• Title, Summary, Keyword: 울릉분지

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Distribution and Origin of Quaternary Mass Transport Deposit in the Ulleung Basin, East Sea (동해 울릉분지 제 4기 질량류 퇴적체 분포 및 기원)

  • Yi, Young-Mi;Yoo, Dong-Geun;Kang, Nyeon-Keon;Yi, Bo-Yeon
    • Geophysics and Geophysical Exploration
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    • v.17 no.2
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    • pp.74-87
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    • 2014
  • Analysis of multi-channel seismic reflection profiles collected from the Ulleung Basin reveals that the Quaternary sequence consists of four stratigraphic units separated by erosional unconformities. Individual stratigraphic unit includes eighteen mass transport deposits which are variable in geometric characteristics and spatial distribution. Each mass transport deposit on the seismic profile is acoustically characterized by chaotic or transparent seismic facies, and shows wedge or lens-shaped external geometry. The mass transport deposits, which comprise a succession of stacked wedges, mainly occur on the southern slope, and their thickness gradually decreases toward the basin plain. The time structure map of erosional unconformities shows that a tectonic-induced structural high and troughs toward the northwest and northeast are developed at the central part of the basin. Based on the isochron map, the mass transport deposits, originated from southern part of the study area, transported to the basin plain and can be divided into two groups by the structural high. Consequently, the mass transport deposits within the Quaternary sequence in the Ulleung Basin are largely controlled by the large amounts of sediment supply, dissociation of gas hydrate during the lowstands, and central structural high.

Muti-variable Sequence Stratigraphic Model and its Application to Shelf-Slope System of the Southwestern Ulleung Basin Margin (다중변수 순차층서 모델 개발을 통한 울릉분지 남서부 대륙주변부의 층서연구)

  • Yoon Seok Hoon;Park Se Jin;Chough Sung Kwun
    • The Korean Journal of Petroleum Geology
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    • v.5 no.1_2
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    • pp.36-47
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    • 1997
  • This study presents multi-variable sequence model for a broader application of sequence concept proposed by Exxon group. The concept of the multi-variable model is based on the fact that internal organization and boundary type of the sequences are determined by three varying factors including 3rd-order cycles of eustasy, and tectonic movement and sediment influx with 2nd-order changes. Instead of Exxon group's systems tracts, this model adopts parasequence sets as the fundamental building blocks of the sequence, because they are descriptive stratigraphic units simply defined by internal stacking pattern, reflecting interactions of accommodation and sediment influx. Seven sequence types which vary in number and type of internal parasequence sets are formulated as associations of four types of accommodation development and three grades of sediment influx. In the southwestern margin of Ulleung Basin, the multi-variable sequence analysis of shelf-slope sequence shows systematic changes in stratal patterns and the numbs, of constituent parasequence sets (i.e. sequence type). These changes are interpreted to reflect temporal and spatial changes in type and rate of tectonic movement and sediment influx, as a result of back-arc opening and closing. During the back-arc opening, rapid subsidence, continuous rise of relative sea level, and high sediment influx gave rise to sequences dominantly of single progradational parasequence set. In the early stage of back-arc closing accompanied by local contractional deformation, different types of sequences contemporaneously formed depending on the spatial changes in tectonically-controlled accommodation and influx rates. During the subsequent slow back-arc subsidence, rise-dominated relative sea-level cycle was coupled with moderate to high sedimentation rate to have resulted in sequences consisting of $2~3$ parasequence sets.

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A Study on the Geophysical Characteristics and Geological Structure of the Northeastern Part of the Ulleung Basin in the East Sea (동해 울릉분지 북동부지역의 지구물리학적 특성 및 지구조 연구)

  • Kim, Chang-Hwan;Park, Chan-Hong
    • Economic and Environmental Geology
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    • v.43 no.6
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    • pp.625-636
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    • 2010
  • The geophysical characteristics and geological structure of the northeastern part of the Ulleung Basin were investigated from interpretation of geophysical data including gravity, magnetic, bathymetry data, and seismic data. Relative correction was applied to reduce errors between sets of gravity and magnetic data, obtained at different times and by different equipments. The northeastern margin of the Ulleung Basin is characterized by complicated morphology consisting of volcanic islands (Ulleungdo and Dokdo), the Dokdo seamounts, and a deep pathway (Korea Gap) with the maximum depth of -2500 m. Free-air anomalies generally reflect the topography effect. There are high anomalies over the volcanic islands and the Dokdo seamounts. Except local anomalous zones of volcanic edifices, the gradual increasing of the Bouguer anomalies from the Oki Bank toward the Ulleung Basin and the Korea Gap is related to higher mantle level and denser crust in the central of the Ulleung Basin. Complicated magnetic anomalies in the study area occur over volcanic islands and seamounts. The power spectrum analysis of the Bouguer anomalies indicates that the depth to the averaged Moho discontinuity is -16.1 km. The inversion of the Bouguer anomaly shows that the Moho depth under the Korea Gap is about -16~17 km and the Moho depths towards the Oki Bank and the northwestern part of Ulleung Island are gradually deeper. The inversion result suggests that the crust of the Ulleung Basin is thicker than normal oceanic crusts. The result of 20 gravity modeling is in good agreement with the results of the power spectrum analysis and the inversion of the Bouguer anomaly. Except the volcanic edifices, the main pattern of magnetization distribution shows lineation in NE-SW. The inversion results, the 2D gravity modeling, and the magnetization distribution support possible NE-SW spreading of the Ulleung Basin proposed by other papers.

