Landslide susceptibility mapping using GIS-based multi-criteria decision analysis,support vector machines,and logistic regression

Identification of landslides and production of landslide susceptibility maps are crucial steps that can help planners, local administrations, and decision makers in disaster planning. Accuracy of the landslide susceptibility maps is important for reducing the losses of life and property. Models used for landslide susceptibility mapping require a combination of various factors describing features of the terrain and meteorological conditions. Many algorithms have been developed and applied in the literature to increase the accuracy of landslide susceptibility maps. In recent years, geographic information system-based multi-criteria decision analyses (MCDA) and support vector regression (SVR) have been successfully applied in the production of landslide susceptibility maps. In this study, the MCDA and SVR methods were employed to assess the shallow landslide susceptibility of Trabzon province (NE Turkey) using lithology, slope, land cover, aspect, topographic wetness index, drainage density, slope length, elevation, and distance to road as input data. Performances of the methods were compared with that of widely used logistic regression model using ROC and success rate curves. Results showed that the MCDA and SVR outperformed the conventional logistic regression method in the mapping of shallow landslides. Therefore, multi-criteria decision method and support vector regression were employed to determine potential landslide zones in the study area.     

Validation of the Meteosat Second Generation (MSG) fire monitoring product using ground observations over Turkey

Validation of the active fire monitoring (FIR) product from Spinning Enhanced Visible and Infrared Imager sensor of Meteosat Second Generation satellite is performed over Turkey. Ground truth data from the Ministry of Environment and Forestry for the years 2007, 2008, and 2009 is used by taking the active fire months of April–September into consideration. The contingency tables are obtained on a monthly basis and categorical statistics of probability of detection (POD) and false alarm rate (FAR) are derived. The results are introduced for each subclass, namely probable, possible, and combined cases. The highest POD amounts of 8.5, 1.93, and 9.4 % are obtained for the possible, probable, and combined cases, respectively, with the lowest FAR amounts of 70.9, 4.5, and 86.1 % for the same categories. FIR product validation with respect to predefined burnt area thresholds is introduced in the second part of the study in order to investigate burnt area effect in active fire detection. Increasing POD values with respect to burnt area amount is obtained with relatively higher values in probable than possible type. On the other hand, FAR variation is observed to be not correlated with the burnt area amount.     

Mapping of total nitrogen,available phosphorous and potassium in Amik Plain,Turkey

Soil nitrogen, phosphorous, and potassium concentrations accurately revealed spatial distribution maps and site-specific management-prone areas through inverse distance weighting (IDW) method in the Amik Plain, Turkey. Spatial mapping of soil nitrogen, phosphorous, and potassium is a very severe need to develop an economically and environmentally sound soil management plans. The objectives of this study were (a) to map spatial variability of total N, available P, and exchangeable-K content of Amik Plain’s soils and (b) to locate problematic areas requiring site specific management strategies for the nutrient elements. Spatial analyses of Kjeldhal-N, Olsen-P, and exchangeable-K concentrations of the soils were performed by the IDW method. Mean N content for surface soils (0–20 cm) was 1.38 g kg⁻¹, available P was 28.19 kg ha⁻¹ and exchangeable-K was 690 kg ha⁻¹ with the differences between maximum and minimum being 7.63 g N kg⁻¹, 242 kg P ha⁻¹, and 2,082 kg K ha⁻¹. For the surface soil, site-specific management-prone areas of Kjeldahl-N, Olsen-P, and exchangeable-K for “low and high + very high” classes were found to be 20.1–17.8%, 24.7–10.0%, and 4.1–39.6%, respectively. Consequently, lands with excessive nutrient elements require preventive-leaching practices, whereas nutrient-poor areas need fertilizer applications in favor of increasing plant production.     

