• Journal of the Korean Geographical Society
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• v.42 no.3 s.120
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• pp.368-387
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• 2007

In order to explain geomorphological characteristics of the Korean Peninsula, it is necessary to understand the spatial distribution of tectonic movements and its causes. Even though geomorphological elements which might have been formed by tectonic movements(e.g. tilted overall landform, erosion surface, river terrace, marine terraces, etc.) have long been considered as main geomorphological research topics in Korea, the knowledge on the spatial distribution of tectonic movement is still limited. This research aims to identify the spatial distributions of tectonic movement via sequential analyses of Digital Elevation Model(DEM). This paper first developed a set of terrain analysis techniques derived from theoretical interrelationships between tectonic uplifts and landsurface denudation processes. The terrain analyses used in this research assume that elevations along major drainage basin divides might preserve original landsurfaces(psuedo-landsuface) that were formed by tectonic movement with relatively little influence by denudation processes. Psuedo-landsurfaces derived from a DEM show clear spatial distribution patterns with distinct directional alignments. Lines connecting psuedo-landsufaces in a certain direction are defined as psuedo-landsurface axes, which are again categorized into two groups: the first is uplift psuedo-landsurface axes that indicate the axis of landmass uplift; and the second is denudational psuedo-landsurface axes that cross step-shaped pusedo-landsurfaces formed via surface denudation. In total, 13 axes of pusedo-landsurface are identified in the Korean Peninsula, which show distinct direction, length, and relative uplift rate. Judging from the distribution of psudo-landsurfaces and their axes, it is concluded that the Korean Peninsula ran be divided into four tectonic regions, which are named as the Northern Tectonic Region, Center Tectonic Region, Southern Tectonic Region, and East Sea Tectonic Region, respectively. The Northern Tectonic Region had experienced a regional uplift centered at the Kaema plateau, and the rate of uplift gradually decreased toward southern, western and eastern directions. The Center Tectonic Region shows an arch-shaped uplift. Its uplift rate is the highest along the East Sea and the rate decreases towards the Yellow sea. The Southern Tectonic Region shows an asymmetric uplift centered a line connecting Dukyu and Jiri Mountains in the middle of the region. The eastern side of the Southern Regions shows higher uplift rate than that of the western side. The East Sea Tectonic Region includes south-eastern coastal area of the peninsula and Gilju-Myeongchun Jigudae, which shows relatively recent tectonic movements in Korea. Since this research visualizes the spatial heterogeneity of long-term tenonic movement in the Korean peninsula, this would provide valuable basic information on long-term and regional differences of geomorphological evolutionary processes and regional geomorphological differences of the Korean Peninsula.

• Journal of The Geomorphological Association of Korea
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• v.26 no.2
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• pp.55-67
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• 2019

This study tries to reveal and compare uplift rates in the southern coast of the Korean Peninsula, based on absolute ages from coastal terrace on the coast. The uplift rate in the East Coast from previous study ranges from 0.258 to 0.357 m/ka with a median rate of 0.262 m/ka and shows an increase trend from north to south. Median uplift rate of 0.082 m/ka with minimum and maximum rates of 0.053 m/ka and 0.127 m/ka, respectively, is calculated in the South Coast from previous and this studies. The uplift rate in the West Coast from 3 absolute ages in this study is 0.082~0.112 m/ka with a median rate of 0.090 m/ka. Based on these uplift rates in the southern coast of the Korean Peninsula, it can be concluded that since MIS 5, the East Coast has experienced 3 to 4 times faster uplift rate than the West and South Coasts. However, this study suggests that more discussion on whether these uplift rates are long-term tectonic movement associated with tilted warping movement since the Tertiary or short-term tectonic movement associated with isostatic rebound due to sea level change since the Last Interglacial is needed.

• Journal of the Korean Geographical Society
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• v.39 no.5 s.104
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• pp.722-734
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• 2004

Longitudinal profiles of bedrock rivers play a fundamental role in landscape history by setting the boundary conditions for landform evolution. Longitudinal profiles are changed with climatic conditions, lithology and tectonic movements. Tectonic movement is an important factor controlling longitudinal profiles, especially in tectonically active area where uplift rates are regarded as a major factor controlling channel gradient. However study on bedrock channel has made little progress, because controls over bedrock river incision are yet to be clarified. Previous numerical simulations have used a simple diffusion model, which links together the overall processes of bedrock channel erosion as in other landform evolution models. In this study, previous bedrock incision models based on physical processes (especially abrasion) are reviewed and new modifications are introduced. Using newly formulated numerical model, the role of spatial pattern and intensity of tectonic uplift on changes in river longitudinal profile was simulated and discussed.

