台湾花東縦谷北部周辺地域で採石発破を利用した屈折法地震探査による地下構造調査を実施した.観測に用いた採石発破場には, 花蓮縣中央にある萬栄(SP.1)と北部の三棧(SP.2)の2箇所を利用した. これらの採石場では, ほぼ週に1度の割合で, 100～300kgの火薬を使用し採石を行っている. 探査測線は, 両端発破となるLine A (測線長約47km), SP.1から花東縦谷を東西に横断する片測線Line B (測線長約10km) と北東方向に延びる片測線Line C (測線長約12km)の3測線とした.

観測の結果は, 短測線Line B と Line C では, 測線全体にわたり良好な波形記録が得られ, それぞれ4.4km/sec・4.5km/secと非常に早い速度の直達波が観測された.一方, 測線Line A ではSP.1とSP.2のそれぞれの発破点から約27kmまで良好な記録を得ることができた. その結果, 発破点付近では4.4km/secの速度を持つ表層の下に, 速度5.7km/secの層が観測された.

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.1 and 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 100-300 kg 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 47 km long was elongated from SP.1 to SP.2, which ran along the valley in the direction of the north-north-east. Line B of about 10 km long was extended to the east from SP.1, which was across the valley. Line C of about 12 km 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 27 km from each end of Line A.They indicated the upper layer with a velocity of 4.4 km/sec and the lower layer with a velocity of 5.7 km/sec. The latter data showed clear records over the entire Lines B and C. Direct wave velocities of 4.4 km/sec and 4.5 km/sec were calculated for Lines B and C, respectively.