3D Seismic Data Interpretation of the Gorse II Area, Block VI-1, Offshore Southeast Korea (한국 대륙붕 VI-1광구 고래 II지역의 3D탄성파 자료해석)

  • Shin Kook Sun;Yu Kang Min;Kim Kun Deuk;Um Chang Lyeol
    • The Korean Journal of Petroleum Geology
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    • v.5 no.1_2
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    • pp.27-35
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    • 1997
  • The Gorae II area is located in the southwestern margin of the Ulleung Basin, East Sea and corresponds to the Ulleung Trough. The survey of 3D seismic data in this area was performed to delineate the structural leads confirmed by the previous 2D seismic data. As a part of 3D interpretation, basement related structural movements and their relationship with the stratigraphy were studied. The study shows that eight sequences were identified which are genetically related to the tectonics and sediment supply in this area. The geologic structures characterizing the study area consist of : (1) block faults developed in the early stage of basin opening, (2) late Miocene thrusts, and (3) Pliocene wrench faults. The eight sequences consist of pre-rift (acoustic basement), syn-rift (Sequence $A_1, A_2$), post-rift (Sequence $B_1{\~}B_3$), syn-compressional sequence (Sequence C), and post-compressional sequence(Sequence D) from oldest to youngest. The time structure and isochron maps were constructed for each sequence and also used in seismic facies analysis and interpretation of sedimentary environment. The interpretation results reveal that the relative sea level changes caused by several stages of tectonic movements and sediment supply control the stratal and structural geometry of Ulleung basin.

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Characteristics of Physical Properties in the Ulleung Basin (울릉분지 내의 물리적 특성)

  • Kim, Kuh;Kim, Kyung-Ryul;Chung, Jong-Yul;Yoo, Hong-Sun;Park, Sang-Gap
    • 한국해양학회지
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    • v.26 no.1
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    • pp.83-100
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    • 1991
  • A layer of salinity-minimum which characterizes the East Sea intermediate Water (ESIW) is found at an approximate depth of 200 m in three CTD section taken in the Ulleung Basin on May 17-21, 1988. Properties at this layer vary in ranges of $1.1^{\circ}C except at stations near the east coast of Korea where temperature is as high as $4.39^{\circ}C$ and salinity is as low as $33.992{\textperthousand}$. To be distinguished from the ESIW the East Sea Proper Water (ESPW) may be characterized by temperature less than $1^{\circ}C$, Salinity at the saliently-minimum layer and 500db increases southward in general, implying that the cold waters, both ESIW and ESPW, formed in the northern basin of the East Sea are spreading southward below the permanent thermocline in the basin. Hydrography in the Ulleung Basin is very similar to that in the Alboran Sea, suggesting a possibility of an anticyclonic circulation in the Ulleung Basin which is controlled strongly by the shoaling bottom.

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Tectonic Structure Modeling around the Ulleung Basin and Dokdo Using Potential Data (포텐셜 자료를 이용한 울릉분지와 독도 주변 지체구조 연구)

  • Park, Gye-Soon;Park, Jun-Suk;Kwon, Byung-Doo;Kim, Chang-Hwan;Park, Chan-Hong
    • Journal of the Korean earth science society
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    • v.30 no.2
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    • pp.165-175
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    • 2009
  • The East Sea including the area of this study is identified as a typical back-arc sea located in the backside of the Circum-Pacific volcanic and earthquake belt. Previous studies reported that the East Sea has begun to open by tensile force and formed its current shape. In this study, we investigate the regional tectonic structure of the East Sea using ship-borne gravity, magnetic, and satellite gravity data. The result of three-dimensional depth inversion shows that Moho depth of the study area is approximately 13-25km and inversely proportional to the thickness of the crust. In addition, as approaching to the center of the Ulleung Basin (UB), the thickness of the crust of the UB becomes thinner due to the extension caused by tensile force which had opened the East Sea.

