红原泥炭苔草的碳同位素组成与全新世季风变化   总被引：3，自引：1，他引：3  

洪冰  林庆华  朱咏煊  冷雪天  王羽  洪业汤 《矿物岩石地球化学通报》2003,22(2):99-103

从红原泥炭中挑选出的单一植物残体——苔草纤维素的δ^13C时间序列是印度洋夏季风强度变化的敏感代用指标，它不仅请楚地指示了过去12000年印度洋夏季风数千年尺度上的变化历史，而义记录下了9次明显的季风突然减弱事件，它们可以与同时期北大西洋发生的冰川漂移碎屑沉积物事件一一对比。红原泥炭混合纤维素δ^13C时间序列也同样请楚地记录了过去12000年印度洋夏季风数千年尺度上的变化历史，对全球大范围的主要气候突然变化事件也有很好的响应。因此，泥炭混合纤维素δ^13C时间序列乃是一种很有实用价值的古气候代用记录。  相似文献   

论滑坡地质模型   总被引：1，自引：1，他引：1  

晏鄂川  刘广润 《水文地质工程地质》2003,(Z1)

在综合性滑坡分类体系基础上,把握滑坡活动各要素的地位与作用,遴选最能表征其活动特点的主要因素,作为建模的基本要素,形成滑坡基本地质模型体系;随着勘探阶段的不同,针对不同的应用目的,建立滑坡具体地质模型体系。滑坡地质模型的建立可为其分析、计算、评价与监测预报奠定模式基础,并有助于对滑坡活动的全面抽象掌握,最终提高滑坡工作的科学系统性和实用性。  相似文献   

Hydrologic conditions responsible for triggering the Sto e landslide, Slovenia   总被引：1，自引：0，他引：1  

《Engineering Geology》2004,73(3-4):193

In two events, on November 15 and 17, 2000, near the Mangart Mountain (2679 m a.s.l.), NW Slovenia, two translational landslides (debris flow slides) with a total volume of more than 1.5 million m³ occurred on the Sto e slope composed of morainic material filled with silt fraction. The first landslide was associated with a dry and the second landslide with a wet debris-flow, respectively. The rain gauging station in the village of Log pod Mangartom recorded 1638.4 mm of rainfall (more than 60% of the average annual precipitation) in the 48 days before the events (rainfall intensity of 1.42 mm/h in 1152 h). The recorded rainfall depth has a recurrence interval of more than 100 years. Other recorded rainfall depths of shorter duration (481.6 mm in 7 days, 174.0 mm in 24 h, 70 mm in 1 h) have recurrence intervals of much less than 100 years. A hydrological analysis of the event showed that the increase in runoff coefficients during the wet period in autumn 2000 before the landslide was as high as two- to threefold. An analysis using natural isotopes of δ¹⁸O and tritium of water samples from the Sto e landslide area has shown permanent but slow exfiltration of underground waters from a reservoir in the slope. In the case of low-intensity and long-duration rainfall in autumn 2000, relatively low permeable (10⁻⁷ m/s) morainic material was nearly saturated but remained stable (average porosity 21%, water content 20%, liquid limit 25%) until high artesian pressures up to 100 m developed in the slope by slow exfiltration from the relatively high permeable (10⁻⁵ m/s) massive dolomite. The Sto e landslide (two debris flow slides) was triggered by high artesian pressures built in the slope after long-duration rainfall. The devastating debris-flows formed from the landslide masses by infiltration of rainfall and surface runoff into the landslide masses and by their liquefaction.  相似文献   

Radiocarbon calibration beyond 20,000 C yr B.P. by means of planktonic foraminifera of the Iberian Margin     

Edouard Bard  Frauke Rostek  Guillemette Ménot-Combes 《Quaternary Research》2004,61(2):204-214

