Based on geologic evidence,the average return period for large Cascadia megathrust earthquakes is in the order of ___________.

Question

Quizplus · Accepted Answer

The best choice based on geologic evidence is option C, 600 years, as studies of sediment layers and other data suggest that large Cascadia megathrust earthquakes occur on average every 500-600 years. Option D, 1,000 years, is also a possibility as some studies suggest a longer average return period, but option C is the most widely accepted estimate. Options A and B are too short for the return period of such large earthquakes.

Based on Geologic Evidence,the Average Return Period for Large Cascadia