More than 4.6 million Arizonans live in the areas where people felt the ground shaking from last nights earthquakes near Black Canyon City, according to information posted by Ramon Arrowsmith, ASU geology professor, on his "Active Tectonics" blog -
http://activetectonics.blogspot.com/2015/11/links-and-commentary-on-earthquakes-11.html. The estimate comes from the USGS.
Ramon's added a number of links to relevant background materials and made the observation that "the mapped active faults to the east (Horseshoe, Carefree, and Sugarloaf--all similar orientation." We have not yet processed the first motions of the quakes to see what type and direction of movement is associated with the ruptures, and whether they correlate with the rough north-south alignment of the epicenters.
Ramon posted seismograms of the three events as recorded at ASU (right).