How do we know if was an aftershock in Haiti, rather than another earthquake?

By definition, - it's an aftershock.

Any smaller tremor after the major earthquake.

Yet again - aftershocks ARE earthquakes.

An aftershock is, simply put, a weaker earthquake:

-That follows the primary seismic event

-That occurs along the same fault

-That occurs on the same fault line a distance from the epicenter no greater than the length of the original tectonic rupture

All aftershocks are earthquakes, but if the earthquake comes after a stronger earthquake, and it is from the same fault line as the bigger quake, then it is called an aftershock.

Aftershocks are smaller earthquakes formed as the crust around the displaced fault plane adjusts to the effects of the main shock.

It occurred in the same area as the original quake; this is a familiar pattern associated with major earthquakes. It takes time for things to settle out after a big tectonic plate shift such as the one that recently happened in Haiti.

when I lived in Redondo Beach Cali, we had a 6.1 doozie, for at least 2 weeks we had 5.0 "after shocks" I considered these quakes, but scientists calle em after shocks :-) I am surprised and Happy they haven't had a tsunami :-) that would further cause mass destruction in an already destroyed land :-( while now living in Washington State, we had a 6. something? with very little if any (that I felt anyhoos) aftershocks??? so I just "roll" with what this world is capable of and Thank God we "haven't" (yet) had a catastrophic event, keep praying for these peoples:-) Peace/Love & God Bless

Check the definition of aftershock at www.dictionary.com ... aftershock means a small earthquake or tremor that follows a major earthquake.

An aftershock is an earthquake.

Again: aftershocks ARE earthquakes.

Umm, no... aftershocks are actually earthquakes that happen after earthquakes.