变异导致的结果,长期气候变化背景下,东亚环流天气系统的长期变化(包括东亚季风强度、夏季风北界的移动,西太平洋副热带高压面积与强度的变化、脊点位置西伸与北进,以及西风指数的强弱变化等),是影响和控制渤海海域波气长期变化的主要原因。     

电磁波SYT法在隐伏区寻找含金矿化 异常带中的应用

通常运用地质、地球物理以及钻探的方法来确定金属矿体的赋存状态,地球物理方法中常用的探测手段主要有地面伽玛能谱测量法、X射线荧光法、浅层地震、地电化学参数法和地电化学提取法等.SYT法接收反射回来的带有地下地质信息的电磁波,再经过特殊的数据处理而得到的反映地下地层物性特征的曲线和柱状,可以用来进行地质解释,运用该方法对山东牟平隐伏区的含金矿化异常带进行了探测研究,探测结果显示,在SYT法探测曲线中,含金矿化带有明显的异常特征,可以用来确定金属矿体的埋深和厚度.     

Theoretical Derivation of a Peak Particle Velocity–Distance Law for the Prediction of Vibrations from Blasting

I would like to suggest a theoretical justification for the mathematical structure of some laws for predicting the maximum particle velocity vibration from blasting operations in the light of some basic notions of elastic and anelastic wave theory. Within this point of view, in dimensionally correct expressions, the terms pertaining to the rock, to the blast and to the seismic wave become evident and recognisable. A law is presented that can be used to forecast the maximum particle velocity on the basis of some blast design and rock parameters. Four tests of the proposed law performed with real data sets seem to confirm fairly well its reliability.     

Fault detection by reflected surface waves based on ambient noise interferometry

Detecting subsurface fault structure is important for evaluating potential earthquake risks associated with active faults. In this study, we propose a new method to detect faults using reflected surface waves observed in ambient noise cross correlation functions. Ambient noise tomography using direct surface waves obtained from ambient noise interferometry has been widely used to characterize active fault zones. In cases where a strong velocity contrast exists across the fault interface, fault-reflected surface waves are expected. We test this idea using a linear array deployed in the Suqian segment of Tanlu fault zone in Eastern China. The fault-reflected surface waves can be clearly seen in the cross-correlation functions of the ambient noise data, and the spatial position of the fault on the surface is close to the stations where the reflected signals first appear. Potentially reflected surface waves could also be used to infer the dip angle, fault zone thickness and the degree of velocity contrast across the fault by comparing synthetic and observed waveforms.     

Research progress on layered seismic anisotropy - A review

Seismic anisotropy is an effective feature to study the inner structure of the Earth. In complex tectonic area, the assumption of single-layer anisotropy is sometimes not well consistent with the observed data; thus, the assumption of multi-layered (i.e. stratified) anisotropy should be considered. At present, the main methods to study anisotropy include receiver functions, shear wave splitting from local and teleseismic events (SKS, SKKS, and PKS, hereafter collectively called XKS), P- and Pn wave travel time inversion, surface wave inversion from far-field earthquakes and ambient noise. Each of the above method has its own advantages and limitations. Thus, one or more of the above methods are often combined to characterize multi-layered anisotropy, of which the depth range of anisotropic layers are different. This paper reviews the research progress of multi-layered anisotropy for the purpose of providing a basis for future seismic anisotropy investigations.     

水深对软刚臂单点系泊FPSO动力响应的影响

系泊系统的定位能力是浅水油田作业的软刚臂式单点系泊FPSO安全作业的重要保障,为研究不同水深/吃水比下单点系泊系统的受力性能,针对一艘16万吨级软刚臂单点系泊FPSO,在线性三维势流理论的基础上,基于多体动力学方法,建立FPSO-系泊腿-软刚臂的耦合模型,采用Newman近似法和Pinkster近似法分析了FPSO所受二阶波浪力,在时域内计算了不同水深/吃水比对系泊系统动力响应性能的影响。结果表明,随着水深/吃水比的增加,Newman近似法计算得到二阶波浪力先增大后减小,引起单点系泊系统载荷先增大后减小;而Pinkster近似法计算得到的二阶波浪力逐渐减下,引起单点载荷逐渐减下。在浅水条件下,Pinkster近似法具有较好的适用性,Newman近似法严重低估了FPSO所受的二阶波浪力;在深水条件下,Newman近似法能满足工程计算的要求;适用两种方法的临界水深/吃水比为1.64。     

Channel response to a dam-removal sediment pulse captured at high-temporal resolution using routine gage data

