https://repository.kopri.re.kr/handle/201206/15861 2026-03-05T09:51:11Z 2026-03-05T09:51:11Z Park, Kwangkyu Khim, Boo-Keun Choi, Hyuk Shin, Kyung-Hun https://repository.kopri.re.kr/handle/201206/16593 2026-02-10T04:07:10Z 2025-05-01T00:00:00Z

Title: Organic carbon stocks of the surficial sediments in the territorial waters of Korea Authors: Park, Kwangkyu; Khim, Boo-Keun; Choi, Hyuk; Shin, Kyung-Hun Abstract: Shallow marine environments, including the continental shelf, are important in the global carbon cycle in which organic carbon is transported from land, produced within the ocean, and buried in sediments. The territorial waters of Korea (Republic of Korea) encompass predominantly shallow continental shelves. This study examined the organic carbon distribution of surficial sediments in the territorial waters of Korea to approximate the carbon stocks in the surficial sediments of the seafloor at a national scale. For the estimation, the reported data (mean grain size (MGS), total organic carbon (TOC) content, and dry bulk density) around the Korean Peninsula were documented and organized to evaluate the potential for carbon sequestration in the territorial waters of Korea. The distribution of the MGS and the TOC content in surficial sediments varied regionally according to the depositional processes, but they exhibited the typical characteristics of marine sediments whose TOC content increased as the MGS decreased. Among the four zones (A, B, C, and D) in the territorial waters of Korea, the estimated total carbon stock was highest (2.27×10^6 Mg C) in zone A and lowest (1.04×10^6 Mg C) in zone C, despite zone C having the highest carbon stock per unit area (1.64 Mg C/ha). However, for a precise assessment of long-term carbon stock and sequestration rates, more comprehensive and robust data along with representative sedimentation rates and the vertical profiles of the TOC content are essential at a national scale.

2025-05-01T00:00:00Z Jeong, Woodon Lee, Chanhee Kang, Seung-Goo https://repository.kopri.re.kr/handle/201206/16272 2025-10-30T05:59:40Z 2024-05-01T00:00:00Z

Title: Single-Channel Seismic Data Processing via Singular Spectrum Analysis Authors: Jeong, Woodon; Lee, Chanhee; Kang, Seung-Goo Abstract: Single-channel seismic exploration has proven effective in delineating subsurface geological structures using small-scale survey systems. The seismic data acquired through zero- or near-offset methods directly capture subsurface features along the vertical axis, facilitating the construction of corresponding seismic sections. However, substantial noise in single-channel seismic data hampers precise interpretation because of the low signal-to-noise ratio. This study introduces a novel approach that integrate noise reduction and signal enhancement via matrix rank optimization to address this issue. Unlike conventional rank-reduction methods, which retain selected singular values to mitigate random noise, our method optimizes the entire singular value spectrum, thus effectively tackling both random and erratic noises commonly found in environments with low signal-to-noise ratio. Additionally, to enhance the horizontal continuity of seismic events and mitigate signal loss during noise reduction, we introduced an adaptive weighting factor computed from the eigenimage of the seismic section. To access the robustness of the proposed method, we conducted numerical experiments using single-channel Sparker seismic data from the Chukchi Plateau in the Arctic Ocean. The results demonstrated that the seismic sections had significantly improved signal-to-noise ratios and minimal signal loss. These advancements hold promise for enhancing single-channel and high-resolution seismic surveys and aiding in the identification of marine development and submarine geological hazards in domestic coastal areas.; 단일 채널 탄성파 탐사는 소규모 자료획득 시스템으로 지하 지질구조를 파악하는 효과적인 방법이다. 영벌림거리 혹은 가까운 벌림거리를 사용하여 획 득한 단일 채널 탄성파 자료는 연직 방향의 지하 지질구조를 직접 반영하므로 탄성파 단면도를 효과적으로 작성할 수 있다. 그러나 공통중간점 중합 과정 을 적용할 수 없어 신호 대 잡음비가 매우 낮으므로 단면에 나타나는 반사 구조의 정밀한 해석에 있어 중합 단면 대비 불리함을 가진다. 본 연구에서는 단일 채널 탄성파 자료의 신호 대 잡음비를 향상시키기 위해 특이 스펙트럼 분석을 기반으로 한 잡음 제거 및 신호 향상 방법을 제안한다. 기존의 특이 스펙트럼 분석 방법은 행렬의 특정 특잇값을 임의로 추출하여 자료 내에 있는 무작위 잡음을 제거하는 방식으로 수행되었으나, 이는 낮은 신호 대 잡음비 나 이상 잡음이 있는 자료에 적용할 수 없다. 따라서 본 연구에서는 행렬의 특잇값을 최적화하고 저계수 근사를 수행하여 무작위 및 이상 잡음을 동시에 효과적으로 제거한다. 또한, 잡음 제거로 인한 신호 손실을 보정하고 탄성파 이벤트의 수평적 연속성을 향상시키기 위해 행렬의 고유 영상에 기반한 가중 치를 계산하여 탄성파 단면의 품질을 향상시킨다. 본 연구에서 제안하는 기술의 적용성 및 우수성을 확인하기 위해 북극해 척치해저고원에서 획득한 단 일 채널 스파커 탄성파 자료에 대한 자료 처리 실험을 수행하였으며, 수치 예제를 통해 매우 높은 수준의 신호 대 잡음비와 최소의 신호 손실을 가진 탄성 파 단면을 얻을 수 있었다. 본 연구에서 제안하는 단일 채널 탄성파 자료 처리 기술은 향후 국내 연안지역의 해양개발과 해저 지질재해를 규명하기 위한 단일 채널 및 초고해상도 탄성파 탐사에 매우 효과적으로 기여할 것으로 기대된다.

