1. If an earthquake's strength was 9.9 what would happen?
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The largest earthquake was a 9.5 event along the coast of
Chile in 1960. The second largest was a 9.2 along the southern
coast of Alaska in 1964. A 9.9 earthquake would be 4/10
of a unit larger than that of Chile, so it would release
10 raised to the power (1.5*4/10) = 4 times as much energy.
The fault length would also be about 4 times longer, or
4,000 km. Although we don't expect an earthquake of this
size, one of the places it might conceivably occur would
be along the Aleutian/Alaska subduction zone. This would
require the entire zone to rupture in one earthquake, which
we don't think has ever happened. Such an earthquake would
both cause strong shaking for 5 minutes or more as well
as generate a large ocean wave (tsunami) that would travel
at 800 km/hour across the entire Pacific Ocean. This wave
could would have low amplitude over the open ocean but would
grow in height as it reached shorelines and could cause
a lot of damage to near shore facilities and homes.
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