基于Monte Carlo方法的由GPS观测计算地应变率的误差分析

在利用GPS观测计算地应变率中,应变率的误差分布在地球动力学研究中非常重要. 为解决这一问题,文中提出基于Monte Carlo技术,利用GPS观测的速度计算地应变率进行误差分析的方法;以青藏高原地区为例,利用带有误差的GPS观测数据进行了大量、独立的应变率重复计算,然后运用统计方法给出了应变率分量及其误差的分布. 结果显示青藏高原的喜马拉雅及中东部地区地应变率的东西向、南北向及剪应变率分量的误差相对较大,但整个青藏高原及附近地区应变率结果稳定可靠;研究结果进一步表明,由GPS观测计算应变率的误差主要决定于GPS观测速度的误差, 在变形小的区域（如中国东部地区）,目前GPS的观测精度还不能完全满足地应变率计算的要求.     

Transpiration and plant water relations of evergreen woody vegetation on a recently constructed artificial ecosystem under seasonally dry conditions in Western Australia

Understanding transpiration and plant physiological responses to environmental conditions is crucial for the design and management of vegetated engineered covers. Engineered covers rely on sustained transpiration to reduce the risk of deep drainage into potentially hazardous wastes, thereby minimizing contamination of water resources. This study quantified temporal trends of plant water potential (ψ_p), stomatal conductance (g_s), and transpiration in a 4‐year‐old evergreen woody vegetation growing on an artificial sandy substrate at a mine waste disposal facility. Transpiration averaged 0.7 mm day^?1 in winter, when rainfall was frequent, but declined to 0.2 mm day^?1 in the dry summer, when the plants were quite stressed. In winter, the mean ψ_p was ?0.6 MPa at predawn and ?1.5 MPa at midday, which were much higher than the corresponding summer values of ?2.0 MPa and ?4.8 MPa, respectively. The g_s was also higher in winter (72.1–95.0 mmol m^?2 s^?1) than in summer (<30 mmol m^?2 s^?1), and negatively correlated with ψ_p (p < 0.05, r² = 0.71–0.75), indicating strong stomatal control of transpiration in response to moisture stress. Total annual transpiration (147.2 mm) accounted for only 22% of the annual rainfall (673 mm), compared with 77% to 99% for woody vegetation in Western Australia. The low annual transpiration was attributed to the collective effects of a sparse and young vegetation, low moisture retention of the sandy substrate, and a superficial root system constrained by high subsoil pH. Amending the substrate with fine‐textured materials should improve water storage of the substrate and enhance canopy growth and deep rooting, while further reducing the risk of deep drainage during the early stages of vegetation establishment and in the long term. Overall, this study highlights the need to understand substrate properties, vegetation characteristics, and rainfall patterns when designing artificial ecosystems to achieve specific hydrological functions. Copyright © 2011 John Wiley & Sons, Ltd.     

A mixing-length model for predicting vertical velocity distribution in flows through emergent vegetation

Abstract

The vertical profiles of streamwise velocities are computed on flood plains vegetated with trees. The calculations were made based on a newly developed one-dimensional model, taking into account the relevant forces acting on the volumetric element surrounding the considered vegetation elements. A modified mixing length concept was used in the model. An important by-product of the model is the method for evaluating the friction velocities, and consequently bed shear stresses, in a vegetated channel. The model results were compared with the relevant experimental results obtained in a laboratory flume in which flood plains were covered by simulated vegetation.     

Induced gravity anomalies and seismic energy as a basis for prediction of mining tremors

The results of prediction of occurrence of mining tremors and bursts in the course of the exploitation of the remaining part of the hard coal in seam 510 of the mine Pstrowski, Upper Silesia, have been presented in the paper. The exploitation has taken place under extremely difficult conditions hazardous for the mining crew.To predict the occurrence of mining tremors, bursts and direction of migration of increased elastic strain in the rock mass, the microgravity method has been applied.The microgravity observations were carried out in the measurement points located at mutual distances equal 20 m in three profiles of the lengths 700 m, 760 m and 260 m respectively. The profiles were located in mining workings in the vicinity of the exploited part of the bed. In the course of exploitation, lasting 25 months, 29 series of measurements including 3600 individual microgravity observations were carried out. Microgravity observations were made with a Worden-Master gravimeter.The observed time changes of gravity microanomalies were essential for prediction. Local negative changes of gravity microanomalies signalled the approaching mining tremor. The tremor would cover an area of the radius 60 m to 100 m. The regional time changes of the gravity microanomalies appearing as linear trends of these anomalies signalled the development of the fields of elastic strain in the whole investigated area and the approaching violent release of elastic strain energy from the rock mass.The values of the amplitudes AMP of the above-mentioned trend were the measure of this hazard. In the course of the investigations each shock was preceded by considerably increased values of AMP.     

