painful fault
Along fault lines.
Because it is a fault and earthquakes usually occur near faults.
The epicenter for the 1960 Great Chilean Earthquake or Valdivia Earthquake happened near the city of Cantete about 100 miles south of the 2010 Chile earthquake.
it happened on a blind fault (one where the fault line does not reach the surface)
Earthquake/volcanic activity occur almost exactly the fault line where plates about
The Chilean earthquake was caused by subduction zone stress, where the Nazca Plate slid beneath the South American Plate. The fault associated with this event was a megathrust fault, specifically the interface between the two plates.
This would have been an aftershock from the main earthquake that occurred on the 27th of February. The aftershocks occur because there are still stress concentrations in the crust around the fault even after the main quake and these concentrations of stress (and their resultant strain) can still cause fault ruptures leading to earthquakes. For more information on the major earthquake in Chile on the 27th of February, please see the related question.
wherever there is a fault line
Along a plate boundary or a fault line.
strike slip
The earthquake of Japan occured because Japan is on a major fault line.
The Great Chilean Earthquake