Journal of The School of Marine Science and Technology,Vol.2 No.3
Exploration of the Underground Structure
in and around the Northern Part of Hua-Tung Longitudinal Valley, Taiwan
by Quarry Blasts:Preliminary Report
Hisatoshi BABA, Yang YI-SHENG, Atsushi IWASHITA and Susumu IIZUKA
Abstract
From March to June in 2004,we carried out the seismic refraction exploration by using quarry blasts to clarify
the sub-surface structure in and around the northern part of Hua-Tung Longitudinal Valley in Taiwan. This
experiment used two quarry sites,SP.1and SP.2,which were located at Wan-Jung and San-Chan in the middle and
northern parts of Hualien prefecture,respectively.The quarry blasts has been performed approximately once a week
by using an explosive of 100-300kg in order to provide stones for constructions and so on.We chose three seismic
lines, Line A, Line B and Line C, in this study area. Line A of about 47km long was elongated from SP.1to SP.2,
which ran along the valley in the direction of the north-north-east.Line B of about 10km long was extended to the
east from SP.1, which was across the valley. Line C of about 12km long was extended to the north-east from SP.
1. Seismic refraction data on Line A were obtained from two sources at both ends of the line,while those on Lines
B and C were obtained from a source only at SP.1. The former data showed clear records to the point 27km from
each end of Line A.They indicated the upper layer with a velocity of4.4km/sec and the lower layer with a velocity
of5.7km/sec.The latter data showed clear records over the entire Lines B and C.Direct wave velocities of4.4km/
sec and 4.5km/sec were calculated for Lines B and C, respectively.