Transtensional deformation in the Lake Tahoe region, California and Nevada, USA

Dextral transtensional deformation is occurring along the Sierra Nevada–Great Basin boundary zone (SNGBBZ) at the eastern edge of the Sierra Nevada microplate. In the Lake Tahoe region of the SNGBBZ, transtension is partitioned spatially and temporally into domains of north–south striking normal faults and transitional domains with conjugate strike-slip faults. The normal fault domains, which have had large Holocene earthquakes but account only for background seismicity in the historic period, primarily accommodate east–west extension, while the transitional domains, which have had moderate Holocene and historic earthquakes and are currently seismically active, primarily record north–south shortening. Through partitioned slip, the upper crust in this region undergoes overall constrictional strain.Major fault zones within the Lake Tahoe basin include two normal fault zones: the northwest-trending Tahoe–Sierra frontal fault zone (TSFFZ) and the north-trending West Tahoe–Dollar Point fault zone. Most faults in these zones show eastside down displacements. Both of these fault zones show evidence of Holocene earthquakes but are relatively quiet seismically through the historic record. The northeast-trending North Tahoe–Incline Village fault zone is a major normal to sinistral-oblique fault zone. This fault zone shows evidence for large Holocene earthquakes and based on the historic record is seismically active at the microearthquake level. The zone forms the boundary between the Lake Tahoe normal fault domain to the south and the Truckee transition zone to the north.Several lines of evidence, including both geology and historic seismicity, indicate that the seismically active Truckee and Gardnerville transition zones, north and southeast of Lake Tahoe basin, respectively, are undergoing north–south shortening. In addition, the central Carson Range, a major north-trending range block between two large normal fault zones, shows internal fault patterns that suggest the range is undergoing north–south shortening in addition to east–west extension.A model capable of explaining the spatial and temporal partitioning of slip suggests that seismic behavior in the region alternates between two modes, one mode characterized by an east–west minimum principal stress and a north–south maximum principal stress as at present. In this mode, seismicity and small-scale faulting reflecting north–south shortening concentrate in mechanically weak transition zones with primarily strike-slip faulting in relatively small-magnitude events, and domains with major normal faults are relatively quiet. A second mode occurs after sufficient north–south shortening reduces the north–south S_hmax in magnitude until it is less than S_v, at which point S_v becomes the maximum principal stress. This second mode is then characterized by large earthquakes on major normal faults in the large normal fault domains, which dominate the overall moment release in the region, producing significant east–west extension.     

攀西生物资源综合开发的项目设计与时序

从攀西生物资源综合开发的指导思想、设计思路和总体目标出发,对生物资源综合开发的项目和实施时序进行系统的设计。对项目实施的时间序列按照三个阶段进行划分:一是生物资源开发的起步阶段(2003-2008); 二是生物资源开发的发展阶段(2009-2015);三是生物资源开发的提高阶段(2016-2020)。生物资源综合开发项目设计按项目层次分:24个国家级项目,39个地方级项目;按资源开发类型分:木本果品类9项,纤维及造纸类3 项,木本油脂类2项,中药材开发与生物制药类8项,生活保健类10项,淀粉类1项,观赏植物及花卉产业开发类5 项,香精香料类2项,特色农业类3项,经济作物类3项,饲料类1项,真菌类3项,生物农药类2项,动物类2项,生态功能类5项,生态旅游类4项;按自然地域分:攀枝花自然地域28项,西昌-德昌自然地域35项,会理-会东自然地域7项;按项目类型分:科技攻关项目20项,科技示范与技术推广项目14项,产业化项目36项。     

攀西地区特色生物资源综合开发与示范意义

在首次对特色生物资源的内涵科学界定的基础上,探讨了特色生物资源开发的理论基础及战略意义,重点介绍了国家“十五”重大科技攻关项目——“攀西地区特色生物资源综合开发与示范”项目的设计思路、研究内容及实施路线,对项目实施的社会、生态与经济效益进行分析,认为该项目为我国特色生物资源开发提供了一些可借鉴的经验。     

试论全球化背景下的非传统安全

非传统安全是近几年频频出现的热点问题。它是在全球化背景下显现的,尤以2001年的“9·11”事件和2003年的非典型肺炎(SARS)为其典型代表。非传统安全越来越受到各国政府和学者们的重视,但它却系不同于过去我们所认识的传统安全,在形成机理、内涵、特点及与其他安全观之间的关系至今还没有得到共识,处于理论的不成熟阶段。因此,文章就以上几点进行了初步的论述。     

合理设计岩屑规程保证正常钻进条件——金刚石钻进技术专题之一

论述了正常钻进的条件，提出了合理岩屑规程是保证正常钻进的关键和设计钻头的主要依据之一，讨论了岩屑规程与金刚石钻头唇面工作状态、孔底表面粗糙度和岩屑粒度的关系，提出了相应的建议。     

