Hydrogeological and Gasgeochemical Earthquake Precursors – A Review for Application

Even if earthquake precursory signals can be identified, how can they be useful? This paper investigates relationships among the attributes of 229 proposed earthquake related gasgeochemical and hydrogeological precursory signals, and applies these results to improve future earthquake prediction strategies. Sub-groups of these reported signals and relationships between sub-groups are established using parameters, including earthquake magnitude, signal duration, precursory time, and epicentral distance to the monitoring site (original studies are used wherever possible to improve data quality). A strong correlation (r=0.86) between signal duration and precursory time was identified. This suggests a relationship between the investigated precursory signals and tectonic processes related to the referenced earthquakes. Moreover, these signals are categorized into four groups, reflecting differences in monitoring station densities, measurement methods and physical processes related to signal occurrence: (a) radon exhalation from the earth’s crust, (b) exhalation of other gases (helium, argon and others), (c) temporal variation in water level or discharge of springs and (d) temporal variation in temperature and dissolved ions in the water of the monitoring sites. In addition, boundary functions are used to separate signal group subsets. Finally, it is shown how these boundary functions can be used in the context of an earthquake prediction strategy by identifying potential minimum magnitudes and maximum epicentral distances from the monitoring site.     

首都圈数字地震台网对微弱爆破信号的检测能力

利用首都圈数字地震台网接收人工地震信号,进行地下结构研究具有重要意义.但人工震源释放的能量小,激发的地震波以短周期为主,因此本文较全面地研究了地震台网对短周期微弱信号（1～20 Hz）的检测能力：(1) 分析了台网的背景噪声,结果表明基岩台址的地震台噪声比沉积盖层台址的地震台噪声低约13 dB,这相当于近1个震级的检测阈值;夜间的噪声比白天低约5 dB;噪声有逐年增高的趋势,2006年比2001年噪声提高约4 dB.(2 )分析了在台网内进行的药量为25 kg的陆地井下爆破实验,一次爆破相当于0.69级（M_L）的天然地震,有18个地震台可辨认爆炸产生的Pg、Pm或Pc波;离爆破点218 km的基岩台,仍可以接收到振幅只有1.6 nm 的Pm波,这个结果可为地震勘探实际工作提供参考.(3) 研究了台网外核爆试验的信号特征,2006年发生在朝鲜的地下核试验是一次检验台网检测微弱信号能力的好机会.波形记录经1～5Hz滤波后,台网中噪声小的18个基岩台可以清晰辨认核爆破产生的P波或Lg波,P波平均振幅为16 nm,计算的平均震级为m_b4.3,和NEIC给出的震级相同;分析还表明背景噪声是影响台站信号检测能力的主要因素之一.     

基于解析信号振幅识别磁源体边界的分析解释方法

解析信号本质上是一种全通滤波器,由于其不受人为因素干扰,能够较好地反映原始信号包含的信息特征。该方法不仅是对非平稳信号进行分析的有效方法,也是检测信号局部特征的有力工具。本文通过对实信号的解析信号处理得到复信号,由该复信号的振幅,能清晰地刻画信号能量空间分布特征。模型试验表明,解析信号振幅方法减小了常规化极方法在勘探程度较低的地区引起假异常的问题,使地下磁性体与振幅中心位置对应。尤其在低纬度或地形切割较大的地区,该方法更具优势。将该方法应用于老挝爬立山铁矿区实测磁异常的分析,由此圈定了磁铁矿分布位置,并由区内56个钻孔证实该推断的可靠性。     

云南地区背景噪声互相关函数中体波信号来源初探

利用云南地区43个宽频带地震台站记录的2008～2010年垂直分量数据,计算了台站对间的互相关函数并得到了5～40 s周期的瑞利面波信号。研究发现在5～10 s周期范围内,瑞利面波信号之前存在很强的前驱信号,该信号能量优势频段为0.1～0.2 Hz,其到时接近噪声互相关函数零点,视速度约为30 km/s。该信号到时随季节存在正负交替变化,进一步的质点分析表明该信号为出射角较小的P波信号。参考已有的研究,认为远场地脉动噪声源中的P波信号穿过地球深部到达云南地区,形成了噪声互相关函数中视速度较高的体波信号,并且相关的噪声源位置在冬季和夏季分别位于北太平洋和南印度洋,具有明显的季节性空间变化。     

