庐枞盆地浅表地壳速度成像与隐伏矿靶区预测

利用反射地震初至波可以精确反演地壳速度结构和构造信息.对庐枞盆地采集的高分辨地震数据,运用初至波层析成像方法,反演得到了该区1200 m以上的浅表地壳速度结构信息.找矿信息总是同地球化学异常联系紧密,对采集于炮孔深处的岩屑、泥砂样品进行了地球化学分析,发现了多处显著的金属元素异常.对五条测线的速度成像结果及其映射的地下岩性结构和炮孔地球化学分析结果进行了相关性对比分析.结果显示,庐枞盆地的沉积岩、火山岩和侵入岩具有不同的速度范围,侵入岩具有高波速特征,地球化学信息高异常往往出现在高速侵入岩体的上方;精细的速度信息蕴含着丰富的浅表地壳结构变化特征,与庐枞矿集区已知的地质、岩体、构造和矿体分布存在着良好的对应关系.速度成像结果可以准确刻画地下隐伏侵入岩体的空间分布形态,结合地球化学分析异常和重磁探测等信息,预测隐伏矿床,提供深部找矿靶区.     

VTI介质多参数联合走时层析成像方法

本文基于球谐展开群速度表达式计算走时关于各向异性参数的Fréchet核函数,利用共轭梯度法对两种参数化方法进行了VTI介质中多参数联合反演方法研究.经过理论分析和数值试验发现,与经典的Thomsen参数化方法相比,垂直慢度、水平慢度与动校正慢度的参数化方式更有利于VTI介质多参数联合走时层析反演.为了克服走时对ε参数的不敏感性,我们采用了两步法进行双参数反演,理论模型试验反演得到了与垂直速度精度相当的ε参数.可以将两步法扩展到三步法以同时反演各向异性介质中的三个参数,数值试验展示了该策略的应用潜力.     

“We will go side-by-side with you.” Labour union engagement with Aboriginal peoples in Canada

The inclusion of new groups of workers has been an important component of union renewal efforts. Several unions in Canada have begun to dedicate significant resources to better organize and represent Aboriginal workers. Drawing on interviews with union activists, organizers and representatives from two national public sector unions in Canada, we present an overview of union strategies to engage with Aboriginal peoples. Results suggest that understanding the distinct territorial context of Aboriginal peoples’ relationships to work and unions has been necessary to the success of these union strategies. This approach begins by drawing connections between Aboriginal peoples’ present-day relationships to work and their prior occupancy of, and dispossession from, lands and resources. Because of the geographical specificity of how the colonial experience affected Aboriginal peoples’ relationships to work and unions, unions have had to adopt non-normative approaches to their engagements with Aboriginal peoples. In workplaces where settlers were dominant, addressing racism in the workplace and gaining support for initiatives to hire and train Aboriginal workers were important. Alternatively, in Aboriginal workplaces, organizing was a priority. Here questions of union legitimacy have taken precedence and the focus of unions has been on partnership building. Most importantly, however, engagement with Aboriginal peoples has brought attention to the colonial practices within unions and helped to foster growing Aboriginal voice within the labour movement.     

The missing half of the subduction factory: shipboard results from the Izu rear arc,IODP Expedition 350

IODP Expedition 350 was the first to be drilled in the rear part of the Izu-Bonin, although several sites had been drilled in the arc axis to fore-arc region; the scientific objective was to understand the evolution of the Izu rear arc, by drilling a deep-water volcaniclastic section with a long temporal record (Site U1437). The Izu rear arc is dominated by a series of basaltic to dacitic seamount chains up to ~100-km long roughly perpendicular to the arc front. Dredge samples from these are geochemically distinct from arc front rocks, and drilling was undertaken to understand this arc asymmetry. Site U1437 lies in an ~20-km-wide basin between two rear arc seamount chains, ~90-km west of the arc front, and was drilled to 1804 m below the sea floor (mbsf) with excellent recovery. We expected to drill a volcaniclastic apron, but the section is much more mud-rich than expected (~60%), and the remaining fraction of the section is much finer-grained than predicted from its position within the Izu arc, composed half of ashes/tuffs, and half of lapilli tuffs of fine grain size (clasts <3 cm). Volcanic blocks (>6.4 cm) are only sparsely scattered through the lowermost 25% of the section, and only one igneous unit was encountered, a rhyolite peperite intrusion at ~1390 mbsf. The lowest biostratigaphic datum is at 867 mbsf (~6.5 Ma), the lowest palaeomagnetic datum is at ~1300 mbsf (~9 Ma), and the rhyolite peperite at ~1390 mbsf has yielded a U–Pb zircon concordia intercept age of (13.6 + 1.6/?1.7) Ma. Both arc front and rear arc sources contributed to the fine-grained (distal) tephras of the upper 1320 m, but the coarse-grained (proximal) volcaniclastics in the lowest 25% of the section are geochemically similar to the arc front, suggesting arc asymmetry is not recorded in rocks older than ~13 Ma.     

