Consequences of anthropogenic activity for two remote alpine lakes in NW Slovenia as tracked by sediment geochemistry

Several geological and geochemical parameters were determined in the sediments of the 5th (5 J) and 6th (6 J) Triglav Lakes, Julian Alps (NW Slovenia), in order to study the impact of natural catchment characteristics and anthropogenic activity. Fish were introduced into both lakes in 1991 and a mountain hut lies on the shore of 5 J. Sedimentary grain size (GS) was distinctly coarser in 5 J than 6 J, with arithmetic means ranging between 46 and 60 and 23–36 μm, respectively. In contrast, the mineralogical composition of the two sediments was similar. Calcite predominated strongly, comprising more than 77 % of total minerals, while dolomite and quartz were rare. Organic carbon (OC) and total nitrogen (TN) concentrations were highest in surficial sediments, with levels of 14.4 and 1.8 %, and 19.3 and 2.4 % observed in 5 J and 6 J, respectively. C/N ratios (atomic) were lowest in the same surface sediments, with the two lakes characterized by similar values (9.6 vs. 9.4, respectively), suggesting a predominance of autochthonous organic matter (OM) in both lakes. Contemporary δ¹³C values were lower in 5 J (?21.0 ‰) than 6 J (?18.5 ‰) sediments. Considerable changes in these four parameters were observed in recently deposited material, reflecting a shift in the trophic status of both lakes that was likely induced by the introduction of fish. In addition, the smaller and shallower 6 J seemed to respond to changes faster than the larger and deeper 5 J, indicating the higher sensitivity of the former. δ¹⁵N values in surface sediments of 5 J and 6 J were ?2.9 and ?4.4 ‰, respectively, with levels increasing gradually with depth to approximately +1.0 ‰ in deeper sediments. The observed changes could most likely be attributed to the atmospheric deposition of reactive nitrogen. The mountain hut has seemingly not had a significant enough impact on the lakes to be recorded in their sediments.     

Post‐earthquake bridge repair cost and repair time estimation methodology

While structural engineers have traditionally focused on individual components (bridges, for example) of transportation networks for design, retrofit, and analysis, it has become increasingly apparent that the economic costs to society after extreme earthquake events are caused at least as much from indirect costs as direct costs due to individual structures. This paper describes an improved methodology for developing probabilistic estimates of repair costs and repair times that can be used for evaluating the performance of new bridge design options and existing bridges in preparation for the next major earthquake. The proposed approach in this paper is an improvement on previous bridge loss modeling studies—it is based on the local linearization of the dependence between repair quantities and damage states so that the resulting model follows a linear relationship between damage states and repair points. The methodology uses the concept of performance groups (PGs) that account for damage and repair of individual bridge components and subassemblies. The method is validated using two simple examples that compare the proposed method to simulation and previous methods based on loss models using a power–law relationship between repair quantities and damage. In addition, an illustration of the method is provided for a complete study on the performance of a common five‐span overpass bridge structure in California. Intensity‐dependent repair cost ratios (RCRs) and repair times are calculated using the proposed approach, as well as plots that show the disaggregation of repair cost by repair quantity and by PG. This provides the decision maker with a higher fidelity of data when evaluating the contribution of different bridge components to the performance of the bridge system, where performance is evaluated in terms of repair costs and repair times rather than traditional engineering quantities such as displacements and stresses. Copyright © 2009 John Wiley & Sons, Ltd.     

Application of Gravity Gradients in the Process of GOCE Orbit Determination

The possibility of improving the Gravity Field and Steady-State Ocean Circulation Explorer (GOCE) mission satellite orbit using gravity gradient observations was investigated. The orbit improvement is performed by a dedicated software package, called the Orbital Computation System (OCS), which is based on the classical least squares method. The corrections to the initial satellite state vector components are estimated in an iterative process, using dynamic models describing gravitational perturbations. An important component implemented in the OCS package is the 8th order Cowell numerical integration procedure, which directly generates the satellite orbit. Taking into account the real and simulated GOCE gravity gradients, different variants of the solution of the orbit improvement process were obtained. The improved orbits were compared to the GOCE reference orbits (Precise Science Orbits for the GOCE satellite provided by the European Space Agency) using the root mean squares (RMS) of the differences between the satellite positions in these orbits. The comparison between the improved orbits and the reference orbits was performed with respect to the inertial reference frame (IRF) at J2000.0 epoch. The RMS values for the solutions based on the real gravity gradient measurements are at a level of hundreds of kilometers and more. This means that orbit improvement using the real gravity gradients is ineffective. However, all solutions using simulated gravity gradients have RMS values below the threshold determined by the RMS values for the computed orbits (without the improvement). The most promising results were achieved when short orbital arcs with lengths up to tens of minutes were improved. For these short arcs, the RMS values reach the level of centimeters, which is close to the accuracy of the Precise Science Orbit for the GOCE satellite. Additional research has provided requirements for efficient orbit improvement in terms of the accuracy and spectral content of the measured gravity gradients.     