2024-05-01T00:00:00Z Kim Sumin Kang, Seung-Goo Choi, Yeonjin Hong, Jong Kuk Kwak Joonyoung https://repository.kopri.re.kr/handle/201206/16001 2025-08-21T02:28:26Z 2024-01-01T00:00:00Z

Title: Seismic Imaging of the Arctic Subsea Permafrost Using a Least-Squares Reverse Time Migration Method Authors: Kim Sumin; Kang, Seung-Goo; Choi, Yeonjin; Hong, Jong Kuk; Kwak Joonyoung Abstract: High-resolution seismic imaging allows for the better interpretation of subsurface geological structures. In this study, we employ least-squares reverse time migration (LSRTM) as a seismic imaging method to delineate the subsurface geological structures from the field dataset for understanding the status of Arctic subsea permafrost structures, which is pertinent to global warming issues. The subsea permafrost structures in the Arctic continental shelf, located just below the seafloor at a shallow water depth, have an abnormally high P-wave velocity. These structural conditions create internal multiples and noise in seismic data, making it challenging to perform seismic imaging and construct a seismic P-wave velocity model using conventional methods. LSRTM offers a promising approach by addressing these challenges through linearized inverse problems, aiming to achieve high-resolution, subsurface imaging by optimizing the misfit between the predicted and the observed seismic data. Synthetic experiments, encompassing various subsea permafrost structures and seismic survey configurations, were conducted to investigate the feasibility of LSRTM for imaging the Arctic subsea permafrost from the acquired seismic field dataset, and the possibility of the seismic imaging of the subsea permafrost was confirmed through these synthetic numerical experiments. Furthermore, we applied the LSRTM method to the seismic data acquired in the Canadian Beaufort Sea (CBS) and generated a seismic image depicting the subsea permafrost structures in the Arctic region.

2024-01-01T00:00:00Z Kim, Sumin Kang, Seung-Goo Choi, Yeonjin Chung W. https://repository.kopri.re.kr/handle/201206/16215 2025-10-27T04:53:48Z 2024-01-01T00:00:00Z

Title: Efficient extended least-squares reverse time migration based on an excitation amplitude imaging condition Authors: Kim, Sumin; Kang, Seung-Goo; Choi, Yeonjin; Chung W. Abstract: In least-squares reverse time migration (LSRTM), which is typically an overdetermined linear inverse problem, the kinematic traveltime error from an inaccurate migration velocity leads to migration image degradation and slow convergence speed. Extended LSRTM (ELSRTM), with an extended imaging condition along the subsurface offset in LSRTM, can effectively mitigate sensitivity to the migration velocity accuracy by adding an extra dimension to the model space. However, for assembling migration images, large imaging condition operations that are proportional to the number of subsurface-offset bins hinder the practical application of ELSRTM. To address this computational problem in ELSRTM, we develop an efficient ELSRTM method based on a modified excitation amplitude (ExA) imaging condition. Furthermore, our ELSRTM method can correctly represent the forward source wavefield by convolving the source wavelet with the ExA. With the forward source wavefield represented this way, Born-modeled data can be simulated efficiently. Thus, wavefield simulation for generating the forward source wavefield is implemented only once at the first iteration. Based on these computational advantages, our ELSRTM method becomes highly efficient. Synthetic data examples on a modified Marmousi2 velocity model demonstrate that our ELSRTM method produces an accurate migration image efficiently even if an inaccurate migration velocity is used. Field data acquired from the Chukchi Sea of the Arctic Ocean also are used to verify the practicality of our ELSRTM method.

2024-01-01T00:00:00Z