Shape analysis and multispectral classification in geological remote sensing

This paper discusses the usage of mathematical morphology in image processing of remotely-sensed data for geologic interpretation. Particular attention is given to noise-reducing transformations of spectral bands before and after different methods of classification, and to the usage of textural context. The development of a viable processing strategy requires a multidisciplinary approach and expert knowledge in different areas: (a) geology, geomorphology, and vegetation in a study area, (b) properties of the sensor for imagery photointerpretation, (c) spectral/spatial properties of the digital data within an integrated dataset (remote sensing and ancillary data), and (d) data-processing tools including mathematical morphology theory. Examples of geometric characterization of Canadian LANDSAT scenes are described in which shape measurements are obtained using a PC-based hybrid image-processing and geographic information system, termed ILWIS, which was developed at ITC, in the Netherlands. Classes from supervised and unsupervised classification are compared to guide in geological mapping. Classes over individual occurrences of broad vegetation-landform units are studied to aid in environmental mapping. Field knowledge is the context necessary to construct expert procedures to drive sequences of data-processing steps toward a target result such as optimal classification, enhancement, or feature extraction. The interaction between expert rules and the image-processing steps can be based on synthetic measurements of shape to quantize the information either spatially or spectrally. Many useful geometrical transformations of spatially-distributed data are extensions or generalizations of spatial analysis functions typical of geographic information systems.     

用数字测高仪漂移测量研究电离层声重波扰动

数字测高仪Digisonde中的漂移测量,常用来研究小尺度电离层扰动,如电离层小不均匀体的漂移。文中提出一种新的分析方法,利用漂移测量数据中多普勒频移和到达角参量的最大熵动态功率谱,估算声重波一类大尺度电离层扰动的水平传播速度和传播方向。作为实例,研究了Millstone Hill测高仪站的漂移观测资料,并对处理结果进行了初步分析。分析结果表明,从数字测高仪漂移测量数据中,可有效地提取声重波一类大尺度电离层扰动的传播参量,在电离层动力过程的研究中很有意义。     

Observations of geomagnetic pulsations and variations with a new borehole magnetometer down to depths of 3000 m

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A triaxial magnetometer has been developed for investigating the in situ skin effect of horizontal geomagnetic pulsations and variations in deep boreholes. The observations were carried out in the pilot borehole of the Continental Deep Drilling Program of Germany (KTB) down to depths of 3000 m and up to temperature of 90 C. A weak skin effect, due to the known very low conductivity of the penetrated crystalline rocks, of 90 to 95 per cent in amplitude and -5 to -10 rotation in phase has been observed at periods of 10 s and magnetometer depth of 2400 m.
An essential prerequisite for all calculations is the accurate determination of the orientation of the downhole magnetometer. It is demonstrated how oriented record samples of temporal variations at depth correlate precisely with those from the surface.
Results from surface magnetotelluric (MT) investigations show strong local distortions of the telluric field. The distortion of the MT tensor response has been determined by means of newly introduced skin-effect transfer functions, which are assumed to be undistorted.     

不等周期断层形变测量环境因子影响的研究

本文在研究和分析环境因子对断层测量年周变和季节性变化影响的基础上，归纳出断层形变测量年周变的变化规律，并针对不等周期观测资料，建立了形变测量的准线性动态数学模型，最后，对门源地震有异常的扁都口资料用上述模型进行了处理，结果是比较满意的。     

Fast-changing processes in a medium subject to loading as detected by resistivity measurements

Making measurements of electric resistivity at 16 s intervals, the authors noticed fast changes of this parameter prior to the occurrence of the main fracture. The changes are superposed on bay pulsations of increasing amplitude and decreasing period. This finding opens prospects for a wider use of an electric resistivity method and proves the high quality of automatic instruments, in particular their high resolution. It also gives evidence for the occurrence of short-period precursors in the fracture zone while the main fracture is being formed.