Methodology for construction, calibration and validation of a national hydrological model for Denmark

An integrated groundwater/surface water hydrological model with a 1 km² grid has been constructed for Denmark covering 43,000 km². The model is composed of a relatively simple root zone component for estimating the net precipitation, a comprehensive three-dimensional groundwater component for estimating recharge to and hydraulic heads in different geological layers, and a river component for streamflow routing and calculating stream–aquifer interaction. The model was constructed on the basis of the MIKE SHE code and by utilising comprehensive national databases on geology, soil, topography, river systems, climate and hydrology. The present paper describes the modelling process for the 7330 km² island of Sjælland with emphasis on the problems experienced in combining the classical paradigms of groundwater modelling, such as inverse modelling of steady-state conditions, and catchment modelling, focussing on dynamic conditions and discharge simulation. Three model versions with different assumptions on input data and parameter values were required until the performance of the final, according to pre-defined accuracy criteria, model was evaluated as being satisfactory. The paper highlights the methodological issues related to establishment of performance criteria, parameterisation and assessment of parameter values from field data, calibration and validation test schemes. Most of the parameter values were assessed directly from field data, while about 10 ‘free’ parameters were subject to calibration using a combination of inverse steady-state groundwater modelling and manual trial-and-error dynamic groundwater/surface water modelling. Emphasising the importance of tests against independent data, the validation schemes included combinations of split-sample tests (another period) and proxy-basin tests (another area).     

Tensor time domain electromagnetic resistivity measurements at Ngatamariki geothermal field, New Zealand

Experimental measurements in the Ngatamariki geothermal field, North Island, New Zealand were made to test the applicability of the time domain electromagnetic method for detailed investigation of the resistivity structure within a geothermal field. Low-frequency square wave signals were transmitted through three grounded bipole current sources sited about 8 km from the measurement lines. Despite high levels of electrical noise, transient electric field vectors could be determined reliably for times between 0.02 and 3.3 s after each step in the source current. Instantaneous apparent resistivity tensors were then calculated. Apparent resistivity pseudosections along the two measurement lines show smooth variations of resistivity from site to site. Over most of the field the images consistently show a three-layer resistivity structure with a conductive middle layer (3–10 Ωm) representing the conductive upper part of the thermal reservoir. A deep-seated region of low resistivity in the northwest of the field may indicate a conductive structure at about 1 km associated with a deeper diorite intrusion. Measurements sited closer than about 100 m to drillholes appear to have been disturbed by metallic casing in the holes. A change in resistivity structure in the east of the field may indicate a major geological or hydrothermal boundary.     

Evaluation of predictors of non‐linear seismic demands using ‘fishbone’ models of SMRF buildings

Predictors (or estimates) of seismic structural demands that are less computationally time‐consuming than non‐linear dynamic analysis can be useful for structural performance assessment and for design. In this paper, we evaluate the bias and precision of predictors that make use of, at most, (i) elastic modal vibration properties of the given structure, (ii) the results of a non‐linear static pushover analysis of the structure, and (iii) elastic and inelastic single‐degree‐of‐freedom time‐history analyses for the specified ground motion record. The main predictor of interest is an extension of first‐mode elastic spectral acceleration that additionally takes into account both the second‐mode contribution to (elastic) structural response and the effects of inelasticity. This predictor is evaluated with respect to non‐linear dynamic analysis results for ‘fishbone’ models of steel moment‐resisting frame (SMRF) buildings. The relatively small number of degrees of freedom for each fishbone model allows us to consider several short‐to‐long period buildings and numerous near‐ and far‐field earthquake ground motions of interest in both Japan and the U.S. Before doing so, though, we verify that estimates of the bias and precision of the predictor obtained using fishbone models are effectively equivalent to those based on typical ‘full‐frame’ models of the same buildings. Copyright © 2003 John Wiley & Sons, Ltd.     

