On internal wave dynamics in the northern basin of the lake of Lugano

Abstract

Data collected from the Lake of Lugano during 3 July to 17 August 1979 are analysed for internal gravity wave motions. We demonstrate that a two-layer linear model is capable of explaining the internal wave response. A numerical finite difference procedure is used to determine the seiche periods and eigenfunctions of this model. The computed results (periods and phase differences between station pair interfacial displacements are then compared with the measured data. This comparison demonstrates that four conspicuous internal mode periods can be identified with fair to excellent statistical coherence between data-set pairs and that even higher order modes can be detected but with less statistical confidence. This identification proves that for the Lake of Lugano, no recourse has to be made to multi-layer models that would account for higher order baroclinicity.     

Kinematics and dynamics of the Mesozoic orogeny and late-orogenic extensional collapse in the Sino-Mongolian border areas

Extensional tectonic models with the major features of metamorphic core complexes were established in the Cordilleran region of western North America dur- ing the late 1970s to early 1980s of last century[1—4].Since there were previous thrust events, some re- searchers attributed the extension to crust-thickening of Mesozoic orogen[5—8], i.e. the crust thickening dur- ing orogeny led to the fact that the materials at depthswere heated and partially melted, and the heated and low-density mat…     

鄂尔多斯东缘地震重定位及拉张盆地过渡区的地震分布特征

利用双差地震定位方法对鄂尔多斯东缘地区（34°N—41°N,110°E—115°E）2008年1月—2012年12月的中小地震进行了重新定位.重定位后,定位精度得到改善,震中分布更加集中.鄂尔多斯东缘拉张盆地内部震源深度较浅,大多小于13 km,向盆地两端震源深度有加深的趋势,特别是太原盆地北端,临汾盆地北端,以及运城与临汾盆地之间的峨眉台地,震源深度可达20~25 km左右.我们认为盆地内部地壳减薄,上地幔上隆,热作用导致地壳内部脆性层减薄,致使最大震源深度变浅;盆地之间的横向隆起区受区域应力场挤压剪切作用以及盆地内部上地幔上拱产生的水平向挤压力作用等,在横向隆起区与盆地接触带易产生应力集中,导致地震的发生,由于受脆性层厚度变化等的影响,在盆地向横向隆起区过渡部位出现震源深度加深的现象.鄂尔多斯东北缘地区地震分布弥散、震源深度相对较浅,可能与源自地幔的大范围深部热作用以及地壳脆性层厚度减薄有关.根据地震的空间分布特征,对部分盆地内部的断层特征进行了讨论.     

System dynamics modeling of transboundary systems: the bear river basin model

System dynamics is a computer-aided approach to evaluating the interrelationships of different components and activities within complex systems. Recently, system dynamics models have been developed in areas such as policy design, biological and medical modeling, energy and the environmental analysis, and in various other areas in the natural and social sciences. The Idaho National Engineering and Environmental Laboratory, a multipurpose national laboratory managed by the Department of Energy, has developed a system dynamics model in order to evaluate its utility for modeling large complex hydrological systems. We modeled the Bear River basin, a transboundary basin that includes portions of Idaho, Utah, and Wyoming. We found that system dynamics modeling is very useful for integrating surface water and ground water data and for simulating the interactions between these sources within a given basin. In addition, we also found that system dynamics modeling is useful for integrating complex hydrologic data with other information (e.g., policy, regulatory, and management criteria) to produce a decision support system. Such decision support systems can allow managers and stakeholders to better visualize the key hydrologic elements and management constraints in the basin, which enables them to better understand the system via the simulation of multiple "what-if" scenarios. Although system dynamics models can be developed to conduct traditional hydraulic/hydrologic surface water or ground water modeling, we believe that their strength lies in their ability to quickly evaluate trends and cause-effect relationships in large-scale hydrological systems, for integrating disparate data, for incorporating output from traditional hydraulic/hydrologic models, and for integration of interdisciplinary data, information, and criteria to support better management decisions.     

