Is it true that earthquakes are not felt in a cave? I took a tour of a cave in northern California last weekend. The tour guide asked us, "If an earthquake occurred, what would we feel in here?"

My answer was, "fear," but she said we would feel nothing - that earthquakes are not felt underground.

Although I did not contest her assertion, I have my doubts about it - after all, don't earthquakes normally have their epicenter underground (well, all the time, I reckon, as they can't emanate from the air)? And if an earthquake happened to erupt from within a cave[rn], wouldn't it most definitely be felt there?

I would think one might even end up with a stalagtite stuck in his noggin.

UPDATE

And, if I'm right (that there could be a whole lotta shakin' goin' on while on a journey to the centre of the earth), has anybody lived to tell the tale and really done it (told the tale)? A first-hand account could be riveting.
Ground motion results due to passage of elastic waves. Now there are different kinds of waves, e.g., P waves, S waves, surface waves, etc. Most of the shaking (and therefore damage) is caused by surface waves. So if you are in a deep cave or mine then the amount of shaking you might experience can be much lower than on the surface. This of course assumes that the mine or cave is not right on the fault, but some distance (10s of km) away.

Having said that, there are some situations (based on the type of earthquake and local geology) in which waves can interfere constructively to cause significant shaking even at large depths, but this only happens in certain areas and not everywhere.

In many ways elastic wave propagation is similar to acoustic or water waves. Imagine a small explosive source in a lake/pond, let's say 50&nbsp;m underwater. After the explosion there will be more 'shaking' on the surface, but not much underwater unless you're extremely close to the explosive source.