• Journal of the Geological Society of Korea
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• v.54 no.6
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• pp.631-640
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• 2018

To understand the formation and evolution of a sedimentary basin in basin analysis and modelling studies, it is important to analyze the thickness and age range of sedimentary layers infilling a basin. Because the compaction effect reduces the thickness of sedimentary layers during burial, basin modelling studies typically restore the reduced thickness using the relation of porosity and depth (compaction trend). Based on the compilation plots of published compaction trends of representative sedimentary rocks (sandstone, shale and carbonate), this study estimates the compaction trend ranges with exponential curves and equations. Numerical analysis of sedimentary compaction is performed to evaluate the variation of porosity and layer thickness with depth at key curves within the compaction trend ranges. In sandstone, initial porosity lies in a narrow range and decreases steadily with increasing depth, which results in relatively constant thickness variations. For shale, the porosity variation shows two phases which are fast reduction until ~2,000 m in depth and slow reduction at deeper burial, which corresponds to the thickness variation pattern of shale layers. Carbonate compaction is characterized by widely distributed porosity values, which results in highly varying layer thickness with depth. This numerical compaction analysis presents quantitatively the characteristics of porosity and layer thickness variation of each lithology, which influence on layer thickness reconstruction, subsidence and thermal effect analyses to understand the basin formation and evolution. This work demonstrates that the compaction trend is an important factor in basin modelling and underlines the need for appropriate application of porosity data to produce accurate analysis outcomes.

• Proceedings of the Korea Water Resources Association Conference
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• 2023.05a
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• pp.220-220
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• 2023

단순한 하상 변동 모형은 단일한 입경으로 구성된 하상재료를 다루는 데에 비해, 실제 하천에서는 다양한 입경의 유사가 섞여있다. 이러한 혼합 입경의 유사 이송을 모의하고자 하면 퇴적층의 생성과 소멸을 어떻게 모의하는지에 대한 기법이 중요해진다. 과거 연구에서는 유수의 영향을 받는 하상 두께가 입도 분포에 따라 다르다고 생각하였다. 반면, 다른 연구들에서는 두께가 합리적인 범위 내에 있다면 모의 결과에 영향을 미치지 않는다고 보고 상수로 설정하였다. 퇴적층의 개수를 어떻게 고려하느냐에 따라서도 모의기법이 나누어진다. 단일한 입경을 모의하는 경우 단일 퇴적층을 고려하지만, 혼합 입경을 고려하는 모형은 크게 2개의 퇴적층(active layer와 non-active layer)으로 나누는 종류와 3개 이상의 퇴적층을 고려하는 모형으로도 나눌 수 있다. 이 연구에서는 혼합 입경의 유사 이송을 모의할 수 있는 전 지형 발달 모형을 활용하여 퇴적층 처리 기법의 차이가 얼마나 모의 결과에 영향을 주는지를 파악하였다. 모의 결과는 기법이 바뀜에 따라 매우 민감하게 변하는 것을 확인할 수 있었다. 또한 이 연구에서는 3개 이상의 퇴적층을 고려함에 있어서 기존 퇴적층에 새로운 물질이 퇴적되었을 때 경계면에서 입자가 섞이는 mixed layer를 고려하는 개념을 제시한다.

• Geophysics and Geophysical Exploration
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• v.10 no.1
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• pp.77-88
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• 2007

