Say you had a home near a cliff facing the ocean. How high would that cliff have to be in order to not have the home destroyed? I’m talking about an average size tsunami. I realize that if a meteor lands in the water 10 miles off shore, all bets are off.
I think this is the highest ever reached, so if you’re 1800 feet up you’re safe. This was an unusual event, akin to your meteor strike, so it’s probably not an answer to the real question you are asking.
Now that we have widespread videos showing what real tsunamis actually look like, it turns out the term “tidal wive” is a fairly apt description. They aren’t real tides but they look more like extreme versions of them rather than one huge wave that rises up out of the ocean. The ocean level itself rises and swallows up everything in its path coming in and going back out as the sea level equalizes again.
That said, the highest tsunamis on record are less than 100 feet high so you should be safe with that as long as it doesn’t destroy the part on the cliff itself that your house sits on (a real possibility).
If you’re in California, you can look it up on a map.
There’s no one answer to this because it depends on how big a particular tsunami is by the time it gets to you.
If you want to evaluate your potential risk at a particular site, most tsunami-prone areas have maps like the one isaiahrobinson provided that combines topography data with historical risk.
If you can’t find one easily, try asking your local city government or maybe even insurance company.