초록 ▼

New Madrid지역에서 수집한 지진관측자료를 분석하여 속도구조와 지진발생단층의 기하학적 양상을 밝히고 기존 연구결과와 비교하여 안정성을 검증하였다. KCRT2008 지각규모 탄성파실험에서 획득한 자료를 분석하고 암석물리학적 해석을 하였다. 해당지역의 2차원 P파 및 S파속도모델과 VP/VS ratio를 결정하였다. 지각에서 P파 평균속도는 6.27 km/s다. S파 평균속도 3.61 km/s다. 경기육괴의 V_P=/V_S= ratio는 다른 조구조구 보다 낮으며, 그 평균값은 1.74로 대륙지

New Madrid지역에서 수집한 지진관측자료를 분석하여 속도구조와 지진발생단층의 기하학적 양상을 밝히고 기존 연구결과와 비교하여 안정성을 검증하였다. KCRT2008 지각규모 탄성파실험에서 획득한 자료를 분석하고 암석물리학적 해석을 하였다. 해당지역의 2차원 P파 및 S파속도모델과 VP/VS ratio를 결정하였다. 지각에서 P파 평균속도는 6.27 km/s다. S파 평균속도 3.61 km/s다. 경기육괴의 V_P=/V_S= ratio는 다른 조구조구 보다 낮으며, 그 평균값은 1.74로 대륙지각의 평균값인 1.76보다 낮다. V_P=/V_S= ratio와 P파 속도는 상부와 중부 지각은 암석조성 상 felsic 하고 하부 지각은 intermediate함을 제시한다. 한반도 남부지역에서 frequency-dependent Q_S를 coda normalization technique을 이용하여 구하였다. 1.5, 3, 6, 12 및 24 Hz 중심주파수에서 도출된Q_S 값은 각각 235.7, 468.0, 851.5, 1099.9, 1222.4이며, 표준편차는 각각 35.1, 53.6, 85.0, 76.2, 44.7이다. 작은 표준편차 값을 고려할 때 결과의 신뢰도는 높을 것으로 사료되며, 회귀분석에 의한 power law 식은 Q_S=321.7f^0.445로 나타난다.

Abstract ▼

Determination of reliable hypocenters of earthquakes is crucial to earthquake seismology and to evaluate hazards associated with earthquakes. There are many associated computer codes for this purpose; however, most of the location algorithms are designed to determine hypocentral parameters based on

