> Right. The "once in X years" reporting is always exaggerated, by subtly constraining it to a specific geographical point. Not really. You got it exactly back

> Right. The "once in X years" reporting is always exaggerated, by subtly constraining it to a specific geographical point. Not really. You got it exactly backwards. The return period of an event is determined based on all recorded events. This does not mean that massive events that took place in the past didn't existed if no record was kept. Consequently, massive events are underrepresented both in magnitude and in frequency, and consequently estimates of their return period tend to be larger. Think of it this way: the concept of the return period of an event (i.e., this is a one in X year's event) is determined based on the average time between similar events.