• Journal of The Geomorphological Association of Korea
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• v.27 no.4
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• pp.29-39
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• 2020

This study estimated influences of the Ulsan Fault on tectonic movement and uplift characteristics in the Eastern Block of the Ulsan Fault. The averaged uplift rate in the Northern Coast of the Eastern Block was 0.202 m/ka, while the site in Seokbyeong-ri, Guryongpo-eup, Pohang-si, showed relatively high rate of 0.249 m/ka, attributable to influences of small fault movement, called the Gangsa Fault. Higher averaged rate of 0.270 m/ka than in the Northern Coast was calculated in the Southern Coast of the Eastern Block. The site in north of Haseo-ri, Yangnam-myeon, Gyeongju-si, showed the highest rate, suggesting influences of the Eupcheon Fault. The Western Block of the Ulsan Fault indicated the averaged rate of 0.208 m/ka, similar to that of the Northern Coast. The sites approximately 10 km apart from the Ulsan Fault showed 1.3 times higher rate in the Eastern Block than in the Western Block, while similar rates were calculated in the sites >20 km apart from the Ulsan Fault. These distributions of the rate suggest that the Ulsan Fault has significantly influenced development of marine terrace and tectonic movement in the study area, while local fault movements have also played a role.

• Journal of The Geomorphological Association of Korea
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• v.25 no.2
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• pp.31-42
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• 2018

This study analyzes the spatial distribution of the highest level terrace which can be regarded as an initial land surface before the uplift of the Taebaek Mountains and estimates spatial characteristics of the incision and uplift rates around the Mountains. The altitude above the riverbed of the 54 highest level terraces seems to be greatly influenced by the incision of large stream and their elevation shows a high correlation with the uplift of the Mountains. The elevation of the terraces in the north and middle parts decreases westward with a rate of 5~6 m/km and meets with the sea level at area 100~120 km apart from the Mountains. Therefore, it can be suggested that the west coast of Korea might have generally experienced subsidence during the Quaternary. The elevation of the terraces suggests that area with a direction of N-S or NNW-SSE from Yeoryang-myeon, Jeongseon-gun to Taebaek-si shows the highest uplift rate around the Mountains and area with a direction of N-S connecting Girin-myeon, Inje-gun and Pyeongchang-eup, Pyeongchang-gun also indicates a high uplift rate.

• Journal of The Geomorphological Association of Korea
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• v.25 no.4
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• pp.49-62
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• 2018

This study tries to reveal uplift rates inferred from relative and absolute ages on coastal terrace in the West and South Coasts of South Korea. Uplift rate from relative ages on Pleistocene coastal terrace in the West Coast rangesfrom approximately 0.059 to 0.282 m/ky, while a range of approximately 0.020~0.385 m/ky is calculated from the South Coast, suggesting that the South Coast shows higher rate than the West Coast. Based on absolute ages on coastal terrace during MIS 5 in the South Coast, on the other hand, the uplift rates 1 and 4 have ranges of approximately 0.042~0.062 m/ky and 0.051~0.087 m/ky, respectively, indicating that uplift rate in the South Coast is one-third to one-fourth to that in the East Coast. No research on absolute ages in West Coast terrace and lack of relative and absolute ages in the West and South Coasts are considered as the limit in this study.

• Journal of the Korean Geographical Society
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• v.49 no.1
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• pp.1-17
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• 2014

