云南地区部分地震的环境应力场特征

利用所获取的云南地区强震加速度观测资料,选取了其中具有震源深度参数及三个方向记录都完整的84次地震,震级范围为3．0～7．6级,震中距为几公里至几十公里(个别为100多公里),根据陈培善用位错理论二维断裂力学模式推导的震源峰值加速度与环境应力场关系式,计算了云南地区部分地震的环境剪应力值,并探讨了云南部分地震的环境应力场特征。     

Distribution of surface imperviousness in small urban catchments predicts runoff peak flows and stream flashiness

Urban growth is a global phenomenon, and the associated impacts on hydrology from land development are expected to increase, especially in peri‐urban catchments. It is well understood that greater peak flows and higher stream flashiness are associated with increased surface imperviousness and storm location. However, the effect of the distribution of impervious areas on runoff peak flow response and stream flashiness of peri‐urban catchments has not been well studied. In this study, a new geometric index, Relative Nearness of Imperviousness to the Catchment Outlet (RNICO), is defined to correlate imperviousness distribution of peri‐urban catchments with runoff peak flows and stream flashiness. Study sites include 21 suburban catchments in New York representing a range of drainage area from 5 to 189 km² and average imperviousness from 10% to 48%. On the basis of RNICO, all development patterns are divided into 3 classes: upstream, centralized, and downstream. Results showed an obvious increase in runoff peak flows and decrease in time to peak when moving from upstream to centralized and downstream urbanization classes. This indicates that RNICO is an effective tool for classifying urban development patterns and for macroscale understanding of the hydrologic behavior of small peri‐urban catchments, despite the complexity of urban drainage systems. We also found that the impact of impervious distribution on runoff peak flows and stream flashiness decreases with catchment scale. For small catchments (A < 40 km²), RNICO was strongly correlated with the average (R² = .95) and maximum (R² = .91) gaged peak flows due to the relatively efficient subsurface routing through stormwater and sewer networks. Furthermore, the Richards–Baker stream flashiness index in small catchments was positively correlated with fractional impervious area (R² = .84) and RNICO (R² = .87). For large catchments (A > 40 km²), the impact of impervious surface distribution on peak flows and stream flashiness was negligible due to the complex drainage network and great variability in travel times. This study emphasizes the need for greater monitoring of discharge in small peri‐urban catchments to support flood prediction at the local scale.     

A dynamic prediction model for time-to-peak

A simplified empirical equation is developed for widespread prediction of dynamic catchment response time. This model allows for time-to-peak prediction to evolve from static, lumped models, thereby providing a single value for any storm within a given catchment, using a single set of input parameters, that can be applied to a dynamic model, thus accounting for the variability between storm sizes and catchment moisture conditions. These dynamic prediction methods are translated to North America for the first time. This allows the concepts and prediction methods for catchment response time prediction previously established for the United Kingdom (UK), to be translated to a simple empirical equation for use in North America, through the use of selected study areas in Canada and the United States. This reconfigured model is statistically successful in both the UK and North America and allows for a straightforward implementation of dynamic time-to-peak prediction. Further, the reconfigured model introduces the use of a runoff coefficient (R_c) to encompass historical catchment wetness, increasing the ease of incorporating antecedent moisture condition into predictions.     

A distributed TOPMODEL for modelling impacts of land‐cover change on river flow in upland peatland catchments

There is global concern about headwater management and associated impacts on river flow. In many wet temperate zones peatlands can be found covering headwater catchments. In the UK there is major concern about how environmental change, driven by human interventions, has altered the surface cover of headwater blanket peatlands. However, the impact of such land‐cover changes on river flow is poorly understood. In particular, there is poor understanding of the impacts of different spatial configurations of bare peat or well‐vegetated, restored peat on river flow peaks in upland catchments. In this paper, a physically based, distributed and continuous catchment hydrological model was developed to explore such impacts. The original TOPMODEL, with its process representation being suitable for blanket peat catchments, was utilized as a prototype acting as the basis for the new model. The equations were downscaled from the catchment level to the cell level. The runoff produced by each cell is divided into subsurface flow and saturation‐excess overland flow before an overland flow calculation takes place. A new overland flow module with a set of detailed stochastic algorithms representing overland flow routing and re‐infiltration mechanisms was created to simulate saturation‐excess overland flow movement. The new model was tested in the Trout Beck catchment of the North Pennines of England and found to work well in this catchment. The influence of land cover on surface roughness could be explicitly represented in the model and the model was found to be sensitive to land cover. Copyright © 2014 John Wiley & Sons, Ltd.     