时间谱电阻率法中的剩余电磁效应研究

根据频谱激电（SIP）法或复电阻率（CR）法中研究剩余电磁（REM）效应的思想，通过分析时间谱电阻率（TSR）法中场的基本特征，在TSR法中建立了与SIP（或CR）法中参数Φmax/Φ0max相类似的参数－Emax/E0，用来描述了TSR法中的REM效应。通过对一维可极化大地模型的REM效应的理论计算，验证了用Emax/E0表示的REM异常可用来形象地反映地电断面电阻率的高低。     

基于Voronoi图的空间方向关系形式化描述模型

运用认知心理学信息加工的观点，建立了基于Voronoi图的空间方向关系形式化描述模型，并详细阐述了模型的逻辑结构、数据结构和空间方向的计算过程。为了验证模型的正确性，列举了该模型计算空间方向的几个例子，并总结了模型的优、缺点。     

Floodplain Residents' Preferences for Water Level Management Options in Flood Control Projects in Bangladesh

A maximum difference conjoint (MDC) model was part of a questionnaire toassess floodplain residents' preferences for the outcomes of water level managementinside an enclosed embankment system on the left bank of the Dhaleswari River, calledthe Compartmentalization Pilot Project (CPP)-Tangail. The outcomes were described as(a) varied flood depths in the rice field, (b) incidence of flooding on the courtyard andinside homes, (c) changes in floodplain and culture fisheries, and (d) varied conditionsof drainage congestion. Following a standard survey, the respondents from inside andoutside a completed section of the compartment (Cluster 1b) were shown profiles of these flood management outcomes and were asked to indicate for each profile the one most preferred and the one least preferred item. The results of the study indicated that the respondents had a clear preference for preventing flooding of their homes and courtyards and for an ideal water depth of 2 ft in the aman rice fields. At the same time, they also showed a strong concern about malfunctioning of sluices and to a lesser extent about the changes in the fish habitat. The successful application of the MDC as an approach to model tradeoffs among rural residents of Bangladesh shows that a relatively complex quantitative survey method, incorporating choice cards as pictograms, can be applied successfully even in a developing country.     

Smoothing and Change Point Detection for Gamma Ray Count Data

Gamma ray detectors are used to measure the natural radioactivity of rocks. For a number of boreholes drilled at a site the gamma ray detector is lowered into each borehole and counts of gamma ray emissions at different depths are recorded as the instrument is gradually raised to ground level. The profile of gamma counts can be informative about the geology at each location. The raw count data are highly variable, and in this paper we describe the use of adaptive smoothing techniques and change point models in order to identify changes in the geology based on the gamma logs. We formulate all our models for the data in the framework of the class of generalized linear models, and describe computational methods for Bayesian inference and model selection for generalized linear models that improve on existing techniques. Application is made to gamma ray data from the Castelreagh Waste Management Centre which served as a hazardous waste disposal facility for the Sydney region between March 1974 and August 1998. Understanding the geological structure of this site is important for further modelling the transport of pollutants beneath the waste disposal area.     

Predictive GIS-Based Model of Rockfall Activity in Mountain Cliffs

Rockfall susceptibility has been analysed in mountain cliffs of the Cantabrian Range, North Spain. The main aim of this analysis has been to build a predictive model of rockfall activity from a low number of environmental and geological variables. The rockfall activity has been quantified in a GIS. The cartographic information used shows the spatial distribution of all the recent talus screes as well as their associated source areas in the rock-slopes. The area relation At/Ar (recent talus scree polygon/source basins) in the rock slopes has been used as the rockfall activity indicator. This relation has been validated in 50 pilot rock-slopes and compared with the relation number of recent rock fragments/source basin, obtained from field work. The environmental factors causing rockfall depend on the rock slope situation, and these are: altitude and sun radiation on the rock cliff. The geological factors considered are: lithology, relative position of the main discontinuities with respect to the topographic surface and two morphologic parameters: the roughness and slope gradient. A logistic regression analysis has been applied to a population of 442 limestone and quartzite rock cliffs. The dependent variable is the rockfall activity indicator, which allows the definition of two classes of rock cliff units: low and high activity. The independent variables are altitude, sun radiation (equinox radiation, summer solstice radiation, winter solstice radiation), slope roughness, slope gradient,anisotropy and lithology. Results suggest that it is possible tobuild a valid cartographic predictive model for rockfall activity in mountain rock cliffs from a limited number of easily obtainable variables. The method is especially applicable in massive rock slopes or in regions with uniform rock mass characteristics.     

