GPS buoy and pressure transducer results from the August 1990 Texaco Harvest Oil Platform Experiment

The Texaco Harvest Oil Platform Experiment took place August 22–28, 1990, off Point Conception, California. This platform has been designated as the NASA/JPL verification site for the TOPEX radar altimeter, which is to be launched in mid‐1992. The purpose of the experiment was to obtain measurements from GPS and other instrumentation that will be used at the site for the verification activities, and to determine the potential effects of the platform environment on the quality of the measurements. In conjunction with this experiment, a buoy equipped with a GPS receiver was floated in the vicinity of the platform for the purpose of measuring sea‐level change and waves relative to a reference receiver located on the platform. A pressure transducer installed at the site also provided sea‐level change and wave measurements relative to the platform. We present the data collection, processing, and analysis results comparing the GPS‐buoy and pressure transducer data. The GPS‐determined sea‐surface height measurements show 1.3‐cm agreement when compared with transducer‐determined heights taken over the same period of time. Low‐rate (15‐s) data were used to measure the change in sea‐level height due to tides, while high‐rate (1‐s) measurements provided temporal resolution sufficient for determining wave spectra.     

The occurrence of Mt Barca flank eruption in the evolution of the NW periphery of Etna volcano (Italy)

Geological surveys, tephrostratigraphic study, and ⁴⁰Ar/³⁹Ar age determinations have allowed us to chronologically constrain the geological evolution of the lower NW flank of Etna volcano and to reconstruct the eruptive style of the Mt Barca flank eruption. This peripheral sector of the Mt Etna edifice, corresponding to the upper Simeto valley, was invaded by the Ellittico volcano lava flows between 41 and 29 ka ago when the Mt Barca eruption occurred. The vent of this flank eruption is located at about 15 km away from the summit craters, close to the town of Bronte. The Mt Barca eruption was characterized by a vigorous explosive activity that produced pyroclastic deposits dispersed eastward and minor effusive activity with the emission of a 1.1-km-long lava flow. Explosive activity was characterized by a phreatomagmatic phase followed by a magmatic one. The geological setting of this peripheral sector of the volcano favors the interaction between the rising magma and the shallow groundwater hosted in the volcanic pile resting on the impermeable sedimentary basement. This process produced phreatomagmatic activity in the first phase of the eruption, forming a pyroclastic fall deposit made of high-density, poorly vesicular scoria lapilli and lithic clasts. Conversely, during the second phase, a typical strombolian fall deposit formed. In terms of hazard assessment, the possible occurrence of this type of highly explosive flank eruption, at lower elevation in the densely inhabited areas, increases the volcanic risk in the Etnean region and widens the already known hazard scenario.     

新疆南天山西段震群活动特征分析

2008年3月—2013年12月新疆南天山西段小震群活动水平较高,系统整理该地区31次小震群,并对震群活动的参数特征进行分析总结,以探讨小震群活动与中强地震的关系,同时检验前兆震群类型的判断指标。结果表明:(1)新疆南天山西段震群活动集中,强度以M_L2.0~3.9地震为主,震群中最大震级多数为M_L3.5左右,而震级值M_L≥4.0共7次,最大为M_L4.9,震群序列总频次多数小于20,持续时间大多为7天以内;震群序列中地震总频次和震群持续时间与震群中最大地震震级之间不成正比。(2)震群活动主要集中在阿图什附近,75%震群发生两个月后对应M5.0以上中强地震,对应范围为0~500km,未来中强地震震中位置主要集中在喀什—乌恰交汇区,震群强度大小与未来中强地震的对应率高低值和对应的地震强度大小之间没有明显的相关性,震群序列频次与震群的地震对应率之间也不存在相关性。(3)采用U-K和U-ρ组合方法判定震群类型的检验效果相对较好,正确率约占总数的32%。分析结果可以为判断震群活动是否具有前兆特征和震情跟踪提供参考依据。     

电离层层析重构的一种新算法

自适应联合迭代重构算法是电离层层析成像中一种收敛速度较快的反演算法.然而,在电离层电子密度重构过程中,该方法对迭代初值的精度要求较高.针对上述问题,本文提出了一种约束自适应联合迭代重构算法,该方法通过附加合理的平滑约束,减弱了没有观测信息的格网对迭代初值精度的依赖性,有效地提高了反演结果精度.数值模拟实验和实测数据的反演结果证实了该算法的可行性和在重构精度上的优越性.     

The use of pseudorandom sweeps for vibroseis surveys

Pseudorandom vibroseis sweeps have long been suggested as an alternative to standard linear sweeps due to their potential for having superior orthogonality, a lower likelihood for infrastructure damage, and increased low‐frequency content. In the past, they were also attractive as they have a better autocorrelation shape, although that is less important today. Their use has been limited but the increasing popularity of simultaneous acquisition techniques has rekindled interest as they offer the ability to reduce interference noise. A wide variety of methods for generating pseudorandom sweeps have been developed over the last 45 years. This paper gives an overview of the motivations for their use before classifying and describing the different sweep types. Finally, the sweeps will be compared in terms of their major attributes including their suitability for simultaneous surveys.     

