TA-Enabled Seismicity Study Lockridge, Fouch, Arrowsmith, 2011 The EarthScope USArray Transportable Array (TA) was deployed within Arizona from April 2006 to March 2009 and provided the opportunity to review seismicity on a statewide scale. In this study, we develop methods for producing an earthquake catalog using waveform data recorded by a TA-like regional array with ~70 km station spacing. Our catalog is complete to ml ~1.2 and contains crustal events as small as ml 0.0. We combine our new catalog generated from TA data with historical earthquake catalogs from various sources to produce the first comprehensive historical earthquake catalog for the state of Arizona. We have detected several previously unidentified areas of seismic activity in Arizona, suggesting that most regions of the state are capable of producing small-magnitude earthquakes. We also identify 16 earthquake clusters, many of which have swarm-like behavior. These swarms and clusters account for 42% of the seismic events that occurred during the TA deployment in Arizona, occur in all physiographic, geophysical and tectonic settings, and may represent an important mechanism for small-scale tectonic strain release within intraplate regions with apparently low seismicity levels. AZ stations EQ density Mag distribution April 2006-November 2008 USGS: ~10 eqs 92 stations Regional nets: ~50 eqs ANF: ~250 eqs 16 swarms/clusters This study: ~600 new eqs