In reply to Andy DB:
What is mapped is usually peak ground acceleration, sort of the maximum shake, thoigh the length of time the shaking occurs for may also be considered. The uniform circles under the sea are likely because the geology is assumed to be uniform. On land it is known not to be creating more complex patterns. An interesting thing to know is solid rock generally has a lower PGA than a sedimentary basin (e.g. dried up lake).
On a more practical note, I'd recommend removing any pictures above your bed, and following the "drop cover hold" if/when you get shaken again.
Also watch out for rocks being dislodged from hillsides when you are at the crag if shaking kicks off.
https://www.google.com/url?sa=t&source=web&rct=j&url=https://ww...