应用高光谱遥感数据估算土壤表层水分的研究

土壤水分是土壤的重要组成部分，它在陆地表层和大气之间的物质和能量交换方面扮演着重要角色，寻求快速而准确的方法估算土壤水分具有重要意义。通常，从可见光一近红外对土壤表层水分的估计多是建立在土壤水分与反射率的关系之上的。而在土壤水分含量不高时，土壤水分的增加使土壤光谱反射率在整个波长范围内降低，尤其在760nm，970nm，1190nm，1450nm，1940nm和2950nm等水分吸收波段，而在土壤水分含量较高时，土壤水分的增加会使土壤光谱反射率在某些光谱波段升高。而土壤水分的估计往往是基于土壤水分与土壤水分吸收波段的吸收强度之间的线性关系上，虽然这些经验的方法对于估算某些土壤的表层水分含量是有效的，但这些关系应用于其它条件(如不同种类土壤、土壤湿度变化范围很大的情况)时却面临很多困难，这与土壤的光谱反射率是由土壤的组成成分(土壤水分、有机质、氧化铁和粘土矿物等)的含量和它们在土壤中的分布密切相关。微分技术处理“连续”的光谱是遥感中常用的数学方法，微分技术能部分消除低频光谱成分的影响。现在微分光谱已广泛地应用于研究植被的生物物理参数、矿物和有机质等。然而利用微分光谱对土壤水分反演的研究却鲜见报道。本文通过对实验室中多种不同类型的土壤进行光谱与土壤表层水分含量进行观测，探讨了通过土壤反射率与微分光谱对土壤表层水分的反演方法。4种类型的土壤光谱数据(反射率(R)，反射率倒数的对数(log(1／R))，反射率的一阶微分光谱(dR／dλ)，反射率倒数的对数的一阶微分光谱(d(log(1／R))／dλ))与土壤表层水分之间的关系在本文中得到分析，R与log(1／R)对于不同土壤类型与土壤表层水分都很敏感，说明通过R与log(1／R)反演土壤表层水分受土壤类型的影响很大，而dR／dλ，d(log(1／R))／dλ)对土壤类型却不敏感，对土壤表层水分较为敏感，说明dR／dλ和d(log(1／R))／dλ)对于反演不同类型土壤具有很大的潜力，微分光谱与土壤水分在某些波段具有显著的相关性。通过随机对9种土壤(各具有4个土壤水分)的数据建立反演土壤水分的模型，并其他9种土壤(各具有4个土壤水分)的数据进行验证模型，结果表明，dR／dλ和d(log(1／R))／dλ)能够显著提高R与log(1／R)对于不同土壤类型土壤表层水分的反演精度，由于吸收过程是非线性的，在四种类型的土壤光谱数据中，总体来说，d(log(1／R))／dλ)具有最好的能力预测不同类型土壤的表层水分含量。     

基于GPS掩星技术反演大气参数模型的优化

准确掌握地球大气中的水气分布，了解水气变化趋势对天气现象、全球气候变化、数值预报具有理论研究及实用价值。以无线电掩星技术为基础，利用掩星数据反演大气参数剖面。对原反演模型的不足进行了论证，并给出了反演个例。详细地论述了通过引入MM5先验温度T再通过线性迭代的方法反演对流层下部水汽廓线原理，给出了优化后模型反演个例。并对模型优化后反演廓线中存在的问题进行了分析，提出了下一步优化方向。     

Upper Pleistocene and Holocene paleosalinity and trophic state changes in relation to sea level variation in Rocha Lagoon, southern Uruguay

Paleolimnological data are presented on trophic development in relation to sea level variation in Rocha Lagoon, a 72 km² coastal lagoon in southern Uruguay. Using sediment cores that extended to ∼20,000 yr BP, analyses of grain size, organic matter, carbonate, total carbon, nutrients, and diatoms allowed us to infer changes in trophic state and paleosalinities, which were closely related to Holocene relative sea level variation. Higher trophic states were observed during regressive events, most probably due to increases in runoff and erosion as regressions progressed. Diatom Association Zones (DAZ) were identified in both cores. Those DAZ corresponding to transgressive events were dominated by marine/brackish taxa and relatively low organic matter and nutrient values, while those DAZ corresponding to regressive events showed increases in brackish/freshwater diatoms and both organic matter and nutrients. Although the lagoon formed after the first Holocene marine transgression, our data indicate the existence of a marine/brackish aquatic system during upper Pleistocene (i.e., before 15,000 yr BP), but by ∼20,000 yr BP, the system was still likely to be a semi-arid terrestrial system.     

Changes in soil organic carbon and other physical soil properties along adjacent Mediterranean forest, grassland, and cropland ecosystems in Turkey

Cultivation, overgrazing, and overharvesting are seriously degrading forest and grassland ecosystems in the Taurus Mountains of the southern Mediterranean region of Turkey. This study investigated the effects of changes on soil organic carbon (SOC) content and other physical soil properties over a 12-year period in three adjacent ecosystems in a Mediterranean plateau. The ecosystems were cropland (converted from grasslands in 1990), open forest, and grassland. Soil samples from two depths, 0–10 and 10–20 cm, were collected for chemical and physical analyses at each of cropland, open forest, and grassland ecosystems. SOC pools at the 0–20 cm depth of cropland, forest, and grassland ecosystems were estimated at 32,636, 56,480, and 57,317 kg ha⁻¹, respectively. Conversion of grassland into cropland during the 12-year period increased the bulk density by 10.5% and soil erodibility by 46.2%; it decreased SOM by 48.8%, SOC content by 43%, available water capacity (AWC) by 30.5%, and total porosity by 9.1% for the 0–20 cm soil depth (p<0.001). The correlation matrix revealed that SOC content was positively correlated with AWC, total porosity, mean weight diameter (MWD), forest, and grassland, and negatively with bulk density, pH, soil erodibility factor, and cropland. The multiple regression (MLR) models indicated that any two of the three ecosystems and one of the two soil depths accounted for 86.5% of variation in mean SOC values ((p<0.001).