Factors are that earthquake insurance has not always been readily available, and that the earthquake hazard of the region has been underrated. All of these earthquakes have magnitude estimated to be about 6.0 or larger. If an earthquake of this magnitude occurs close to a population center, it is likely to cause at least some damage. Thus the probability of a magnitude 6 or greater event is more than the annual probability of a fire. However, because the area is so large, the chance of it being close enough to damage a randomly placed house in the area is small.
Earthquakes happen on faults.
For that reason, one might decide to study a fault map of the area, and use the distance to the nearest fault to help decide whether to buy insurance. Unfortunately, it is likely that numerous faults in the area are still undiscovered. Furthermore, most of the small earthquakes recorded by the Seismological Laboratory do not show a clear relationship with the large mapped faults. Earthquakes with magnitude less than about 6.5 are not very likely to break the surface. Thus, although the fault map may show you where the nearest earthquake with magnitude 7.0 or greater could occur, a magnitude 6.0 or greater could occur closer.