This study estimates geomorphological processes of fluvial terraces by uplifts and bedrock features, by the analyses of topography, distribution, formation age and incision rate of fluvial terraces using Gwang-cheon River in Uljin, Namdae-cheon River in Pyeonghae and Osip-cheon River in Yeongdeok located in the southern Taebaek Mountain Range. The tectonic and climatic terraces I in the upper reaches of Gwang-cheon River with an altitude from riverbed of 9~12m indicate the formation age of MIS 2 with a incision rate of 0.40m/ka. However, the tectonic and climatic terraces I in the upper reaches of Osip-cheon River with an altitude from riverbed of 7~10m show the formation age of MIS 3 with an incision rate of 0.10m/ka. These results suggest that the uplift rate in the Gwang-cheon River basin is likely to be higher than that in the Osip-cheon River basin. Unlike the lower reaches of Osip-cheon River, the thalassostatic terraces are not found in the lower reaches of Gwang-cheon River, because the basin has low maintainable ability of landforms in river valley due to high uplift rate and bedrock properties resistant to weathering and erosion. On the other hand, the lowest tectonic and climatic terraces in the study areas indicate different formative ages and the terraces during the cooling stage in interglacial as well as during interstadial are also found. Therefore, this study suggests that chronological method for fluvial terrace by the previous developmental model of climatic terrace should be reconsidered.

• Economic and Environmental Geology
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• v.53 no.5
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• pp.585-596
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• 2020

The 2017 Pohang Earthquakes occurred near a drill site in the Pohang Enhanced Geothermal System. Water injected for well stimulation was believed to have reactivated the buried near-critically stressed Miocene faults by the accumulation of the Quaternary tectonic strain. However, surface expressions of the Quaternary tectonic activity had not been reported near the epicenter of the earthquakes before the site construction. Unusual, large-scale water-escaped structures were identified 4 km away from the epicenter during a post-seismic investigation. The water-escaped structures comprise Miocene mudstones injected into overlying Pleistocene coastal sediments that formed during Marine Isotope Stage 5. This indicates the vulnerable state of the mudstones long after deposition, resulted from the combined effects of rapid tectonic uplift (before significant diagenesis) and the development of an aquifer at their unconformable interface of the mudstone. Based on the detailed field analysis and consideration of all possible endogenic triggers, we interpreted the structures to have been formed by elevated pore pressures in the mudstones (thixotropy), triggered by cyclic ground motion during the earthquakes. This interpretation is strengthened by the presence of faults 400 m from the study area, which cut unconsolidated coastal sediment deposited after Marine Isotope Stage 5. Geological context, including high rates of tectonic uplift in SE Korea, paleo-seismological research on Quaternary faults near the study area, and historical records of paleoearthquakes in SE Korea, also support the interpretation. Thus, epicenter and surrounding areas of the 2017 Pohang Earthquake are considered as a paleoseismologically active area, and the causative fault of the 2017 Pohang Earthquakes was expected to be nearly critical state.

• Journal of the Korean Geographical Society
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• v.44 no.1
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• pp.31-55
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• 2009

This research aims 1) to characterize the spatial distribution of low relief landforms (plains) via analyses of a Digital Elevation Model (DEM), 2) to classify plains according to morphological and genetic similarity, and 3) to develop a model to explain forming processes of plains in the Korean peninsula. Plains can easily be separated from high relief mountaneous areas by analyzing the DEM. The overall morphological and locational characteristics of plains can be categorized into lava plains, fluvial-marine plains, erosional plains, intermontane basins, and higher ground plains. It is concluded that the characteristic of each plain type is decided by base-level changes caused by tectonic uplift and sea-level changes, and topological relationship of different rock types. Different plain types do not exist independently, but connected with each others along stream networks. The model developed is able to combine the morphological characteristics of plains with the channel network to conceptualize characteristics and development pathways of plains in the Korean Peninsula.

• Journal of the Korean earth science society
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• v.33 no.6
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• pp.534-543
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• 2012

The relationship between tectonic uplift and geophysical analysis of gravity anomalies and the in-situ stress fields in the Otway Ranges, SE Australia is addressed in this study to understand the nature and possible mechanism for the neotectonic movements. The uplift axis of the ranges is coincident with the regional Bouguer gravity highs whereas thick Tertiary sedimentary successions are highly correlated with the gravity lows along the basin rift geometry. This result suggests that the gravity highs are separated by the thick Tertiary sedimentary successions. Regional structural trends associated with faults and foldings of the deformed surfaces are consistent with the prevailing NW-SE $S_{Hmax}$ trend in this part of the continent. The anomalously positive correlation between topography and Bouguer gravity fields suggests possibly a lithospheric flexural deformation mode at a long wavelength (order of $10^2$ kms) in the region. It also suggests that the reactivation of pre-existing lithospheric structures driven by plate boundary forces plays a key role in this mode.