Following a successful bathymetric mapping demonstration in a previous study, the potential of airborne EM for seafloor characterisation has been investigated. The sediment thickness inferred from 1D inversion of helicopter-borne time-domain electromagnetic (TEM) data has been compared with estimates based on marine seismic studies. Generally, the two estimates of sediment thickness, and hence depth to resistive bedrock, were in reasonable agreement when the seawater was ${\sim}20\;m$ deep and the sediment was less than ${\sim}40\;m$ thick. Inversion of noisy synthetic data showed that recovered models closely resemble the true models, even when the starting model is dissimilar to the true model, in keeping with the uniqueness theorem for EM soundings. The standard deviations associated with shallow seawater depths inferred from noisy synthetic data are about ${\pm}5\;%$ of depth, comparable with the errors of approximately ${\pm}1\;m$ arising during inversion of real data. The corresponding uncertainty in depth-to-bedrock estimates, based on synthetic data inversion, is of order of ${\pm}10\;%$. The mean inverted depths of both seawater and sediment inferred from noisy synthetic data are accurate to ${\sim}1\;m$, illustrating the improvement in accuracy resulting from stacking. It is concluded that a carefully calibrated airborne TEM system has potential for surveying sediment thickness and bedrock topography, and for characterising seafloor resistivity in shallow coastal waters.

• The Journal of the Acoustical Society of Korea
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• v.27 no.2
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• pp.92-101
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• 2008

To dissolve the multi-layered model problems, and to complement 2-layered model's simplicity, assumed fluid-fluid-solid 3-layered model. Generally it is known that if the sediment thickness is more than 10 wavelength, the half space's influence to the in-water acoustic field could be disregarded. By tracking the maximum correlation coefficient of calculated results and experimental ones we confirmed that the requirement could be more realized. To calculate the maximum correlation coefficient we used single sensor transmission loss. On the assumption that the sediment sound velocity was 1813 m/s and frequency range 50 kHz to 120 kHz, the conversion condition was from 2.5 to 7.7 wavelength.

• The Journal of the Acoustical Society of Korea
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• v.29 no.4
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• pp.223-228
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• 2010

High-frequency bottom loss measurements for grazing angle of $82^{\circ}$ in frequency range 17-40 kHz were made in Jinhae bay in the southern part of Korea. Observations of bottom loss showed the strong variation as a function of frequency, which were compared to the predicted values using two-layered sediment reflection model. The geoacoustic parameters including sound speed, density and attenuation coefficient for the second sediment layer were predicted from the empirical relations with the mean grain size obtained from sediment core analysis. The geoacoustic parameters for the surficial sediment layer were inverted using Monte Carlo inversion algorithm. A sensitivity study for the geoacoustic parameters showed that the thickness of surficial sediment layer was most sensitive to the variation of the bottom loss.

• The Journal of the Acoustical Society of Korea
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• v.18 no.8
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• pp.32-41
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• 1999

In this paper, an inversion method using chirp signals and two near field receivers is proposed. Inversion problems can be formulated into the probabilistic models composed of signals, a forward model and noise. Forward model to simulate chirp signals is chosen to be the source-wavelet-convolution planewave modeling method. The solution of the inversion problem is defined by a posteriori pdf. The wavelet matching technique, using weighted least-squares fitting, estimates the sediment sound-speed and thickness on which determination of the ranges for a priori uniform distribution is based. The genetic algorithm can be applied to a global optimization problem to find a maximum a posteriori solution for determined a priori search space. Here the object function is defined by an L₂norm of the difference between measured and modeled signals. The observed signals can be separated into a set of two signals reflected from the upper and lower boundaries of a sediment. The separation of signals and successive applications of the genetic algorithm optimization process reduce the search space, therefore improving the inversion results. Not only the marginal pdf but also the statistics are calculated by numerical evaluation of integrals using the samples selected during importance sampling process of the genetic algorithm. The examples applied here show that, for synthetic data with noise, it is possible to carry out an inversion for sedimentary layers using the proposed inversion method.

• The Korean Journal of Quaternary Research
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• v.8 no.1
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• pp.23-32
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• 1994

고생대(폐름기)의 육성 퇴적층(옥갑산층) 일부분이 고기 우각호(ox-bow lake)에 서 퇴적된 것으로 해석된다, 옥갑산층의 하부층서의 일부분은 암회색 이암/담회색 사암의 호층 단위가 평균 5.1cm 두께로 약 80회반복하는 암상을 나타낸다. 이 암상의 퇴적환경은 층서적 상하 암상의 연합에 근거하면 해안 평야로서 하천 범람원 분지의 쇄설성 퇴적환경의 일부이 면서 사행천과 연관된 우각호 퇴적환경으로 해석된다.

