It isn’t due to extreme cold, nor latitude, I don’t believe. The body of water in the embedded Google Map here is in a very cold area, e.g. -20 F average winter temperatures, in the northern part of Canada’s Northwest Territories. Yet even chillier bodies of water are blue e.g. in the Arctic Ocean, some distance due north.Possibilites
I don’t know if this reveals anything or not. The first (and only) thought that occurred to me was that it was a good idea that no one decided to build any nuclear power plants along the San Andreas Fault. Other than the two reactors in California, there are hardly any nuclear power plants within 1000 miles of any high seismic activity areas.
What if I interpreted this data visualization to mean that nuclear power plants dramatically reduce or even stop earthquakes? After all, who is to say in what direction the "causally correlated" data should point? Just think of the action item that would suggest to policy makers!
Ignore the fact that seismic activity was already well-known and recorded by the time nuclear power plants were built. Presumably, it was taken into consideration as a risk factor by those who were making decisions about where to build them.