Papers by Derman Dondurur
Yeraltında sığ derinliklerde gömülü metal boru ve kablolar çizgisel iletkenler olarak adlandırılı... more Yeraltında sığ derinliklerde gömülü metal boru ve kablolar çizgisel iletkenler olarak adlandırılır ve belirli bazı jeofizik yöntemlerle araştırılabilirler. Bu tür hedeflerin aranması problemiyle genelde şehirsel alanlarda karşılaşıldığı için, ortamların statik gürültü seviyesi yüksek olmakta ve beklenen anomalilerde farklılıklar gözlenebilmektedir. Ayrıca, yeraltı çizgisel iletkenleri, genellikle plastik veya beton borular içine konulur ve bu durum elde edilen anomalilerin doğasını bozabilir. Arazide elde edilen anomalilerin yorumlanması, bu tür iletkenlerin klasik tepkilerinin modellenerek belirlenmesi durumunda doğru şekilde yapılabilir. Ancak Elektro Manyetik (EM) yöntemler için bu işlemi analitik veya sayısal olarak yapmak birçok durumda mümkün değildir. Böyle durumlarda EM analog modellemelere başvurulabilir. Bu çalışmada, EM Slingram yöntemi kullanılarak çizgisel iletken hedeflerin EM Slingram tepkileri analog olarak modellenmiştir. İki ayrı frekansta ve iki ayrı bobin aralığı için analog tepkiler elde edilmiştir. Ayrıca Slingram ile kullanılabilen üç farklı maksimum etkileşimli bobin sisteminin anomalileri birbiri ile karşılaştırılmıştır. Bunların yanı sıra, çizgisel iletkenin yalıtım malzemesinin anomaliler üzerindeki etkisi de incelenmiştir. Karşılaştırma için, tüm anomaliler ard-arda ve paralel-hat profilleri için elde edilmiştir.
Wave" fi elds have long been recognized in marine sediments on the fl anks of basins and oceans i... more Wave" fi elds have long been recognized in marine sediments on the fl anks of basins and oceans in both tectonically active and inactive environments. The origin of "waves" (hereafter called undulations) is controversial; competing models ascribe them to depositional processes, gravity-driven downslope creep or collapse, and/or tectonic shortening. Here we analyze pervasive undulation fi elds identifi ed in swath bathymetry and new high-resolution multichannel seismic (MCS) refl ection data from the Sea of Marmara, Turkey. Although they exhibit some of the classical features of sediment waves, the following distinctive characteristics exclude a purely depositional origin: (1) parallelism between the crests of the undulations and bathymetric contours over a wide range of orientations, (2) steep fl anks of the undulations (up to ~40°), and (3) increases in undulations amplitude with depth. We argue that the undulations are folds formed by gravity-driven downslope creep that have been augmented by depositional processes. These creep folds develop over long time periods (≥0.5 m.y.) and stand in contrast to geologically instantaneous collapse. Stratigraphic growth on the upslope limbs indicates that deposition contributes to the formation and upslope migration of the folds. The temporal and spatial evolution of the creep folds is clearly related to rapid tilting in this tectonically active transform basin. (TUBITAK)-BİDEB supported a six-month research visit for Kurt to LDEO and the University of Missouri. We thank the captains and crew of the R/V K. Piri Reis, who made the acquisition of these data possible despite challenging conditions. We thank Hydroscience Technologies Inc. for supporting the seismic systems of R/V K. Piri Reis, Landmark for ProMAX software, and Seismic
Global and Planetary Change, 2013
A source to sink system describes the natural link between mountains, plains and deltas, by analy... more A source to sink system describes the natural link between mountains, plains and deltas, by analysing the (re)distribution of material at shallow crustal depth and at the Earth's surface, exploring the links between coupled tectonic and surface processes. Sediment fluxes are the product of erosion and movement of material in and from sources (mountains), the transport and movement of sediments and solutes by river systems to the plains, and deposition and storage in sink zones. The ESF-EUROCORES TOPO-EUROPE SourceSink programme is a fully integrated research effort to significantly advance our predictive capabilities on the quantitative analyses of coupled active and past drainage systems by means of step-wise 4D reconstructions of sediments mass transfer, integrating geophysics, geology, geomorphology, state of the art high-resolution dating, and numerical and analogue modelling. The area selected for this programme is the Danube River Basin-Black Sea source to sink system, a world-class natural laboratory that is uniquely suited in the heart of Europe's topography, covering almost half of its surface, providing opportunities for excellent field sites to study in integration surface and subsurface data that cover the complete chain of source, carrier and sink. Quantifying and modelling the complete system in relation to the controlling parameters has resulted in significant understanding of forcing factors and linking temporal and spatial scales across multiple orogen and basin systems. This research has provided the opportunity to widen the geographical scope to other natural scenarios, where a number of mountain chains with similar geodynamic genesis separate sedimentary basins with comparable evolution.