Determination of the Croatian geomagnetic observatory location

Ground survey within the Nature Park Lonjsko Polje, placed in the middle-northern Croatia was performed during the time interval 2007–2010 in order to find the best location for installing the geomagnetic observatory. The total magnetic field has been measured a few times using the Overhauser proton magnetometers. The horizontal and vertical gradients of the total field, and its temporal behaviour were investigated over the restricted region that we estimated as suitable for the observatory. The results obtained from thoroughly conducted measurements allowed us to find definitive positions for the instrument pillars. These results are in agreement with previously suggested location found based on combination of Comprehensive CM4 model prediction and measurements conducted from 2003 to 2005. This study contributes to the development of geomagnetism in Croatia and paves a way to install the first geomagnetic observatory in Croatia.     

Dynamic response analysis of solitary flexible rocking bodies: modeling and behavior under pulse‐like ground excitation

Results obtained for rigid structures suggest that rocking can be used as seismic response modification strategy. However, actual structures are not rigid: structural elements where rocking is expected to occur are often slender and flexible. Modeling of the rocking motion and impact of flexible bodies is a challenging task. A non‐linear elastic viscously damped zero‐length spring rocking model, directly usable in conventional finite element software, is presented in this paper. The flexible rocking body is modeled using a conventional beam‐column element with distributed masses. This model is verified by comparing its pulse excitation response to the corresponding analytical solution and validated by overturning analysis of rocking blocks subjected to a recorded ground motion excitation. The rigid rocking block model provides a good approximation of the seismic response of solitary flexible columns designed to uplift when excited by pulse‐like ground motions. Guidance for development of rocking column models in ordinary finite element software is provided. Copyright © 2014 John Wiley & Sons, Ltd.     

Deficit and surplus of precipitation as a continuous function of time

The quantitative measure of drought is a complex problem. A common factor in all types of drought is that they originate from a deficiency of precipitation. The difference between the real and potentially expected daily precipitation amount is what we have used to define the continuous function of daily deficit and surplus of precipitation (DSP). We have also defined the monthly and yearly DSP. We tested the precipitation data series for the normal climatic period 1961–1990 observed at the Meteorological Observatory of Belgrade. The DSP considers that the intensity of drought during the current period is dependent upon the current precipitation plus the cumulative precipitation of the previous period. When applied to longer periods, this function denotes dry and wet periods.     

Absolute Sea Level Surface Modeling for the Mediterranean from Satellite Altimeter and Tide Gauge Measurements

Changes in the height of the ocean can be described through the relative and absolute sea level changes depending on the geodetic reference the sea level records are related to. Satellite altimetry provides absolute sea level (ASL) measurements related to the global geodetic reference, whereas tide gauges provide relative sea level (RSL) measurements related to the adjacent land. This study aims at computing the ASL surfaces for different time epochs from combined satellite altimeter and tide gauge records. A method of sea level data fusion is proposed to enable modeling of the impact of present and future sea level changes on the coast. Sea surface modeling was investigated for ten different gridding methods commonly used for the interpolation of altimeter data over the open ocean and extrapolation over the coastal zones. The performance of gridding methods was assessed based on the comparison of the gridded altimeter data and corrected tide gauge measurements. Finally, the sea level surfaces related to the GRS80 global reference ellipsoid were computed for the Mediterranean Sea over the altimeter period. In addition, the current sea level trends were estimated from both sea level measurements.     

Ophiolitic detritus in Cretaceous clastic formations of the Dinarides (NW Croatia): evidence from Cr-spinel chemistry

Cr-spinel is a common heavy mineral in the sandstones of Cretaceous synorogenic sedimentary formations of the NW Dinarides, Croatia. The rocks occur in isolated exposures in the uplifted basement units of Medvednica, Ivanščica, Žumberak and Samobor Mountains near Zagreb. In this area, evidence of the early Alpine evolution of the Dinarides is obscured due to strong dismemberment of pre-Tertiary tectonostratigraphic units resulting from an intense tectonic history, as well as due to the widespread sedimentary cover of the Pannonian Basin. Electron microprobe analyses of detrital Cr-spinels from the Oštrc Formation reveal that in the Early Cretaceous the ophiolitic source area was predominantly composed of harzburgite peridotites and associated cumulate rocks, which developed in a supra-subduction zone setting. The supply of Cr-spinels with the same chemical signature remained dominant until the end of the Cretaceous, suggesting that exposed remnants of the same ophiolite belt persisted through the Cretaceous and/or that recycling was significant. Similarities with data reported from the Northern Calcareous Alps and the Transdanubian Central Range imply that a rather extensive harzburgitic ophiolite belt probably extended along the Adriatic margin during the Early Cretaceous. A slight trend of increasing variation in the Cr# is observed from the Early to the latest Cretaceous, suggesting that the source areas became more heterogeneous with the ongoing Cretaceous tectonic evolution. Differences in Cr-spinel compositions in two contemporaneous latest Cretaceous formations are well in line with existing data on heavy mineral proportions, which together identify contrasting hinterland geology for these formations and strongly suggest the coeval existence of two separate basins. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.