基于概率密度分布的地电场地震前兆异常提取方法

随着地电场观测技术的不断提高, 高采样率的观测资料中蕴含着丰富的与地下构造活动有关的信息, 如何从高采样率的观测资料中提取有效的地震前兆异常, 是目前地震电磁学科分析人员最为关注的问题之一。 本文利用概率密度分布方法, 分析了2013年芦山M_S7.0地震和岷县漳县M_S6.6地震震中周围9个地电场台站的观测数据, 分析得到: 在芦山地震和岷县漳县地震前, 平凉台、 古丰台和松山台出现高频异常信息, 地电场干扰增强。 据此分析, 初步研究认为概率密度分布法是一种有效的地电场高频异常信息提取方法。     

Organochlorine contaminants in endangered Hawaiian monk seals from four subpopulations in the Northwestern Hawaiian Islands

We analyzed blubber and blood samples for organochlorines (OCs) from 158 Hawaiian monk seals (Monachus schauinslandi) at four of their six primary breeding colonies in the Northwestern Hawaiian Islands. Levels of OCs in blubber were lower in adult females compared to juveniles or adult males, evidently owing to the transfer of these lipophilic compounds to pups by pregnant and lactating females. Concentrations of SigmaPCBs and p,p'-DDE in blubber generally increased with age until seals were sexually mature and then continued to increase with age in males after puberty. Average levels of PCBs and PCB toxic equivalents (TEQs) in blubber were significantly higher in adult male and juvenile seals at Midway Atoll than the same age class of seals at the other colonies. Unlike concentrations of OCs in blubber, circulating levels of OCs in blood did not vary consistently among age classes of seals or among breeding colonies. Though the concentrations of OCs measured in Hawaiian monk seals were generally equal to or lower than those reported for other pinniped species in the North Pacific Ocean, they were high enough in a few seals to potentially affect their health.     

地震地磁效应的分形布朗运动的性质及应用

重标极差分析法（R/S,rescaled range analysis method）,是研究分数布朗运动及自然现象的自仿射分形的有力工具之一,对于所有时间序列分析都有着广泛的用途．通过对天水台绝对地磁观测Z分量数据序列R/S分析,计算分段数据序列的Hurst指数H发现,昆仑山口西MS8.1地震和汶川MS8.0地震震前2—3个月,H值减小,分维数D增大,相关系数C为负值．这一动态变化表明,地震前数据序列由持久性序列发展为反持久性序列,观测数据的成分发生了改变．这与地壳内部应力变化和岩石破裂实验结果相符．所以,这一动态变化过程可以看作是强震前的一种前兆信号．      

Using atmospheric tracers to reduce uncertainty in groundwater recharge areas

A Monte Carlo-based approach to assess uncertainty in recharge areas shows that incorporation of atmospheric tracer observations (in this case, tritium concentration) and prior information on model parameters leads to more precise predictions of recharge areas. Variance-covariance matrices, from model calibration and calculation of sensitivities, were used to generate parameter sets that account for parameter correlation and uncertainty. Constraining parameter sets to those that met acceptance criteria, which included a standard error criterion, did not appear to bias model results. Although the addition of atmospheric tracer observations and prior information produced similar changes in the extent of predicted recharge areas, prior information had the effect of increasing probabilities within the recharge area to a greater extent than atmospheric tracer observations. Uncertainty in the recharge area propagates into predictions that directly affect water quality, such as land cover in the recharge area associated with a well and the residence time associated with the well. Assessments of well vulnerability that depend on these factors should include an assessment of model parameter uncertainty. A formal simulation of parameter uncertainty can be used to delineate probabilistic recharge areas, and the results can be expressed in ways that can be useful to water-resource managers. Although no one model is the correct model, the results of multiple models can be evaluated in terms of the decision being made and the probability of a given outcome from each model.     