Geophysical Research Letters, 2013
Image, 2002
Abstract: The seismic characteristics of the lower crust of Serre Mountains, South Calabria (Sout... more Abstract: The seismic characteristics of the lower crust of Serre Mountains, South Calabria (Southern Italy) were investigated by a Deep Seismic Sounding experiment along the main profile of about 30 km long. In this profile, 31 dynamite shots (10-95 kg) recorded by five ...
We collected high-resolution multichannel seismic reflection (MCS) and chirp seismic data across ... more We collected high-resolution multichannel seismic reflection (MCS) and chirp seismic data across the North Anatolian Fault (NAF) system in the Marmara Sea aboard the R/V K. Piri Reis during July 2008. Three 1200+ m-deep bathymetric basins are arrayed along the North strand of the NAF. This strand passes closest to Istanbul and is considered to carry most of the current
Wiener deconvolution is generally used to improve resolution of the seismic sections, although it... more Wiener deconvolution is generally used to improve resolution of the seismic sections, although it has several important assumptions. I propose a new method named Gold deconvolution to obtain Earth's sparse-spike reflectivity series. The method uses a recursive approach and requires the source waveform to be known, which is termed as Deterministic Gold deconvolution. In the case of the unknown wavelet, it is estimated from seismic data and the process is then termed as Statistical Gold deconvolution. In addition to the minimum phase, Gold deconvolution method also works for zero and mixed phase wavelets even on the noisy seismic data. The proposed method makes no assumption on the phase of the input wavelet, however, it needs the following assumptions to produce satisfactory results: (1) source waveform is known, if not, it should be estimated from seismic data, (2) source wavelet is stationary at least within a specified time gate, (3) input seismic data is zero offset and does not contain multiples, and (4) Earth consists of sparse spike reflectivity series. When applied in small time and space windows, the Gold deconvolution algorithm overcomes nonstationarity of the input wavelet. The algorithm uses several thousands of iterations, and generally a higher number of iterations produces better results. Since the wavelet is extracted from the seismogram itself for the Statistical Gold deconvolution case, the Gold deconvolution algorithm should be applied via constant-length windows both in time and space directions to overcome the nonstationarity of the wavelet in the input seismograms. The method can be extended into a two-dimensional case to obtain time-and-space dependent reflectivity, although I use onedimensional Gold deconvolution in a trace-by-trace basis. The method is effective in areas where small-scale bright spots exist and it can also be used to locate thin reservoirs. Since the method produces better results for the Deterministic Gold deconvolution case, it can be used for the deterministic deconvolution of the data sets with known source waveforms such as land Vibroseis records and marine CHIRP systems.
