1.  Brkić, M. (2019): Monitoring geomagnetic information in the territory of Croatia.

In orientation and navigation using compass, reliable map's marginal information of Earth's magnetic field declination and its annual variation, namely geomagnetic information (GI), is crucial. Monitoring geomagnetic information means observing declination and its annual variation and checking the reliability of the actual GI model. A typical way of monitoring GI across a national territory involves conducting periodic geomagnetic network surveys to assess and update the model. The objective of the paper was to investigate improving the GI model reliability when an earlier model's error was raised to standard accuracy, and repeat station network surveys were not yet completed. A series of processing steps in modelling were revised to preserve the original data reliability. The partial 2008.5, 2009.5 and 2010.5 declination solutions were directly reduced to epoch 2015.0, and then to 2016.0, using the IGRF-12 model. The next step was to use 2016 and 2017 quiet daily declination means to estimate corresponding annual variations at surrounding observatories and repeat stations. Normal declination annual variation models were then built for further reductions to epoch 2017.0, and 2018.0, and for forward extrapolations. The quiet days observatory data were analysed to estimate the effect of the input time series length and linear extrapolated time span on forward extrapolation error. Thus, the reliability decline of the initial GI model slowed down in the sequence of models presented. The final GI2018v2 model, valid for 2018.0-2019.0, proved reliable in comparison to the repeat station declination observations of 2018.

Keywords: declination, annual variation of declination, reduction, geomagnetic information model

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2.  Varga, M., M. Grgić, O. Bjelotomić Oršulić and T. Bašić: Influence of digital elevation model resolution on gravimetric terrain correction over a study-area of Croatia.

High-resolution digital elevation models (DEMs) have become available in the last decade. They are used in geodesy and geophysics as the main data for modeling of topographic mass effects included in gravimetric and gradiometric measurements. In modeling process, gravimeric terrain correction is the central quantity which accounts for the variations of topographic masses around measured stations. This study deals with one segment of terrain correction computation: the impact of the resolution of digital elevation models. Computations are performed on study area of Republic of Croatia. Newly created DEM/DBM for the study area is created from global digital surface model ASTER for continental area, and digital bathymetric model GEBCO for the sea area. DEMs with lower resolution were created by resampling of the created ASTER/GEBCO DEM/DBM in 1" resolution. Terrain correction map is computed and published for the first time for the Republic of Croatia. The differences between terrain correction solutions obtained by using lower resolution DEMs compared to the solution obtained by using DEM with 1" are indicating average influence of DEM resolution on terrain correction from 0.5.10^-5 to 3.10^-5 ms^-2, for DEMs with lower resolution than 5". The results also reveal that rugged and mountainous areas are particularly problematic in such computations.

Keywords: ASTER, digital elevation model, GEBCO, resolution, terrain correction

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3.  Tiryakioglu, I., Yigit, C. O., Ozkaymak, C., Baybura, T., Yilmaz, M., Ugur, M. A., Yalcin, M., Poyraz. F., Sözbilir, H. and Gulal, V. E.: Active surface deformations detected by precise levelling surveys in the Afyon-Akşehir Graben, Western Anatolia, Turkey.

In the actively deforming region of western Anatolia, crustal deformation is accommodated by destructive earthquakes and a variety of aseismic events. In this study, we investigated the 2016-2017 aseismic sequence located in the Bolvadin Fault, one of the segments of the Akşehir-Simav Fault System of western Anatolia by analysing surface deformation derived from detailed geological mapping. Our findings suggest that surface deformation in the Bolvadin Fault is accommodated by aseismic episodes. During the field studies in the Bolvadin area, progressive surface deformations, such as surface faults and earth fissures with a length of 800 meters to 3 kilometres and strike of N15°E to N70°E were mapped on a 1/5000 scale. Furthermore, a levelling network was established to calculate the vertical displacements and deformation rate along the surface deformations. Precision level measurements were undertaken in 2016 and 2017. On the routes to the NW of the Bolvadin settlement, a vertical deformation rate of 30 mm/yr was detected in the period of 2016-2017, and a large deformation rate of 40 mm/yr was detected in the same period.

Keywords:Akşehir-Simav Fault System, surface deformation, digital levelling, Bolvadin fault, Western Anatolia

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4.  Dogru, F. and Pamukçu, O.: Analysis of gravity disturbance for boundary structures in the Aegean Sea and Western Anatolia.

