• Journal of the Korean Geophysical Society
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• v.9 no.4
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• pp.351-359
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• 2006

We investigated subsurface structures of the Bransfield Basin, the Antarctic with AUH (Autonomous Underwater Hydrophne) which was designed to record abyssal T-waves generated from submarine earthquakes. The data obtained from a multi-channel seismic survey and an AUH were used for this study. A seismic reflection method was applied to the multi-channel seismic survey data in order to identify bathymetry and sedimentary structures, and the signals recorded in the AUH were used to obtain deep structures as we applied a seismic refraction method. Even though we couldn’t investigate deeper and detailed structure in study area because of lack of Airgun’s capacity, the AUH showed possibilities for being used for a marine seismic survey. From this experiment, we decided the upper and lower sediment layer velocities, detected irregular basement topography probably caused by submarine volcanic/magmatic activities, and retrieved the velocity of the basement and the depth of the sediment layer/basement boundary.

• 한국지구물리탐사학회:학술대회논문집
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• 2003.11a
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• pp.449-454
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• 2003

The accurate mapping of the basement is one of the most crucial factors in construction of harbour facilities and bridges in the coastal areas. In shallow waters, the seismic reflection method often fails to image the basement geometry beneath the sediment cover in many cases. We present the result of a shallow marine seismic refraction survey using two ships, l2-channel hydrophone arrays deployed on the bottom and a borehole sparker or percussion powder as sources. Velocity structure could be computed by tomography algorithm since more than 6 different source points had been applied for one spread. The comparison of the results of the refraction survey with drilling logs demonstrates remarkable consistency in basement geometry. It thus appears that the refraction method in this study is an efficient and cost-effective way to investigate the basement structure in coastal area, river, and lake.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2023.05a
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• pp.393-394
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• 2023

This paper provides an overview of seismic design considerations for vertical construction joints of a slurry walls used as a permanent basement walls.

• Journal of the Korean Geophysical Society
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• v.9 no.3
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• pp.249-262
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• 2006

The 29 May 2004 offshore Uljin, Korea earthquake was predominantly thrust-faulting at a depth of approximately 12 (±2) km. The mainshock attained the seismic moment of M0 =5.41 (±1.87)  1016 N m (Mw = 5.1). The focal mechanism indicates a subhorizontal P-axis trending 264° and plunging 2°. The orientation of P- and T-axis is consistent with the direction of absolute plate motion generally observed within the plates, hence the cause of the May 29 shock is the broad-scale stress pattern from the forces acting on the downgoing slab along the Japan trench and inhibiting forces balancing it. The 29 May 2004 earthquake occurred along a deep seated (~12 km), pre-existing feature that is expressed on the surface as the basement escarpment along the western and southern slopes of the Ulleung basin. The concentrated seismicity along this basement escarpment suggests that this feature may qualify as a seismic zone - the Ulleung basement escarpment seismic zone (UBESZ).

• 한국지구물리탐사학회:학술대회논문집
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• 2007.06a
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• pp.349-352
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• 2007

Estimating the physical properties of the survey area and mapping the geotechnical basement play an important role in ocean engineering and construction field. In this study, we performed marine seismic reflection and refraction survey as an engineering application at shallow marine. We made use of the dual boomer - single channel streamer as a source-receiver in reflection seismic survey and air-gun source - the manufactured OBC(Ocean Bottom Cable)-type streamer in refraction survey. In the seismic reflection data, we could easily find the geological layers and basement. Moreover, seismic refraction data could present sediment thickness and velocity distribution.

