Lateral variations of coda Q and attenuation of seismic waves in Southwest Anatolia

The seismic quality factor (Q _c) and the attenuation coefficient (δ) in the earth’s crust in southwest (SW) Anatolia are estimated by using the coda wave method based on the decrease of coda wave amplitude by time on the seismogram. The quality factor Q _o, the value of Q _c at 1 Hz, and its frequency dependency η are determined from this method depending on the attenuation properties of scattered coda waves. δ is determined from the observations of amplitude variations of seismic waves. In applying the coda wave method, firstly, a type curve representing the average pattern of the individual coda decay curves for 0.75, 1.5, 3.0, 6.0, 12.0, and 24.0 Hz values was estimated. Secondly, lateral variation of coda Q and the attenuation coefficients for three main tectonic patterns are estimated. The shape of the type curve is controlled by the scattering and attenuation in the crustal volume sampled by the coda waves. The Q _o and η values vary from 30 to 180 and from 0.55 to 1.25, respectively for SW Anatolia. In SW Anatolia, coda Q–f relation is described by and δ = 0.008 km⁻¹. These results are expected to help in understanding the degree of tectonic complexity of the crust in SW Anatolia.     

Deliniation of Weathering in the Çatalca Granite Quarry with the Very Low Frequency (VLF) Electromagnetic Method

Faulting and weathering can endanger quarry operations by decreasing the total reserve, quarry’s useful life and production value. We investigated weathering and faulting problems in the Çatalca granite quarry at Istanbul in Turkey, using the Very Low Frequency (VLF) method. VLF method is an electromagnetic method which is very successful in locating vertical discontinuities such as faults and fracture zones. This method measures the apparent resistivity of the rocks in the region, besides the electromagnetic parameters such as tilt angle and ellipcity. Apparent resistivity is a very sensitive parameter to water presence inside the pores and fractures of the rocks. This feature enables the VLF method to map the boundaries between the fresh and cracked granite and altered zones in the quarry. In this work we mapped the faults and weathered zones within the granite in Çatalca quarry and found a high resistivity zone at the central part of the survey area which may be suitable for production. This study also shows the efficiency of the VLF method in understanding the structural and textural features of a quarry and estimating zones with high quality rocks for production planning.     

Mathematical modelling of a potential tsunami associated with a late glacial submarine landslide in the Sea of Marmara

Potential tsunami waves were modelled on the basis of the morphology and geological setting of a late glacial submarine landslide localized in the north-eastern sector of the Sea of Marmara, using a three-dimensional algorithm with the purpose of assessing the future risk of tsunamogenic landslides in the region. The landslide occurred off the Tuzla Peninsula on the north-eastern slope of the Ç?narc?k Basin, the easternmost of the three deep Marmara basins. The mass movement appears to be related to the Main Marmara Fault that passes below the toe of the failed mass. Observations from earlier manned submersible dives suggest that the initiation of the slide was facilitated by secondary faults associated with the Hercynian orogeny and involved Palaeozoic shales dipping southwards towards the deep basin. Radiocarbon dating of core material, together with the well-dated Marmara sapropel above the chaotically mixed landslide surface, reveal that the latest landslide event occurred about 17 ¹⁴C ka b.p. The uppermost scar of the landslide is found at 250 m and its toe at about 1,200 m below the present sea level. At the time of the slide, the Marmara Sea Basin was lacustrine, with its water level at ?85 m. In plan view the landslide has a distinctively triangular shape and the lateral extent of its toe is about 10 km. Multibeam bathymetric data indicate that the sliding motion probably occurred in two phases: a slower phase affecting the eastern part, characterized by an undulating surface, and a more rapid phase affecting the western part that possibly created tsunami waves. In the seismic sections, older failed slide masses can be clearly identified; these were probably displaced during marine isotopic stage 6 (～127–160 ka b.p.). The front of this buried material is located more than 1.5 km further south of the fault. We used a three-dimensional, Green’s function-based potential theory approach, rather than shallow-water equations commonly used in conventional tsunami simulations. The solution algorithm is based on a source-sink formulation and an integral equation. The results indicate that the maximum height of the tsunami in the Ç?narc?k Basin could have reached about half the average thickness of the sliding mass over a lateral extent of 7 km. Assuming an average thickness of 30 m for the landslide, and considering that the water level at 17 ka b.p. was at about ?85 m, the modelling shows that the maximum wave height generated by the slide would have been about 15–17 m.     

