Seismotectonic database of Turkey

Turkey is located in one of the most seismically active regions in the world. Characterizing seismic source zones in this region requires evaluation and integration of geological, geophysical, seismological and geodetical data. This first seismotectonic database for Turkey presented herein was prepared, under the framework of the National Earthquake Strategy and Action Plan—2023. The geographic information system (GIS)-based database includes maps of active faults, catalogues of instrumental and historical earthquakes, moment tensor solutions and data on crustal thickness. On the basis of these data, 18 major seismotectonic zones were delineated for Turkey and the surrounding region. The compilation and storage of the seismotectonic data sets in a digital GIS will allow analyses and systematic updates as new data accrete over time.     

Unsaturated characteristics of undisturbed expansive shale from Saudi Arabia

The aim of this paper is to evaluate the soil water characteristic curves (SWCC) of undisturbed expansive shale identified at different locations of Kingdom of Saudi Arabia. The SWCCs were evaluated for suction ranging from 0.5 to 400 MPa. Based on test results, all SWCCs reveal a bimodal curve indicating the presence of two distinct pore size distributions referred to as small and large micropores. Volume change measurements were performed to evaluate void ratio–suction relationships which confirmed the expansive nature of shale. Similarities between measured SWCCs and void ratio–suction relations developed for expansive shale originating from same geological formation suggests the impact of geological and environmental conditions on the unsaturated behavior of shale samples. Finally, a modified approach based on Mckeen’s classification methodology was proposed to assess the swelling potential using bimodal SWCCs. The modified approach was used to assess the relative contribution of different micropores on the swelling potential of shale.     

A new approximation in determination of zonation boundaries of ignimbrite by ground penetrating radar: Kayseri,Central Anatolia,Turkey

Ground penetrating radar (GPR) method is used as a tool to identify the zonation boundaries in ignimbrite series through their columnar section. Ignimbrites can be classified in terms of welding degree, colour, texture and mineralogical compositions. The research area comprises a part of İncesu (Kayseri) ignimbrite at Central Anatolia, Turkey. This ignimbrite is divided into three levels and each level has clear differences in terms of macroscopic and microscopic views. This paper presents the results of an application of GPR for the determination of zonation boundary within the ignimbrite flow unit in the view of their textural and petrological features. RAMAC CU II equipment was used with 250 MHz shielded antenna on parallel ten profiles to observe the physical difference among the ignimbrite levels of the study area. Two levels out of three have been defined at the İncesu ignimbrite and supported by field geology and petrographical studies. The first level, which is extremely fractured structure, is about 1.5 m thick and matches with middle level of the İncesu ignimbrite. The second level has an average 50–75 cm thickness and matches with lower level of the ignimbrite. In this manner, vertical lithological variations should be taken into consideration during petrological investigation of the ignimbrites.     

Performances of Reverse Osmosis Membranes for Treatment of Olive Mill Wastewater

In the following study, two methods were employed in which olive mill wastewaters were treated by using reverse osmosis membranes (BW30 and XLE). In the first, wastewater was centrifuged and then passed through the reverse osmosis whereas in the second, an ultrafiltration was placed between the centrifuge and the reverse osmosis. The reverse osmosis experiments were conducted under 10, 15, 20, and 25 bar. The chemical oxygen demand (COD) removal efficiencies under 25 bar were found to be 97.5% for both BW30 and XLE membranes. The highest conductivity removal rates obtained under 25 bar for BW30 and XLE membranes were found to be 95.6 and 96.2%, respectively. As for the highest permeation flux values obtained under 25 bar, they were separately determined for BW30 and XLE as 15.3 and 21.2 L m^?2 h^?1, respectively. The performances of the membranes were also evaluated in terms of their mass transfer coefficients. According to this, all mass transfer coefficients were found to be <1 and also in proximate to one another; this clearly reflects the results as COD and conductivity removals were approximate and there was a lack of any significant difference, whether ultrafiltration was applied or not.     

On the short term variations of solar activity during solar cycle 21

Short-term variations of the last solar activity cycle were studied by the flare and coronal indices using Gleissberg method. Systematic short-term variations are found from their course during the 21st solar activity cycle. Comparison of their autocorrelograms constructed by the new set of data obtained from the magnitude of the fluctuations showed us the existence of the phase shift between the temporal variations of the two indices.     

A probabilistic seismic hazard assessment for the Turkish territory: part II—fault source and background seismicity model

Over the years, several local and regional seismic hazard studies have been conducted for the estimation of the seismic hazard in Turkey using different statistical processing tools for instrumental and historical earthquake data and modeling the geologic and tectonic characteristics of the region. Recently developed techniques, increased knowledge and improved databases brought the necessity to review the national active fault database and the compiled earthquake catalogue for the development of a national earthquake hazard map. A national earthquake strategy and action plan were conceived and accordingly with the collaboration of the several institutions and expert researchers, the Revision of Turkish Seismic Hazard Map Project (UDAP-Ç-13-06) was initiated, and finalized at the end of 2014. The scope of the project was confined to the revision of current national seismic hazard map, using the state of the art technologies and knowledge of the active fault, earthquake database, and ground motion prediction equations. The following two seismic source zonation models are developed for the probabilistic earthquake hazard analysis: (1) Area source model, (2) Fault and spatial smoothing seismic source model (FSBCK). In this study, we focus on the development and the characterization of the Fault Source model, the background spatially smoothed seismicity model and intrinsic uncertainty on the earthquake occurrence-rates-estimation. Finally, PSHA results obtained from the fault and spatial smoothed seismic source model are presented for 43, 72, 475 and 2475 years return periods (corresponding to 69, 50, 10, and 2% probability of exceedance in 50 years) for PGA and 5% damped spectral accelerations at 0.2 and 1.0 s.     

