Okay so you need to tell your kids to either get under a table or desk or in a doorway. I grew up on the San Andreas fault so I've been in my share of earthquakes...they never get less scary...if it's a big one(like 7.0) it can last up to a few minutes with some large aftershocks, but a 4-5 pointer will last around 30secs - 1 minute. Make sure you don't have anything that could potentially fall on you or your kids over their beds in case it's the middle of the night. Need any other pointers give me a call. Love ya.