How does an ant know about Earthquake is it because of an organ or due to other factors?
No, they may not sense Earthquake by an organ but due to other reasons. This may be any other physical factors which can be measured.
"...There is therefore little reason to believe that these ants react to earthquake precursors other, perhaps, than those that may affect colonies directly, by altering physical variables that can be directly measured by other means..."
Fascinating though the behavior and physiology of ants may be, they cannot be employed as reliable predictors or even sensors of earthquakes.