华南陆块陆内成矿作用的一些科学问题

华南陆块由扬子地块和华夏地块组成,是全球罕见的世界级多金属成矿省,成矿潜力巨大。华南陆块的形成和演化,受到了很有特色的陆内大陆动力学过程的影响,其中的晚古生代地幔柱成矿系统、中生代大面积低温成矿系统、中生代大花岗岩省成矿系统等陆内成矿系统,在全球背景中很有特色,是全球研究陆内成矿作用的理想基地。对华南陆块地质历史时期的大陆动力学过程如何制约上述成矿作用的发生,以往已开展不同程度的研究并取得重要成果。笔者在论述这些研究进展的基础上,提出了三大成矿系统需要进一步研究的一些科学问题。     

汶川大地震前后GPS观测的精密单历元解得到的震区地壳运动

利用BERNESE软件的单历元观测值双差定位功能,获取了接近2008年5月12日汶川Ms8.0大地震震中5个GPS观测站(PIXI,CHDU,JYAN,NEIJ和LUZH站)震前的短临位移过程及震后短时间的位移.通过拟合和对比分析,讨论了单历元解的精度.计算结果表明,以YANC站为固定站,LUZH站震前5月9日N(南北...     

巨厚黄土塬区地震采集技术

黄土塬地质条件非常复杂,是地震勘探中的困难区域。宁夏南部六盘山盆地属于典型黄土塬地貌的沉积盆地。该区勘探程度低,勘探潜力大,但该区表层沉积了巨厚黄土层、深层不同构造单元差异大,在采集上需克服地表和地下的双重影响。笔者详细分析了该区地质条件以及勘探难点,并结合该区的攻关实际资料和应用的新技术、新方法,总结出一套针对该区的地震采集技术系列,可以指导该区后期地震勘探工作。     

The coupling status of alluvial fans and debris cones: a review and synthesis

Alluvial fans and debris cones link two zones of the fluvial system (e.g. hillslope gully systems to stream channels; mountain catchment sediment source areas to main river systems or to sedimentary basins) and therefore have important coupling or buffering roles. These roles may be both functional and preservational. The functional role includes debris‐cone coupling, which controls sediment supply from hillslope gully systems to stream channels, influencing channel morphology. Coupling through larger alluvial fans, expressed by fanhead trenching, causes a distal shift in sedimentation zones, or when expressed by through‐fan trenching, causes complete sediment by‐pass. The preservational role stems from the fact that fans and cones are temporary sediment storage zones, and may preserve a record of source–area environmental change more sensitively than would sediments preserved further downsystem. Fan coupling mechanisms include distally‐induced coupling (basal scour, ‘toe cutting’, marginal incision) and proximally‐induced coupling (fanhead and midfan trenching). These mechanisms lead initially to partial coupling, either extending the immediate sediment source area to the stream system or shifting the focus of sedimentation distally. Complete coupling involves transmission of sediment from the feeder catchment through the fan environment into the downstream drainage or a sedimentary basin. The implications of coupling relate to downstream channel response, fan morphology, sedimentation patterns and vertical sedimentary sequences. Temporal and spatial scales of coupling are related, and with increasing scales the dominant controls shift from storm events to land cover to climatic and base‐level change and ultimately to the relationships between tectonics and accommodation space. Finally, future research challenges are identified. Modern dating techniques and sophisticated analysis of remotely sensed data can greatly improve our understanding of fan dynamics, and should lead to better cross‐scale integration between short‐term process‐based approaches and long‐term sedimentological applications, while maintaining high quality field‐based observations. Copyright © 2011 John Wiley & Sons, Ltd.     

像素工厂在宿迁市第二次土地调查中的应用

近年来,出于处理海量数字影像的需要,法国Infoterra公司的“像素工厂”(Pixel Factory,简称PF)系统已被引入到国内.像素工厂是一种能够处理海量数据、进行并行计算和高度自动化的新一代数字影像处理系统.利用像素工厂能够进行高精度的DSM、DEM、DOM和True DOM产品的生产与制作.     

Writing in Undergraduate Geography Classes: Faculty Challenges and Rewards

Abstract

Numerous studies have shown both anecdotal and formal evidence of the benefits students obtain from doing writing activities in classes. Little formal discussion exists about how student writing in geography classes professionally affects faculty. In this article, focus shifts from student-derived benefits of writing in classes to faculty challenges and rewards for implementing writing in their classes. Based on the experience of participating in a Writing Across the Curriculum (WAC) Fellows program, the authors discuss how faculty overcame challenges and reaped the benefits of student writing in their teaching and scholarly pursuits.     

地球早期碳循环与大氧化事件

碳是影响地球宜居性的重要元素,地表系统和地球深部之间的碳循环作用对于全球气候的变化具有非常重要的影响.现今地球主要通过俯冲作用和火山作用调节全球碳循环过程,然而地球早期的碳循环过程和现今地球存在显著的差异.本文结合前人的相关研究成果,综合探讨了地球原始碳的来源、地球早期碳循环过程及其与大氧化事件的联系等问题.地球是从太...     

