There is also a strong correlation between the phases of the moon and strong earthquakes. And a cool urban legend story to go along with it.
I'd have to say there are probably a lot of additional ideas and theories on what might add to the events, Ken. This information seems as plausible as I've seen or heard.

Years ago in college I jokingly made a diagram on a black board of what my thoughts on causes of quakes using the state of California as the primary target point if you will. My thought was based more on geological with oil drilling, ground water consumption, overall weight of buildings, population, freeways, along the fault lines. As well as a variety of other factors including atomic bomb tests below ground level in Nevada, etc. etc. Of course today you could factor in fracking too. It was all done in jest back then, but one has to wonder if there are possible contributing factors........