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Variable Chandler and Annual Wobbles in Earth’s Polar Motion During 1900–2015

The Chandler wobble (CW) and annual wobble (AW) are the two main components of polar motion, which are difficult to separate because of their very close periods. In the light of Fourier dictionary and basis pursuit method, a Fourier basis pursuit (FBP) spectrum is developed, which can reduce spectral smearing and leakage caused by the finite length of the time series. Further, a band-pass filtering method based on FBP spectrum (FBPBPF), which can effectively suppress the edge effect, is proposed in this paper. The simulation test results show that the FBPBPF method can effectively suppress the edge effect caused by spectral smearing and leakage and that its reconstruction accuracy at the boundary is approximately three times higher than the Fourier transform band-pass filtering method, which is based on Hamming windowed FFT spectrum, in extracting quasi-harmonic signals. The FBPBPF method is then applied to Earth’s polar motion data during 1900–2015. Through analyzing the amplitude and period variations of CW and AW, and calculating the eccentricity variation of the AW, we found that: (1) the amplitude of the CW is currently at a historic minimum level, and it is even possible to diminish further until a complete stop; and (2) the eccentricity of the AW has a gradually decreased fluctuation during the last 116 years.     

Shear wave velocity measurements and soil–pile system identifications in dynamic centrifuge tests

This paper presents a pre-shaking technique for measuring the $V_{s}$ profile of sand deposits and determining the natural frequencies of the sand bed and soil-structure system in a centrifuge model at an acceleration of 80 g. The pre-shaking technique is a non-destructive test. It uses a shaker as a wave generation source and a vertical array of accelerometers embedded in the sand bed and the accelerometers attached to the pile head as receivers. The pre-shaking method can be easily used for in-flight subsurface exploration ( $V_{s}$ profile measurements) and in-flight system identification of soil-structure systems (natural frequency measurements). A soil–pile centrifuge model is used to demonstrate the versatility of pre-shaking during a routine centrifuge shaking table test. This paper discusses the testing setup, testing procedures, related SI techniques, and signal processing for the soil–pile system. The natural frequencies measured by the pre-shaking tests are consistent with theory-based results. This technique can be conducted at any time before and after major earthquake events occur in a test.     

X射线极光强度与亚暴指数AE的相关关系

研究了Polar卫星的极区电离层X射线成像仪（PIXIE）得到的极光X射线成像强度AI（Auroral Intensity）与磁层亚暴指数的相关关系.本文发现,在所选取的1997年至2001年的部分数据中,从完整的X射线图像得到的极光X射线总强度和AE指数有很好的线性相关关系,在全部83组数据中有566％的数据的线性相关系数都在060以上（相关系数最大为097）.所以本文认为极光X射线总强度可以作为新的磁层亚暴卫星实时监测指数.     

20世纪全球温度场趋势变化的区域特征分析

利用 1 90 0～ 1 998年全球 5°× 5°年平均表面温度场序列 ,提取具有不同温度变化型态的显著区域 ,探讨温度背景趋势的区域性及其对变暖显著性、稳定性的影响。同时结合对Hadley中心HadCM2海气耦合模式模拟结果的初步分析 ,研究温度背景趋势地域性差异的可能成因。结果表明 ,全球年际至世纪尺度温度变化距平场存在差异显著的 2 0个区域。温度场的背景趋势主要表现为两大类 ,背景增暖型和背景波动型 ,其中背景波动型以准 70a的波动变化为主 ,主要存在于北半球中高纬海域 ,并以北大西洋地区尤为显著 ;背景增暖最为稳定、显著的区域则是南印度洋中纬度地区。不同条件下海气耦合模式数值试验的结果也表明 ,南印度洋中纬度地区是温室效应等外强迫的稳定响应区域 ,温度背景趋势的地域性差异 ,一方面可能与温室效应等外强迫变化在不同区域的响应稳定性有关 ,另一方面也可能与海气系统年代际以上尺度耦合振荡的区域性有关。     