济阳坳陷石炭二叠系暗色泥岩微量元素赋存特征及其地质意义

在对Sc、Co、Ni、Ga、Rb、Sr、Mo、Ba等微量元素进行电感耦合等离子体质谱（ICP-MS）测试和对泥岩粘土矿物进行x射线衍射相对定量分析的基础上,结合骨架砂岩岩石薄片镜下观察结果,采用Sr-Rb—Ba-Sc多元素标准化图解,分析了济阳坳陷石炭二叠系暗色泥岩微量元素赋存特征及其所指示的海陆沉积相变化、火山事件、物源等方面的地质意义。研究结果表明：（1）济阳坳陷暗色泥岩微量元素含量普遍比华北地台同时期沉积物高（Ba除外）。（2）济阳坳陷本溪组和太原组下部发育海相沉积以及上石盒子组曾发生数次规模较大的海侵,表现为在Sr-Rb-Ba-Sc标准化图解中sr上扬,或Rb-Ba—Sc近似呈直线;局限台地相沉积可能造成其上部相邻地层泥岩中Rb、Sr发生异常。（3）在济阳坳陷石炭二叠系骨架砂岩岩石薄片中观察到自形石英、港湾状石英、聚片双晶长石、保存较好的挠曲状云母,推测石炭二叠系受到多次火山作用影响;Sr-Rb—Ba-Sc标准化图解中Rb异常可能揭示火山作用的影响,而Rb异常的泥岩样品通常高岭石含量非常高（〉70％）,且伊利石含量非常低（〈5％）。（4）Rb-Ba-Sc标准化图解显示济阳坳陷石炭二叠系物源区可能是华北地台北部的古老岩体,母岩岩浆来自上地壳。     

利用混沌粒子群算法确定河流水质模型参数

将混沌寻优思想引入到粒子群优化算法中,提出了混沌粒子群算法,这种方法利用混沌运动的随机性、遍历性和规律性等特性对当前粒子群体中的粒子进行混沌寻优。通过这种处理使得粒子群体的进化速度加快,从而改善了粒子群优化算法摆脱局部极值点的能力,提高了算法的收敛速度和精度。并将混沌粒子群算法应用于求解分析瞬时投放示踪剂情况下的一维河流水团示踪试验数据以及确定河流水质参数的函数优化问题,结果表明,混沌粒子群算法的收敛性能明显优于粒子群优化算法。     

发射光谱深孔大电极法测定硼、锡、银

以Al2O3、NaF和K2S2O7作为缓冲剂,以Ge为内标,与样品研磨混匀,装入石墨深孔大电极中作为样品电极,石墨电极平头柱形空腔为上电极,样品电极为下电极进行摄谱,由光电译谱仪测定谱线的黑度值。用发射光谱法深孔大电极一次性摄谱,对农业地质样品中硼、锡、银的测定,经过反复实验取得了较好的效果。本法测定了国家一级标准物质,结果与标准值相符。本法灵敏度高,背景浅,能满足多目标地质样品分析的要求。     

北斗三期试验卫星精密定轨及对PPP定位影响的分析

基于北斗三期试验卫星的实测数据确定其精密轨道和钟差,结果表明三期试验卫星IGSO径向重叠弧段精度优于7.0 cm,MEO优于5.3 cm,与二期非GEO卫星相当。采用相应轨道和钟差产品进行静态精密单点定位结果表明,在加入北斗三期试验卫星后,监测站坐标平面精度优于1.0 cm,高程精度优于2.6 cm,相对于仅采用北斗二期卫星定位结果分别提高0.5 cm和1.2 cm,且收敛时间缩短约2 h 35 min。     

Tianhui-1C卫星数据质量分析及精密定轨

对Tianhui-1C卫星的星载双频GPS数据进行质量分析,利用伪随机脉冲方法进行简化动力学定轨,采用重叠弧段比较法对其精密定轨精度进行初步分析,并从理论上分析星载GPS接收机由单频改为双频对测图精度的影响。实验表明,Tianhui-1C卫星的星载GPS观测数据完整率优于80%,周跳比优于47,L1频点的多路径误差约0.22 m,L2频点的多路径误差约0.23 m,LC组合观测值的验后残差RMS优于9.7 mm。采用轨道重叠弧段比较法对两个时段共48 h的星载GPS数据进行精密定轨精度比较,三维精度优于3.65 cm。定轨精度的提高,可使无地面点控制条件下等高线间距（CI）精度提高3.866 m,高程误差提高1.171 m。