大渡河次级支流斯合沟泥石流特征研究   总被引：1，自引：1，他引：1  

王小群  王兰生  李天斌  赵其华 《中国地质灾害与防治学报》2004,15(1):28-32

泥石流作为地质环境较差、的山区的主要自然灾害之一，对它的研究尤其是泥石流规律方面的研究已取得了较大的成绩。但是对于泥石流的研究思路却有待进一步发展和完善，这在很大程度上将对山区的工程建设有很重要的指导意义。论文从工程地质研究思路的角度出发，对位于大渡河支流官料河上某水电站下闸址区的斯合沟泥石流进行了研究。文中采用工程地质分析的方法对大渡河次级支流斯台沟泥石流的形成环境(地层岩性条件、构造条件、地貌条件、气象条件、植被发育及人类活动)、基本特征(泥石流沟的基本特征、泥石流的堆积特征)进行了系统的研究，提出了该泥石流的形成演化过程及其机制模型(初期是堰塞式沟谷型泥石流，后期逐渐转向汇聚式沟谷型泥石流)。并在此基础上对泥石流沟沿岸的岸坡稳定性(可能泥石流的物源)等进行了评价分析。将定性分析和定量分析相结合，对泥石流的活动趋势以及可能泥石流的体积(未来泥石流形成将主要是在面蚀和沟蚀作用下的坡面泥石流。泥石流规模较小，且由于沟谷中下游坡降的进一步减缓，形成的泥石流物质一般将沿途停积．实际进入官料河内的体积很小)做出了较为科学的评价预测。经过这样的系统分析对工程建设中的泥石流防治有着积极的指导意义。  相似文献   

昆明白泥井3号隧道围岩稳定性FLAC3D模拟   总被引：4，自引：2，他引：4  

吴传斌  施斌  孙宇  赵永贵 《水文地质工程地质》2004,31(6):52-55

应用FLAC^3D数值模拟软件对昆明白泥井3号隧道围岩稳定性进行了分析和评价。结果表明隧道支护后围岩的最大变形出现在隧道右侧拱顶，为1．00cm；隧道支护后左侧拱和右侧拱脚处剪应变明显增大，为应力集中区；围岩可以通过自身应力、应变和能量的调整，使整个隧道围岩处于稳定状态；同时也表明FLAC^3D用于隧道围岩变形分析是可行的。  相似文献   

水布垭面板堆石坝的三维弹塑性数值分析研究   总被引：2，自引：0，他引：2  

汪明元  程展林  林绍忠  陈琴 《岩土力学》2004,25(Z2):507-512

在建的清江水布垭面板堆石坝高达233 m,是目前同类坝型中最高的.采用MSC.Marc非线性有限元程序,发展了三维子模型法,对该坝进行了三维弹塑性有限元仿真分析,模拟了面板的分缝、坝体材料分区、填筑及蓄水过程,采用双屈服面弹塑性模型模拟堆石体的变形特征.根据数值分析的结果,对坝体和面板的应力变形分布规律进行了探讨.  相似文献   

Preliminary study on the occurrence of geothermal systems in the tectonic compressional regions: an example from the Derman geothermal field in the Biga Peninsula, Turkey     

Zeynel Demirel  Talat Yildirim  Musa Burak 《Journal of Asian Earth Sciences》2004,22(5):495

There are numerous hot springs with temperatures ranging from 30 to 100 °C in Biga peninsula and they occur throughout the peninsula. The result of this study shows that the region is under a tectonic compressional regime. The investigation of the faults and fractures in the region indicates that the region has been affected first by N–S and then E–W compression since the Middle Miocene. Opening fractures and antithetic and synthetic faults due to the compressional movements provide paths for the deep circulation of water. In addition, the tectonic movements, granitic intrusion and volcanic activity have also played important roles as heat sources for the geothermal systems.  相似文献   