Applications of hybrid genetic algorithms in seismic tomography

Almost all earth sciences inverse problems are nonlinear and involve a large number of unknown parameters, making the application of analytical inversion methods quite restrictive. In practice, most analytical methods are local in nature and rely on a linearized form of the problem equations, adopting an iterative procedure which typically employs partial derivatives in order to optimize the starting (initial) model by minimizing a misfit (penalty) function. Unfortunately, especially for highly non-linear cases, the final model strongly depends on the initial model, hence it is prone to solution-entrapment in local minima of the misfit function, while the derivative calculation is often computationally inefficient and creates instabilities when numerical approximations are used. An alternative is to employ global techniques which do not rely on partial derivatives, are independent of the misfit form and are computationally robust. Such methods employ pseudo-randomly generated models (sampling an appropriately selected section of the model space) which are assessed in terms of their data-fit. A typical example is the class of methods known as genetic algorithms (GA), which achieves the aforementioned approximation through model representation and manipulations, and has attracted the attention of the earth sciences community during the last decade, with several applications already presented for several geophysical problems.In this paper, we examine the efficiency of the combination of the typical regularized least-squares and genetic methods for a typical seismic tomography problem. The proposed approach combines a local (LOM) and a global (GOM) optimization method, in an attempt to overcome the limitations of each individual approach, such as local minima and slow convergence, respectively. The potential of both optimization methods is tested and compared, both independently and jointly, using the several test models and synthetic refraction travel-time date sets that employ the same experimental geometry, wavelength and geometrical characteristics of the model anomalies. Moreover, real data from a crosswell tomographic project for the subsurface mapping of an ancient wall foundation are used for testing the efficiency of the proposed algorithm. The results show that the combined use of both methods can exploit the benefits of each approach, leading to improved final models and producing realistic velocity models, without significantly increasing the required computation time.     

Ambient vibration based seismic evaluation of isolated Gülburnu highway bridge

This paper describes ambient vibration based seismic evaluation procedure of an isolated highway bridge. The procedure includes finite element modeling, ambient vibration testing, finite element model updating and time history analysis. Gülburnu Highway Bridge located on the Giresun–Espiye state highway is selected as a case study. Three dimensional finite element model of the bridge is created by SAP2000 software to determine the dynamic characteristics analytically. Since input force is not measured, Operational Modal Analysis is applied to identify dynamic characteristics. Enhanced Frequency Domain Decomposition and Stochastic Subspace Identification methods are used to obtain experimental dynamic characteristics. Analytical and experimental dynamic characteristic are compared with each other and finite element model of the bridge is updated by changing of material properties to reduce the differences between the results. Analytical model of the bridge after model updating is analyzed using 1992 Erzincan earthquake record to determine the seismic behavior. EW, NS and UP components of the ground motion are applied to the bridge at the longitudinal, transverse and vertical directions, respectively. It is demonstrated that the ambient vibration measurements are enough to identify the most significant modes of highway bridges. Maximum differences between the natural frequencies are reduced averagely from 9% to 2% by model updating. It is seen from the earthquake analyses that friction pendulum isolators are very effective in reducing the displacements and internal forces.     

Monitoring the tectonic plate movements in Turkey based on the national continuous GNSS network

In recent decades, the space geodesy has been applied to the areas such as transportation, infrastructure planning, navigation, etc. Among them, the precise positioning at the Global Navigation Satellite System (GNSS) stations yields better view in the understanding of the crustal deformation that requires global-scale measurements. There have been numerous studies examining the data process of continuous GNSS observations in the field of earth monitoring. More recently, GNSS stations established for continuously operating reference station networks have been beneficial resources in the tectonic plate-monitoring studies in lieu of campaign-type observations. However, this requires that the Continuously Operating Reference Station (CORS) should be established on stable structures acting like foundations and requires investigation of the long-term repeatability time series. This study aims to introduce recently established national CORS network, named CORS-TR, covering the entire Turkey and Northern Cyprus, and to explain the process of the long-term data obtained from the network on the characteristics of the tectonic plate movement within the area. The results of the CORS-TR data process present a great potential of using continuously operating reference stations not only in real-time kinematic applications of conventional geodesy studies but also in detecting and monitoring the crustal deformations of those that are crucial in earthquake-prone areas like Turkey. Since the findings are computed from the results of the all permanent stations of CORS-TR network, this study also examines the GNSS observation quality of the network for the given time interval. One of the major conclusions of the data process conducted in the study displays that the CORS-TR stations established on the carefully selected large and low-rise existing building had been more stable than the stations on the ground which have been subjected to soil settlement since the construction.     

