• Journal of the Korean Geographical Society
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• v.36 no.2
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• pp.93-110
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• 2001

한반도 남동부지역에서 이루어진 활단층에 대한 일련의 연구들은 구조운도에 대한 관심을 불러 일으키고 우리나라가 안정지괴라는 생각에 변화를 일으키고 있다. 본고에서는 조선시대 한반도에서 발생한 지진 기록을 세계적으로 유례가 드물게 역사적 사실을 정확하게 기록한 조선왕조실록에서 확인하였다. 이 자료와 20세기에 이루어진 계기관측자료를 종합하여 지난 600년 간의 지진발생의 주기성과 공간분포를 검토하였다. 한반도 지진발생은 시.공간적으로 일정한 패턴이 있었으며, 대략 100-150년을 주기로 활성기와 잠복기를 반복하였다. 지진은 평안분지서안, 옥천변성대와 혼성구, 경상분지에서 높은 빈도로 발생하였다.

• Tunnel and Underground Space
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• v.23 no.6
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• pp.457-469
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• 2013

We have analyzed the regional in-situ stress pattern using 460 stress measurement data at about 100 test sites in Korea, and suggested correlation equations of stress-depth and stress ratio-depth. We made Korea Stress Map(KSM) as in-situ stress fields of the Korean peninsula, combining with a paleo-stress analysis according to the geological period and a stress estimation from focal mechanism. We confirmed the reliability and applicability of correlation equations derived in this study, comparing with worldwide stress-depth patterns, and also estimated the pattern of in-situ stress fields of north-eastern Asia including Korea, China and Japan, comparing with World Stress Map.

• Geophysics and Geophysical Exploration
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• v.12 no.1
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• pp.132-142
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• 2009

The Tamar rift valley runs through the City of Launceston, Tasmania. Damage has occurred to city buildings due to earthquake activity in Bass Strait. The presence of the ancient valley, the Tamar valley, in-filled with soft sediments that vary rapidly in thickness from 0 to 250mover a few hundreds metres, is thought to induce a 2D resonance pattern, amplifying the surface motions over the valley and in Launceston. Spatially averaged coherency (SPAC), frequency-wavenumber (FK) and horizontal to vertical spectrum ratio (HVSR) microtremor survey methods are combined to identify and characterise site effects over the Tamar valley. Passive seismic array measurements acquired at seven selected sites were analysed with SPAC to estimate shear wave velocity (slowness) depth profiles. SPAC was then combined with HVSR to improve the resolution of these profiles in the sediments to an approximate depth of 125 m. Results show that sediments thicknesses vary significantly throughout Launceston. The top layer is composed of as much as 20m of very soft Quaternary alluvial sediments with a velocity from 50 m/s to 125 m/s. Shear-wave velocities in the deeper Tertiary sediment fill of the Tamar valley, with thicknesses from 0 to 250m vary from 400 m/s to 750 m/s. Results obtained using SPAC are presented at two selected sites (GUN and KPK) that agree well with dispersion curves interpreted with FK analysis. FK interpretation is, however, limited to a narrower range of frequencies than SPAC and seems to overestimate the shear wave velocity at lower frequencies. Observed HVSR are also compared with the results obtained by SPAC, assuming a layered earth model, and provide additional constraints on the shear wave slowness profiles at these sites. The combined SPAC and HVSR analysis confirms the hypothesis of a layered geology at the GUN site and indicates the presence of a 2D resonance pattern across the Tamar valley at the KPK site.

• Tunnel and Underground Space
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• v.19 no.3
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• pp.236-247
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• 2009

Overpopulation has significantly increased the use of underground spaces in urban areas, and led to the developments of shallow-depth underground space. Due to unexpected rock fall, however, it is very necessary to understand and categorize the rock mass behaviors prior to the tunnel excavation, by which unnecessary casualties and economic loss could be prevented. In case of cave-in, special attention should be drawn since it occurs faster and greater in magnitude compared to rock fall and plastic deformation. Types of cave-in behavior are explained and categorized using seven parameters - Uniaxial Compressive Strength (UCS), Rock Quality Designation (RQD), joint surface condition, in-situ stress condition, ground water condition, earthquake & ground vibration, tunnel span. This study eventually introduces a new index called Cave-in Behavior Index (CBI) which explains the behavior of cave-in under given in-situ conditions expressed by the seven parameters. In order to assess the mutual interactions of the seven parameters and to evaluate the weighting factors for all the interactions, survey data of the experts' opinions and Rock Engineering Systems (RES) were used due to lack of field observations. CBI was applied to the tunnel site of Seoul Metro Line No. 9. UDEC analyses on 288 cases were done and occurrences of cave-in in every simulation were examined. Analyses on the results of 288 cases of simulations revealed that the average CBI for the cases when cave-in for different patterns of tunnel support was estimated by a logistic regression analysis.