Cause they just are.
the first is colon cancer.
the earthquakes that happened
Diarrhea is the biggest kill in the developing world.
Are you referring to Earthquakes during or before our human race cultivated the planet because to answer this question the biggest Earthquakes happened before our existence. During our existence I'm sure you can find the largest Earthquakes in Asia.
The biggest earthquakes in the world are expected along the plates that are on the inside of our earths crust like the mid Atlantic plate or the plate that caused the earthquake in Haiti
The one with the biggest gun.