We present a new set of ¹⁴C ages obtained by accelerator mass spectrometry (AMS) on planktonic foraminifera from a deep-sea core collected off the Iberian Margin (MD952042). This site, at 37°N, is distant from the high-latitude zones where ¹⁴C reservoir age is large and variable. Many independent proxies — alkenones, magnetic susceptibility, ice-rafted debris, foraminifera stable isotopes, abundances of foraminifera, pollen, and dinoflagellates — show abrupt changes correlative with Dansgaard-Oeschger and Heinrich events of the last glacial period. The good stratigraphic agreement of all proxies — from the fine to the coarse-size fractions — indicates that the foraminifera ¹⁴C ages are representative of the different sediment fractions. To obtain reliable ¹⁴C ages of foraminifera beyond 20,000 ¹⁴C yr B.P., we leached the shells prior to carbonate hydrolysis and subsequent analysis. For a calendar age scale, we matched the Iberian Margin U₃₇^K′ profile with that of Greenland Summit δ¹⁸O. Both are proxies for temperature, which in models varies synchronously in the two areas. The match creates no spurious jumps in sedimentation rate and requires only a limited number of tie points. Except for ages older than 40,000 ¹⁴C yr B.P., Greenland's GISP2 and GRIP records yield similar calendars. The ¹⁴C and imported calendar ages of the Iberian Margin record are then compared to data — from lacustrine annual varves and from corals and speleothems dated by U-Th — previously used to extend the calibration beyond 20,000 ¹⁴C yr B.P. The new record follows a smooth pattern between 23,000 and 50,000 cal yr B.P. We find good agreement with the previous data sets between 23,000 and 31,000 cal yr B.P. In the interval between 33,000 and 41,000 cal yr B.P., for which previous records disagree by up to 5000 cal yr, the Iberian Margin record closely follows the polynomial curve that was previously defined by an interpolation of the coral ages and runs between the Lake Suigetsu and the Bahamian speleothem data sets.  相似文献   

"雪球"假说与塔里木板块新元古代冰川事件   总被引：3，自引：0，他引：3  

陈鹏  徐备  郑海飞 《新疆地质》2004,22(1):87-93

近年来．新元古代冰期的奇特地层引发了学们对新元古代冰期环境特征与成因演化的研究热潮．各类假说和模型不断提出，Hooffman等人运用“雪球”假说对冰川沉积的低纬度和低海拔特征、冰室效应和温室效应的相互交替、盖碳酸盐岩的成因、稳定同位素变化的含义、冰期地层中铁矿的成因等均进行了较为合理的解释．近年国内在新疆塔里木展开了对新元古代冰川事件的研究．碳同位素和微量元素比值的研究成果，不仅进一步证明了前人提出的三期冰期的观点．而且从地球化学角度验证了“雪球”假说．  相似文献   

Survey and monitoring of landslide displacements by means of L-band satellite SAR interferometry   总被引：2，自引：2，他引：2  

Tazio Strozzi  Paolo Farina  Alessandro Corsini  Christian Ambrosi  Manfred Thüring  Johannes Zilger  Andreas Wiesmann  Urs Wegmüller  Charles Werner 《Landslides》2005,2(3):193-201

This paper illustrates the capabilities of L-band satellite SAR interferometry for the investigation of landslide displacements. SAR data acquired by the L-band JERS satellite over the Italian and Swiss Alps have been analyzed together with C-band ERS-1/2 SAR data and in situ information. The use of L-band SAR data with a wavelength larger than the usual C-band, generally considered for ground motion measurements, reduces some of the limitations of differential SAR interferometry, in particular, signal decorrelation induced by vegetation cover and rapid displacements. The sites of the Alta Val Badia region in South Tyrol (Italy), Ruinon in Lombardia (Italy), Saas Grund in Valais (Switzerland) and Campo Vallemaggia in Ticino (Switzerland), representing a comprehensive set of different mass wasting phenomena in various environments, are considered. The landslides in the Alta Val Badia region are good examples for presenting the improved performance of L-band in comparison to C-band for vegetated areas, in particular concerning open forest. The landslides of Ruinon, Saas Grund, and Campo Vallemaggia demonstrate the strength of L-band in observing moderately fast displacements in comparison to C-band. This work, performed with historical SAR data from a satellite which operated until 1998, demonstrates the capabilities of future planned L-band SAR missions, like ALOS and TerraSAR-L, for landslide studies.  相似文献   

Analysis of time-varying rainfall infiltration induced landslide   总被引：5，自引：0，他引：5  

Chen Chien-Yuan  Chen Tien-Chien  Yu Fan-Chieh  Lin Sheng-Chi 《Environmental Geology》2005,48(4-5):466-479