• The Journal of the Acoustical Society of Korea
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• v.35 no.6
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• pp.419-426
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• 2016

Measurements of bottom loss as a function of grazing angle (in range of $9{\sim}14^{\circ}$) at a frequency range of 4 ~ 8 kHz were conducted on an experimental site off Geoje island in October 2015. Geoacoustic inversion of the surficial sediment thickness is performed using the arrival time difference between the surficial layer and the sub-bottom layer reflected signal. To invert the thickness of surficial sediment, we used the grain size of $8{\sim}10{\phi}$ obtained by KIGAM (Korea Institute of Geoscience and Mineral Resources). The thickness of the surficial sediment was estimated to be 4 ~ 7 m. Finally, this inversion result was compared with the geoacoustic observation conducted by the KIOST (Korea Institute of Ocean Science & Technology) using sub-bottom profiler.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2002.09a
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• pp.144-147
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• 2002

효과적인 국내 충적층 지하수의 이용을 위해서는, 충적 대수층의 내부 구조를 정밀하게 평가하여야 한다. 특히, 강변여과, 인공 침투지 등의 적극적인 충적 대수층의 활용을 위해서는 충적 대수층의 퇴적 환경에 대한 이해가 요구된다. 국내 충적층의 대부분은 하천 둔치 주변에서 하도의 수평 이동에 의해 형성된 경사 지층으로, 니질 박층이 협재하므로 내부의 분균일성에 의해 인접한 취수 공간에도 지하수체의 이동 특성 및 화학적 특성이 달라질 수 있다. 본 연구는 이러한 불균질성을 박히기 위해 지하투과레이다(GPR)를 이용하여 부여 군수리 지역의 천부 충적층에 대한 퇴적학적 분석을 시도하였다. 군수리 지역은 크게 상하 두 개의 충적층으로 구분되며, 상부 수평층은 범람에 의해 형성된 것으로 수직 불균질성이 크고 수평 불균질성은 낮다. 하부 경사층은 수평, 수직 불균질성이 모두 크다. 특히 하부 경사층내에 발달한 하도곡은 인접한 충적층과 분리되어 이 층내의 지하수체 이동은 제한적일 것이고 수질 특성 또한 크게 다를 것으로 판단된다. 본 연구는 충적 대수층에 대한 물리 화학적 특성의 정확한 해석을 위해서 퇴적학적 해석이 선행되어야 함을 시사한다.

• The Korean Journal of Petroleum Geology
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• v.3 no.1 s.4
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• pp.1-15
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• 1995

Seismic reflection profiles and exploratory drilling well samples from the southern marginal-continental shelf basin of Korea delineate that the Tertiary sedimentary sequences can be grouped into five sequences (Sequence A, Sequence B, Sequence C, Sequence D and Sequence E, in descending order). Paleontologic data, K-Ar age datings, correlation with tuff layers and sequence stratigraphic analysis reveal that the sequences A, B, C, D and E can be considered as the deposits of Holocene $\~$ Pleistocene, Pliocene, Late Miocene, Early $\~$ Middle Miocene and Oligocene, respectively. The sequence stratigraphic and structural analyses suggest that the southern part of the Cheju Basin had experienced severe folding and faulting. NE-SW trending strike-slip movement is responsible for the deformation. The sinistral movement of strike-slip fault ceased before the deposition of Sequence B. Age dating and rare-earth elements analysis of volvanic rocks reveal+ that the Sequence D was deposited during the Early $\~$ Middle Miocene and the Sequence I was deposited earlier than the deposition of the Green Tuff Formation. Sedimentary petrological studies indicate that sediments of the Sequence I came from the continental block provenance. After the deposition of the Sequence E, uplift of the source area resulted in increase of sediment supply, subsidence and volcanic activities. The Sequence D show these factors and the sediments of the Sequence D are considered to be transported from the recycled orogenic belt.