장대단층 중부 모곡리 지점 단층의 최후기 운동 시기와 지진 규모 추정

초록

The Mogok-ri site, located in the central part of the Jangdae Fault, is considered to have been reactivated during the Quaternary, displacing unconsolidated deposits. However, the numerical dating to understand the timing of most recent fault movement and the estimation of the seismic magnitude have not been performed. In this study, luminescence dating was carried out on the unconsolidated deposits exposed at the Mogok-ri site, and the moment magnitude was estimated based on the displacement measured from the outcrop. The luminescence dating results indicate that, considering the ages of the sediments cut by and overlying the fault, the timing of the most recent fault movement of the Mogok-ri site is constrained to be ca. 212~178ka. Assuming pure reverse dip-slip movement the maximum displacement of the Mogok-ri site is estimated to be approximately 0.8m. Applying this value to the empirical relationship yields an estimated moment magnitude of approximately Mw 6.5. The Jangdae Fault is located near densely populated areas and industrial facilities. The results of this study suggest that the Mogok-ri site, located in the central part of the Jangdae Fault, may have been associated with an earthquake of approximately Mw 6.5 during the Quaternary. Therefore, continued investigations of the Mogok-ri site are necessary from the perspective of seismic hazard assessment, including additional fault outcrop surveys, geomorphic offset analysis, and slip-rate estimation.

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