As part of a recent update for hazard mitigation strategies in Arizona, the Arizona Geological Survey is characterizing seismicity and faulting for each county in the state. By far the most active county, Coconino hosted almost 50% of the activity that has occurred since 1830. Mohave is the second most active county with about 30% of the activity. Together with Yavapai, these three counties account for nearly 90% of all known historic activity in the state.The figure above shows the clustering of events within the Northern Arizona Seismic Belt and some of the known quaternary structures in the area.

Lisa Linville (6 May, 2011)