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111.
112.
基于大炮初至的近地表层析反演方法研究及应用 总被引:1,自引:0,他引:1
详细研究了射线追踪、层析反演方法原理以及层析反演数值求解算法,提出了利用大炮初至直接建立初始地震模型,由小折射和微测井进行约束的层析反演近地表速度模型的处理流程,提出了基于多次回溯的高精度快速射线追踪算法和层析反演数值求解算法。采用双重网格技术提高正演模拟计算精度和层析反演的成像质量,另外,充分考虑多种质量控制方案,确保最终的反演速度模型精确。设计了10种不同地表地质条件的理论模型,进行模型试算,并在实际生产中应用,理论模型试算和实际资料反演结果证明了本文方法的正确性。 相似文献
113.
地下水温度示踪理论与方法研究进展 总被引:6,自引:0,他引:6
对地下水温度示踪理论与方法的相关研究做了评述,介绍了当前地质体中温度场与渗流场耦合作用模型、数值模拟技术和渗流参数反演方法,并从温度示踪方法的两个主要应用领域:地表水与地下水交换和工程地下水渗漏探测(以堤坝为例),说明地下水温度示踪的应用研究.在地质体中温度场与渗流场耦合模型方面,裂隙介质、非饱和带、复杂边界条件和非D... 相似文献
114.
115.
《Geomechanics and Geoengineering》2013,8(3):171-183
Block detection is one of the most important steps in all discontinuous methods of analysis like Discontinuous Deformation Analysis (DDA) and Discrete Element Method (DEM). This is in fact a pre-processing step for those methods. In this study, a comprehensive computational algorithm, for tracing rock block created by discontinuities, has been developed. Using square matrices with integer elements and performing edge regularization step, reduce the size of the matrices due to elimination of unnecessary edges and vertices. Therefore speed and accuracy of block tracing operation will be increased. This algorithm is able to trace and identify all kind of blocks including convex and concave blocks formed by limited or unlimited fractures. The algorithm was programmed in C#.Net by over 3400 code lines and some cases were modeled by the code as example. 相似文献
116.
This paper raises fundamental questions about the sole use of paleolimnological techniques to identify sediment sources and
develop catchment management plans. The concept of an integrated lake: catchment framework was established 30 years ago, yet
paleolimnologists occasionally fail to appreciate the dynamics of the contributing catchment. This is especially critical
when the predominant source of sediment accumulating in a lake is allochthonous. In this paper we argue that a detailed appraisal
of catchment sources and investigation of historical documentary evidence is needed to identify and evaluate the relative
significance of sediment sources. We used such an approach at Aqualate Mere, Shropshire, UK. Mineral magnetic and radionculide
signatures of potential catchment sources and accumulating lake sediments were compared in an attempt to match the sources
to sediments deposited in the Mere. Dated lake sediments indicate there has been an increase in sedimentation rate and the
relative amount of minerogenic material delivered to the Mere over the last 200 years. In contrast to a previous study at
the same site, there is no evidence to attribute this increase to an overspill from a nearby canal. Other catchment disturbances
include landscaping in parkland surrounding the Mere in the early nineteenth century and drainage systems installed to improve
catchment agriculture over the last ca. 150 years. Both activities may explain the change in sedimentation rates and types,
independent of the hypothesized canal origin. Although our results exclude the canal as a major sediment source, identifying
the contribution of other potential catchment sources remains problematic. 137Cs inventories for the lake are similar to those recorded at a local reference site, suggesting little influx of 137Cs-bearing topsoil, yet 137Cs activities remain high in the upper 20–30 cm of the lake sediment profile, indicating a topsoil origin. Combined radionuclide
and mineral magnetic signatures proved to be relatively poor discriminators of potential sources, and the high atmospheric
pollution load from the West Midland conurbation has probably altered recent lake sediment signatures. Although further research
is required to identify the origins of recent (last ca. 200 years) minerogenic sediment inputs to the Mere, we suggest that
the combined lake: catchment approach offers a more rigorous method for understanding the impact of catchment disturbance
than analysis of the paleolimnological record alone. 相似文献
117.
The solution of second order elliptic partial differential equations typically arising for flow problems, e.g., in porous media, is frequently expressed as face fluxes of a flow field at hexahedral cells. In this letter, we show by example that the following properties are incompatible: (1) A local velocity reconstruction, (2) reproduction of uniform flow for general hexahedral cells, and (3) a flow field in H(div). This is in particular relevant to mixed finite element methods approximating H(div), and to other methods trying to reconstruct a flow field in a hexahedron using only local face fluxes, e.g., streamline tracing methods for reservoir simulation. 相似文献
118.
119.
Geocentre motion from the DORIS space system and laser data to the Lageos satellites: comparison with surface loading data 总被引:3,自引:0,他引:3
F. Bouillé A. Cazenave J. M. Lemoine J. F. Crétaux 《Geophysical Journal International》2000,143(1):71-82
Surface mass redistribution within the Earth system, especially in the atmosphere, oceans, continents and ice sheets, causes the position of the centre of mass to vary in a reference frame attached to the solid Earth. Space techniques are now precise enough to measure the centre of mass motion. Here we present a determination of the centre of mass coordinates at regular monthly intervals using DORIS data on SPOT‐2, SPOT‐3 and Topex–Poseidon (1993–1997) and laser data on Lageos‐1 and Lageos‐2 (1993–1996). The amplitude and phase of the space‐geodesy‐derived annual cycle for each coordinate are further compared to estimates based on surface mass redistribution at the Earth surface derived from various climatic data sources: surface pressure, soil moisture, snow depth and ocean mass variations. 相似文献
120.
An anomalous high-velocity layer at shallow crustal depths in the Narmada zone, India 总被引:2,自引:0,他引:2
The Narmada zone in central India is a zone of weakness that separates the region of Vindhyan (Meso-Neoproterozoic) deposition to the north from Gondwana (Permo-Carboniferous–lower Cretaceous) deposits to the south. The reinterpretation of analogue seismic refraction data, acquired during the early 1980s, using 2-D ray-tracing techniques reveals a basement (velocity 5.8–6.0 km s−1 ) topography suggesting that the Narmada zone, bounded by the Narmada North and Narmada South faults is a region of basement uplift. A layer of anomalously high velocity (6.5–6.7 km s−1 ) at depths between 1.5 and 9.0 km appears to be present in the entire region. Within the Narmada zone this layer occurs at shallower depths than outside the Narmada zone. At two places within the Narmada zone this layer is at a depth of about 1.5 km. This layer cannot be considered as the top of the lower crust because in this case it should have produced large positive gravity anomalies at the shallowest parts. Instead, these parts correspond to Bouguer gravity lows. Furthermore, lower crust at such shallow depths has not been reported from any other part of the Indian shield. Therefore, this layer is likely to represent the top of a high-velocity mafic body that has different thicknesses in different places. 相似文献