As I have previously mentioned earthquakes can be caused by volcanoes or human activity.
(I; have mentioned; earthquakes can be caused by volcanoes or human activity; T:previously) Context(I have mentioned,List([3, 30))):(earthquakes; can be caused; by volcanoes or human activity)
I have mentioned,List([3, 30))
I earthquakes
have mentioned can be caused
earthquakes can be caused by volcanoes or human activity T:previously
by volcanoes or human activity