遥感信源色彩信号的提取与复现

提出遥感信源色彩信号的提取及复现理论,给出了可操作的技术路线,设计了提取与复现程序,用MODIS(中等分辨率航天成像光谱仪)数据提取并复现了色彩信号,生成了色彩信号图像。未进行大气校正的色彩信号图像等效于太空对地摄影,从图像可看出,地物被笼罩在瑞利散射形成的蓝色“云雾”下。经瑞利散射纠正后的色彩信号图像接近于地面真彩色摄影,非专业人员能根据地物颜色及阴影判读出常见地物。理论可用于遥感信源地面真彩色图像重建、色彩信号不完整信源彩色仿真、航天对地真彩色摄影、信源质量评价。     

Quantifying flows along hydrological pathways by applying a new filtering algorithm in conjunction with master recession curve analysis

Quantifying the proportion of the river hydrograph derived from the different hydrological pathways is essential for understanding the behaviour of a catchment. This paper describes a new approach using the output from master recession curve analysis to inform a new algorithm based on the Lyne and Hollick ‘one‐parameter’ signal analysis filtering algorithm. This approach was applied to six catchments (including two subcatchments of these) in Ireland. The conceptual model for each catchment consists of four main flow pathways: overland flow, interflow, shallow groundwater and deep groundwater. The results were compared with those of the master recession curve analysis, a recharge coefficient approach developed in Ireland and the semi‐distributed, lumped and deterministic hydrological model Nedbør‐Afstrømings‐Model. The new algorithm removes the ‘free variable’ aspect that is typically associated with filtering algorithms and provides a means of estimating the contribution of each pathway that is consistent with the results of hydrograph separation in catchments that are dominated by quick response pathways. These types of catchments are underlain by poorly productive aquifers that are not capable of providing large baseflows in the river. Such aquifers underlie over 73% of Ireland, ensuring that this new algorithm is applicable in the majority of catchments in Ireland and potentially in those catchments internationally that are strongly influenced by the quick‐responding hydrological pathways. Copyright © 2013 John Wiley & Sons, Ltd.     

井中磁测资料预处理与弱信号识别

井中磁测仪器距离场源近,磁测资料受到钻孔打穿磁性体产生的内磁场影响,往往存在强干扰压制有用信号,因此研究井中磁测资料预处理与弱信号识别方法具有重要意义。笔者将地面重磁资料边界识别中倾斜角总水平导数和解析信号振幅方法改进后应用于井中磁测资料预处理中,提出倾斜角垂向导数和均值归一解析信号振幅方法。通过模型分析证明了两种方法都可识别强弱不同的井旁磁性体位置,反映边界信息,且给出了计算均值归一解析信号振幅过程中窗口选择的依据。将两种方法应用于江苏某工区ZK002孔磁测资料预处理中,得出倾斜角垂向导数方法应用于实测资料中会放大干扰,而均值归一解析信号振幅方法增强了该钻孔弱异常信息,且压制了干扰信号,处理结果与磁化率测井和钻孔资料相对应。     

不同防风标准雨量计的观测差异

针对不同的防风标准在翻斗雨量计观测时对风场变形误差的防护作用,从降水总量随风速波动的变化、设备间的均方差及其相关系数和观测时间灵敏度等几个方面对观测数据进行分析。数据分析表明不同的防风标准翻斗式雨量计对风场变形误差的防护作用存在一定的差异,其中SMALLDIFR具有更高的时间灵敏性,在雨量比较大时,偏斜式雨量计更优。     

地勘单位转变经济增长方式若干问题的思考

转变地勘单位的经济增长方式,提高各生产要素的使用效率,进而提高经济效益,推动地勘单位的经济持续、健康、全面的发展是当前急需解决的首要问题。本文在分析了地勘单位经济增长方式现状的基础上,指出了优化认识、优化资金配置、优化资本运行机制、优化内部管理、优化经营规模、优化人才成长环境等六个方面是转变地勘单位经济增长方式可选择的主要思路和途径。     

高性能瞬变电磁仪的研制及应用

瞬变电磁勘探法是目前在地球物理勘探领域里新兴的1种很有前途的测量方法,它简单实用,能测量从浅地表到深层的地质结构。本文介绍了利用工控机组成高性能瞬变电磁仪的方法,并就其应用作了简要介绍。