A close-up of the US National Oceanic & Atmospheric Administration (NOAA) equipment funded by the US Department of Commerce. Why spend billions on a system that cannot react to a 7.1 (a biggeee) such as the one in Haiti.
In order to determine the likelihood of future seismic activity, geologists and other scientists examine the rock of an area to determine if the rock appears to be "strained". Studying the faults of an area to study the buildup time it takes for the fault to build up stress sufficient for an earthquake also serves as an effective prediction technique.
Despite considerable research efforts by seismologists, scientifically reproducible predictions cannot yet be made to a specific hour, day, or month but for well-understood faults, seismic hazard assessment maps can estimate the probability that an earthquake of a given size will affect a given location over a certain number of years.
When living in the Caribbean island of Grenada, I saw these and met the staffs who operated them. Now tell me they didn't know!