The porosity of saturated shallow sediments from seismic compressional and shear wave velocities

This study devises a new analytical relationship to determine the porosity of water-saturated soils at shallow depth using seismic compressional and shear wave velocities. Seismic refraction surveys together with soil sample collection were performed in selected areas containing water-saturated clay–silt, sand and gravely soils. Classification of clay–silt, sand and gravel dense soils provided the coefficient of experimental equation between the data sets, namely, Poisson's ratio, shear modulus and porosity values. This study presents a new analytical relationship between Poisson's ratio and shear modulus values, which are obtained from seismic velocities and porosity values of water-saturated material computed from water content and grain densities, which are determined by laboratory analysis of disturbed samples. The analytical relationship between data sets indicates that when the shear modulus of water-saturated loose soil increases, porosity decreases logarithmically. If shear modulus increases in dense or solid saturated soils, porosity decreases linearly.     

Producing forest fire susceptibility map via multi-criteria decision analysis and frequency ratio methods

Natural Hazards - Located in the Mediterranean basin, one of the world’s leading places in terms of forest fires, Turkey is one of the countries where forest fires are experienced very often...     

Comparison of GPS TEC with modelled values from IRI 2016 and IRI-PLAS over Istanbul,Turkey

The Total Electron Content (TEC) prediction performances of the empirical IRI model and IRI-PLAS model were investigated by comparing the GPS-based TEC values provided by the IONOLAB group. TEC values were obtained on equinox (March 21 and September 23) and solstice (June 21, and December 21) days in low (2009), medium (2012) and high (2015) solar activity periods at Istanbul, Turkey. The prediction performances of the models were statistically analyzed based on the differences between the GPS-TEC and the empirical models, considering the maximum and minimum deviations, the correlation analysis and the root mean square error (RMSE). As a result of the investigation, it is seen that the empirical models have similar predictive performances when the plasmaspheric effects are neglected, and the IRI-PLAS estimations are generally a little closer to the observed GPS-TEC values than all options of IRI-2016 model. Also, it can be said that “IRI2001”, one of the IRI-2016’s “topside” options, can make better predictions than other options and “IG” solar proxy option of IRI-PLAS model is a more appropriate option than the others in TEC calculations over Istanbul, Turkey.     

Upper crustal Poisson’s ratio and coda-wave attenuation beneath Eastern Anatolia

The attenuation of seismic waves reflects the elastic nature of the media within which the waves propagate. In this study, we calculate the Coda-Q(Q_c), frequency dependence(η), Vp/Vs and Poisson's(υ) ratios by using 2621 vertical component seismograms generated by 987 earthquakes recorded by 13 seismic stations in Eastern Anatolia, and creat a 2-D seismic tomographic Q_c model for the region. The obtained model provides significant information for exploring the boundaries of adjacent tectonic units within the upper crust and interpreting their dynamic characteristics. The 2-D Q_c model and the other parameters are consistent with the seismotectonic features of Eastern Anatolia. Highly heterogeneous Q_c values are observed in the study area dividing it into north-south directed bands of low and high attenuation. The highest η values were obtained beneath the northwestern and eastern parts of the study region. Clear, high and low υ values are obtained in the western and eastern parts of the study area, respectively. The spatial variations in the measured parameters are consistent with many geophysical observations including low Pn velocities, efficient Sn blockage, high heat flow, and widespread volcanism. Different upper crustal thicknesses and inhomogeneous stress distribution along the East and North Anatolian Fault Zones may also contribute to the observed heterogeneities.     

