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- 저자 : Horozal, Senay (검색결과 10 건)
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Horozal, Senay,Kim, Gil Young,Bahk, Jang Jun,Wilkens, Roy H.,Yoo, Dong Geun,Ryu, Byong Jae,Kim, Seong Pil Elsevier 2015 Marine and petroleum geology Vol.59 No.-
<P><B>Abstract</B></P> <P>We analyzed the data consist of core digital images and X-rays, core-logs, LWD (logging-while-drilling), and sediment grain-size from the second Ulleung Basin Gas Hydrate Expedition (UBGH2) in the East Sea. Core digital images and X-rays were spliced as a complete composite core in meters below seafloor (mbsf) for five sites; UBGH2-1_1 (Hole D), 2_1 (B), 2_2 (B), 2-6 (B) and 2-10 (C–D), and were correlated with the core-log and LWD measurements showing that possible gas hydrate bearing layers are between the depths of about 60–180 mbsf at these sites. Bulk densities generally increase with depth from 1.3 to 2.0 g/cm<SUP>3</SUP> in LWD data, and from 1.1 to 1.8 g/cm<SUP>3</SUP> onboard which measured lower than in-situ. Gas hydrate bearing sediments respond with an increase of LWD densities (1.4–1.6 g/cm<SUP>3</SUP>) and a decrease in core-logs (1.1–1.4 g/cm<SUP>3</SUP>). P-wave velocity values of LWD increase (1400 to 1700 m/s) with depth for non-reservoirs, and are high (1500 and 2000 m/s) within the gas hydrate bearing intervals depending on the hydrate saturations.Resistivity values logged onboard range from less than 1.0 to over 10.0 Ω-m, while LWD records are around 1.0 Ω-m and between 5.0 and 30.0 Ω-m in background sediments and possible gas hydrate reservoirs, respectively. High resistivity values were observed (5.0–30.0 Ω-m) within coarse-grained turbidites (mean grain-size between 2.9 and 5.1 ϕ; laminated sandy mud or muddy sands). Medium resistivities were observed (5.0 Ω-m) within the silt-dominant hemi-pelagic and turbiditic sediments (5.1–7.4 ϕ; crudely laminated, bioturbated, homogeneous sand, and disintegrated sand and sandy mud facies) bearing pore-filling gas hydrates, or disseminated gas hydrates either formed in pores or small fractures of fine-grained sediments. Core-log measurements are highly fluctuating and sensitive but mostly lower (e.g., density and resistivity) than LWD records.</P> <P><B>Highlights</B></P> <P> <UL> <LI> UBGH2 (the Ulleung Basin Gas Hydrate Expedition 2) was performed. </LI> <LI> Digital images and X-rays of gas hydrate bearing-sediments were examined. </LI> <LI> Core image data and LWD log data were compared and studied. </LI> <LI> We suggest the relationships between gas hydrate occurrences and lithological conditions and physical properties. </LI> </UL> </P>
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Seismic stratigraphy and structural analysis of the western South Korea Plateau (WSKP), East Sea
Cukur, D.,Kim, S.P.,Horozal, S.,Ryu, B.J.,Kim, G.Y.,Kong, G.S. Pergamon Press 2015 Quaternary international Vol.384 No.-
The western South Korea Plateau (WSKP), situated on the southwestern part of East Sea, is characterized by rifted continental fragments that were formed in the early phase of back-arc opening. In this work, we analyze multi-channel seismic reflection profiles from the WSKP to document the structural and stratigraphic framework of the area. We also present fault-derived stretching (beta) factors related to the continental rifting along two regional seismic profiles. Our data reveal several graben and half graben subbasins, up to 1300 m thick, bound by N-S trending normal faults. We show that, on the basis of constructed isopach maps, tectonic activity was the main controlling factor on the sedimentation through much of the plateau history. The seismic data reveal that the sedimentation history of the WSKP is characterized by four main phases (Phase 1 to Phase 4; P1-P4) separated by regional unconformities. Rapid extension and subsidence took place at an early stage of P1 leading to the graben and half-graben openings. Volcanic activity was widespread at early times and ~700 m thick succession of lacustrine and fluvial sediments was deposited. Following P2 (early mid Miocene - latest Miocene), dramatic extension and subsidence changed the lacustrine environment into marine, enabling to the deposition of thick marine sediments (~750 m) over the subbasins. Extension ceased during P3 (latest Miocene - early Pliocene) and less pronounced subsidence continued. At this time, the sedimentation was uniform over the area and included the cyclic succession of hemipelagic deposits and turbidites which were probably expressed by climatic forcing. P3 was interrupted by regional compression, when normal fault movement was reversed and gentle anticlines formed as a result of inversion. The latter was accompanied by widespread uplift and erosion along the western margin of the plateau, and substantial erosion took place on the crests of the folds. The uplift also shifted the main depocenters of the plateau which were ultimately filled by thick mass-transport deposits during the following phase of P4 (early Pliocene - Holocene). Subsidence has been dominant in the area since the beginning of P4, which was locally interspersed by inversion along the reactivated normal faults. Total upper-crust (βf) and whole-crust extension (βc) estimates in the WSKP show similarities, suggesting that the observed rift structure in WSKP has resulted from uniform pure-shear stretching.
