심부 퇴적층 탐사를 위한 수신함수와 표면파 위상속도를 이용한 다측점 자료의 복합 역산

Multi-station joint inversion of receiver function and surface-wave phase velocity data for exploration of deep sedimentary layers

  • Kurose, Takeshi (Interdisciplinary Graduate School of Science and Engineering, Tokyo Institute of Technology) ;
  • Yamanaka, Hiroaki (Interdisciplinary Graduate School of Science and Engineering, Tokyo Institute of Technology)
  • 발행 : 2007.02.28

초록

이 연구에서는 심부 퇴적층의 S-파 속도구조 추정을 위하여 여러 지점에서 획득된 수신함수와 표면파 위상속도 자료를 이용하는 유전자 알고리즘 기반 복합 역산기법을 제안하였다. 이 방법은 서로 다른 지점에서 획득된 자료를 동시에 역산하기 위해, 역산대상 지역 내 모든 측점 상부의 지층 물성 - 특히 S-파 속도 -이 균열하다고 가정하는 방식으로 역산대상 지역 상부층의 층서적 연속성을 고려한다. 인공합성 자료를 이용한 수치실험 결과, 본 방법은 제한된 주기대역을 가지는 표면파 위상속도 자료만을 모델링 할 때 발생하는 심부 지층 물성정보에 대한 불확실성을 효과적으로 줄일 수 있음을 보여주었다. 또한 본 연구에서는 한 지점에서 획득된 지진파 기록으로부터 구해진 수선함수와, 일본 동경 중부지역에서 수행된 미소진동탐사로부터 획득된 두 개의 레일리파 위상속도 자료에 대해 제안된 기법을 적용하였다. 그 결과, 추정된 지하 구조는 선행된 탄성파 굴절법 탐사와 심부 시추공 자료와 잘 일치하는 양상을 보여주었다. 이러한 측면에서, 제안된 방법은 수신함수만을, 흑은 표면파 위상속도 자료만을 이용하는 개별역산에 비해 보다 정확하고 신뢰할 수 있는 모델을 제공하는 방법이 될 수 있을 것으로 판단된다.

In this study, we propose a joint inversion method, using genetic algorithms, to estimate an S-wave velocity structure for deep sedimentary layers from receiver functions and surface-wave phase velocity observed at several sites. The method takes layer continuity over a target area into consideration by assuming that each layer has uniform physical properties, especially an S-wave velocity, at all the sites in a target area in order to invert datasets acquired at different sites simultaneously. Numerical experiments with synthetic data indicate that the proposed method is effective in reducing uncertainty in deep structure parameters when modelling only surface-wave dispersion data over a limited period range. We then apply the method to receiver functions derived from earthquake records at one site and two datasets of Rayleigh-wave phase velocity obtained from microtremor array surveys performed in central Tokyo, Japan. The estimated subsurface structure is in good agreement with the results of previous seismic refraction surveys and deep borehole data. We also conclude that the proposed method can provide a more accurate and reliable model than individual inversions of either receiver function data only or surface-wave dispersion data only.

키워드

참고문헌

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