2008年5月12日四川汶川8.0级地震与部分余震的震源机制解

采用区域和远台Pn或Pg初至波初动符号, 利用下半球等面积投影, 求解了2008年5月12日四川汶川8.0级地震和截止到2008年12月10日发生的部分4级以上余震的震源机制解。 汶川8.0级地震的震源机制为: 节面Ⅰ的走向为5°, 倾角为48°, 滑动角为39°; 节面Ⅱ的走向为247°, 倾角为62°, 滑动角为131°。 P轴方位角为309°, 仰角为8°, T轴方位角为208°, 仰角为54 °, B轴方位角为44°, 仰角为35°。 结合地质构造和余震空间分布, 可以确定节面Ⅱ为发震断层面。 根据震源机制解, 引发本次地震的断层活动主要表现为逆冲, 主破裂面为S67°W与该地震所在断层的走向基本一致(断裂总体走向N45°E)^[1]; 主压应力轴P轴为N51 °W, 主压应力轴P轴方位与该区域构造应力场方向基本一致。 根据余震震源机制解结果, 龙门山断裂带南段发生的余震与北段发生的余震的震源机制都具有优势分布, 且两者差异明显。 早期发生在南段的余震的破裂是以逆倾滑动为主, 兼有走向滑动; 而随着时间的推移, 余震向北段迁移, 在龙门山构造的北段地震震源的破裂方式以走向滑动为主, 兼有一定的逆倾滑动; 龙门构造带南段震源应力场受主震应力场的控制, 而龙门构造带北段震源应力场不仅受区域应力场的影响, 还受主震应力场的影响。     

华北地区第三、 四活动期平静幕后期中强地震活动与未来强震

本文通过分析、 研究华北地区第三、 四活动期各平静幕后期的中强地震活动特征, 认为: ① 华北地区第三、 四活动期9个活跃幕中有7个在首发强震前3年内发生中强地震, 其中第四活动期1～4活跃幕首发强震前2年内都发生了中强地震, 未来第5活跃幕首发强震前, 以发生中强地震作为序幕的可能性较大; ② 华北地区平静幕后期的中强地震活动, 对其后活跃幕首发强震在时间和地点上有一定指示作用。 由于华北地区可能即将进入新的强震活跃幕, 该研究对判断华北地区未来强震趋势具有实用意义。     

Accelerated aqueous leaching of selenium and arsenic from coal associated rock samples with selenium speciation using ultrasound extraction

Ultrasound extraction was used to compare the accelerated release rates of selenium and arsenic from three rocks (BT700, BT 571 and BT 60) that are associated with mountaintop mining and valley fill coal mining practiced in southern parts of West Virginia, USA. The concentrations of arsenic released from rocks were found to be three orders of magnitude higher than that of selenium. The accelerated leaching rate constants were ten times higher for arsenic compared to selenium. Se (IV) was found to be stable under ultrasound extraction conditions used whereas As (III) was quickly oxidized to As (V). BT700 was found to have more Se (IV) compared to BT571 while BT60 did not have any significant Se (IV) concentrations. Such compositional and kinetic information becomes important when determining suitable mining waste treatment protocols that have to be undertaken to different types of overburden before it is dumped in valleys.     

Characteristics of quadrant and octant advection schemes in wave models

We point out one problem of the grid advection schemes when used in wave models in coastal areas. The deficiency of the schemes is investigated by means of the ‘third' generation WAM wave model, in which the wave energy is advected by a first order upwind scheme. Two similar, alternative modifications of this scheme are analyzed, the second of which is shown to solve most of the problems encountered with advection along the co-ordinate axes.     

Uncovering Influences on the Form of Oil and Gas Field Size Distributions

A detailed understanding of the processes that led to empirical oil and gas field size distributions, especially the dynamic character of the discovery process, is needed to improve the quality of forecasts of oil and gas resources. An empirical distribution results from a complex interaction of economic, technical, and social factors with geology in the form of a distribution of deposits. These factors may cause an empirical distribution to mutate nonrandomly through time. Changes in the price of oil, the cost of exploration and development, technology, and access to prospects influence the discovery process. Failure to recognize and account for them in the modeling process can result in serious bias in estimates of the number and volume of future discoveries. In addition, the broad range of some forecasts for a given region may be explained by differences in perspective of those involved in the process. Geologists who understand the basic processes and collect the data may be scientific determinists. Statisticians who model and analyze the data are trained to think in terms of random variables and stochastic processes.     

广东前汛期异常旱涝的大气环流特征

用1957～1999年广东省19个代表站4～6月降水资料和500hPa高度场资料，着重分析和讨论了广东省前汛期异常旱、涝年的同期和前期500hPa合成平均场的主要差异,以及前期关键月、关键区的特点，为广东省前汛期异常旱、涝的预测提供判别依据。