초록 ▼

연차 목표
○ 강원도 북부해역 해저지진 정밀 진원결정과 지진원 분류
○ 근/중거리 공중음파 위상 특성 연구 및 SI 광역 관측망 확충
○ 수중 음파 관측기술 개발
○ SHI 융합분석기술 사례연구
○ 동해 해저관측기지용 해상 플랫폼 설치 및 원격감시기술 적용
○ 수중 고주파수 음파 계측 모듈 제작 완료
개발내용 및 결과
○ 강원도 북부해역 해저지진 정밀 진원결정과 지진원 분류
- 강원도 북부해역에서 발생하는 소규모의 지진이벤트들의 진앙을 이중차분 진원위치 재결정방법으로 재결정하고 진원

연차 목표
○ 강원도 북부해역 해저지진 정밀 진원결정과 지진원 분류
○ 근/중거리 공중음파 위상 특성 연구 및 SI 광역 관측망 확충
○ 수중 음파 관측기술 개발
○ SHI 융합분석기술 사례연구
○ 동해 해저관측기지용 해상 플랫폼 설치 및 원격감시기술 적용
○ 수중 고주파수 음파 계측 모듈 제작 완료
개발내용 및 결과
○ 강원도 북부해역 해저지진 정밀 진원결정과 지진원 분류
- 강원도 북부해역에서 발생하는 소규모의 지진이벤트들의 진앙을 이중차분 진원위치 재결정방법으로 재결정하고 진원 분포특성 및 관측된 지진파 특성 규명
○ 근/중거리 공중음파 위상 특성 연구 및 SI 광역 관측망 확충
- 전파거리 별 공중음파 수평전파속도, 위상속도 범위 분석
- KSRS 지진관측소에 공중음파 센서 추가
○ 수중음파 관측기술 개발
- 수중 배열식 관측자료 분석을 통한 강원도 북부 해역지진의 지진원 식별
- 해양 지진파 관측을 위한 부유형 수중음파 관측기술 조사 및확보
○ SHI 융합분석기술 사례연구
- 발파검증자료를 통한 SI 자동분석기술 성능 향상
- 지반붕괴에 의한 지진파, 공중음파 신호 분석
○ 동해 해저관측기지 해상 플랫폼 설치 및 원격감시기술 적용
- 강원도 고성군 앞바다에 해저관측기지용 해상 플랫폼 3기 설치
- 해상 악 조건에서 해상부이의 거동확인 및 보강대책 수립
- SOH 원격 감시 체계 운영을 통한 태양광발전 및 통신망 시험
○ 서해 중부 해저관측기지 설치 사전 준비
- 실해역 통신 테스트를 통한 통신 기반 환경 조사 실시
- 서해 격렬비열도 부근 해저정밀지형조사를 통한 3차원 해저지형도 작성 및 해저면 특성 파악
기대효과
○ 해저지진 정밀관측 및 해석을 통한 육상-해양지역을 아우르는활성 지구조 해석
○ 자연적, 인위적, 군사적, 생태학적 수중음원 DB 제공
○ 핵실험, 수중폭발, 주변국 군사활동 동향 감시
○ 해저관측소 상시 운영기술 확보
○ 해저 관측모듈 및 부이시스템 설계의 기초자료 및 해저면 관측기지 설치에 적합한 최적의 장소 도출에 적용
적용분야
○ 해저지진 위험도 평가를 포함한 종합적 지진 대책 수립
○ 대규모 탄성에너지원 탐지와 분석을 위한 지역관측망에서의 SHI 융합분석 및 탐지체계 구축에 활용
○ 북한 핵실험 등 인위적 발생 지진에 대한 신속, 정확한 탐지기술 개발에 활용
○ 해역조건에 적합한 해저면 관측기지 구축에 활용
○ 고품질, 안정적 지구물리 관측자료 획득을 위한 운영기술 개발에 활용
○ 해상-육상 간 융복합 무선 데이터 통신
○ 해양 수중음향 환경 모니터링

