That is an individual decision, which depends on the risk that homeowners are financially willing to take. It also depends on their confidence in the quality of their homes, since there is quite a large deductible on most policies. Some seismologists do have it. All of these are earthquakes. Aftershocks are smaller earthquakes occurring after a main shock, and they keep the hazard relatively high for a certain period after any large earthquake.
Foreshocks are smaller earthquakes occurring before a main shock.
Only with hindsight can we distinguish what are foreshocks and aftershocks. Ideally you should get the same magnitude for an earthquake no matter where you measure it. Seismologists also use an intensity scale to quantify the effects of an earthquake at particular places. Each step of one in magnitude is an increase of thirty times in the total energy of the earthquake. That is the same as an increase of ten times in amplitude, or the size of typical ground motion.