Kinematics of the eastern part of the North Anatolian Fault Zone

The North Anatolian Fault Zone (NAFZ), which marks the boundary between Anatolia and the Eurasian plate, is one of the world's most seismically active structures. Although the eastern part of NAFZ has high seismic hazard, there is a lack of geodetic information about the present tectonics of this region. Even though many scientists would like to study this area, geographical and logistical problems make performing scientific research difficult. In order to investigate contemporary neotectonic deformation on the eastern NAFZ and in its neighborhood, a relatively dense Global Positioning System (GPS) monitoring network was established in 2003. Geodetic observations were performed in three GPS campaigns in an area of 350 km × 200 km with 12-month intervals. In addition, 14 new GPS stations were measured far from the deforming area. Since this region includes the intersection of the NAFZ and the East Anatolian Fault Zone (EAFZ), deformation is complex and estimating seismic hazard is difficult. One important segment is the Yedisu segment and it has not broken since the 1784 earthquake. After the 1992 Erzincan and 2003 Pulumur earthquakes, the Coulomb stress loading on the Yedisu segment of the NAFZ has increased significantly, emphasizing the need to monitor this region. We computed the horizontal velocity field with respect to Eurasia and strain rates field as well. GPS-derived velocities relative to Eurasia are in the range of 16–24 mm/year, which are consistent with the regional tectonics. The principal strain rates were derived from the velocity field. Results show that strain is accumulating between the NAFZ and EAFZ along small secondary fault branches such as the Ovacik Fault (OF).     

Algorithms for staggered-grid computations for poroelastic,elastic, acoustic,and scalar wave equations

Heterogeneous wave equations are more complicated numerically than homogeneous wave equations, but are necessary for physical validity. A wide variety of numerical solutions of seismic wave equations is available, but most produce strong numerical artefacts and local instabilities where model parameters change rapidly. Accuracy and stability of heterogeneous equations is achieved through staggered-grid formulations. A new pseudospectral staggered-grid algorithm is developed for the poroelastic (Biot) equations. The algorithm may be reduced to handle the elastic and acoustic limits of the Biot equations. Comparisons of results from poroelastic, elastic, acoustic and scalar computations for a 2D model show that porous medium parameters may affect amplitudes significantly. The use of homogeneous wave equations for modelling of a heterogeneous medium, or of a centred rather than a staggered grid, or of simplified (e.g. acoustic) wave equations when elastic or poroelastic media are synthesized, may produce erroneous or ambiguous interpretations.     

Methyltins in the marine environment

Methyltins were occasionally observed in some natural waters. The nature of a marine sediment determines its organotin burdens. Mono- and dimethyltin compounds were found in polluted marine sediments whereas non-polluted, oxiccoastal sediments contained primarily trimethyltin. The net methylation rate is evidently independent of the inorganic tin content of a sediment. Methyltin in fish is about 3–6% of the total tin content while limpets contain significant amounts of organotin compounds, ranging between 35 and 75% of the total tin. No trimethyltin was detected in green macro-algae and seawater, although limpets, fish and sediments have measurable levels.     

Trace metal levels in fish and crustacea from Northeastern Mediterranean coastal waters

Some fish and crustacea caught near the northeastern Mediterranean coast of Turkey between 1977 and 1980 have been analysed by the AAS technique for their H Hg, Cd, Pb, Zn, Cu, Fe, Ni, Cr and Mn contents. In the crustacea Portunus pelagicus (crab) and Penaeus keratherus (shrimp), the two essential elements Zn and Cu, showed a linear correlation. Among the bony fish, Upeneus moluccensis (gold band goat fish), a member of the Mullidae family, and Portunus pelagicus showed a much greater tendency to accumulate Hg than other species. Although Cr concentrations in the sediments of the area studied were high, Cr levels in the organisms studied were found to be relatively low. The highly toxic metals Hg, Cd and Pb were found to be present in concentrations lower than those reported from other areas of the Mediterranean.     

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.     