Abstract ▼

Microearthquakes in offshore Gangneung-Sokcho-Goseong area of northeastern South Korea are reviewed and the hypocenters of these events are relocated by double-difference algorithm. We focused on 61 events occurred in the area of N37°40´-38°40´ and E128°30´-129°20´ during Oct. 2014 - Oct. 2015. Tota

Microearthquakes in offshore Gangneung-Sokcho-Goseong area of northeastern South Korea are reviewed and the hypocenters of these events are relocated by double-difference algorithm. We focused on 61 events occurred in the area of N37°40´-38°40´ and E128°30´-129°20´ during Oct. 2014 - Oct. 2015. Total 1,036 arrival times of direct P-wave phase are retrieved from 26 stations of which epicentral distance is less than 100 km. The epicenters of small events are classified into three clusters; two major clusters in offshore Goseong and Yangyang provinces that already identified by previous study and one cluster in far offshore. Total 45 events are relocated by double difference algorithm. The waveform of relocated events are similar to those from explosion rather than earthquake and spectrum analysis shows energy concentration on low frequencies below 20 Hz.
The offshore events in the midwest coast of the Korean peninsular are reviewed. The 2,244 events information from KEMS database are searched and compiled in the area of N36°20´-37°20´ and E125°00´-126°20´ during Jan. 2010 - Oct. 2015. The largest event (ML 5.1) on 1. Apr. 2014. is occurred in offshore area, 100 km distance from the Gyeongnyeonlbiyeoldo. The epicenters of events are scattered while some events seems to be aligned in NE-SW direction. The small repeating events are found near the Gureopdo and Deokjeokdo. We installed two temporary seismic stations(MLP and IWM) in Taean peninsular to improve the event detection capability and improve accuracy of event relocation. The assessment of background noise level confirms the seismic stations are running in stable and calm environment.
The portable Ocean Bottom Seismometer(OBS) are deployed near the offshore platform in the East Sea and successfully recorded seismic signals from offshore seismic events for 4 months. The Guralp CMG-6T seismometer and hydrophone both recorded clear first arrival signals from the event on 10. Aug. 2015.
High resolution 3-D acoustic mapping and characterization of subsea area for the 2nd underwater multidisciplinary geophysical observatory are done by multibeam echosounding survey and subsequent data and image processing. A detailed 3-D bathymetric image of 16 km2 offshore area are obtained as well as backscattering image that can infer the material properties in the sea bottom. The water depth in the area of the offshore platform is 39 - 41 m. We found the sea bottom is smooth and slightly (0.3°) dipping toward southeast. The pressure level of backscattered multibeam signals does not significantly change and the strength of the signals suggests the bottom sediments seems to mostly be sand.
Repetitive infrasound series from active volcanoes, mines, and other sites transfer along path-transient features of the atmosphere, and their evolutions into ground receivers in time resolution correspond to repeating intervals. In this report, we used near-surface blasting (surface explosions) at mines as repetitive sources of infrasound. As a result, the variation in travel time was more prominent in the case of M3 source (distance of 181 km to CHNAR). Systematic variations with little fluctuation from May to September were attributed to steady and favorable stratospheric winds (westerly stratospheric winds in summer);marked variations in travel times are observed from October to April. These seasonally dependent characteristics also appear as travel times of shorter propagation distances, M1 and M2 sources, but to a much lesser degree. M2 and M3 are in opposite directions to each other with respect to CHNAR; thus,seasonal detectability showed the reverse trends with regard to zonal wind directions, e.g., favorable zonal winds to M3 in the summer. As propagation distances increased from the mines to CHNAR, celerity decreased by shifting infrasound from the tropospheric to the stratospheric phase. Compared with the effective sound speeds on the ground, the celerity range of M1 shows that the infrasound arrivals were direct waves propagating through the lower troposphere with a refraction height of a few kilometers. The celerity range of M2 is indicative of refractions at greater heights, including tropospheric and stratospheric phases. In the case of M3, all arrivals typically showed stratospheric phases, with celerity in the range of 261-289 m/s.
KSIAR, a new infrasound array, was installed on the existing four short-period seismic stations of KSRS in April 2014. In 2015, KSIAR was expanded from 3.3km aperture array to 6.8 km array with the installation of five Chaparral sensors on the short-period seismic stations of KSRS including KS01, KS015, KS17, KS18 and KS19.