Measurements and numerical simulations of the degree of activity and vegetation cover on parabolic dunes in north-eastern Brazil

In this work we present measurements of vegetation cover over parabolic dunes with different degrees of activation along the north-eastern Brazilian coast. We extend the local values of the vegetation cover density to the whole dune by correlating measurements with the relative brightness index C of high resolution QuickBird panchromatic satellite images of the dune field. We then introduce the vegetation data into a continuous model for vegetated dunes, coupling sand erosion and vegetation growth, and perform simulations of the evolution of the morphology and vegetation cover of parabolic dunes. Finally, from the comparison of both, the measurements and the simulation results, we show that the model is able to predict the dune shape and the vegetation distribution of real parabolic dunes as result of the evolution of a blow-out.     

Adiabatic expansion, early X-ray data and the central engine in GRBs

The Swift satellite early X-ray data show a very steep decay in most of the gamma-ray bursts light curves. This decay is either produced by the rapidly declining continuation of the central engine activity or by some leftover radiation starting right after the central engine shuts off. The latter scenario consists of the emission from an 'ember' that cools via adiabatic expansion and, if the jet angle is larger than the inverse of the source Lorentz factor, the large angle emission. In this work, we calculate the temporal and spectral properties of the emission from such a cooling ember, providing a new treatment for the microphysics of the adiabatic expansion. We use the adiabatic invariance of   p ²_⊥/ B ( p _⊥  is the component of the electrons' momentum normal to the magnetic field, B ) to calculate the electrons' Lorentz factor during the adiabatic expansion; the electron momentum becomes more and more aligned with the local magnetic field as the expansion develops. We compare the theoretical expectations of the adiabatic expansion (and the large angle emission) with the current observations of the early X-ray data and find that only ∼20 per cent of our sample of 107 bursts are potentially consistent with this model. This leads us to believe that, for most bursts, the central engine does not turn off completely during the steep decay of the X-ray light curve; therefore, this phase is produced by the continued rapidly declining activity of the central engine.     

Malibogazi groundwater dam: an alternative model for semi-arid regions of Turkey to store and save groundwater

In central Turkey, there are serious groundwater quality problems in the main river valleys and plains, and even in the lower parts of the secondary basins due to the underlying evaporitic geological formations. Groundwater quality improves towards the upstreams in the alluvium aquifers in most secondary valleys; however, groundwater potential decreases as well due to the reduced basin area, areal extent and thickness of the aquifers. The Malibogazi valley is situated to some 100 km north of Ankara. The dam constructed in the narrowest section of the valley has an average storage coefficient of 0.2 and the total and active storage capacities of 110,000 and 55,000 m³, respectively. The 20-m-thick aquifer extends for 6–7 km till the dam site within valley with an average width of 50–70 m. It mostly comprises sandy–gravely alluvial deposits. Malibogazi groundwater dam is a valve-controlled gravity flow dam. When the valves are opened, the water from the aquifer reservoir flows by gravity through supply pipe to the main irrigation channel, but when the valves are closed the water is stored in the aquifer and groundwater level begins to rise. Average groundwater discharge was about 20 l/s in 2005–2006 irrigation period. In this period, groundwater levels were about 2 m higher compared to the groundwater levels in the same seasons before the construction of the groundwater dam. Because the dam is of gravity flow type, it means an important contribution to the farmers since the operation cost is quite low. Malibogazi groundwater dam represents one of the first experiences of Turkey in the field of groundwater storage. Although the dam has small storage capacity, it may be a model for Turkey from the viewpoints of investigation, construction, dam wall, intake facility and measurements etc.     

Variance component estimation applied to satellite laser ranging

The variance component estimation (VCE) method as developed by Helmert has been applied to the global SLR data set for the year 1987. In the first part of this study the observations have been divided into two groups: those from ruby and YAG laser systems, and their weights estimated over several months. It was found that the weights of both sets of stations altered slightly from month to month, but that, not surprisingly, the YAG systems consistently outperformed those based on ruby lasers. The major part of this paper then considers the estimation of the variance components (i.e. weights) at each SLR station from month to month. These were tested using the F-statistic and, although it indicated that most stations had significant temporal variations, they were generally small compared with the differences between the stations themselves, i.e. the method has been shown to be capable of discriminating between the precision with which the various laser stations are operating. The station coordinates and baseline lengths computed using both a priori, and estimated, weights where also compared and this showed that changes in the weights can have significant effects on the estimation of the station positions, particularly in the z component, and on the baseline lengths - so proving the importance of proper stochastic modelling when processing SLR data.