In order to investigate in detail structures of the fractured fault band, the VSP tests were conducted using a 750m deep borehole penetrating the Nojima fault in Awaji Island. The borehole penetrates the fault clay band at a depth of 624m in the Hirabayashi area. The offset VSP survey, conducted by the aid of hydrophone through the naked borehole, detects many characteristic phenomena resulting from the fault fracture. Largely fractured lithofacies are found by the core observation at a depth in a range from 557 to 673m. P-waves propagate at 4.6 and 5.1km/s above and below the fractured band, respectively. The fractured band is subdivided into 2 sections, both being of low speed of 4.5 and 3.1km/s. The X1 and X2 phases resulting from the fault fracture are also observed, above and below the fractured band. The causes for these wave phases are now under investigation. 4 figs.