In June 9, 1994 what caused an earthquake occurred in Bolivia?

Answer 1

The movement of tectonic plates that are being pushed in different directions, either to the side or up an down. Eventually the fault can't take the pressure anymore and move the material that is far down in the earth which also moves the surface. The energy builds up and lets go all at once.

Answer 2

I forget if this one was caused by the lunar eclipse (sun and moon in alignment causing greater gravitational pull on the gelanous core of the earth that actually wobbles around offcenter following the moon), especially when the moon s at it's closest (apogee) of it's ellipitical orbit.