Why is it important to study prehistoric earthquakes?

 It is important to study prehistoric earth quakes because they want to be able to tell if they are recurring, how big the earth quakes are. and it could also help in the future to help locals  know how to plan for a event like so.  I'm sorry if I'm too late.. 

Avertical or horizontal line used in graphs is called a(n) equatorhope this

Answer metamorphic rock;