Arizona experienced 100+ in the past quarter, of which 32 were accurately plotted. Brendan Hodge at the Arizona Earthquake Information Center (AEIC), forwarded this preliminary map of epicenters.
Mimi Diaz, who heads our Phoenix branch and is the PI on the AZ Integrated Seismic Network, reports that "The Halloween Swarm had over 100 microquakes, most less than M2.5. All of those are not represented on that map. However, there were a couple dozen in the M2.0-2.5 range that are shown on the map. The Hoover Dam earthquake was a discrete event, the Fredonia earthquake had a foreshock and a main shock, and the Wild Bend event had a main shock and an aftershock."