藏西南纳木那尼峰地区第四纪以来的冰川演化

藏西南纳木那尼峰地区第四纪以来经历了多阶段的冰川演化,遗留了各个阶段不同类型的冰川堆积地貌和冰川侵蚀地貌。文章通过对各阶段冰积地貌的分布范围、特征的描述,并根据保存程度确定其相对地貌年龄,初步认为本地区第四纪以来倒数第3次冰期发育了规模最大的冰原冰川,倒数第2次冰期时冰原缩小并逐渐解体,末次冰期以来完全解体为山谷冰川。根据本地区槽谷的形态特征及冰川堆积物的分布,认为本地区末次间冰期前后有一次活跃的构造运动。     

北美东部下方岩石层—软流层边界的清晰成像

板块构造理论关键在于相对坚硬的岩石层在松软的软流层上方运动的概念,但是目前人们对岩石层与软流层边界的性质还知之甚少。在这一边界中地震波速的梯度变化主要反映了造成这两层岩石强度不同的物理和化学特性。比如,如果岩石层仅仅是热边界层,由于其较低温度而比较坚硬,那么地幔对流模型(Kinget al,2000;Zaraneket al,2004)揭示在其底部的波速梯度可能持续数十千米。相反,如果软流层由于内部挥发物富集(Hirth and Kohlstedt,1996;Gahertyet al,1999;Karato and Jung,1998;Hirthet al,2000)或存在部分熔融(Anderson,1989)而变弱,那么岩…     

用活火山喷发前震相资料模拟强地面运动及其对工程结构的影响

世界上有些火山地震位于人口密集区，因此与喷发前地震活动有关的地震危险性及其对工程结构的潜在破坏应该是危险性评估及管理的一部分。维苏威火山（意大利南部）就是如此，在那里数十万人面临火山及相关的地震危险的威胁。通过对维苏威火山地震活动相应的震级、震中及震源机制进行地震波形的大量模拟，本文研究了喷发前地震活动的影响。进行地震合成处理，以求得强地面运动特征参数，这有利于估计建筑物多的地区由期望的最大单个地震事件和大量小地震的累积效应所造成的地震破坏。选择一组所记录的地震比较合成的和观测的强地面运动参数，以证实模拟方法是否可靠。由于在维苏威地区下面的浅深度存在明显的速度不连续性，不同距离的峰值地面加速度（PGA）似乎受地震深度的影响。另一方面，滞后能量谱与结构物的塑性变化有关，它明显取决于古登堡-里克特定律（G-R）的b参数。1997年在意大利翁布里亚-马尔凯发生的地震（M5．8），虽然并未记录到很大的峰值地面加速度值，但却造成了建筑物和基础设施的严重破坏，通过在合理的期望范围内改变G—R定律参数，我们注意到累积滞后能量与在翁布里亚-马尔凯震源附近的观测值是相当的。     

Dusts from dry lakebeds： Mineralogical and geochemical characteristics of potential health concern

Dry lakebeds can be important sources of dusts that are potentially deleterious to the health of chronically exposed populations. The lakebeds accumulate and can concentrate natural and anthropogenic contaminants transported in particulate and dissolved form from the surrounding watersheds. The lakebed sediments are commonly enriched in respirable-size, detrital clay particles that can be disturbed to form dust. Evaporative concentration of ephemeral lake waters following intermittent wet periods, and of near-surface ground waters beneath some lakebeds, can enrich the sediments in diverse alkaline sulfate, carbonate, and chloride salts. Chemical reactions between alkaline evaporative waters and detrital silicates in the sediments can produce secondary silicates such as zeolites. Lakebeds with abundant salts and intermingled silicates can be highly susceptible to wind erosion, and repeated regeneration of salts in surface sediments may maintain a sustained source of salt-rich dusts. Potential health concerns arise in part from the large load of respirable particles emanating from some dry lakebeds. These concerns are exacerbated if the dusts have elevated metals, particularly metals enriched in soluble evaporative salts. For example, Owens-a dry lake, California, which was prior to mitigation the largest source of PM10 dust in the continental United States, contains elevated As in its dusts. Chemical leach tests using water and simulated gastric and lung fluids indicate that dry lakebed sediments and dusts can contain bioaccessible As, Mn, Al, Zn, Cu, Pb, U, W, Mo, and other potentially toxic metals. Another possible health issue is the occasional presence in lake sediments of secondary erionite, a fibrous zeolite associated with asbestos-related diseases. The potential presence of pathogens, as well＇as enrichments, bioaccessibility, and toxicity of pesticides and other organic pollutants in the dusts must also be evaluated. Earth scientists can help assess potential health effects of dry lakebed dusts by developing predictive models for dust generation and dust toxicity based on the geology,     

Naphthalene and phenol degradation by Flavobacterium sp. DQ398100 and Pseudomonas putida, DQ399838 isolated from petroleum polluted soil