Temporal dynamics,meteorological effects,secondary organic aerosol estimation,and source identification of size-segregated carbonaceous aerosols

During the period 2019–2020, size-segregated aerosol samples containing elemental and organic carbon (EC and OC) were investigated. These samples were collected weekly using an eight-stage cascade impactor from an urban site located at Aksaray University, Aksaray. The quantification of EC and OC was carried out through a thermal-optical transmission device. The results revealed consistent size distribution attributes of EC and OC between winter and summer. Although EC accounted for an insignificant percentage (4.4%) of particulate matter (PM) in the PM_9.0–10.0 fraction during winter, a more substantial portion of OC in the same fraction (13.4%) comprised EC. Seasonal variations were distinct for EC but not significant for OC. Strong correlations between OC and EC were observed in coarse particle fractions, indicating a common source, with weaker correlations in fine particles. The highest OC/EC ratio was in the PM_0.43–0.65 fraction, followed by PM_2.1–3.3. The ratio of OC to EC in fine PM exceeded the threshold of 15 consistently. The observation indicates that as particle size increases, there is a noticeable decline in the OC to EC ratios. Secondary organic aerosols (SOA) accounted for 60.8% (winter) and 89.8% (summer) of OC values, emphasizing the substantial impact of SOA on Aksaray's atmosphere. Both seasons exhibited a multimodal distribution of ambient OC. In winter, the EC distribution was dominated by fine particles, with a bimodal pattern (PM_1.1–2.1 and PM_0.43–0.65 peaks). Common pollutant sources, including traffic emissions, road dust, biogenic emissions, and coal combustion, were identified for both seasons in coarse and fine particle fractions. These findings underscore the importance of emission control strategies targeting fine PM in Aksaray.     

Spatial Heating Monthly Degree-Day Features and ClimatologicPatterns in Turkey

Summary  Degree-days as a measure of accumulated temperature deviations from a base temperature have many practical applications in various human related activities such as home cooling, heating, plant growth in agriculture and power generation in addition to energy requirement. Long temperature records are necessary for their reliable estimations at given stations. In this paper, degree-day measure has been applied to monthly temperature records for systematically changed base temperature values from − 25 °C to + 35 °C with 5 °C increments at 255 meteorology stations in Turkey. The results are represented in the form of spatial degree-day distribution maps, which are then related to various climatic, meteorological and topographic features of Turkey. For instance, free surface water bodies in forms of surrounding seas, lakes and rivers insert retardation in the expansion of heating degree-days over large regions. On the other hand, cold air penetration from polar regions in the northeastern Turkey originating from Siberia appears at moderate base temperature heating degree-days. Received August 20, 1998 Revised June 21, 1999     

Geological evolution of the Gulf of Saros,NE Aegean Sea

 The Gulf of Saros is an Upper Miocene transtensional basin in NW Anatolia, formed by the interaction between the North Anatolian Fault and the N-S extensional tectonic régime of the Aegean. The present configuration of the basin evolved mainly during the Plio-Quaternary under the increased activity of the North Anatolian Fault. During the late Miocene-late Quaternary, no sedimentation took place on the shelves. After this long hiatus, an important change in tectonic style about 0.2 Ma BP allowed sedimentation to resume in the gulf. Received: 14 February 1997 / Revision received: 12 November 1997     

Investigation of groundwater contamination using electric and electromagnetic methods at an open waste-disposal site: a case study from Isparta, Turkey

 Geophysical methods, when integrated with soil chemical and hydrogeological methods, can be used to investigate groundwater contamination. Direct current (DC) resistivity geo-electrical sounding and very-low-frequency electromagnetic (VLF-EM) data were collected at an open waste site used by the municipality of the city of Isparta, Turkey. The groundwater at shallow depths in alluvium, which is composed of gravel, sand and clay, were expected to be hazardously contaminated under and around the open waste-disposal site, in which both household and industrial wastes are known to be disposed of improperly. In this study, we mapped the spread of groundwater contamination using a VLF-EM method, which allows fast and inexpensive data collection. The method complements the results of geo-electrical sounding. There is a good correlation between the results of the VLF-EM and the DC-resistivity methods employed for the investigation of subsurface structure of the site, where soil chemical and previous hydrogeological surveys have indicated high levels of chemical concentrations. Received: 17 January 2000 · Accepted: 12 August 2000