中国中强地震前地电阻率中短期异常特征及其可能原因

地电阻率已经发展成为我国地震地球物理场观测的重要方法,通过标示一定区域范围内介质电阻率随时间的变化特征和空间分布,应用于探索地震孕育发生的过程。在50多年的观测过程中,记录到了近百次5～8级地震前的中短期异常和部分强震前的临震变化以及地震发生之后的恢复过程。电阻率是地下介质重要的物性参数,与岩土骨架和裂隙内流体电阻率、裂隙率、裂隙结构以及流体饱和度等因素有关。其中,应力作用导致的微裂隙结构变化是引起电阻率变化的重要因素。已有相关研究分别从岩石物理实验、介质电阻率模型、震例研究等方面讨论了地震前地电阻率变化的可能机理。本文对其中具有代表性的研究结果进行梳理,以“介质变形-电阻率变化”为纽带,将岩石物理实验和电阻率模型给出的细观尺度介质电阻率变化机制与震中周围地电阻率异常变化的宏观现象联系起来,介绍地震晚期孕育阶段地电阻率异常变化的可能原因。地震孕育引起发震断层周围介质变形,由发震断层向外围方向附加变形程度逐渐衰减; 地表浅层介质处于低围压状态,新生微裂隙将大致沿最大主压应力方向扩展,进而引起介质电阻率发生变化; 同一台站不同方向观测的地电阻率呈现出与P轴方位有关的各向异性异常变化,与P轴方向夹角越大的测道异常幅度越大,与P轴方向平行或近于平行的测道异常幅度最小或无异常变化; 地震前挤压变形增强区域地电阻率异常呈现下降变化,相对膨胀区域呈现上升变化或变化不明显。     

腾冲台强震前地电场线性极化特征

分析了位于云南西南部的腾冲地震台自1986年以来的大地电场记录资料, 分别针对4次远强震和中等地方震前的电场极化特征进行了分析。 结果表明, 在地震发生前3个月的时间内, 电场极化逐渐趋于线性, 而不象正常时段时数据分布比较分散。 地震越强, 其线性极化特征出现得越早。 电场异常的方向性与震中方位有一定关系, 但也与震源区的活动断裂走向有关。 综合分析了异常产生的机理, 认为异常可能来自震源, 而震源区构造是信号传播的最佳通道。 电场的震前线性极化异常具有非常典型的短临性, 对未来地震方位及时间预测具有一定的参考价值。     

如何在地理课堂中让学生“动”起来

随着新课程的进一步深入,目前许多教师已经深刻体会到课堂教学不能只强调讲授,必要时需要组织学生进行合作的学习活动,因此学生活动将会成为课堂教学的主要方式。但是,在实际课堂中有些小组互动形式看似热闹,但效果并不好,仅仅是为活动而活动,为互动而互动。那么如何在地理课堂中让学生真正"动"起来,就成为当下地理教学中亟待解决的问题。笔者认为,从教师角度出发,可从以下几方面考虑如何提高学生活动的有效性。以高二年级新授课(选修地理班)中     

Effects of barium and cadmium on the population development of the marine nematode Rhabditis (Pellioditis) marina

Offshore oil and gas drilling often involves the use of fluids containing barium and traces of other heavy metals. These may affect the environment, but information on their toxicity to benthic biota remains scant. Here, we present results of a 10-day bioassay with the marine nematode Rhabditis (Pellioditis) marina at different loads of barium (0-10 ,000 ppm nominal concentrations) and cadmium (0-12 ppm) in the range of concentrations reported from drilling-impacted sediments. Barium did not affect the fitness and population development of R. (P.) marina at concentrations up to 300 ppm, but did cause a decrease in population abundance and an increase in development time from concentrations of 400-2000 ppm onwards. Increased mortality occurred at 4800 ppm Ba. For cadmium, LOEC and EC?? values for total population abundance were 2.95 and 8.82 ppm, respectively. Cd concentrations as low as 2.40 to 2.68 caused a decrease in the abundance of adult nematodes, indicating that assays covering more generations would likely demonstrate yet more pronounced population-level effects. Our results indicate that oil and gas drilling activities may potentially have important implications for the meiobenthos through the toxicity of barium and associated metals like cadmium.     

The molecular emission-line spectrum of IRC +10216 between 330 and 358 GHz

We have conducted a spectral line survey of IRC +10216 using the Caltech Submillimeter Observatory to an average sensitivity of < or approximately 95 mK. A deconvolution algorithm has been used to derive the continuous single-sideband spectrum from 330.2 to 358.1 GHz. A total of 56 spectral lines were detected of which 54 have been identified with 8 molecules and a total of 18 isotopomers. The observed lines are used to derive column densities and relative abundances for the detected species. Within this frequency range the spectral lines detected contribute the majority of the total flux emitted by IRC +10216. We use the derived column densities and excitation temperatures to simulate the molecular line emission (assuming LTE) at frequencies up to 1000 GHz. The observed and simulated flux from line emission is compared to broadband total flux measurements and to dust emission assuming a power-law variation of the dust emissivity. We conclude that significant corrections for the line flux must be made to broadband flux measurements of IRC +10216 at wavelengths longer than approximately 750 micrometers.