Charnockitic magmatism in southern India   总被引：2，自引：0，他引：2  

H. M. Rajesh  M. Santosh 《Journal of Earth System Science》2004,113(4):565-585

Large charnockite massifs cover a substantial portion of the southern Indian granulite terrain. The older (late Archaean to early Proterozoic) charnockites occur in the northern part and the younger (late Proterozoic) charnockites occur in the southern part of this high-grade terrain. Among these, the older Biligirirangan hill, Shevroy hill and Nilgiri hill massifs are intermediate charnockites, with Pallavaram massif consisting dominantly of felsic charnockites. The charnockite massifs from northern Kerala and Cardamom hill show spatial association of intermediate and felsic charnockites, with the youngest Nagercoil massif consisting of felsic charnockites. Their igneous parentage is evident from a combination of features including field relations, mineralogy, petrography, thermobarometry, as well as distinct chemical features. The southern Indian charnockite massifs show similarity with high-Ba-Sr granitoids, with the tonalitic intermediate charnockites showing similarity with high-Ba-Sr granitoids with low K₂O/Na₂O ratios, and the felsic charnockites showing similarity with high-Ba-Sr granitoids with high K₂O/Na₂O ratios. A two-stage model is suggested for the formation of these charnockites. During the first stage there was a period of basalt underplating, with the ponding of alkaline mafic magmas. Partial melting of this mafic lower crust formed the charnockitic magmas. Here emplacement of basalt with low water content would lead to dehydration melting of the lower crust forming intermediate charnockites. Conversely, emplacement of hydrous basalt would result in melting at higher {ie565-01} favoring production of more siliceous felsic charnockites. This model is correlated with two crustal thickening phases in southern India, one related to the accretion of the older crustal blocks on to the Archaean craton to the north and the other probably related to the collision between crustal fragments of East and West Gondwana in a supercontinent framework.  相似文献   

Crustal Growth by Magmatic Accretion Constrained by Metamorphic P-T Paths and Thermal Models of the Kohistan Arc, NW Himalayas   总被引：2，自引：0，他引：2  

YOSHINO  TAKASHI; OKUDAIRA  TAKAMOTO 《Journal of Petrology》2004,45(11):2287-2302

Magmatic accretion is potentially an important mechanism inthe growth of the continental crust and the formation of granulites.In this study, the thermal evolution of a magmatic arc in responseto magmatic accretion is modeled using numerical solutions ofthe one-dimensional heat conduction equation. The initial andboundary conditions used in the model are constrained by geologicalobservations made in the Kohistan area, NW Himalayas. Takingconsideration of the preferred intrusion locations for basalticmagmas, we consider two plausible modes of magmatic accretion:the first involves the repeated intrusion of basalt at mid-crustaldepths (‘intraplate model’), and the second evaluatesthe simultaneous intrusion of basalt and picrite at mid-crustaldepths and the base of the crust respectively (‘double-platemodel’). The results of the double-plate model accountfor both the inferred metamorphic P–T paths of the Kohistanmafic granulites and the continental geotherm determined frompeak P–T conditions observed for granulite terranes. Thedouble-plate model may be applicable as a key growth processfor the production of thick mafic lower crust in magmatic arcs. KEY WORDS: thermal model; magmatic underplating; P–T path; granulite; lower crust  相似文献   

A quantitative, three-dimensional depositional model of gravelly braided rivers   总被引：2，自引：0，他引：2  

I. A. Lunt  J. S. Bridge  R. S. Tye† 《Sedimentology》2004,51(3):377-414

A quantitative, three‐dimensional depositional model of gravelly, braided rivers has been developed based largely on the deposits of the Sagavanirktok River in northern Alaska. These deposits were described using cores, wireline logs, trenches and ground‐penetrating radar profiles. The origin of the deposits was inferred from observations of: (1) channel and bar formation and migration and channel filling, interpreted from aerial photographs; (2) water flow during floods; and (3) the topography and texture of the river bed at low‐flow stage. This depositional model quantitatively represents the geometry of the different scales of strataset, the spatial relationships among them and their sediment texture distribution. Porosity and permeability in the model are related to sediment texture. The geometry of a particular type and scale of strataset is related to the geometry and migration of the bedform type (e.g. ripples, dunes, bedload sheets, bars) associated with deposition of the strataset. In particular, the length‐to‐thickness ratio of stratasets is similar to the wavelength‐to‐height ratio of associated bedforms. Furthermore, the wavelength and height of bedforms such as dunes and bars are related to channel depth and width. Therefore, the thickness of a particular scale of strataset (i.e. medium‐scale cross‐sets and large‐scale sets of inclined strata) will vary with river dimensions. These relationships between the dimensions of stratasets, bedforms and channels mean that this depositional model can be applied to other gravelly fluvial deposits. The depositional model can be used to interpret the origin of ancient gravelly fluvial deposits and to aid in the characterization of gravelly fluvial aquifers and hydrocarbon reservoirs.  相似文献   

Gravity anomalies and associated tectonic features over the Indian Peninsular Shield and adjoining ocean basins     