Determination of reliable hypocenters of earthquakes is crucial to earthquake seismology and to evaluate hazards associated with earthquakes. There are many associated computer codes for this purpose; however, most of the location algorithms are designed to determine hypocentral parameters based on previously determined velocity models. In contrast, we employed a location method that is independent of the initial velocity model, by using a genetic algorithm to determine an optimal 1D velocity model and the locations of earthquakes. Using this genetic algorithm, we have relocated earthquakes that occurred in the New Madrid Seismic Zone (NMSZ) in the central United States between October 1989 and August 1992. The goal of this work was to delineate the possible fault planes by reliable relocation of those earthquakes and to determine a 1D velocity structure for the NMSZ. A total of 502 earthquakes recorded by 37 Portable Array for Numerical Data Acquisition (PANDA) stations have been used in the relocation study. In the relocation process, the root mean square traveltime residuals were reduced by ~35% corresponding to an average of 2.3 km deeper in depth, 0.7 km shift in latitude and 0.8 km shift in longitude than those in the initial catalog locations. The hypocenters of the earthquakes can be subdivided into four groups based on their spatial distributions. The group which corresponds to the Cottonwood Grove Fault (CGF) in the southwestern NMSZ represents a very steep plane, whereas the other three groups fall into Reelfoot Fault (RF). We inverted P- and S-wave traveltimes from the new hypocentral parameters to determine 1D velocity models. The resulting eight-layered velocity models consist of a 2-km thick surface layer followed by seven 2-km thick layers, with VP ranges from 5.36 to 6.74 km/s, and V_S ranges from 2.83 to 3.90 km/s for both CGF and RF regions.
We present the results of a seismic experiment along the KCRT2008 profile. KCRT2008 was the third crustal scale seismic experiment in the southern Korean Peninsula and was carried out along a 300-km-long NW-SE-trending transect. Two-dimensional P- and S-wave velocity models beneath the profile were determined from seismic data acquired during the KCRT2008 experiment. The Vp/Vs ratio was also determined from P- and S-wave velocity models. The P-wave velocity in the crust ranges between 4.40 and 6.85 km/s, with an average of 6.27 km/s. The S-wave velocity varies between 2.51 and 3.88 km/s, with an average of 3.61 km/s. The Pn phase velocity, which represents the velocity in the uppermost mantle, is estimated to be 7.82-7.88 km/s. The Moho depths are 30.00-34.00 km and the crustal thickness becomes shallower toward both ends of the profile. The V_P/V_S ratio in the crust ranges between 1.71 and 1.77 and its value increases with depth. The V_P/V_S ratio of the Gyeonggi massif in the northwestern part of the profile is lower than that of other tectonic units. The average V_P/V_S ratio is 1.74, which is lower than the average (1.76) for continental crust. The VP/VS ratio and P-wave velocity values suggest that the upper and middle crust is felsic and the lower crust is intermediate in composition. These results also agree with those of a previous experiment (KCRT2004).
The measured gravity data were collected as much as possible, and they were reprocessed. After the terrain correction, the digital Bouguer anomaly map was produced. To determine the density model the Bouguer anomalies were inverted. The inversion was constrained by the crustal velocity structure published by KCRT. The depth distribution of the moho which indicates the major density change appears clearly, and show good agreement with the KCRT velocity cross-sections. The only low wavenumber features were, however, found in the results. Based on the hypothesis that the young Jurassic granite body is less dense than thev Precambrian granite body, densities were modified and the gravity anomalies were computed again. The results showed high wavenumber features, and agreed with the observed gravity anomalies. MT resistivity cross-sections were also used in modifications of density structures, and the improved results were came out.
Frequency-dependent Q_S-values in the southern Korean Peninsula were determined using the coda normalization technique. At 1.5, 3, 6, 12, and 24-hz central frequencies, Q_S-values were 235.7, 468.0, 851.5, 1099.9, and 1222.4 with standard deviations of 35.1, 53.6, 85.0, 76.2, and 44.7, respectively. The power law was assumed, and Q_S-values were regressed, and the result was Q_S=321.7f^0.445. This Q_S appeared to be less frequency-dependent compared to previous independent results, and to be reliable based on small standard deviation values.
Background seismic noise was measured at selected sites on the planned Kunsan-Geoje survey line and possible sites for explosions were searched for an crustal-scale seismic experiment in the near future. The results were transferred to "Tectonic structure and analysis of fault activity in the Yellow Sea”project. The international cooperative experiments were discussed with Dr. Jinwei Ren, Director of Earthquake Science Division, China Earthquake Administration and Professor Tianyao Hao, Chinese Academy of Science, and agreed to continuous efforts for future collaboration. The results were transferred to "Tectonic structure and analysis of fault activity in the Yellow Sea”project.

목차 Contents

• 표지 ... 1
• 제 출 문 ... 2
• 보고서 요약서 ... 3
• 요 약 문 ... 4
• SUMMARY ... 8
• CONTENTS ... 10
• 목 차 ... 11
• 제 1 장 연구개발과제의 개요 ... 12
• 제 1 절 연구개발의 목적 및 필요성 ... 12
• 제 2 절 연구개발의 내용 및 범위 ... 13
• 제 2 장 국내외 기술개발 현황 ... 14
• 제 3 장 연구개발수행 내용 및 결과 ... 16
• 제 1 절 New Madrid 지역 진원요소 재결정: 1D 속도구조와 지진발생 단층의 기하학적 양상 ... 16
• 제 2 절 한반도 남부의 강화-영덕 측선에서의 지각 속도구조 ... 40
• 제 3 절 지질과 속도구조를 구속조건으로 하는 한반도 남부지역의 밀도구조 ... 61
• 제 4 절 한반도 남부 지역에서의 Qs값 ... 84
• 제 5 절 논문게재 및 기타성과 ... 110
• 제 4 장 목표달성도 및 관련분야에의 기여도 ... 111
• 제 1 절 연구개발 목표달성도 ... 111
• 제 2 절 관련분야에의 기여도 ... 112
• 제 5 장 연구개발결과의 활용계획 ... 113
• 제 6 장 연구개발과정에서 수집한 해외과학기술정보 ... 114
• 제 7 장 연구개발결과의 보안등급 ... 115
• 제 8 장 국가과학기술 정보시스템에 등록한 연구시설ㆍ장비현황 ... 116
• 제 9 장 참고문헌 ... 117
• 끝페이지 ... 127