In 2011, there were 131 earthquakes detected by instruments in Arizona. The largest events of the year were magnitude (Md) 3.7 and 3.6 near Clarkdale in central Arizona, according to a summary compiled by AZGS seismologist Lisa Linville, and published today in our online magazine, Arizona Geology.
In 2010, there were 53 earthquakes recorded. Overall, seismic activity in 2011 represents a 160% increase from 2010, a 100% increase from 2009, and a 31% increase from 2008. About 36% of the quakes in 2011 were associated with swarms of small magnitude events that occurred over the space of a few days.