Vibration characteristics of a suspension bridge under traffic and no traffic conditions

This paper presents the variations of vibration under different traffic conditions on the Fatih Sultan Mehmet suspension bridge in Istanbul, Turkey.The main intention is to determine the vibration amplifications under heavy-traffic as opposed to no-traffic conditions. This is the first study in this particular area that has been performed on this bridge, over which an average of 200,000 cars pass daily. Two full-scale ambient vibration surveys were carried out on two different days to determine the response of the bridge to diverse traffic conditions. Initial measurements were taken as the bridge experienced heavy stress conditions caused by rush-hour traffic. Secondary measurements were recorded after closing the bridge to traffic. The data were analyzed to gauge the vibration effects of heavy-traffic conditions on the bridge and to determine the effects of different traffic conditions on the free vibration characteristics of the bridge. The analyses were performed utilizing different amplification methods. Results show that there are important differences in the amplifications of the vibration amplitudes. Especially heavy-traffic on the bridge causes the vibration response of the bridge to be intensified in comparison to no-traffic conditions. Additionally, predominant frequencies are shifted as a direct result of traffic load acting on the bridge. Even more importantly and is probably analogous for all long-span bridges, is the fact that any movement causing vibration on the bridge is carried and amplified along its length. These significant amplifications indicate the important effect of varying traffic loads and how the bridge responds to the diverse movements it experiences. Copyright © 2011 John Wiley & Sons, Ltd.     

Hydrological trend analysis with innovative and over-whitening procedures

Different statistical methodologies can be employed to identify possible trend components in any hydro-meteorological time series. A pre-whitening (P-W) procedure has been suggested to reduce the serial correlation effect on Mann-Kendall (M-K) trend analysis. In this paper, instead of P-W, an over-whitening (O-W) procedure is suggested, which generates serially independent series with the same trend slope value. Analytically necessary formulations for O-W are presented with a non-parametric but simple innovative trend assessment procedure, which are supported by extensive simulation studies. The applications of the methodology are presented for eight factual time series records from tropical, temperate and arid regions including temperature, rainfall, streamflow, relative humidity and CO₂ concentrations for different short and long durations. Relative humidity and CO₂ records are monthly time series and, hence, there are trend and periodicity components. It is noticed in all cases that the natural trends remain as they were after the O-W procedure, thus providing an opportunity to determine reliably the trends embedded even in the serially dependent series. The O-W procedure is applicable even in the cases of periodicity in the original records.     

Markov Models and Polygon Diagrams for Climatological Interpretations of Cyclones and Anticyclones over the Northern Hemisphere

Summary Annual cyclone and anticyclone numbers in addition to the temperature data for the northern hemisphere are processed through simple models leading to meaningful interpretations. Historical climatological characteristics of the cyclone and anticyclone numbers are modeled by a first order Markov process. Statistically indistinguishable synthetic cyclone and anticyclone numbers are generated. Polygon diagrams which show the mutual relationships between average cyclone (anticyclone) numbers and the temperature are employed for finding possible relevant climatological changes during the record period. A polygon diagram concept is proposed and applied in order to identify sub-period warming and cooling spells of any desired short or long term durations and their relationship to the annual number of cyclone (anticyclone) occurrence numbers. The results indicate a decrease (increase) in the cyclone and anticyclone numbers during cooling (warming) periods. The methodologies proposed in this paper can be easily adopted for cyclone and anticyclone numbers modeling in any part of the world. Received July 15, 1997 Revised January 22, 1999     

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     

Long-Term 3D Hydrodynamic Modeling and Water Surface Statistics in Marmara Sea

Marmara Sea (MS) lies in the strategic crossroad, accommodating one of the busiest shipping routes in the world. In general, there is a two-layer current system in the MS and Turkish Straits system; the brackish waters originating in the Black Sea (BS) (18 PSU) moving southward to the Aegean Sea (AS), and a lower layer return flow of saltier Aegean waters (38.5 PSU) back to the BS. This variability poses a challenging task within the modeling perspective. In this research, 3D hydrodynamic modeling of MS is performed in order to investigate the spatial and temporal behavior of elevations between years 2000 and 2015. During the calibration process, the grid configuration, time step, and model coefficients (Manning bed roughness coefficient, a wind drag coefficient and horizontal viscosity are coefficients) are adjusted until the computed solution produced the best match to the observed data such as water surface elevations, velocities, and net discharges. To this end, a series of simulations are made. As a result, the observed and the predicted water surface elevations follow each other very closely. The developed model could accurately estimate the net discharge as well. In order to understand the behavior of MS, elevation pattern is calculated and depicted both on annual and seasonal scales. It is demonstrated that the influence of seasonally varying strong fresh water river discharges of Danube in BS have strong influence on the water mass characteristics of the MS.