A semi‐analytical approach for predicting peak discharge of floods caused by embankment dam failures

This study presents an analytical solution of dam‐break floods in a trapezoidal channel with detailed solution procedure. An approach predicting the peak discharge of floods caused by embankment dam failures was derived from the aforementioned analytical solution with a database of 27 historical dam failures. The prediction performance of this approach has been proved by comparing with other 14 straightforward equations for estimating the peak discharge. The proposed model with a small uncertainty of predicted peak flow rates has a high coefficient of determination and a small standard error, being ranked in the top four of the 15 methods considered in this paper. The robustness and predictive capability of the proposed model are further demonstrated in two case studies, and both were considered in the previous analyses performed by other investigators. This method provides a simple and transparent tool for engineers to predict the peak discharge and is easy to implement for trial and error calculation. Copyright © 2016 John Wiley & Sons, Ltd.     

True amplitude imaging by inverse generalized Radon transform based on Gaussian beam decomposition of the acoustic Green's function

True amplitude migration is one of the most important procedures of seismic data processing. As a rule it is based on the decomposition of the velocity model of the medium into a known macrovelocity component and its sharp local perturbations to be determined. Under this decomposition the wavefield can be considered as the superposition of an incident and reflected/scattered waves. The single scattering approximation introduces the linear integral operator that connects the sharp local perturbations of the macrovelocity model with the multishot/multioffset data formed from reflected/scattered waves. We develop the pseudoinverse of this operator using the Gaussian beam based decomposition of acoustic Green's functions. The computation of this pseudoinverse operator is done pointwise by shooting Gaussian beams from the target area towards the acquisition system. The numerical implementation of the pseudoinverse operator was applied to the synthetic data Sigsbee2A. The results obtained demonstrate the high quality of the true amplitude images computed both in the smooth part of the model and under the salt body.     

吉林伊通M4.3地震强震记录分析

2009年吉林伊通M4.3地震,辽宁省及吉林省强震动台网有8个强震台站记录到地面运动,记录的最大加速度为30.8 cm·s-2,初步展现了强震动台网建设的功效.     

张家界砂岩地貌形成时代:来自阶地与溶洞对比的证据

张家界以其独特罕见的石英砂岩峰林地貌闻名于世,一直是地貌学家、地质学家们关注的焦点,但关于其形成年代问题尚显薄弱,一直缺乏系统深入的研究.本文对索溪流域不同层状地貌进行了地貌学、沉积学和年代学综合研究.研究结果表明,索溪河谷普遍发育三级阶地,T;很少发育,主要表现为河流两侧化置较高的古宽谷或剥蚀面.岩溶洞穴黄龙洞从上往...     

基于TerraSAR-X强度图像相关法测量三峡树坪滑坡时空形变

三峡工程蓄水之后,有可能引起两岸滑坡的发生.本文以三峡库区树坪为研究区域,对不同时相的TerraSAR-X的强度图进行相关计算,求解出2009年2月至2009年10月期间发生的滑坡位移场时空演化.结果表明,在滑坡发生的前几个月,累积变形量很小;在滑坡发生的两三个月当中,变形量比较大,平均位移达到51cm;之后的几个月中,变形量又恢复到平静期的数值,与布设在该区的位移伸缩计结果一致.从本文的研究可以看出,该方法不仅能计算出滑坡引起的形变场,而且能探测地面形变的早期信号,可以用它作为三峡库区未来滑坡监测的重要技术手段.     

重力勘探中位场增强新方法

实测异常往往因受到外界环境的影响而导致其形态特征不明显,从而无法准确地得到异常体的位置、范围、走向等信息.针对该问题,人们提出了很多方法来使异常特征明显化,如阴影图、分析信号、斜导数法等,以上方法都能很好的完成这项操作.本文提出了高低帽变换和小波分析方法来进行异常形态特征增强,通过实测数据的处理结果可以看出,这两种方法...