A TEST OF THE SUPERCONDUCTING GRAVIMETER AS A LONG-PERIOD SEISMOMETER

Normal modes excited by the Minhasa peninsula earthquake of 18 April 1990 (M(s) = 7.5) are used to test the response of the Canadian superconducting gravimeter (GWR 12) in the long-period seismic band. The periods and associated Q values compare very well with those determined elsewhere. Splitting of a number of the higher order spheroidal modes (0S13 to 0S26) has been observed because of the low ambient noise at the site. The combined instrument and ground noise is nearly flat and close to 1 x 10(-19) cm2 s-4(0.1 nGal2) in the 1-5 mHz band.