A network performance capability was assessed before and after the adding KSIAR in KIN with utilization of a weighting function. The assessment with the add of KSIAR in KIN shows relatively better network performance capability compared to that without KSIAR. Two large explosions occurred in Tianjin on 12 August, 2015 generated strong acoustic-gravity waves as well as infrasound signals. These signals were well recorded across KIN and the long period acoustic-gravity wave at frequencies less than 0.01 Hz were recorded at KSIAR. KSIAR’s large aperture which is about 7 times larger than the aperture of regular infrasound array has a benefit for analyzing long period acoustic waves at frequencies less than 0.01 Hz.
Three hydroacoustic data acquisition system were installed at the elastic beacons in the East Sea. Various kinds of underwater acoustic signals were recorded. By co-seismic analysis, we could find hydroacoustic signatures from underwater seismic events that are frequently reported by KIGAM earthquake monitoring system. We could deduce that the events might be underwater explosions from time series and frequency spectra of the hydroacoustic signals. Dr. Frederik Simons of Princeton university is developing lagrangian monitoring system for acquisition of teleseismic data in the ocean. This year, we have discussed on an applicability of the langrangian system. From Dr. Simon’s deployment at east coast of USA, it will take 3 more years to develop the system which might be used.
On the morning of 31 January 2015, a ground subsidence occurred over underground limestone mine area in Samcheok. Seismic waves related with the event were observed at many seismic stations in South Korea, and local magnitude of the event is estimated to be 2.5. In addition to seismic signals, acoustic waves were also detected at infrasound arrays with the frequency of 0.4 Hz. Azimuths of the infrasound signals are nearly directing to the source site, and infrasound source location determined by BISL algorithm is locating 4.5 km offset from the source. Celerity of the infrasound signals indicates that their propagation paths are stratospheric or thermospheric phase. Based on the low frequency contents and short signal duration of the observations, we suggest that acoustic resonance of air column within underground tunnels is one of possible source mechanisms for the generation of infrasound. Acoustic resonance frequency of an air column of length of 500 meters results in a fundamental frequency of 0.17 Hz and first harmonic frequency of 0.51 Hz, which resonance frequencies are similar to observed ones. In future, in order to explain the source mechanism clearly, it needs to prove resonance frequency by numerical modeling for the air column in complicated tunnel geometry or by in situ measurement of the fundamental frequency at the source region.
In this year, we installed 3 elastic beacon type buoys at the eastern coast of South Korea as a platform for the first multidisciplinary geophysical observatory. These installed platforms make a small triangular shaped array, and they are deployed about 4.5 km away from the coast. The distance between each platform is about 500 meters. In order to evaluate these platforms’ capacity and stability, we also installed a temporary observation system with them. The temporary observation system includes S-H-I acquisition system, bi-directional telecommunication system, independent solar energy generating system, and state-of-health monitoring system. Through this temporary observation system, we could have a better understanding of the platforms and we could design better system for a multidisciplinary geophysical observation system which will be installed in the next year.
In order to measure underwater sound in a higher frequency range a prototype of a sound measurement system with an array of four hydrophone has been developed last year. This year some modification has been applied to improve the performance such as wider bandwidth of the analog filter, time synchronization using PPS signals by GPS or NTP protocol through ethernet, software optimization to reduce CPU usage, remote control of the system over wired or wireless network, automatic data acquisition and data transfer etc. One channel system has been also developed to temporarily installed on the KIGAM’s buoy and operated in the East Sea. The total power consumption of the both systems are less than 10 W. For the verification of the performance tests in a KRISO’s water tank and at a pier at the southern coast of Korea have been done. The results show good performance in the estimation of the spectrum and source direction finding. For the sea trial a multi-function buoy of USV type has been developed. It has capability of position control, optical image transmission, RF communication, underwater acoustic communication, electrical power supply, and real-time system monitoring.
As a reference ocean environmental data around the potential installation site in Yellow Sea such as tidal height, water temperature, salinity, wind speed, current, etc. were collected. Underwater sound propagation characteristics around the area was analyzed. The numerical analysis of the KIGAM’s buoy was performed to estimate its position displacement, pitch motion, and drag force.

