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Comparison of seismic interferometry for surface wave extraction from traffic noise
강태섭(Tae-Seob Kang),이한별(Han Byeol Lee),안병석(Byeong Seok Ahn) 대한지질학회 2024 지질학회지 Vol.60 No.3
도로를 주행하는 차량으로 발생하는 교통 잡음을 활용하여 표면파 경험 그린함수를 추출하기 위해 네 가지 지진파 간섭법을 비교 분석하였다. 단순 및 초기백색화 상호상관, 역합성곱, 상호간섭 방법 모두 짧은 시간의 지진기록으로부터 표면파를 효과적으로 추출할 수 있음을 확인하였다. 초기백색화를 적용한 상호상관법과 상호간섭법은 단순 상호상관법보다 더 명확한 표면파 경험 그린함수를 제공하였다. 역합성곱 방법은 비물리적 혼선이 상대적으로 두드러졌다. 분산 분석 결과, 주파수 10 Hz 이상에서 수치 모델의 전단파 속도 400 m/s와 700 m/s에 상응하는 표면파의 기본 모드와 고차 모드를 명확히 확인할 수 있었다. 야외 실험 결과, 200 - 300 m/s 범위의 일정한 위상 속도를 확인하였으며, 이는 실험 지역 지표층의 전단파 속도를 적절하게 반영한 것으로 보인다. 교통 잡음을 이용한 지진파 간섭법이 천부 지층 전단파 속도 구조를 파악하는 데 효과적임을 확인하였다. This study compares and analyzes four seismic interferometry methods to extract empirical Green’s functions of surface waves from traffic noise generated by vehicles traveling on roads. The cross-correlation, deconvolution, and cross-coherency methods were evaluated using synthetic seismic records and field data. All methods effectively extracted surface waves from short-duration seismic records. Pre-whitened cross-correlation and cross-coherency methods provided clearer empirical Greens functions than raw cross-correlation. The deconvolution method exhibited non-physical crosstalk relatively. Dispersion analysis confirmed the fundamental and higher modes of surface waves above 10 Hz, corresponding to shear wave velocities of 400 m/s and 700 m/s in the numerical model. Field experiments showed consistent phase velocities in the range of 200 - 300 m/s, reflecting the shear wave velocity of the surficial layers in the study area. The findings confirm that seismic interferometry using traffic noise is effective for determining the shear wave velocity structure of shallow subsurface layers.
강태섭 ( Tae Seob Kang ) 한국지구물리·물리탐사학회 2012 지구물리와 물리탐사 Vol.15 No.2
Three-dimensional finite-difference simulation in a small-scale half-sphere basin with planar free-surface is performed for an arbitrary shear-dislocation point source. A new scheme to deal with free-surface boundary condition is presented. Then basin parameters are examined to understand main characteristics on ground-motion response in the basin. To analyze the frequency content of ground motion in the basin, spectral amplitudes are compared with each other for four sites inside and outside the basin. Also particle motions for those sites are examined to find which kind of wave plays a dominant role in ground-motion response. The results show that seismic energy is concentrated on a marginal area of the basin far from the source. This focusing effect is mainly due to constructive interference of the direct Swave with basin-edge induced surface waves. Also, ground-motion amplification over the deepest part of the basin is relatively lower than that above shallow basin edge. In the small-scale basin with relatively simple bedrock interface, therefore, the ground-motion amplification may be more related to the source azimuth or direction of the incident waves into the basin rather than depth of it.
강태섭 ( Tae Seob Kang ),이준기 ( Jun Kee Rhie ),최남수 ( Nam Soo Choi ) 한국지구물리·물리탐사학회 2015 지구물리와 물리탐사 Vol.18 No.1
Induced seismicity has been observed in the relation with lots of anthropogenic influence and at variety of geological conditions over the last several decades. This paper reviews those induced earthquakes and compares with each other as well as with natural tectonic earthquakes. Hydraulic fracturing is commonly used to enhance the permeability through new cracks in the rock formation. The process triggers the induced seismicity, which can give crucial information on the fracture network and oil/gas migration. In the similar way, unintentionally induced events during the production procedure of the field, dam reservoir, minig activity, or wastewater injection can be used to give insight into various hydrodynamic processes and changes of reservoir properties at a various scales. The general conclusion summarizes the uncertainty or limitations of knowledge up to date and presents some issues to be dealt with in the future research.