Well dont they have those 'thingee ma jigs' that I have seen in countless movies in the 80????
Apparently now you can buy cheaper version of some high tech ones for your homes
There are various scientific and geological as well as natural phenomenons to predict the whereabouts and magnitute of earthquakes.....sometimes the roundabout time as well!
And even if its harder to predict what, where and when on a bigger scale, it is still possible to warn sometimes upto a few hours in advance......very useful when even a few minutes count!!!