A case study of rainstorm-induced landslide is modeled following the hourly rainfall time series from the stage of infiltration caused by induced slope movement and soil saturated to excess pore pressures—Transient Rainfall Infiltration and Grid-based Regional Slope-Stability Analysis (TRIGRS). The grid-based landslide stability analysis was conducted to model the increased pore pressures and runoff in the study area under the specified rainfall conditions. The generated time variances of pore pressures help determine landslide characteristics and mechanisms under rainfall conditions. Inputs of soil properties and permeability parameters for landslide stability analysis in the study area were prepared by TRIGRS adopted for transient infiltration analysis. Results of the analyses show that under heavy rainfall conditions, the infiltrated slope is unstable and the time of debris masses movement initiated is correlated to the recorded time. In the initiated landslide, characteristics and effects are considered and reflected in the numerical modeling under combinations of topography, land use, climatic and geological conditions. Results reveal that there is a plane failure surface and a potential circular failure surface at the study site besides the rock topple failures in the crest. A grid-based slope-stability analysis incorporated with the GIS spatial functions is more advantageous than the traditional two-dimensional analysis for specified slope profiles to determine the whole behavior of a slope.  相似文献   

Probabilistic landslide susceptibility and factor effect analysis   总被引：18，自引：0，他引：18  

S Lee  Jasmi Abdul Talib 《Environmental Geology》2005,47(7):982-990

The susceptibility of landslides and the effect of landslide-related factors at Penang in Malaysia using the geographic information system (GIS) and remote sensing data have been evaluated. Landslide locations were identified in the study area from interpretation of aerial photographs and from field surveys. Topographical and geological data and satellite images were collected, processed, and constructed into a spatial database using GIS and image processing. The factors chosen that influence landslide occurrence were: topographic slope, topographic aspect, topographic curvature and distance from drainage, all from the topographic database; lithology and distance from lineament, taken from the geologic database; land use from Landsat Thermatic Mapper (TM) satellite images; and the vegetation index value from SPOT HRV (High-Resolution Visible) satellite images. Landslide hazardous areas were analyzed and mapped using the landslide-occurrence factors employing the probability–frequency ratio method using the all factors. To assess the effect of these factors, each factor was excluded from the analysis, and its effect verified using the landslide location data. As a result, all factors had relatively positive effects, except lithology, on the landslide susceptibility maps in the study area.  相似文献   

Basic theory of three-dimensional landslide modeling based on the logical model of geologic structure     

A. Kajiyama  K. Shiono  S. Masumoto  T. Fujita 《Landslides》2005,2(3):212-220

Dynamic visualization of landslide cross-sections is important for understanding the structure and mechanism of landslide formation. Moreover, the modeling of geologic information plays an effective role in geo-hazard assessment and their mitigation. In this study, we developed the basic theory of a three-dimensional landslide modeling and applied it to the Nigawa landslide of the Hyogo Prefecture in central Japan. The construction of this model is based on the boundary surfaces of slump blocks and geologic units, and the hierarchical relationships between these surfaces. An application algorithm was validated and the model proved efficient in depicting the nature of landslides in the Nigawa area.  相似文献   

Systematic GIS-based landslide inventory as the first step for effective landslide-hazard management   总被引：1，自引：1，他引：1  

A. Colombo  L. Lanteri  M. Ramasco  C. Troisi 《Landslides》2005,2(4):291-301

The purpose of the so-called IFFI project (Inventario dei Fenomeni Franosi in Italia—Inventory of Landslides in Italy) and of many other related activities carried out by the Centro Regionale per le Ricerche Territoriali e Geologiche of ARPA Piemonte (Agenzia Regionale per la Protezione Ambientale—Regional Agency for Environmental Protection), is to map all the existing landslides in Piemonte (including both results of monitoring data and available historical data). ARPA carried out new systematic surveys using airphoto interpretation and created a specific alphanumeric geological information systems (GIS)-based database to store and process all the collected data. In order to obtain proper landslide-hazard zoning, it is necessary to provide a landslide inventory and to define the relationship between landslides and geological setting. A landslide inventory represents a fundamental base of knowledge, is a very basic tool for land planning, and strongly helps the local authorities in their decision making.  相似文献