Toroidal splitting observations from the Great 1994 Bolivia and Kuril Islands Earthquakes

The June 9, 1994, Bolivia earthquake and the October 4, 1994, Kuril Islands earthquake provide a unique opportunity for a splitting analysis of the Earth's long‐period toroidal free oscillations. We present toroidal splitting observations for the 6 fundamental modes ₀T₄, ₀T₅, ₀T₆, ₀T₇, ₀T₈, and ₀T₉, and for the 5 first overtones ₁T₁, ₁T₂, ₁T₃, ₁T₄ and ₁T₆. The first identification of mode ₁T₁ is made possible by simultaneously fitting the multiplets ₁T₁ and ₀T₇. The observed splitting is reasonably well explained by current shear velocity models of the mantle. Our analysis yields new estimates of the center frequencies and quality factors of these 11 toroidal modes.