准噶尔盆地古生代末大地构造动力学数值模拟

大地构造动力学数值模拟是构造物理研究的重要方向.本文利用有限元数值模拟方法研究准噶尔盆地古生代末的构造应力场.根据准噶尔盆地西部岩墙群和准噶尔盆地内部及周边地区应力标志,确定了晚二叠世准噶尔地区最大主应力方向为NW-SE向,方位在295°左右,局部地区略有偏转.以实测古构造应力场为拟合标志,对S,engr和Allen提出的关于本地区演化的两种大地构造模式进行了构造应力场反演,从而为确定本地区晚二叠世比较合理的大地构造动力学机制提供限制.通过模拟对比发现,晚二叠世末准噶尔盆地可能处于张扭与压扭复合作用的大地构造动力学机制之下,即:盆地南北两侧的北天山断裂与额尔齐斯断裂为张扭性左行走滑断裂,而东西两侧的博格达山前断裂和达拉布特断裂是一对压扭性的右行走滑断裂系统,这两条断裂在晚二叠世准噶尔盆地古构造应力场的形成过程中起到了重要的作用.     

On shear-wave splitting in the Los Angeles basin

Three-component seismograms at the three USC stations, PVP, GFP and DHB, have been examined. Most earthquakes, with magnitudes ranging from 1.4 to 5.0, within a period from 1985 to 1988, show evidence of shear-wave splitting. The preferred polarization of the first split-shear wave arrivals at PVP is nearly in N-S which is consistent with both regional maximum horizontal compressive stress direction and local subsurface fault strike, showing that shear-wave splitting is caused by liquid-filled cracks or fractures associated with the N-S faulting. The polarizations of first shear wave arrivals at GFP are roughly divided into two almost perpendicular directions, ENE-WSW and NNW-SSE, which are parallel or perpendicular to the strike of the geology or topography near the station. Because GFP is near the foothills of Santa Monica Mountains, the shear-wave arrivals may be disturbed by topographic irregularities and by subsurface dipping interfaces. Two examples at DHB clearly display shear-wave splitting. Their polarizations of shear wave are in the direction of N-S, which agree with the fragmentary surface and fracturing direction there. From some relatively reliable delay times, the crack densities at three stations are given, that is, 0.025 at PVP, 0.020 at GFP and 0.045 at DGB. No systematic change of shear-wave polarization is discovered in this study.     

Suspended sediment dynamics in a large drainage basin: the River Rhine

The behaviour of suspended sediment in rivers is often a function of energy conditions, i.e. sediment is stored at low flow and transported under high discharge conditions. The timing of maximum sediment transport can, however, also be related to mixing and routing of water and sediment from different sources. In this study suspended sediment transport was studied in the River Rhine between Kaub and the German–Dutch border. As concentrations decrease over a runoff season and as the relationship between water discharge and suspended sediment concentrations during most floods is characterized by clockwise hysteresis, it is concluded that sediment depletion occurs during a hydrological year and during individual floods. However, analyses of the sediment contribution from the River Mosel indicate that clockwise hysteresis may result from sediment depletion as well as from early sediment supply from a tributary. Thus, although the suspended sediment behaviour in the downstream part of the River Rhine is partly a transport phenomenon related to energy conditions, mixing and routing of water from different sources also plays an important role. Suspended sediment transport during floods was modelled using a ‘supply‐based’ model. Addition of a sediment supply term to the sediment rating curve leads to a model that produces better estimates of instantaneous suspended sediment concentrations during high discharge events. A major constriction of the model is that it cannot be used to predict suspended sediment concentrations as long as the amount of sediment in storage and the timing of sediment supply are unknown. Copyright © 1999 John Wiley & Sons, Ltd.     

Incorporating the spatio-temporal distribution of rainfall and basin geomorphology into nonlinear analyses of streamflow dynamics

Many recent studies have been devoted to the investigation of the nonlinear dynamics of rainfall or streamflow series based on methods of dynamical systems theory. Although finding evidence for the existence of a low-dimensional deterministic component in rainfall or streamflow is of much interest, not much attention has been given to the nonlinear dependencies of the two and especially on how the spatio-temporal distribution of rainfall affects the nonlinear dynamics of streamflow at flood time scales. In this paper, a methodology is presented which simultaneously considers streamflow series, spatio-temporal structure of precipitation and catchment geomorphology into a nonlinear analysis of streamflow dynamics. The proposed framework is based on “hydrologically-relevant” rainfall-runoff phase-space reconstruction acknowledging the fact that rainfall-runoff is a stochastic spatially extended system rather than a deterministic multivariate one. The methodology is applied to two basins in Central North America using 6-hour streamflow data and radar images for a period of 5 years. The proposed methodology is used to: (a) quantify the nonlinear dependencies between streamflow dynamics and the spatio-temporal dynamics of precipitation; (b) study how streamflow predictability is affected by the trade-offs between the level of detail necessary to explain the spatial variability of rainfall and the reduction of complexity due to the smoothing effect of the basin; and (c) explore the possibility of incorporating process-specific information (in terms of catchment geomorphology and an a priori chosen uncertainty model) into nonlinear prediction. Preliminary results are encouraging and indicate the potential of using the proposed methodology to understand via nonlinear analysis of observations (i.e., not based on a particular rainfall-runoff model) streamflow predictability and limits to prediction as a function of the complexity of spatio-temporal forcing relative to basin geomorphology.     

