[1] School of Civil, Urban and Geosystem Engineering, Seoul National University, Shinlimdong, Kwanak-gu, Seoul, 151-742, Korea, Republic of
[2] Division of Resources Development, Korea Inst. of Geology, Mining/Mat., Kajung-dong, Yusung-gu, Taejon, 305-350, Korea, Republic of
[3] Department of Civil Engineering, University of Suwon, Wawu-ri San 2-2, Bongdameup, Whasung-gun, Kyungki-do, 445-743, Korea, Republic of
[4] Geospace Development Team, Sunkyong Eng. and Constr. Ltd., Kwanhun-dong, Jongro-gu, Seoul, 110-300, Korea, Republic of