The Vp/Vs ratio of crustal material is estimated to be 1.73 (¦Ò = 0.249) for the upper and middle crust and the ratio increases with the depth in the lower crust. The Gyeonggi massif in the north of the profile has a lower Vp/Vs ratio than other tectonic units. The average crustal Vp/Vs ratio of 1.74 (¦Ò = 0.253) is remarkably lower than the average value 1.78 (¦Ò = 0.27) for the bulk continental crust. The low average crustal Vp/Vs ratio is similar to that measured in eastern China. The empirical analysis using both P-wave velocity and Vp/Vs ratio shows that the upper and middle crust is dominantly felsic and the lower crust is intermediate in composition. The absence of the mafic material in the lower crust that is also found in eastern China contrasts with the generally accepted global model of the mafic lower crust.