Caldera subsidence in extensional tectonics

A 45-km-long regional dike was emplaced over a period of 2 weeks in August 2014 at the boundary between the East and North Volcanic Zones in Iceland. This is the first regional dike emplacement in Iceland monitored with modern geophysical networks, the importance of which relates to regional dikes feeding most of the large fissure (e.g., Eldgja 934 and Laki 1783) and lava shield (e.g. early Holocene Skjaldbreidur and Trölladyngja) eruptions. During this time, the dike generated some 17,000 earthquakes, more than produced in Iceland as a whole over a normal year. The dike initiated close to the Bardarbunga Volcano but gradually extended to the northeast until it crossed the boundary between the East Volcanic Zone (EVZ) and the North Volcanic Zone (NVZ). We infer that the strike of the dike changes abruptly at a point, from about N45°E (coinciding with the trend of the EVZ) to N15°E (coinciding with the trend of the NVZ). This change in strike occurs at latitude 64.7°, exactly the same latitude at which about 10 Ma dikes in East Iceland change strike in a similar way. This suggests that the change in the regional stress field from the southern to the northern part of Iceland has been maintained at this latitude for 10 million years. Analytical and numerical models indicate that the dike-induced stress field results in stress concentration around faults and particularly shallow magma chambers and calderas in its vicinity, such as Tungnafellsjökull, Kverkfjöll, and Askja. In particular, the dike has induced high compressive, shear, and tensile stresses at the location of the Bardarbunga shallow chamber and (caldera) ring-fault where numerous earthquakes occurred during the dike emplacement, many of which have exceeded M5 (the largest M5.7). The first segment of the dike induced high tensile stresses in the nearby part of the Bardarbunga magma chamber/ring-fault resulting in radially outward injection of a dike from the chamber at a high angle to the strike of the regional dike. The location of maximum stress at Bardarbunga fluctuates along the chamber/ring-fault boundary in harmony with dike size and/or pressure changes and encourages ring-dike formation and associated magma flow within the chamber. Caldera collapse and/or eruption in some of these volcanoes is possible, most likely in Bardarbunga, but depends largely on the future development of the regional dike.     

On the prediction of the Toce alpine basin floods with distributed hydrologic models

With the objective of improving flood predictions, in recent years sophisticated continuous hydrologic models that include complex land‐surface sub‐models have been developed. This has produced a significant increase in parameterization; consequently, applications of distributed models to ungauged basins lacking specific data from field campaigns may become redundant. The objective of this paper is to produce a parsimonious and robust distributed hydrologic model for flood predictions in Italian alpine basins. Application is made to the Toce basin (area 1534 km²). The Toce basin was a case study of the RAPHAEL European Union research project, during which a comprehensive set of hydrologic, meteorological and physiographic data were collected, including the hydrologic analysis of the 1996–1997 period. Two major floods occurred during this period. We compare the FEST04 event model (which computes rainfall abstraction and antecedent soil moisture conditions through the simple Soil Conservation Service curve number method) and two continuous hydrologic models, SDM and TDM (which differ in soil water balance scheme, and base flow and runoff generation computations). The simple FEST04 event model demonstrated good performance in the prediction of the 1997 flood, but shows limits in the prediction of the long and moderate 1996 flood. More robust predictions are obtained with the parsimonious SDM continuous hydrologic model, which uses a simple one‐layer soil water balance model and an infiltration excess mechanism for runoff generation, and demonstrates good performance in both long‐term runoff modelling and flood predictions. Instead, the use of a more sophisticated continuous hydrologic model, the TDM, that simulates soil moisture dynamics in two layers of soil, and computes runoff and base flow using some TOPMODEL concepts, does not seem to be advantageous for this alpine basin. Copyright © 2006 John Wiley & Sons, Ltd.     