Based on high-resolution Chirp seismic, multibeam bathymetry and side scan sonar data collected i... more Based on high-resolution Chirp seismic, multibeam bathymetry and side scan sonar data collected in the _ Izmir Gulf, Aegean Sea in 2008 and 2010, gas-related structures have been identified, which can be classified into three categories: (1) shallow gas accumulations and gas chimneys, (2) mud diapirs, and (3) active and inactive pockmarks. On the Chirp profiles, shallow gas accumulations were observed along the northern coastline of the outer _ Izmir Gulf at 3e20 m below the seabed. They appear as acoustic turbidity zones and are interpreted as biogenic gas accumulations produced in organicerich highstand fan sediments from the Gediz River. The diapiric structures are interpreted as shale or mud diapirs formed under lateral compression due to regional countereclockwise rotation of Anatolian microplate. Furthermore, the sedimentary structure at the flanks suggests a continuous upward movement of the diapirs. Several pockmarks exist close to fault traces to the east of Hekim Island; most of them were associated with acoustic plumes indicating active degassing during the survey period in 2008. Another Chirp survey was carried out just over these plumes in 2010 to demonstrate if the gas seeps were still active. The surveys indicate that the gas seep is an ongoing process in the gulf. Based on the Chirp data, we proposed that the pockmark formation in the area can be explained by protracted seep model, whereby sediment erosion and reedistribution along pockmark walls result from ongoing (or long lasting) seepage of fluids over long periods of time. The existence of inactive pockmarks in the vicinity, however, implies that gas seepage may eventually cease or that it is periodic. Most of the active pockmarks are located over the fault planes, likely indicating that the gas seepage is controlled by active faulting.
Much of the northern strand of the North Anatolia Fault system in the Marmara Sea, the Main Marma... more Much of the northern strand of the North Anatolia Fault system in the Marmara Sea, the Main Marmara fault, is a seismic gap, posing a high risk for Istanbul. Deep bathymetric and sedimentary basins are structurally associated with the Main Marmara fault. Basin growth including tilting of their margins is thus linked to fault slip through releasing and restraining segments of this and other branches of the North Anatolian Fault system. Whether this system has been steady state through at least the last half of the Quaternary, or whether the Main Marmara fault more recently propagated through and deactivated pull-apart basins is one of the main controversies. A published age model and stratigraphic framework for these basins has been lacking, and tectonic history models for the Marmara Sea have relied on extrapolating present deformation rates back through time. Over 3000 km of new high-resolution multichannel seismic reflection combined with existing lowerresolution seismic reflection and multibeam bathymetric data make possible a detailed regional stratigraphic interpretation. In particular, a stack of shelf-edge deltas are imaged, and interpreted as glacial period deposition during low sea/lake levels. Reflections from the tops of these deltas, and from unconformities were correlated across much of Marmara Sea basins and highs, providing critical stratigraphic control. We correlate the low-stand deltas with known eustatic sea level minima by developing proxies for time from vertical separation of strata across normal faults, tilts, and sedimentary volumes. A preferred age model is proposed at least back to Oxygen Isotopic stage 14 at 536 ka. During this time interval, tilting of basin margins, vertical separation across the Main Marmara fault adjacent to western Istanbul, and tilt-related slow collapse on the south flank of the Çinarcik basin all indicate steady-state basin growth and fault slip.
The conventional method to remove swell noise from raw seismic data is band-pass filtering (BPF).... more The conventional method to remove swell noise from raw seismic data is band-pass filtering (BPF). It ideally removes whole low frequency band of the spectral content, which results in a total loss of the amplitudes concerning the low frequency reflections from deeper reflectors, and hence lower resolution in the deeper reflection events. The procedure described here attenuates swell noise from seismic data while preserving the reflection amplitudes at low frequency band. The proposed Wiener prediction filter (WPF) method is used to estimate the swell noise embedded in the raw marine seismic data and then the estimated noise is subtracted from shots by a trace-by-trace basis. It is observed that the deeper reflections have significantly higher amplitudes and show better trace-by-trace consistency in the final migration sections obtained by the WPF application. The WPF method removes most of the swell noise and may be an alternative filtering technique to the conventional BPF method. It can be used with high resolution marine seismic data which may have weaker reflection amplitudes from deeper reflectors. It also improves the lateral continuity of the events which may be useful for auto-picking tools such as automatic event tracking. We propose that the method can effectively be used to remove any type of coherent noise providing that a suitable noise model can be determined from the data itself.
