A Study on the Deep Structure of Yangsan Fault by Electric and Electromagnetic Surveys in Unyang and Bong-gye Areas, Kyeongnam Province, Korea

경상남도 언양 및 봉계리 지역에서의 전기, 전자탐사에 의한 양산단층의 심부구조 연구

Electromagnetic and electric surveys were performed to reveal the deep structure of the Yangsan fault in the Bong-gye and Unyang areas, Kyeongnam Province, Korea. Especially, high-frequency magnetotelluric (HFMT) method of EM survey was mainly employed to study the deep subsurface configuration of Yangsan fault. HFMT survey was performed at 25 points of spacing 50 m, making 1.3 km survey line in Unyang area and 13 points of spacing 50 m, making 0.6 km survey line in Bong-gye area. Two 2-D cross-sections (Unyang and Bong-gye areas) were achieved as results. Electric survey by dipole-dipole array was performed to study the structure of shallow subsurface and compare the results with HFMT surveys. The results of HFMT and electric surveys show that Yangsan fault is a geologic boundary. It is very narrow and steep (about $80^{\circ}C$), and extends to 1~1.5 km depth.