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Roger Urgeles,박장준,이상훈,Senay Horozal,Deniz Cukur,김성필,김길영,정승원,엄인권 한국지질과학협의회 2019 Geosciences Journal Vol.23 No.3
In this study we use a scenario-based approach to highlight potential tsunami hazard from actual Late Pleistocene submarine landslides in the Ulleung Basin: two submarine landslides on the western slope of the Ulleung Basin, north and south of the Hupo Bank (2.53 and 1.12 km3 respectively) and a landslide (15.1 km3) on the continental slope south of the Ulleung Basin. The simulations attempt to highlight the consequences, should one of these events occur at Present. Results of the simulations indicate potential local hazard zones with very local waves < 2 m high in the Korean coast of the East Sea that could result from midsized landslides, not exceeding 3 km3 on the western slope of the basin. Time available for early warning since onset of these events is between 15–30 minutes. On the other hand, the continental margin south of the Ulleung Basin is an area where landslide tsunamis with significant hazard potential could originate. New landslides of similar size to those of the Late Pleistocene could produce tsunami waves > 3 m in the stretch of coastline from Ulsan in the south to Uljin in the north. The timing available for early warning from landslide tsunamis originating in this area is 15–30 minutes along the affected section of the shoreline. We also suggest a Probabilistic Tsunami Hazard Assessment (PTHA) for comprehensive assessment of the Korean coast of the East Sea. PTHA accounts for uncertainties in location, release mechanisms, evolution, and return periods of submarine landslides as well as epistemic uncertainty. However, to constrain these uncertainties detailed information on source areas, recurrence period and dynamics of submarine landslides is necessary and calls for additional data collection and further studies.
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이상훈,주형태,박장준,전형구,문성훈,김한준,Senay Horozal,Deniz Cukur,엄인권,유동근,Roger Urgeles 한국지질과학협의회 2021 Geosciences Journal Vol.25 No.2
In the western margin of the Ulleung Basin, a detailed analysis of cores with geophysical data from a fan-shaped body, just downslope of a submarine gully associated upslope with failure scars, reveals various modes of mass-transport processes. The arcuate failure scars occurs in water depths exceeding 600 m. The fan-shaped body, less than ca. 10 km long in radius, displays strong backscatter intensity in sonar images, and corresponds to the uppermost transparent mass in Chirp sub-bottom profiles. Sediment cores penetrating to the uppermost transparent mass consist mostly of various facies of mass-transport deposits (MTDs), causing the strong back-intensity in the sonar images. The interval of MTD facies comprises the upper and lower units without hemi-pelagic muds between them, implying that the fan-shaped body was probably deposited during a single event separated in at least two stages without a significant time break. The lower unit shows brittle to plastic deformation of soft muds (slides/slumps), whereas the upper units exhibits fully fragmented soft mud clasts (low viscous debris flows). Both the upper and lower units involve same original lithology (i.e., soft hemi-pelagic mud) prior to failures, suggesting that the lithology could not significantly affect depositional processes. The fully fragmented soft mud clasts of the upper unit are probably indicative of more shearing than the brittle to plastic deformation of soft muds in the lower unit. Considering the small dimension of the failure scars/gully and the same original lithology, the more shearing of the upper unit was most likely caused by longer transport distance than that of the lower unit. The rare turbidites with absence of channellevee systems in the fan-shaped body and the failure scars confined in the upper to middle slopes suggest that the submarine gully probably formed by slope failures, not by erosion of turbidity currents.