Wave" fi elds have long been recognized in marine sediments on the fl anks of basins and oceans i... more Wave" fi elds have long been recognized in marine sediments on the fl anks of basins and oceans in both tectonically active and inactive environments. The origin of "waves" (hereafter called undulations) is controversial; competing models ascribe them to depositional processes, gravity-driven downslope creep or collapse, and/or tectonic shortening. Here we analyze pervasive undulation fi elds identifi ed in swath bathymetry and new high-resolution multichannel seismic (MCS) refl ection data from the Sea of Marmara, Turkey. Although they exhibit some of the classical features of sediment waves, the following distinctive characteristics exclude a purely depositional origin: (1) parallelism between the crests of the undulations and bathymetric contours over a wide range of orientations, (2) steep fl anks of the undulations (up to ~40°), and (3) increases in undulations amplitude with depth. We argue that the undulations are folds formed by gravity-driven downslope creep that have been augmented by depositional processes. These creep folds develop over long time periods (≥0.5 m.y.) and stand in contrast to geologically instantaneous collapse. Stratigraphic growth on the upslope limbs indicates that deposition contributes to the formation and upslope migration of the folds. The temporal and spatial evolution of the creep folds is clearly related to rapid tilting in this tectonically active transform basin. (TUBITAK)-BİDEB supported a six-month research visit for Kurt to LDEO and the University of Missouri. We thank the captains and crew of the R/V K. Piri Reis, who made the acquisition of these data possible despite challenging conditions. We thank Hydroscience Technologies Inc. for supporting the seismic systems of R/V K. Piri Reis, Landmark for ProMAX software, and Seismic
sliding Amasra mass failure zone debris flows gas hydrate dissociation In recent years, the weste... more sliding Amasra mass failure zone debris flows gas hydrate dissociation In recent years, the western Black Sea margin has become well-studied due to its potential for petroleum plays in relatively deeper waters. In 2010, multi-channel seismic, multibeam bathymetry and Chirp high resolution seismic data were collected in order to define the existing geohazards along the margin, to identify the seabed morphology and to determine mass movement types and their run-out distances. Seismic data indicate that the western Black Sea margin is an unstable region with sediment erosion. Particularly, an unstable area offshore of Amasra in the NW consisting of four slides and four buried debris lobes is named the Amasra mass failure zone. Different types of sliding with varying sizes and different mechanisms are observed. These include sliding in the steep slope zones where block-type sliding occurs, smaller-scale slides on the canyon walls, and relatively larger slides in the Amasra mass failure zone. Block-type sliding is observed on the upper continental slope to the south as well as on the canyon walls. They are formed along the rotational faults and occur due to the gravitational loading on the steep slope zones possibly triggered by local seismic activity. In addition, seven large debris lobes identified in the northern toe of the slope buried in the Quaternary sediments triggered by excess pore pressures due to high sediment input and submarine fluid flow. We suggest that earthquake activity may be an important agent for all kind of mass movements in the area. In addition, we propose that the slides in the Amasra mass failure zone are triggered by excess pore pressures in shallow sediments due to the submarine fluid flow possibly produced from gas hydrate dissociation. Warmer Mediterranean seawater input during the rapid transgression period after the Last Glacial Maximum in the Black Sea together with the rapid sedimentation resulted in destabilization of gas hydrates, which caused excess pore pressures in shallow sediments leading to massive sediment failures. Small-scale normal faults around the scarps may be a secondary factor promoting the failures providing the suitable pathways for the fluid flow as well as the suitable weak surfaces for the sliding.
Side lobes of the wavelets arise from the lack of low frequency content in a reflection wavelet. ... more Side lobes of the wavelets arise from the lack of low frequency content in a reflection wavelet. They tend to increase the time span of an individual reflection event and interfere with the other primary reflections or side lobes. Furthermore, their trace-by-trace consistency may produce pseudo-reflections and may cause misinterpretations of the side lobes as weak reflections. A procedure in order to improve the low frequency content of the seismic traces by suppressing the side lobe amplitudes based on the complex trace envelope is proposed. Using the average energies of the seismic trace and its envelope, the polarity table of the trace is obtained and used to correct the phase of the envelope. The resultant trace is termed "side lobe reduced (SLR) trace". The method can be applied to the stack or migrated seismic data by a trace-by-trace basis. The only required parameter of the method is the moving average operator length which is used to calculate average energies of the input traces. In general, shorter operator lengths yield better results when the dominant frequency of the input increases. Results from synthetics and real seismic data sets show that the procedure improves the low frequency components of the input trace and side lobes in the output SLR trace are significantly suppressed. The method may be considered as a seismic amplitude attribute, which aids the interpreter to obtain the true seismic signature of the geological formations by removing the side lobes of the wavelet and restoring the low frequency components if the lower frequencies of deeper reflections are of primary concern.
ciesm.org
High resolution seismic reflection data were collected onboard R/V K. Piri Reis, research vessel ... more High resolution seismic reflection data were collected onboard R/V K. Piri Reis, research vessel of Dokuz Eylül University, in Sigacik Gulf (Seferihisar-Izmir) and surrounding regions in August-2005. On 17 October 2005, a series of earthquakes occurred in the same area just two months after the cruise. Seismic cross-sections indicate fault zones which probably caused earthquake series.