Cenozoic extensional stress evolution in North China

Since the beginning of the Cenozoic, north China has been fragmented by intensive intracontinental rifting and extensional tectonics, which resulted in the formation of two extensional domains: the graben systems around the Ordos block in the west and North China Plain in the east. How to link this Cenozoic extensional tectonics to plate kinematics has long been an issue of debate. This paper presents updated results of fault slip data sets collected in different zones in north China and addresses the changes in the direction of extensional stresses over the Cenozoic. A chronology of three successive extensions has been established and provides evidence for constraining the timing and location of either subduction-induced back-arc tectonics along the western Pacific or collision-related extrusion tectonics in Tibet. The oldest NW–SE trending extension occurred concomitantly with the early Tertiary rifting phase, which was initiated in a back-arc setting associated with westward subduction of the Pacific plate under the Asia continent. North China had been subjected, during the Miocene, to regional subsidence with widespread basalt flow, and the direction of extension changed to NE–SW to NNE–SSW, consistent with the spreading direction of the Japan Sea. The dynamic origin of this extension is poorly understood. Since the latest Miocene or earliest Pliocene, north China has been dominated by NW–SE extension resulting in the formation and development of the elongate graben systems around the rigid Ordos block. This extensional phase is accompanied by counterclockwise rotation of blocks such as Ordos, Taihangshan Massif etc., which are bounded to south by the left-lateral strike-slip Qinling fault system. The overall Pliocene-Quaternary deformation in north China accommodates an ESE-ward extrusion of the south China block relative to the Gobi-Mongolia plateau, as the consequence of late-stage India–Eurasia convergence.     

On the evaluation of snow water equivalent estimates over the terrestrial Arctic drainage basin

Comparisons between snow water equivalent (SWE) and river discharge estimates are important in evaluating the SWE fields and to our understanding of linkages in the freshwater cycle. In this study, we compared SWE drawn from land surface models and remote sensing observations with measured river discharge (Q) across 179 Arctic river basins. Over the period 1988‐2000, basin‐averaged SWE prior to snowmelt explains a relatively small (yet statistically significant) fraction of interannual variability in spring (April–June) Q, as assessed using the coefficient of determination (R²). Averaged across all basins, mean R²s vary from 0·20 to 0·28, with the best agreement noted for SWE drawn from a simulation with the Pan‐Arctic Water Balance Model (PWBM) forced with data from the European Centre for Medium‐Range Weather‐Forecasts (ECMWF) Re‐analysis (ERA‐40). Variability and magnitude in SWE derived from Special Sensor Microwave Imager (SSM/I) data are considerably lower than the variability and magnitude in SWE drawn from the land surface models, and generally poor agreement is noted between SSM/I SWE and spring Q. We find that the SWE versus Q comparisons are no better when alternate temporal integrations–using an estimate of the timing in basin thaw–are used to define pre‐melt SWE and spring Q. Thus, a majority of the variability in spring discharge must arise from factors other than basin snowpack water storage. This study demonstrates how SWE estimated from remote sensing observations, or general circulation models (GCMs), can be evaluated effectively using monthly discharge data or SWE from a hydrological model. Copyright © 2007 John Wiley & Sons, Ltd.     

Effects of terrain attributes on snow-cover dynamics in parts of Chenab basin,western Himalayas

ABSTRACT

Terrain variables are the main factors affecting the spatial distribution of snow cover. This paper aims to find a relationship between snow-cover area (SCA) and topographic variables (elevation, slope and aspect), using MODIS Terra data (MOD09A1) in parts of the Chenab basin, western Himalayas. The inter-annual variability of SCA% for each month has been analysed for the years 2000 to 2011. The analysis reveals that mean annual SCA value was maximum (37.89%) in 2005 and minimum (32.07%) in 2001. The slope classes with maximum and minimum SCA% are 5°–10° and 30°–35°, respectively. Among the 16 aspect classes, the ESE-facing slope evinces maximum SCA%. During the snow accumulation period, the expanse at 3600–4300 m elevation, and in the depletion period, 4300–5000 m elevation are found to have maximum rate of change in SCA% per 100 m rise in elevation, i.e. 3.37% and 3.67%, respectively.

EDITOR Z.W. Kundzewicz; ASSOCIATE EDITOR not assigned     

On the recent dynamics of the earth's surface of the Little Carpathians

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Intramontane basin development related to contractional and extensional structure interaction at the termination of a major sinistral fault: The Huércal-Overa Basin (Eastern Betic Cordillera)