The solubilization and degradation of polycyclic aromatic hydrocarbons （PAHs） in soil was amending by many microorganisms. One of these microorganisms is Bacteria, which were isolated from different contaminated areas at Kafer El Zyat City, Gharbia governorate, Egypt. Wastes samples were collected and bacterial isolation was carried out using enriched media technique. More than 78 isolates were obtained and the degradation capability was examined for all of them. Fingerprinting was carried out for all the isolates using REP-PCR and the obtained results grouped them into 10 groups. Two bacterial strains from the isolated bacteria were showed high degradation talent and specificity for the type of the polyaromatic hydrocarbons （naphthalene or phenol）. Pseudomonas putida （DQ399838） and Flavobacterium sp. （DQ398100） were identified and their degradation capacity was examined using real time method. Strain P. putida showed degradation rate for naphthalene reached to 50% after 20 hours from inoculation. However, Flavobacterium sp. reached 50% rate of degradation after 17 hours from inoculation time. Whenever, the soil degradation rate can be enhanced by adding these adapted bacteria to the soil and amendment of these bacteria which will help in bioremediation technology.     

北海维京地堑Beryl湾多井沉降分析的应用

Beryl湾位于北海维京地堑的最南端,有三组断层,走向分别为北东向、北西—南东向和北东—南西向。本文利用73口井的高分辨率沉降分析,结合部分区域地震,来阐述中—晚侏罗世的沉降模式。已经完成的高分辨率(每个点间隔仅1～2Ma)沉降分析可以用来研究不同走向断层的时间演化,以及东舍德兰边界断层的连锁和对沉积相的控制作用。计算结果表明,东舍德兰断层可以划分为南、北两段,它们在早—中牛津期连锁成一条断层。中—晚侏罗世裂谷期可以进一步划分为4个阶段:巴通—中卡洛夫期初始裂陷期,卡洛夫—中牛津期为早期裂陷同旋转期,晚牛津—早波特兰…     

华北中部造山带在2560~1850Ma期间发生了什么地质事件?

华北中部带是一条古元古代陆-陆碰撞带,沿此碰撞带华北东部陆块与西部陆块拼合形成统一克拉通基底。近期获得的地质、构造、地球化学和同位素资料显示,华北中部带是在位于东、西陆块之间的古大洋岩石圈向东部陆块下面俯冲所形成的大陆边缘弧或日本式岛弧基础上发展而成。在2550~2520Ma期间,俯冲致使中-下地壳发生部分熔融,导致大量花岗质岩浆上侵至地壳浅部层次,形成与绿岩伴生的花岗质侵入体。在2530~2520Ma期间,大洋岩石圈俯冲和脱水导致其上部的地幔楔发生部分熔融,熔浆喷出地表形成中部带内绿岩组合中的镁铁质-长英质火山岩。同时,广泛的镁铁质-长英质熔浆上侵导致一些弧后或弧间盆地在中部带内形成。在2520~2475Ma期间,大洋岩石圈俯冲导致下地壳进一步熔融,形成钙碱性花岗质岩浆,在中部带内形成大量TTG岩套。在元古宙期间,由于弧后盆地的进一步拉张,华北中部带内经历了2360Ma、~2250Ma、2110~21760Ma和~2050Ma等若干幕偏碱性花岗质岩浆活动.与此同时,在这些弧后盆地或弧间盆地形成一系列古元古代火山-沉积建造。在2150~1920Ma期间,可能由于大洋中脊的俯冲,华北中部带经历一次强烈的拉张事件...     

断层之间的相互作用及其地震地质意义

从断层间相互作用产生的同震库仑应力改变入手,提出了断层间相互作用的触震与缓震效应,探讨了断层间的相互作用对断层活动性、断层未来地震潜势及余震活动分布图像的影响.从断层间相互作用的角度分析了大陆强震准周期丛集复发行为的可能的物理机制.认为断层间的相互作用具有重大的地震地质意义,在进行断层活动习性和断层地震危险性定量评价及余震分布图像预测时,应该充分考虑断层间相互作用的影响.     

Nonparametric method for transmissivity distributions along boreholes

The transmissivities of individual fractures along a borehole are difficult to obtain unless each fracture is tested. To estimate a fracture-transmissivity distribution from section transmissivities, a method was developed based on fixed-interval-length transmissivities and the corresponding number of fractures for each interval. The method is nonparametric and iterative, and the fractures are viewed as two-dimensional features, in which the total transmissivity of a borehole is equal to the sum of individual fracture transmissivities. Initially, a linear a priori assumption of the transmissivity distribution is made, and from this a so-called mean transmissivity function is derived. Subsequently, the mean transmissivity of the Nj fractures within a section, j, of the borehole is estimated, and the same value of the mean transmissivity function represents Nj possible fracture transmissivities from the initial distribution. This is repeated for each borehole section, and, eventually, all fracture transmissivities are sorted to give the next iteration's transmissivity distribution and the corresponding mean transmissivity function. Finally, the distributions converge, yielding a possible fracture-transmissivity distribution. The method was verified for a synthetic data sample and then tested on a sample from a borehole at the Asp? Hard Rock Laboratory, Sweden. For the synthetic data, the method gave a distribution that was fairly close to the original one; for the Asp? data, 15% of the fractures had a transmissivity larger than the measurement limit (1 x 10(-9) m2/sec), and these transmissivities follow a log-normal distribution.