L045 Rosedale No. 1 Bore, A.P.M Seismic survey , VIC, 1960

A seismic velocity survey of the APM Development Pty Limited No. 1 bore at Rosedale, Victoria, was made by the Geophysical Branch of the Bureau on the 3rd May 1960 using a TIC three-component well geophone. Measurements were taken with the geophone suspended in the well at selected intervals down to 5500 ft. It was apparent that signals reached the geophone by transmission along the cable by which it was suspended, and these interfered with the signals reaching the geophone along a path directly through the ground. This made interpretation difficult; however, by careful inspection of both the vertical and horizontal components of the signals received by the geophone at each depth, an interpretation has been made that yields a series of velocity/depth determinations. The average vertical velocity increases from 5000 ft/sec at the surface to 8930 ft/sec at a depth of 5500 ft. The average velocity in the Tertiary (0-2159 ft below datum) was computed to be 6420 ft/sec; the -werage velocity in the Mesozoic rocks penetrated (2159-5314 ft below datum) was 12,180 ft/sec. Two reflection spreads laid out and recorded in the vicinity of the bore showed the presence of reflectors at depths estimated to be in excess of 7700ft.