Weak compositional zonation in a silicic magmatic system: Incesu ignimbrite,Central Anatolian Volcanic Province (Kayseri – Turkey)

The Central Anatolian Volcanic Province (CAVP), one of four major volcanic provinces in Turkey, plays a significant role in the interpretation of the tectonic evolution of Central Anatolia. The CAVP developed within a complex collisional system involving the African, Arabian and Eurasian plates during the Miocene. The volcanism exhibits complicated variations in mineralogical, petrological and geochemical compositions resulting from post-collisional lithospheric dynamics. The Incesu ignimbrite has 5–20 m thick and covers an area of ～7800 km². It is composed of three stratigraphic levels. The lower level (LL) shows blackish brown and glassy welded structure. The middle level (ML) is a well-welded, reddish pink in color and has large amounts of fiamme. The upper level (UL) is grayish pink, weakly welded and has rock fragments of different compositions. The Incesu ignimbrite is composed of plagioclase (oligoclase, andesine) + pyroxene (augite, clinoenstatite) + opaque minerals and low amount of amphibole, biotite and quartz. Eutaxitic texture is dominant in ML and LL samples; these levels are more strongly and contain more flattened pumice fragments and volcanic glass shards than in the UL. A sharp color contrast defines the contact between LL and ML.Major, trace and rare earth element of the Incesu ignimbrite, characterized by their rhyolite, rhyodacite–dacite composition, medium–high K, calcalkaline and peraluminous nature, show fractional crystallization primarily controlled by plagioclase, clinopyroxene, magnetite, ilmenite and titanomagnetite. Sr and Nd isotopic ratios of Incesu ignimbrite display isotopic variations between the ignimbrite levels; they exhibit a limited range in ⁸⁷Sr/⁸⁶Sr (0.7043–0.7049) and ¹⁴³Nd/¹⁴⁴Nd (0.512716–0.512760). The Sr–Nd isotopic ratio of Incesu ignimbrite reveals an age of 3 Ma. The ignimbrite evolved through fractional crystallization and crystal contamination of the parent magma derived from Ocean Island Basalt (OIB) like magma. This suggestion is supported by the AFC modeling based on the trace elements and Sr isotope data.Variation of several major oxide concentrations (Fe₂O₃, TiO₂, CaO and K₂O), trace element concetrations (V, Sr, Cs and Rb) and trace element ratios (Ba/Rb, Sr/, K/Sr, K/Nb, Rb/Sr, Rb/Y and Rb/Nb) versus SiO₂ concentration show the magma chamber that generated the Incesu ignimbrite was compositionally zoned. All geochemical and Sr–Nd isotpic datas can be interepreted to be the result of a subduction related source.     

The analysis of 2004 flood on Kozdere Stream in Istanbul

The climatic and physiographical factors of the Kozdere Creek Watershed are examined to find out the causes of the flood of August 11, 2004. Actual land use has been obtained from forest management stand plans and classified satellite images. The multispectral digital satellite data set belonging to years 1992, 1993, and 2005 was used to determine the status of land use. Physiographic factors, including the slope and the aspect, have been identified from digitized ortho-photo maps in the GIS environment. Since flow records of Kozdere are not available, flow values corresponding to different return periods were obtained using regression analysis of neighboring streams. No noticeable alteration of the land use occurred between 1992 and 2005. Since the physical factors are the same as they were during the 1985 rain, the flood after the 2004 rainfall cannot be due to the physiographical factors of the upper watershed. The existing channel in the neighborhood is not enough to convey even the 10-year return period flow. Thus, the 2004 flow did not fit into this cross-section and flooded houses on the alluvial fan. The cross-section of the Kozdere Creek passing through the PTT neighborhood should be increased, and the surface roughness should be decreased by covering the channel with concrete in order to prevent floods.     

Assessment of rockfall hazard around Afyon Castle,Turkey

The Afyon Castle is a tourist destination and a historical site in the City of Afyon in Turkey. The Castle is located on a steep hill, with a height of 226 m. In close proximity to the Castle there are settlements. The hill consists of trachitic andesite. The rock contains columnar joints and flow layering. Owing to these discontinuities, blocks of varying sizes had fallen down. The settlement areas near the Castle are now in danger because of the rockfall risk. In this study, rockfall analysis was carried out along nine profiles of the hill. Fall-out distance, bounce height, kinetic energy and velocity of the rocks along each profile were investigated. The results of the analyses were evaluated, and the areas delineated as susceptible to rockfall risk are highlighted. Remedial measures including rock bolts and protective fences were suggested on the basis of the field observations and the rockfall risk evaluation.