What's it called when an earthquake happens in a place that used to be an ancient lakebed? It happened to Mexico City. Well anyway, The Salt Lake Valley is an ancient lakebed. I think I felt a little bit of that effect after the main shaking was over, there was a bit of "my girlfriend is getting out of the waterbed" feeling where there were some waves that lasted for several seconds. In a major earthquake that reverberation can cause a lot of additional damage.