Hazard Zoning for Landslides Connected to Torrential Floods in the Jerte Valley (Spain) by using GIS Techniques

The Jerte Valley is anortheast-southwest tending graben located in the mountainous region of west central Spain (Spanish Central System). Mass movements have been a predominant shaping process on the Valley slopes during the Quaternary. Present day activity is characterized as either `first-time failure' (shallow debris slides and debris flows) or `reactivations' of pre-existing landslides deposits.A delineation of landslide hazard zoningwithin the Valley has been carried out by using the detailed documentation of a particular event (a debris slide and a sequel torrential flood, which occurred on the Jubaguerra stream gorge), and GIS techniques. The procedure has had four stages, which are: (1) the elaboration of a susceptibility map (spatial prediction) of landslides; (2) the elaboration of a map of `restricted susceptibility' in the particular case of slopes that are connected to streams and torrents (gorges); (3) the elaboration of a digital model which relates the altitude to the occurrence probability of those particular precipitation conditions which characterized the Jubaguerra event and (4) the combination of the probability model with the `restricted susceptibility map', to establish `critical zones' or areas which are more prone to the occurrence of phenomena that have same typology as this one.     

Geomechanical model for the post-Variscan evolution of the Permocarboniferous–Mesozoic basins in Northeast Germany

The Permocarboniferous basins in Northeast Germany formed on the heterogeneous and eroded parts of the Variscan orogene and its deformed northern foreland. Transtensional tectonic movements and thermal re-equilibration lead to medium-scale crustal fragmentation, fast subsidence rates and regional emplacement of large amounts of mostly acidic volcanics. The later basin formation and differentiation was triggered by reversals of the large-scale stress field and reactivation of prominent zones of weakness like the Elbe Fault System and the Rhenohercynian/Saxothuringian boundary that separate different Variscan basement domains in the area. The geomechanical behaviour of the latter plays an important role for the geodynamic evolution of the medium to large-scale structural units, which we can observe today in three dimensions on structural maps, geophysical recordings and digital models. This study concentrates on an area that comprises the southern Northeast German Basin, the Saale Basin, the Flechtingen High, the Harz Mountains High and the Subhercynian Basin. The presented data include re-evaluations of special geological and structural maps, the most recent interpretation of the DEKORP BASIN 9601 seismic profile and observations of exposed rock sections in Northeast Germany. On the basis of different structural inventories and different basement properties, we distinguish two structural units to the south and one structural unit to the north of the Elbe Fault System. For each unit, we propose a geomechanical model of basin formation and basin inversion, and show that the Rhenohercynian Fold and Thrust Belt domain is deformed in a thin-skinned manner, while the Mid-German Crystalline Rise Domain, which is the western part of the Saxothuringian Zone, rather shows a thick-skinned deformation pattern. The geomechanical model for the unit north to the Elbe Fault System takes account to the fact that the base of the Zechstein beneath the present Northeast German basin shows hardly any evidence for brittle deformation, which indicates a relative stable basement. Our geomechanical model suggests that the Permocarboniferous deposits may have contributed to the structural stiffness by covering small to medium scale structures of the upper parts of the brittle basement. It is further suggested that the pre-Zechstein successions underneath the present Northeast German basin were possibly strengthening during the Cretaceous basin inversion, which resulted in stress transfer to the long-lived master faults, as indicated for example by the shape of the salt domes in the vicinity of the latter faults. Contrary to this, post-Zechstein successions deformed in a different and rather complex way that was strongly biased by intensive salt tectonic movements.