Analysis of the Causes of Clustered Scismicity Registered in Yeoncheon, the Middle Part of the Korean Peninsula through Gravity Field Interpretation and Modeling

Abstract

Gravity data were analyzed to identify the cause of clustered seismicity that occurred intensively in Yeoncheon, located in the central part of the Korean Peninsula. Our analysis suggests that the En echelon faults developed in the northwest-southeast direction. In addition, in the eastern part of the Dongducheon Fault, it was interpreted that high-density lower bedrock intermittently lifts close to the surface due to vertical tectonic movement accompanied by a flower structure. The fracture zone of the Dongducheon Fault is estimated that the width is about 200 m, the depth is at least 5 km, and the density is about 15% lower than the adjacent rocks. It is analyzed that the shallow earthquakes that occurred within 5 km depth was concentrated along the low-density En echelon fault fracture zone developed between the high-density rocks intruding close to the surface. Therefore, the earthquakes can be interpreted as the result that the north-south stress caused by the dextral tectonic movement of the Dongducheon Fault activated the En echelon fault in the northwest-southeast direction.

Displacement of Dongducheon and Wangsukcheon Fault Observed by Gravity Field Interpretation

“…1, Choi et al, 2012;Chung et al, 2014;Choi et al, 2021;Kil et al, 2021;Lee et al, 2022 (Kim, 1973). 암석학적인 연구 결과 (Kim, 1973;Yoon, 1997) Kil et al, 2021;Malehmir et al, 2022;Lee et al, 2022;Choi et al, 2022) 이후 동두천 단층의 활성화 여부에 관한 관심은 더 욱 커졌으나, 우향의 이동 변위를 보인다는 보고 이외에 는 지구조 운동의 규모에 관한 연구가 부족하다 (Kim, 1973;Chwae et al, 1996;Kee et al, 2005;2008;Kho and Song, 2005).…”