D.C. Mishra  K. Arora  V.M. Tiwari 《Tectonophysics》2004,379(1-4):61-76

A combined gravity map over the Indian Peninsular Shield (IPS) and adjoining oceans brings out well the inter-relationships between the older tectonic features of the continent and the adjoining younger oceanic features. The NW–SE, NE–SW and N–S Precambrian trends of the IPS are reflected in the structural trends of the Arabian Sea and the Bay of Bengal suggesting their probable reactivation. The Simple Bouguer anomaly map shows consistent increase in gravity value from the continent to the deep ocean basins, which is attributed to isostatic compensation due to variations in the crustal thickness. A crustal density model computed along a profile across this region suggests a thick crust of 35–40 km under the continent, which reduces to 22/20–24 km under the Bay of Bengal with thick sediments of 8–10 km underlain by crustal layers of density 2720 and 2900/2840 kg/m³. Large crustal thickness and trends of the gravity anomalies may suggest a transitional crust in the Bay of Bengal up to 150–200 km from the east coast. The crustal thickness under the Laxmi ridge and east of it in the Arabian Sea is 20 and 14 km, respectively, with 5–6 km thick Tertiary and Mesozoic sediments separated by a thin layer of Deccan Trap. Crustal layers of densities 2750 and 2950 kg/m³ underlie sediments. The crustal density model in this part of the Arabian Sea (east of Laxmi ridge) and the structural trends similar to the Indian Peninsular Shield suggest a continent–ocean transitional crust (COTC). The COTC may represent down dropped and submerged parts of the Indian crust evolved at the time of break-up along the west coast of India and passage of Reunion hotspot over India during late Cretaceous. The crustal model under this part also shows an underplated lower crust and a low density upper mantle, extending over the continent across the west coast of India, which appears to be related to the Deccan volcanism. The crustal thickness under the western Arabian Sea (west of the Laxmi ridge) reduces to 8–9 km with crustal layers of densities 2650 and 2870 kg/m³ representing an oceanic crust.  相似文献   

Regional moment tensor uncertainty due to mismodeling of the crust     

Jan ílený 《Tectonophysics》2004,383(3-4):133-147

The retrieval of earthquake moment tensor (MT) requires the response of the medium, in which seismic waves travel from the hypocenter to the stations, to be known. In inverting long-period (LP) seismic data (teleseismic and LP regional records), a gross earth model is sufficient; with decreasing periods, a more detailed model is needed. This is the case when waveforms of weak earthquakes at regional distances are to be inverted. Regional moment tensors (RMTs) of mostly Mediterranean earthquakes are determined on a routine basis by the Swiss Seismological Survey (SED) by using averaged models of the earth's crust. By inverting broad-band records of the M_w=4.8 earthquake near Udine, N Italy, on Feb. 14, 2002, we tested the sensitivity of the MT solution with respect to possible errors in the earth model used and in the location of the hypocenter depth. We perturbed the P and S velocities and the thickness in the 1-D earth model in the range from 3% to 30% of the parameter values and constructed estimates of confidence regions of the MT and error bars of the source time function (STF) and scalar moment in three frequency bands. Similarly, these error characteristics were determined assuming a mislocation in the hypocenter depth. We found that, in the band of periods from 25 to 50 s, the mechanism is resolved well (at the confidence level 95% at least) up to an earth model uncertainty of 30%, in the passband 10–25 s up to about 10%, but it is undetermined completely at periods of 5–10 s. An error in hypocenter depth of as much as double the value reported by the location procedure does not destroy the resolution of the mechanism at periods above 10 s. In the RMT catalog of the SED, earthquakes of M_w greater than about 3.5 are processed at periods above 30 s; thus, the solutions for these events are robust with respect to a possible uncertainty in the earth model used. Mechanisms of weaker earthquakes, retrieved from short periods, should be interpreted with caution.  相似文献   

Analysis of geomagnetic field along seismic profile P4 of the International Project POLONAISE'97     

T. Grabowska  G. Bojdys 《Tectonophysics》2004,383(1-2):15-28

This paper presents relative secular variations of the total intensity of the geomagnetic field against a background of results of magnetic anomaly interpretation along seismic profile P4. Profile P4 crosses a Variscan folding zone in the Paleozoic Platform (PLZ), the Trans-European Suture Zone (TESZ), and the Polish part of the East European Craton (EEC). Secular geomagnetic field variations measured in 1966–2000 along a line adjacent to seismic profile P4 were analysed. The study of secular variations, reduced to the base recordings at the Belsk Magnetic Observatory, showed that the growth of geomagnetic field at the East European Craton was slower than in the Trans-European Suture Zone and the Paleozoic Platform.A 2D crustal magnetic model was interpreted as a result of magnetic modelling, in which seismic, geological and geothermal data were also used. The modelling showed that there were significant differences in the magnetic model for geotectonic units, which had been earlier determined based on deep seismic survey data. It should be noted that a fundamental change of trend of the relative secular variations was observed at the slope of the Precambrian Platform. After analysing the geomagnetic field observed along profile P4, the hypothesis that the contact between Phanerozoic and Precambrian Europe lies in Poland's territory can be proven.  相似文献