목차 Contents

• 표지 ... 1
• 제출문 ... 2
• 연차보고서 요약서 ... 4
• 요약문 ... 6
• SUMMARY ... 10
• CONTENTS ... 14
• 목차 ... 16
• 표목차 ... 20
• 그림목차 ... 22
• 제1장 연구개발과제의 개요 ... 28
• 제1절 연구개발의 목적 및 필요성 ... 28
• 가. 기술적 측면 ... 30
• 나. 경제·산업적 측면 ... 30
• 다. 정책적 측면 ... 30
• 제2절 연구개발 범위 ... 31
• 가. 연구개발 목표 ... 33
• 나. 연구개발 내용 및 범위 ... 35
• 제2장 국내외 기술개발 현황 ... 36
• 제1절 국외 기술개발 현황 ... 36
• 1. 해저지진 관측 및 SHI 융합분석 연구 ... 36
• 2. 해저면 관측기지 구축 및 운영 기술 ... 37
• 3. 수중 고주파수 음파 관측시스템 및 수중음향 무선통신 채널 구축 – 협동연구 ... 40
• 제2절 국내 기술개발 현황 ... 44
• 1. 해저지진 관측 및 SHI 융합분석 연구 ... 44
• 2. 해저면 관측기지 구축 및 운영 기술 ... 45
• 3. 수중 고주파수 음파 관측시스템 및 수중음향 무선통신 채널 구축 – 협동연구 ... 45
• 제3장 연구개발수행 내용 및 결과 ... 49
• 제1절 대정부/대국민 지진분석정보 제공 ... 49
• 1. 한반도 주변 특이 동향 안보기관 정보제공 ... 49
• 제2절 SHI 요소 기술 개발 ... 51
• 1. 해역지진 정밀 진원분석(seismic) ... 51
• 2. 수중음파 분석 기술 개발 ... 60
• 3. 공중음파 분석기술 고도화 연구 ... 65
• 4. SHI 융합분석 정의 및 사례 연구 ... 72
• 제3절 해저면 복합지구물리 관측기술 개발 ... 77
• 1. 1차 해저관측기지(동해) 플랫폼 설치 ... 77
• 2. 1차 해저관측기지 자료 수신 및 관측기지 안정성 평가 ... 113
• 3. 해저면 모듈 제작 ... 122
• 4. 2차 해저관측기지(서해 중부) 설치 사전 준비 ... 124
• 제4절 수중 고주파수 음파 관측시스템 및 수중음향 무선통신채널 구축 ... 137
• 1. 단일채널 수중 고주파수 음파계측 모듈 개발 ... 137
• 2. 4 채널 수중 고주파수 음파 계측 모듈 개발 ... 155
• 3. 해저관측시스템 설계 및 구축 ... 174
• 4. 수중음향 무선통신 시스템 구축 ... 184
• 5. 해저면 복합지구물리 통합관측플랫폼 설계·제작·운용을 위한 기술 지원 ... 189
• 6. 내압용기 내식(耐蝕) 성능 시험 ... 209
• 7. 수중음파 신호 측정 및 분석 ... 221
• 제4장 목표달성도 및 관련분야의 기여도 ... 222
• 수중 고주파수 음파 관측시스템 및 수중음향 무선통신 채널 구축 – 협동연구 ... 224
• 1. 연구개발목표 달성도 ... 224
• 2. 대외기여도 ... 224
• 제5장 연구개발결과의 활용계획 ... 225
• 수중 고주파수 음파 관측시스템 및 수중음향 무선통신 채널 구축 – 협동연구 ... 226
• 제6장 연구개발과정에서 수집한 해외과학기술정보 ... 227
• 기술 보고서 ... 227
• 세미나 발표 자료 ... 227
• 제7장 참고문헌 ... 228
• 끝페이지 ... 232