Fifteen million years ago, during the Miocene Period, an uplift of the Intermountain West began. This geologic process continued into the Pliocene, adding up to 5000 feet of elevation to the landscape and producing east to west tension on the crust of the Great Basin. This tugging, which accelerated with the rise of the Sierra Nevada batholith, has thinned and fractured the crust, leading to the development of north to south fault lines throughout the Basin. Indeed, most of the Great Basin ranges are "fault block" uplifts, with a steep edge adjacent to the fault and a more gentle slope on the opposite side of the range.
The rise of the Sierra batholith and the stretching of the Great Basin continues today and, as one might expect, earthquakes are common throughout the region. Many of these are triggered deep in the crust and are barely noticeable at the surface; others, like those in Reno this past week, are closer to the surface and can produce significant damage. While the Great Basin quakes are not likely to be as powerful as those along plate margins (e.g. the San Andreas Fault), they could be catastrophic in populated areas.
Whether Reno, sitting near the eastern edge of the Sierra uplift, has endured the worst of this round is hard to predict. But it is safe to say that there will be plenty more regional earthquakes in the decades and centuries to come. Taking the long view, this rifting process will eventually split the Continent, the ocean will reclaim the Basin and the desert peaks will form islands in a vast, inland sea.