Geological and Geochemical Studies on the Late Quaternary Sedimentary Environment of the Southwestern Ulleung Basin, East Sea. (울릉분지 남서부 해역의 제4기 후기 퇴적환경에 대한 지질${\cdot}$지화학적 연구)

  • 김일수;박명호;이영주;류병재;유강민
    • Economic and Environmental Geology
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    • v.36 no.1
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    • pp.9-15
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    • 2003
  • Two piston cores, obtained from the southwestern Ulleung Basin in East Sea, were analyzed to study the geochemical characteristics of the late Quaternary sediments and to detect any changes in sedimentary environment. The results show that the capacity of Total Organic Carbon is remarkably higher (average 1.8%) than that known from general open-sea. According to tephrochronology from known eruption ages, the sedimentation rates are high, ranging from 12.1 to 14.9 cm/kyr. The ratios of nitrogen and TOC (average 6.18-7.42) imply that the organic matter in the study area would be of oceanic origin. The correlation between sedimentation rates and sulfur contents suggests that the study area may be on the whole anoxic and somewhat high in primary productivity. During the Termination 1, inflows of organic matters were high. The sedimentary environments are characterized by rapid rates of sedimentation, and high anoxic values were compatible with accumulation of organic matters.

Numerical Analysis on Flow Behavior of Gas Hydrate Bearing Sediments in the Ulleung Basin, East Sea of Korea (동해 울릉분지 가스하이드레이트 퇴적층의 해리 유동 전산 분석 연구)

  • Kim, Ji-Su;Lee, Rok-Sang;Lim, Jong-Se;Kim, Se-Joon
    • Journal of Energy Engineering
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    • v.23 no.3
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    • pp.102-115
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    • 2014
  • In the Ulleung basin in the East Sea of Korea, it is assumed that huge amounts of gas hydrate(GH) are buried. In 2010, drilling operation was performed at the 2nd Ulleung Basin Gas Hydrate Drilling Expedition(UBGH2) to designate a site for field production test. In this study, based on the field production test site model reflecting geological properties, GH dissociation flow interpretation is analyzed and sensitivity analysis is performed to gain understanding of production behavior properties following bottomhole pressure(BHP) variation by using the numerical simulation. The results of this study provide a basis for the preliminary analysis of field production test site.

Seismic Sequence Stratigraphy in the Southwestern Margin of the Ulleung Basin, East Sea (울릉분지 남서연변부의 탄성파 시퀀스 층서분석)

  • CHOI Dong-Lim
    • The Korean Journal of Petroleum Geology
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    • v.6 no.1_2
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    • pp.1-7
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    • 1998
  • A multichannel seismic profile from the southwestern margin of the Ulleung Basin, East Sea, was analysed in detail to interpret the middle to late Miocene sequence stratigraphic evolution of the area. A regressive package is overlying a transgressive package which, in turn, is underlain by older uplifted and deformed sedimentary layers. A prominent condensed section separates the regressive and transgressive packages. The transgressive package is characterized by onlapping onto the underlying uplifted and deformed strata. The regressive package contains six prograding sequences composed of seismically resolvable lowstand, highstand, and transgressive systems tracts. Most of the depositional sequences comprise lowstand systems tracts consisting of basin-floor fan, slope fan, and prograding complex. Potential reservoirs in the regressive package are turbidite sands in basin-floor fans, channel-fill sands and overbank sand sheets in slope fans, and incised valley-fill sands in the shelf. The shallow marine sands in transgressive packages are another type of reservoir. Detailed sequence stratigraphic analysis, seismic data reprocessing, and 3-D seismic survey are suggested for the successful hydrocarbon exploration in the study area.

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Velocity Anisotropy of Unconsolidated Sediment in the Ulleung Basin, East Sea (동해 울릉분지 미고결퇴적물의 속도비등방성)

  • 김길영;김대철
    • The Journal of the Acoustical Society of Korea
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    • v.20 no.4
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    • pp.87-93
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    • 2001
  • Velocity anisotropy of unconsolidated sediments in the Ulleung Basin, East Sea were studied by using 22 piston cores. Velocity anisotropy shows about 0.4 and 1.2% in the Plain and Slope sediments, respectively. Horizontal velocity is greater than vertical velocity. It is resulted in positive anisotropy. Thus, bedding must be regarded as the principal cause of acoustic anisotropy in the Ulleung Basin sediments. The differences of the value are different from 5 m/s to 18 m/s in the Plain and Slope area, respectively. The relationships between physical properties and velocity anisotropy are clearly grouped. This result suggests that the slope sediments are probably affected by sedimentological (esp. physical properties) changes resulting from diagenesis.

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