That's a hard one, Roger. Just how much ground motion is required to trigger
rupture has never really been determined, as far as I know. It is generally
accepted, however that earthquakes in Yellowstone were triggered by the Lander's
earthquake (Mw 7.6) That is a distance of about 1300 km.
The energy of seismic waves of Mw 8.5 is about 30 times this although the
amplitude is only about 10 times as great. At cusps near 120 degrees distance
the amplitude of body waves is about 10 times smaller than at 1300 km (from
seismological observation). Since the original amplitude of the Rat Island
waves was 10 times greater than Landers, but we are looking at a distance where
they are 10 times smaller than at Yellowstone, these cancel out, and the amplitude
of the Rat Islands waves at Chile were on the same order as those from
Lander's at Yellowstone.
Since we accept that triggering did occur at Yellowstone, it seems to me
that triggering is likely in Chile on the basis of this back of the envelop calculation.