Western Anatolia has been shaped N-S-trending extensional tectonic regime and W-E trending horst, grabens and active faults due to the collision of Africa, Arabian and Eurasia plates. The borders of the Aegean Sea tectonic is limited between eastern of Greece, western of Anatolia and Hellenic subduction zone in the south of Crete. To evaluate these tectonic elements gravity disturbance data of the Aegean Sea and Western Anatolia was used in this study. It is thought that the gravity disturbance data reflects the tectonic elements and discontinuities way better than gravity anomaly due to the calculation from the difference between gravity and normal gravity at the same point so thus the tensors and invariants of the study area were calculated and the power spectrum method was applied to the gravity disturbance data. Various boundary analysis methods were applied to the gravity disturbance data to compare the discontinuities obtained from the tensors both theoretical and case study. These methods were tested initially on theoretical data. Within the scope of the theoretical study, a single model and three bodies model were taken into consideration. When the results are examined, it is observed that the T_zz tensor component gives very clear information about the location of the structure. Likewise, when the T_xx, T_yy components and invariant results are examined, the vertical and horizontal boundaries were successfully obtained. In addition, the mean depths of these structures were determined using the power spectrum method. In the case application stage, the gravity disturbance data obtained from the Earth Gravitational Model of the eastern of the Aegean Sea and western of Anatolia were evaluated. The tensor and invariants of this gravity disturbance data were first calculated. New possible discontinuities have been identified in the tensors and some of the obtained discontinuities were clarified in their previous discussions. Also, the mean depths of the possible structures were calculated by the power spectrum method at four profiles taken from gravity disturbance data. These depth values are consistent with the depth values of the structural discontinuities obtained from previous studies. Finally, the upward continuation was applied to T_yy, T_yz and T_zz tensors up to 20 km. The positive anomaly values in T_yz and T_zz components and negative anomaly values in T_yy component are consistent with the Western Anatolia Transfer Zone. The structural differences between the eastern and the western of Western Anatolia are noteworthy in the upward continued results of the tensors. In addition, the positive and negative anomalies are notable in areas where the big earthquakes occurred in the last 3 years in the T_yz invariants.

Keywords: gravity disturbance, the Aegean Sea, Western of Anatolia, tensor, invariant

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5.  Tripathy, D. P. and T. R. Dash: Measurement of respirable dust concentration and assessment of health risk due to metals around an opencast coal mine of Talcher, Odisha.

Atmospheric pollution due to particulate matter in opencast coal mining area is a very important environmental problem and is fetching the attention of researchers worldwide since few decades. The particulate matter not only affects human but also have tremendous effects on nearby flora and fauna by degrading the ecological environment in many ways. High mechanization in mining operations leads to add heavy load of dust to the surrounding area. The adverse effects of dust depends on the quantity as well as the characteristics of the dust and the exposure dose. Taking the importance of the dust pollution in mines, a coal mine area of Talcher coalfield, was selected, which is one of the oldest coalfields of India and a very limited work has been carried out in that area on the regards of assessment of health risk due to metals on the local population. Monitoring of respirable dust (PM₁₀ and PM_2.5) were performed at eight monitoring stations around a high mechanised opencast coal mine for three seasons i.e., post monsoon, winter, and summer in the year 2015 as per the standard criteria of Central Pollution Control Board (CPCB), India. The seasonal variation of dust concentration was found in the order of winter > summer > post monsoon. Ten trace metals were analysed from the dust samples. Statistical analysis such as univariate (correlation study) and multi-variate statistical analysis were carried out including principal component analysis (PCA) for source identification and respective contribution to particulate matter. Lastly, the health risk in terms of hazards quotient (HQ) and hazards index (HI) were calculated for both children and adults for the three exposure path ways (Inhalation, ingestion and dermal exposure). The carcinogenic effects due to the presence of trace metals in the PM₁₀ were evaluated for both children and adults in terms of excess cancer risk (ECR ). The combined carcinogenic effects of all the trace metals also calculated (ECR_Total ). The HQ values for Cr and Cd were found above the safe limit in that area for both children and adults. Likewise the ECR values for Cr and Cd also were at a very risk level for both the age group. However the risk related to other metals were found well within the safe limit. The HI and ECR_Total values were found above the safe limit which indicate the combine effect of trace metal on the children and adult were at a very high risk level in the study area.

Keywords: PM₁₀, PM_2.5, heavy metals, correlation analysis, PCA, health risk

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