Wind control on the accumulation of heavy metals in sediment of Lake Ulubat,Anatolia, Turkey

Freshwater Lake Ulubat (z _mean = 1.5–2.0 m and Area = ~138 km²), NW Anatolia, Turkey was filled in by fine-to-medium-grain silts during the late Holocene. Deposition in Lake Ulubat has been 1.6 cm year⁻¹ for the last 50 years, but the sedimentation rate over the last ~1,600 years was lower (0.37 mm year⁻¹). The organic matter and carbonate contents of the infill show cyclic changes that reflect environmental fluctuations. The silt-dominated lithology and the vertically uniform heavy metal distributions are probably due to wind-controlled sedimentation in the lake. Heterogeneous mud, derived from a large, mountainous drainage basin, is deposited in the lake mostly during summer, June to October, when conditions are hot and calm. Winter months are stormier and sediments are re-suspended due to the shallow water depth and the effect of waves on the lake bottom. It is likely that re-suspended sediments, particularly fine-grained particles, together with the heavy metals, are transported out of the lake via the outlet, especially during periods of high lake level. This resuspension and removal process probably caused the lake sediments to become silt-dominated and depleted in heavy metals. The role of broad shallow lakes in sequestering sediments and heavy metals can be described more accurately when wind data are considered. Such information may also be helpful for land-use planning in downstream areas.     

Architecture of late orogenic Quaternary basins in northeastern Mediterranean Sea

In the northeastern Mediterranean Sea, Pliocene to Quaternary depocentres have formed in extensional basins bounded by splays of the East Anatolian Transform Fault. This tectonic regime is superimposed on a Miocene and older back-arc environment, that experienced late Miocene compression along the Misis-Kyrenia thrust, which now lies in the middle of the extensional zone. The thrust zone is now represented by a narrow horst that appears to be bounded by strike-slip faults. Pliocene-Quaternary extension took place on listric fault fans that are orthogonal to the bounding transform splays and sole at a Messinian evaporite horizon, and on some deeper-soling listric faults parallel to and near the bounding faults. The rapid extension has resulted in progressive landward migration of paleoshorelines and low depositional gradients. Glacio-eustatic fluctuations in shoreline positions strongly influenced sediment distribution. Most sediment dispersion was from deltaic plumes, with turbidites of minor significance. Depocentres landward of the maximum seaward extent of paleoshorelines were formed almost entirely by tectonic subsidence. Minor deep-water depocentres, controlled by halokinesis, accumulated mud turbidites during extreme low-stands of sea-level.     

An alternative method for estimating densification point velocity based on back propagation artificial neural networks

The establishment of Turkish National Fundamental GPS Network (TNFGN) was completed in 2001 and Large Scale Map and Map Information Production Regulation (LSMMIPR) came into force in 2005 in parallel with the establishment of TNFGN and the increase in the use of GPS applications. TNFGN has been designed as first order GPS network and it comprises second-, third- and fourth-order GPS densification networks. LSMMIPR has required determining the positions of first-, second- and third-order GPS densification (C1, C2 and C3) points with the reference epoch besides the measurement epoch. Therefore, it is necessary to estimate the velocity vectors of the densification points. In practise, the velocity vectors of C1, C2 and C3 points are estimated from TNFGN points or higher-order densification points velocity vectors by interpolation methods but LSMMIPR did not specify the interpolation method for this procedure. The objective of this study is to use a back propagation artificial neural network (BPANN) that has been more widely applied in engineering among all other neural network models for estimating the velocity of the densification point as an alternative to the interpolation methods. BPANN and selected ten interpolation methods are evaluated over a test area, in terms of root mean square error (RMSE). The results showed that the employment of BPANN estimated the densification point velocity (V_X,Y,Z) with a better accuracy (±5.0 mm, ±4.0 mm, ±3.9 mm, respectively) than the interpolation methods in the test area and indicated that BPANN can be a useful tool for estimating point velocity in the densification networks as a real alternative to the interpolation methods.