In this study, we captured how a river channel responds to a sediment pulse originating from a dam removal using multiple lines of evidence derived from streamflow gages along the Patapsco River, Maryland, USA. Gages captured characteristics of the sediment pulse, including travel times of its leading edge (~7.8 km yr⁻¹) and peak (~2.6 km yr⁻¹) and suggest both translation and increasing dispersion. The pulse also changed local hydraulics and energy conditions, increasing flow velocities and Froude number, due to bed fining, homogenization and/or slope adjustment. Immediately downstream of the dam, recovery to pre-pulse conditions occurred within the year, but farther downstream recovery was slower, with the tail of the sediment pulse working through the lower river by the end of the study 7 years later. The patterns and timing of channel change associated with the sediment pulse were not driven by large flow or suspended sediment-transporting events, with change mostly occurring during lower flows. This suggests pulse mobility was controlled by process-factors largely independent of high flow. In contrast, persistent changes occurred to out-of-channel flooding dynamics. Stage associated with flooding increased during the arrival of the sediment pulse, 1 to 2 years after dam removal, suggesting persistent sediment deposition at the channel margins and nearby floodplain. This resulted in National Weather Service-indicated flood stages being attained by 3–43% smaller discharges compared to earlier in the study period. This study captured a two-signal response from the sediment pulse: (1) short- to medium-term (weeks to months) translation and dispersion within the channel, resulting in aggradation and recovery of bed elevations and changing local hydraulics; and (2) dispersion and persistent longer-term (years) effects of sediment deposition on overbank surfaces. This study further demonstrated the utility of US Geological Survey gage data to quantify geomorphic change, increase temporal resolution, and provide insights into trajectories of change over varying spatial and temporal scales.     

2020年新疆于田MS6.4地震前地磁谐波振幅比变化特征分析

以2020年6月26日于田M_S6.4地震为例, 采用地磁谐波振幅比法, 选用距震中370 km和360 km范围内的且末台、 狮泉河台所记录到的秒值连续波形数据, 对震前地磁异常进行了提取和回溯性分析, 发现地磁谐波振幅比反映了观测点深部电阻率变化, 2020年于田M_S6.4地震前且末台和狮泉河台地磁谐波振幅比出现了较明显的异常现象。 异常特征有: ① 地磁谐波振幅比Y_ZHx和Y_ZHy主要表现为“下降—转折—恢复”的形态, 地震发生在下降型变化恢复之后上升阶段; ② 震前约2年起, 且末台和狮泉河台谐波振幅比表现长短周期变化不同步或NS向与EW向变化不同步的现象; ③ 且末台Y_ZHx(NS)和狮泉河台Y_ZHy(EW)谐波振幅比异常变化中的转折上升形态具有自较长周期向较短周期的迁移现象; ④ 狮泉河台谐波振幅比趋势性异常起始时间早于且末台, 持续时间平均2年左右, 最大异常幅度达到0.04; ⑤ 且末台Y_ZHx(NS)和狮泉河台Y_ZHy(EW)异常相比对应其他分量更为显著, 这也许震中和台站所在位置有关系; ⑥ 地震前和田大地电场(距震中约265 km)岩体裂隙优势方位角(α)也显示异常变化, 可见该地震前多地球物理探测参量的异常响应, 呈现多地球物理量耦合, 增加了异常可信度。     

Acoustic-Gravity Waves from Bolide Sources

We have developed a new approach to modeling the acoustic-gravity wave (AGW) radiation from bolide sources. This first effort involves entry modeling of bolide sources that have available satellite data through procedures developed in ReVelle (Earth Moon Planets 95, 441–476, 2004a; in: A. Milani, G. Valsecchi, D. Vokrouhlicky (eds) NEO Fireball Diversity: Energetics-based Entry Modeling and Analysis Techniques, Near-earth Objects: Our Celestial Neighbors (IAU S236), 2007b). Results from the entry modeling are directly coupled to AGW production through line source blast wave theory for the initial wave amplitude and period at (at 10 blast wave radii and perpendicular to the trajectory). The second effort involves the prediction of the formation and or dominance of the propagation of the atmospheric Lamb, edge-wave composite mode in a viscous fluid (Pierce, J. Acoust. Soc. Amer. 35, 1798–1807, 1963) as a function of the source energy, horizontal range and source altitude using the Lamb wave frequency that was deduced directly during the entry modeling and that is used as a surrogate for the source energy. We have also determined that Lamb wave production by bolides at close range decreases dramatically as either the source energy decreases or the source altitude increases. Finally using procedures in Gill (Atmospheric-Ocean Dynamics, 1982) and in Tolstoy (Wave Propagation, 1973), we have analyzed two simple dispersion relationships and have calculated the expected dispersion for the Lamb edge-wave mode and for the excited, propagating internal acoustic waves. Finally, we have used the above formalism to fully evaluate these techniques for four large bolides, namely: the Tunguska bolide of June 30, 1908; the Revelstoke bolide of March 31, 1965; the Crete bolide of June 6, 2002 and the Antarctic bolide of September 3, 2004. Due to page limitations, we will only present results in detail for the Revelstoke bolide.     

临潼-蒲城数字微波时间传输系统建设及初步结果

中国科学院国家授时中心的临潼--蒲城微波时间传输系统承担着守时基准钟房(临潼)与发播控制钟房(蒲城)之间的时间同步比对任务.截至2006年底,该系统已经连续工作了28年,由于设备老化等原因,系统的可靠性和性能指标严重下降.概括介绍了微波时间传输系统的技术改造方案和数字微波系统实现的功能,初步结果表明改造后的微波时间传输系统的性能得到了提高.