Marine geology, Jan 1, 2007
High-resolution acoustic data indicate that sediment erosion is a significant process in the cont... more High-resolution acoustic data indicate that sediment erosion is a significant process in the continental slope of Yeşilırmak River Fan, occurring both related to the submarine canyons and in the open continental slope. The sediment processes observed along the slope consist of sliding and debris flows on the canyon walls together with the recent erosional surfaces at the canyon heads wherever the canyons exist, and slides and related scarp features structurally controlled by rotational faults in the central part of the open continental slope.
Turkish Journal of Earth Sciences (Turkish J. …, Jan 1, 2009
Some strong reflections about 3 to 5 m thick were observed at depths of 25-60 metres below the se... more Some strong reflections about 3 to 5 m thick were observed at depths of 25-60 metres below the sea floor using deeptowed, 5 kHz subbottom profiler data in the Turkish shelf and upper slope of the Eastern Black Sea at water depths of 250 to 700 m. Strong reflections of this kind are generally attributed to shallow and localized gas accumulations. We, however, observed that the reflection polarity of these strong reflections was positive, suggesting that they do not correspond to reflections from the upper boundary of a possible gas front. In this study, we evaluate these reflections to determine if they represent hydrogen sulphide-rich shallow gas hydrate layers, which would be an unusual gas hydrate occurrence in a shallow marine environment.
Turkish Journal of Earth …, Jan 1, 2002
The Black Sea is one of the largest inland seas in the world. Off the shelf, the water depth quic... more The Black Sea is one of the largest inland seas in the world. Off the shelf, the water depth quickly plunges to an average depth of 2 km. The Black Sea sediments are rich in calcite and organic carbon, the latter showing a high degree of preservation due to anoxia in the waters below 100-150 m. Slope failures and sediment instability related to immense gas and gas hydrate accumulations are serious problems that can lead to the failure of offshore installations. Marine geophysical surveys have been carried out in the Eastern Black Sea basin using state-of the-art technology to produce sonar and high-resolution maps. A number of prominent structures were detected in the area such as slumping, sliding, pockmarks, faults and dome-like structures. In the Turkish near shore and the abyssal plain, shallow gas accumulations have been detected and are continuous about 25-65 m beneath the seafloor. The gas-bearing strata appear as bright spots and cloudy spots, sometimes pockmarks and acoustic blanking. The sediments on the Turkish shelf contain certain concentrations of gas which can seep to the seabed surface and generate pockmarks. Gas-hydrate layers in the sediments often appears as dark and strong reflection pockets on sub-bottom profiler records.
Journal of the Balkan Geophysical Society, Jan 1, 2003
A theoretical and a field study were performed for the interpretation of the vertical component m... more A theoretical and a field study were performed for the interpretation of the vertical component magnetic anomalies from dipping dike model with infinite depth extent. Damped least squares inverse solution, Hilbert transform and power spectrum methods were used in interpretation. The parameters affecting the power spectrum of the analytical model response were determined and discussed. Damped least squares inverse solution, Hilbert transform and power spectrum methods were examined on a theoretical anomaly of a magnetic dike model. The methods were then applied to a magnetic field anomaly from northeastern Turkey to obtain the dike parameters. Only the depth of the dike can be obtained in the power spectrum method, but it is also possible to find out the width of the structure if the slope of the dike is known. In the inversion method, it is possible to obtain all the dike parameters. The depth, width and the location of the origin of the dike can be obtained by Hilbert transform method. It was observed that the results obtained from all of the three methods are evidently consistent with each other.
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Papers by Derman Dondurur