• The Journal of Engineering Geology
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• v.16 no.2 s.48
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• pp.161-169
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• 2006

A short seismic reflection survey was performed to map the basement and the upper units in the Gomso Bay. This research was mainly aimed at clarifying the basement by improving the signal-to-noise ratio in data processing steps. The strategies employed in this research included enhancement of the signal interfered with large-amplitude noise, through pre- and post-stack processing such as time-variant filtering, bad trace edit, careful muting after f-k filter and NMO correction. The subsurface structure mapped from this survey mainly consists of the top of basement and the upper three units, which were well correlated to the result from the previously conducted MT survey. Furthermore seismic section clarifies approximately 30m deep subhorizontal event of the top of the basement, which was not shown in the central portion of the MT section due to data qualify.

• 한국지구물리탐사학회:학술대회논문집
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• 2005.05a
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• pp.79-86
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• 2005

The apparent source spectrum of the Fukuoka earthquake is estimated at the seismic basement by removing from the observed spectra at Korean seismic stations the path and site responses that were previously revealed through inversion process applied to large spectral D/B accumulated until 2004. The approximate source spectrum is also estimated by using data recorded near the epicenter from various Japanese seismic networks and compared with the Korean source spectrum. The comparison result shows that there is good agreement among source spectra estimated based on the data from seismic networks of Korea at large distances (190km

• Journal of the Korean Geophysical Society
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• v.8 no.1
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• pp.15-21
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• 2005

The apparent source spectrum of the Fukuoka earthquake is estimated at the seismic basement by removing from the observed spectra at Korean seismic stations the path and site responses that were previously revealed through inversion process applied to large spectral D/B accumulated until 2004. The approximate source spectrum is also estimated by using data recorded near the epicenter from various Japanese seismic networks and compared with the Korean source spectrum. The comparison result shows that there is good agreement among source spectra estimated based on the data from seismic networks of Korea at large distances (190 km

• The Korean Journal of Petroleum Geology
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• v.1 no.1 s.1
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• pp.37-46
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• 1993

Two-dimensional gravity and magnetic models were constructed for seismic profiles in Block Ⅵ-2, offshore Korea. For each seismic profile, a longer length model showing geometric configurations of all employed polygonal bodies and an expanded version of the area of interests were made. The results of this modeling study indicate 1) that the depth to the deeper basement surface appear to be shallower than indicated in the seismic sections, 2) that the Middle Miocene section (the bottom formations in the models) appears to contain significant amounts of volcanic materials, 3) that identification and/or determination of depth to the top of basement is difficult in the study area due to thick volcanic materials in the lowermost formation (Middle Miocene), and 4) that the study area is unfavorable for hydrocarbon generation and accumulation due to wide spread volcanic activities during the Middle Miocene Epoch. The maximum calculated depth to the magnetic basement in the study area is approximately $4{\cal}km$ sub-sea.

• Ocean and Polar Research
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• v.29 no.4
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• pp.411-418
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• 2007

We studied the bottom morphology and sedimentary environments of the Masan Bay using high-resolution Chirp seismic profiles and sediments data. According to deep-drilled core samples (up to 20 m thick) penetrated into the weathered rock basement, the sediments consist largely of three sediment types: the lower sandy gravel facies (Unit I) of 1-4 m in thickness, the middle sandy mud and/or muddy sand facies(Unit II) of 1-2 m thick and the upper mudfacies (Unit III) of over 10 m in thickness. The sedimentary column above the acoustic basement can be divided into two major sequences by a relatively strong mid-reflector, which show the lower sedimentary sequenc e(T) with parallel to subparallel internal reflectors and the upper sedimentary sequence(H) with free acoustic patterns. Acoustic basement, the lower sedimentary sequence (T), and the upper sequence (H) are well correlated with poorly sorted massive sandy gravels (Unit I), the sand/mud-mixed sediment (Unit II), and the muddy facies(Unit III), respectively. The acoustic facies and sediment data suggest that the Masan bay is one of the most typical semi-enclosed coastal embayments developed during the Holocene sea-level changes. The area of the Masan Bay reduced from about $19\;km^2$ in 1964 to about $13\;km^2$ in 2005 by reclamation, and its bottom morphology changed as a result of dredging of about $2{\times}10^7\;m^3$.