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Cukur, Deniz,Um, In-Kwon,Bahk, Jang-Jung,Chun, Jong-Hwa,Horozal, Senay,Kim, So-Ra,Kong, Gee-Soo,Kim, Kyong-O.,Kim, Seong-Pil Elsevier 2018 Marine and petroleum geology Vol.98 No.-
<P><B>Abstract</B></P> <P>The northeastern continental margin of Korea in the East Sea (Japan Sea) is a narrow sedimentary apron 20–30 km wide, 50–1300 m below sea level, with an average gradient of less than 2°. The present study focuses on seismic stratigraphy of the sedimentary section and the underlying basement structure of the margin based primarily on multi-channel seismic reflection profiles. Major accumulation of sediment is centred in a graben depocenter in the northern part of study area, where more than 2 km of sediments have been deposited. This graben widens towards north and is flanked by two major basement bounding faults. The sedimentary succession of the margin can be divided into six seismic stratigraphic units based on reflection character, onlapping, and erosional truncation. The lowermost seismic unit (SU1) is characterized by parallel-to subparallel-reflections with varying amplitudes and is interpreted to be representing shallow-to non-marine sediments that were deposited during the active extensional phase of margin development. The presence of erosional channels in the uppermost section of SU1 further suggests a lowstand period after the deposition of SU1. Unconformably overlying the SU1 is a few hundred metres of SU2 that is characterized by continuous, high-amplitude reflections. Continuous seismic reflections within SU2 are indicative of sea level rise immediately following the lowstand period. The overlying seismic unit sets include SU3, SU4, and SU5 with well-stratified seismic reflections. The consistent reflection pattern and high continuity of the reflections within these units are indicative of relatively stable depositional environments within the margin. Hemipelagic sediments and turbidites are probably the main components of these units. The youngest seismic unit SU6 comprises well-stratified seismic reflections in the upper slope and chaotic-to transparent-seismic reflections in the lower slope. The sedimentary units characterized by well-stratified seismic reflections are typical for hemipelagic slope sediments while chaotic seismic reflections are diagnostic features for mass-transport sediments (MTDs; i.e., slides/slumps, debris-flow deposits). The preferential occurrence of MTDs adjacent to the major faults suggests that they may be due to earthquakes associated with tectonic activity.</P> <P>Seismic reflection data from the margin reveal the coexistence of four structural styles including the basement-involved normal faults, reverse faults, reactivated normal faults, and anticline folds. The basement-bounding normal faults are associated with the initial extension of the continental margin while the others are postulated as resulting from contractional tectonism of the eastward movement of the Amur Plate that began in the early Pliocene. The prominent seafloor erosion over the folded/inverted blocks further suggests that inversion continues today.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A tectonostratigraphic framework for the northeastern margin of Korea is developed. </LI> <LI> Six seismic units have been defined in analysis of the seismic reflection profiles. </LI> <LI> Primary deposits consist chiefly of hemipelagites interbedded with turbidites. </LI> <LI> Basement structure and seismic stratigraphy suggest a rift origin for the margin. </LI> <LI> Regional compression in the Pliocene reactivated the earlier extensional faults. </LI> </UL> </P>
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Cukur, D.,Kim, S. P.,Kong, G. S.,Bahk, J. J.,Horozal, S.,Um, I. K.,Lee, G. S.,Chang, T. S.,Ha, H. J.,Vö,lker, D. Springer Science + Business Media 2016 Geo-marine letters Vol.36 No.6
<P>Submarine landslides form very complex depositional and erosional features on the seafloor, and their dynamics and triggering processes are yet to be understood completely. Numerous studies are being undertaken both because of the scientific significance but also for their potential harm to seafloor infrastructure and coastal areas. This study investigates the styles and causes of landsliding along the western margin of the Ulleung Basin in the East Sea, based on multiple sparker, subbottom profiler, multibeam echosounder and sediment core datasets collected in 2015. The bathymetric analyses indicate that the southern slope of the Ulleung Basin has experienced at least seven submarine failures. These failures left clear arcuate-shaped scarps that initiated at water depths of similar to 600 m. The observed headwall scarps have heights that exceed 60 m and appear to be the result of retrogressive-type failures. Seismic reflection data clearly image the basal sliding surface that is characterized by a prominent high-amplitude reflector. Chaotic-totransparent seismic facies occur immediately downslope of the headwall scarps; these represent similar to 20 m thick landslide deposits. Gravity cores taken from areas adjacent to the scars suggest that these slides are older than ca. 97 ka. Interpretation of the present data shows that faults appear to cut recent sediments upslope of scarps, and that the slope may still be in an active phase of failure. Seismic data also image various overpressurized gases and/or gas fluids, as evidenced by the occurrence of pockmarks and seismic chimneys in upslope or adjacent areas of the scarps. Hence, earthquakes associated with tectonic activity and development of fluid overpressure may have acted as the main conditioning factor for destabilizing the slope sediments. Geotechnical stability analyses indicate that the sampled slope sediments are exceptionally stable under present-day conditions, even under seismic loading. This finding points to additional forces such as excess pore pressure caused by gas fluids at the times of slide emplacement.</P>
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Efficient hydrogen generation from the NaBH4 methanolysis by waste material: banana peel
Elma Karakaş Duygu,Kaya Mustafa,Horoz Sabit 한국탄소학회 2022 Carbon Letters Vol.32 No.6
The aim and originality of our current study are to use the original biomass (activated carbon) obtained by functionalizing waste banana peels (commonly found in Turkey) with acid in NaBH4 methanolysis and to examine its contribution to the hydrogen generation rate (HGR). Our study consisted of three stages. In the first stage, the optimum conditions were determined by examining the catalyst under parameters such as different acid types, different carbonization temperatures, and different carbonization times. Thus, based on the maximum HGR value, the optimum conditions were determined as H3PO4, 600 °C, and 40 min. In the second step, the effects of parameters such as acid concentration, NaBH4 concentration, catalyst amount, and temperature on HGR were investigated. As a result of methanolysis experiments (condition: catalyst amount: 100 mg, acid amount: 30%, NaBH4 concentration: 2.5%, temperature: 30 °C, carbonization temperature: 400 °C, and carbonization time: 40 min.), the maximum HGR value, the reaction completion time and activation energy were found as 65,625 mLmin−1gcat−1, 0.233 min, and 4.56 kJ/mol, respectively. It was observed that the obtained activation energy was lower than that of some catalysts available in the literature. In addition, the structural and morphological examination of the banana peel (catalyst) with high HGR and low activation energy revealed that the acid functionalization process was successfully carried out.
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