Among the classical minor structural associations on the termination of transcurrent faults are horsetail splays formed by reverse, normal or strike-slip faults developing duplexes. However, temporal and spatial coexistence of contractional and extensional structures is very rarely documented. We discuss the relationships of contractional and extensional structures and associated sedimentary depocenters at the termination of a major strike-slip fault in the Eastern Betic Cordillera. Field mapping, kinematic fault analysis, paleostress determination and gravity prospecting in the Huércal-Overa Basin, at the southern termination of the NE–SW Alhama de Murcia transcurrent fault (AMF), are used to establish the relationships of tectonic structures and associated sedimentary depocenters. Here, ENE–WSW and WNW–ESE folds interact with two sets of normal faults having the same orientation as well as ENE–WSW reverse faults. Progressive unconformities associated with folds reveal that the beginning of the AMF activity occurred in the Tortonian. The folds progressively grew and rotated from ENE–WSW up to WNW–ESE close to the transcurrent fault. We propose that the development of the normal faults developed during short-term episodes characterized by vertical major stress axis and are, in turn, related to gravitational instability linked to the thickening of a crust relatively hot at depth. This setting may have become predominant in between the main activity, compressive pulses along transcurrent faults.     

On the accuracy of mode superposition analysis in structural dynamics

It is pointed out that the number of modes which should be included in a mode superposition dynamic response analysis depends on both the frequency content and the distribution of the loading. If the loading frequency is low the effect of the higher modes can be approximated by a static analysis. A technique is described for calculating this static contribution from the higher modes; the total response is then represented by the sum of the lower mode dynamic response and the higher mode static effects. The effectiveness of the procedure is demonstrated by a numerical example.     

Soil moisture dynamics across landscape types in an arid inland river basin of Northwest China

A combination of field measurements, continuous monitoring and numerical modelling was used to evaluate soil moisture regimes at four sites across a landscape gradient of the Heihe River Basin. Recorded data of precipitation, irrigation and floods were used to build the model, and an optimization technique was employed to calibrate the parameters. Based on the optimized parameters and estimates of future scenarios, the modelling structure was employed to predict the changes in the growing season soil moisture regimes due to climate change and intensive management. The results suggest that the upper‐reach Yeniugou and Xishui sites will become wetter because of alterations in the precipitation regime, and this trend could be strengthened by the expected amplified interannual variability. Precipitation features at middle‐reach Linze and lower‐reach Ejina, however, are not expected to change in the future. We assumed that a more water‐saving irrigation system will replace the current traditional one, and hence, the soil moisture probability density function at the Linze site would tend to be narrowed to ranges around either the wilting point or the point of incipient water stress, depending on how the intervention point and target level are settled. Ejina is expected to experience the most extreme ecological conversion effects in the future, and soil moisture would be more frequently recharged by water delivery. However, the soil moisture regime would not change much because of the poor water‐holding capacity and intensive evaporation. The revealed patterns and predicted shifts in soil moisture dynamics could provide a useful reference for identifying robust long‐term water resource management strategies for the Heihe River Basin. Copyright © 2015 John Wiley & Sons, Ltd.     

Physically based modeling of many-year dynamics of daily streamflow and snow water equivalent in the Lena R. basin

The applicability of a procedure, developed previously for evaluating runoff hydrographs of northern rivers, to the largest Russian river—the Lena—which flows under severe conditions of the Northeastern Siberia, is examined. The procedure is based on the land surface model SWAP in combination with input data derived from global databases of land surface parameters and meteorological forcing data derived from observations at meteorological stations located in the basins of the rivers or near them. Also studied was the ability of the model SWAP to reproduce the many-year dynamics of the values of snow water equivalent averaged over the Lena basin and their distribution over the basin area.     

Mesozoic doming extensional tectonics of Wugongshan, South China

Wugongshan in Jiangxi Province, China was a Mesozoic granitic dome-type extensional tectonics that is composed of metamorphic core complexes, ductile and brittle shear-deformed zones distributed around Mesozoic granites. Within it, the foliation defines an E-W elliptical shape and bears S-N stretching lineations. The axial part is located in Hongjiang-Wanlongshan area and occupied by oriented granites with coaxial symmetric shear fabrics. The southem and northern flanks, including rocks in the Anfu Basin to the south and the Pingxiang Basin to the north, display top-to-south and top-to-north motions, respectively. The ductile and brittle structures indicate a geometric and kinematic consistency. The extensional tectonics is developed on a Caledonian metamorphic basement and is unconformably covered by Late Cretaceous red beds. Isotopic ages on muscovite, biotite and whole rock by⁴⁰Ar-³⁹Ar, K-Ar and Rb-Sr suggest that the Wugongshan extensional doming began from the Triassic and ended in the Late Cretaceous. A geodynamic model is discussed. Project supported by the National Natural Science Foundation of China (Grant Nos. 49632080, 49572141)