中国大陆8级大震有序网络结构及其预测研究

中国是一个多地震的国家,1303—2011年的700多年间,中国大陆共发生M≥8大震23次,呈现出显著的自组织有序性,其主要有序值为252~258 a,108~112 a,94~98 a,44~47 a,24~25 a,16~19 a 和 11~14 a.以翁文波信息预测理论为指导,将有序性分析与复杂网络技术相结合,努力探索具有中国特色自主创新的大震中长期预测方法,构建了中国大陆8级大震信息有序网络结构.在总结21世纪初中国大陆西部所发生的2次8级大震(2001年昆仑山8.1级大震、2008年汶川8.0级大震)预测研究的基础上,根据所建网络结构对中国大陆未来8级大震提出中长期预测意见:2022、2026、2045、2065年前后仍有可能发生M≥8大震.研究结果表明,大震是可以预测的,大震形成的机制具有网络特性.有序网络方法是大震中长期跨越式预测的有效方法.     

1995年7—9月的全球地震动态

１９９５年第三季度，全球地震活动为显著的高水平，其活动强度与第二季度相近，智利北部近海和所罗门群岛先后发生Ｍｓ７．７以上大地震，时间仅相隔半月。墨西哥和缅甸中国边界附近分别发生７．２级地震。全球各大地震带呈现全面活跃的局面。亚欧带东段地震活动强于西段，未来亚欧带也有可能出现Ｍｓ７．７以上地震，以发生于西段较为可能。     

MIGRATION OF LARGE EARTHQUAKES IN TIBETAN BLOCK AREA AND DISSCUSSION ON MAJOR ACTIVE REGION IN THE FUTURE

On the basis of summarizing the circulation characteristics and mechanism of earthquakes with magnitude 7 or above in continental China, the spatial-temporal migration characteristics, mechanism and future development trend of earthquakes with magnitude above 7 in Tibetan block area are analyzed comprehensively. The results show that there are temporal clustering and spatial zoning of regional strong earthquakes and large earthquakes in continental China, and they show the characteristics of migration and circulation in time and space. In the past 100a, there are four major earthquake cluster areas that have migrated from west to east and from south to north, i.e. 1)Himalayan seismic belt and Tianshan-Baikal seismic belt; 2)Mid-north to north-south seismic belt in Tibetan block area; 3)North-south seismic belt-periphery of Assam cape; and 4)North China and Sichuan-Yunnan area. The cluster time of each area is about 20a, and a complete cycle time is about 80a. The temporal and spatial images of the migration and circulation of strong earthquakes are consistent with the motion velocity field images obtained through GPS observations in continental China. The mechanism is related to the latest tectonic activity in continental China, which is mainly affected by the continuous compression of the Indian plate to the north on the Eurasian plate, the rotation of the Tibetan plateau around the eastern Himalayan syntaxis, and the additional stress field caused by the change of the earth's rotation speed.
Since 1900AD, the Tibetan block area has experienced three periods of high tides of earthquake activity clusters(also known as earthquake series), among which the Haiyuan-Gulang earthquake series from 1920 to 1937 mainly occurred around the active block boundary structural belt on the periphery of the Tibetan block region, with the largest earthquake occurring on the large active fault zone in the northeastern boundary belt. The Chayu-Dangxiong earthquake series from 1947 to 1976 mainly occurred around the large-scale boundary active faults of Qiangtang block, Bayankala block and eastern Himalayan syntaxis within the Tibetan block area. In the 1995-present Kunlun-Wenchuan earthquake series, 8 earthquakes with M_S7.0 or above have occurred on the boundary fault zones of the Bayankala block. Therefore, the Bayankala block has become the main area of large earthquake activity on the Tibetan plateau in the past 20a. The clustering characteristic of this kind of seismic activity shows that in a certain period of time, strong earthquake activity can occur on the boundary fault zone of the same block or closely related blocks driven by a unified dynamic mechanism, reflecting the overall movement characteristics of the block. The migration images of the main active areas of the three earthquake series reflect the current tectonic deformation process of the Tibetan block region, where the tectonic activity is gradually converging inward from the boundary tectonic belt around the block, and the compression uplift and extrusion to the south and east occurs in the plateau. This mechanism of gradual migration and repeated activities from the periphery to the middle can be explained by coupled block movement and continuous deformation model, which conforms to the dynamic model of the active tectonic block hypothesis.
A comprehensive analysis shows that the Kunlun-Wenchuan earthquake series, which has lasted for more than 20a, is likely to come to an end. In the next 20a, the main active area of the major earthquakes with magnitude 7 on the continental China may migrate to the peripheral boundary zone of the Tibetan block. The focus is on the eastern boundary structural zone, i.e. the generalized north-south seismic belt. At the same time, attention should be paid to the earthquake-prone favorable regions such as the seismic empty sections of the major active faults in the northern Qaidam block boundary zone and other regions. For the northern region of the Tibetan block, the areas where the earthquakes of magnitude 7 or above are most likely to occur in the future will be the boundary structural zones of Qaidam active tectonic block, including Qilian-Haiyuan fault zone, the northern margin fault zone of western Qinling, the eastern Kunlun fault zone and the Altyn Tagh fault zone, etc., as well as the empty zones or empty fault segments with long elapse time of paleo-earthquake or no large historical earthquake rupture in their structural transformation zones. In future work, in-depth research on the seismogenic tectonic environment in the above areas should be strengthened, including fracture geometry, physical properties of media, fracture activity behavior, earthquake recurrence rule, strain accumulation degree, etc., and then targeted strengthening tracking monitoring and earthquake disaster prevention should be carried out.