藏东南帕隆藏布现今河流地貌特征 及其晚第四纪演化

河流沉积与地貌对构造与气候的变化极为敏感,可记录区域构造活动、气候变化和环境演变等多方面的丰富信息。由于独特的构造背景与气候条件,帕隆藏布不仅成为雅鲁藏布水系水量最大的支流,而且其流域在藏东南地区占有重要的地位。帕隆藏布流域内地表过程活跃且河流地貌演化过程快速,是揭示青藏高原东南部构造地貌演化的重要载体。通过对该河流地貌的形态学和沉积学分析发现,帕隆藏布河流形态具有明显的线状特征,其干流近似直线展布,而主要支流呈羽状分布,两者多呈直角交汇,表明河流形态明显受到嘉黎断裂带的构造形迹控制。进一步利用光释光和¹⁴C定年方法,对帕隆藏布的晚第四纪河流地貌演化,尤其是干流和东久河支流的晚第四纪河流阶地进行研究后发现,末次冰期以来的气候变化导致帕隆藏布的晚第四纪河流地貌呈现出典型的分段式特征,根据海拔高度主要可划分为3段：1）海拔2 600 m以下的河谷地貌呈V形峡谷,河谷比降大,阶地沉积年龄均在9.0～2.0 kaBP间,沉积属性以河流相和坡积相为主,表明是全新世以来气候变暖条件下形成的;2）海拔2 600～3 300 m的中游段河谷呈冰蚀围谷盆地、U形槽谷等,河谷比降小,河岸谷坡坡度小,主谷两岸冰碛垄发育,存留了古冰缘地貌遗迹,阶地沉积属性以古湖相、冰水相及河流相为主,测年结果在29.8～10.9 kaBP和50.9～39.8 kaBP间,显示其曾经为末次冰期和冰消期冰缘湖泊体系,后被现今的帕隆藏布所贯通;3）海拔3 300 m以上河流地貌为典型的冰川U形槽谷,谷底平坦,发育现代冰湖,仅发育Ⅰ级阶地并上面覆有冰碛物堆积体,有末次冰期的冰缘地貌遗迹,但主要受周围海洋性冰川作用,呈现现代冰缘地貌特征。整体上看,帕隆藏布的现今河流地貌上、下游两端年轻,主要形成于全新世期间;中游的河流地貌出现较早,残留了末次冰期和冰消期的冰缘地貌特征,并保留了广泛的古冰湖相沉积物。因此,帕隆藏布现今的河流形态主要出现在末次冰期以来。     

应用CRInSAR技术监测三峡库区滑坡形变

在对CRInSAR技术的基本理论和处理算法及实际应用进行研究的基础上,比较CRInSAR技术与传统InSAR技术的异同后认为,CRInSAR技术更适合三峡库区的滑坡监测。     

Maintenance of estuarine water quality by mangroves occurs during flood periods: A case study of a subtropical mangrove wetland

Seasonal changes in water quality were measured in samples taken at various distances from shallow water across mudflat to mangroves during flood period and from mangroves across mudflat to shallow water during ebb period in a subtropical mangrove estuary (Zhangjiang Estuary, Fujian, China). The TN (total dissolved nitrogen), TP (total dissolved phosphorus), COD (chemical oxygen demand), and DOC (dissolved organic carbon) contents during the flood period were significantly higher than those during the ebb period. In contrast, the opposite was true for the POC (particulate organic carbon) content and transparency. The mangroves at Zhangjiang Estuary may trap nutrients at rates of 90.5 g N/m²/yr, 2.2 g TP/m²/yr, and 13.7 g C/m²/yr in the form of DOC, and export POC at a rate of 81.8 g/m²/yr. Our results support the hypothesis that the maintenance of estuarine water quality by mangroves occurs during flood periods.     

东欢坨矿8煤瓦斯异常的地质因素

运用压汞法和等温吸附法对开滦矿区东欢坨矿8煤储层特征进行研究,结合矿井实测瓦斯涌出量数据,分析了控制东欢坨矿8煤瓦斯异常涌出的地质因素。结果表明:瓦斯异常主控地质因素为地质构造及水文地质特征,东欢坨矿"水大瓦斯小,水小瓦斯大"的赋存规律明显。矿井瓦斯赋存形式主要为游离态,表现出在压性断层带时,瓦斯涌出量较小;在未导通煤系含水层情况下,张性断层带往往煤体破碎、孔裂隙相对发育,瓦斯涌出量显著增大,而在断层导通煤系含水层的水文异常区,瓦斯涌出量有明显减小的趋势。东欢坨矿瓦斯涌出量受多种因素的控制,筛选出煤层埋深、煤层厚度、煤层顶板含泥率和断层数作为主要控制因素,建立了具有较好相关性的瓦斯涌出量多变量数学预测模型;并通过灰色系统理论建模软件对瓦斯涌出量和各影响因子之间的关联度进行分析,得到断层数是瓦斯涌出量的最主要影响因素。      

舟山地区静压管桩时间效应初步研究

通过复压及静载试验,对舟山地区软土地基静压管桩的时间效应进行了初步研究,指出压桩力在不同性质土层中变化特点,压桩力与休止时间,以及恢复系数与桩侧软弱土性质的关系.