TOROIDAL SPLITTING OBSERVATIONS FROM THE GREAT 1994 BOLIVIA AND KURILISLANDS EARTHQUAKES

The June 9, 1994, Bolivia earthquake and the October 4, 1994, Kuril Is lands earthquake provide a unique opportunity for a splitting analysis of the Earth's long-period toroidal free oscillations. We present tor oidal splitting observations for the 6 fundamental modes T-0(4), T-0(5 ), T-0(6), T-0(7), T-0(8) and T-0(9), and for the 5 first overtones T- 1(1), T-1(2), T-1(3), T-1(4) and T-1(6). The first identification of m ode T-1(1) is made possible by simultaneously fitting the multiplets T -1(1) and T-0(7) The observed splitting is reasonably well explained b y current shear velocity models of the mantle. Our analysis yields new estimates of the center frequencies and quality factors of these 11 t oroidal modes.