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Magnitude 5.9 and 6.1 Earthquakes on December 21, 2007 near Adak, Alaska
Two strong earthquakes occurred approximately 175 km (109 miles) WSW of Adak, Alaska at 2:24 PM EST, December 21, 2007. For more information on this event, see these USGS web sites:
https://earthquake.usgs.gov/eqcenter/recenteqsus/Quakes/us2007leaj.php
https://earthquake.usgs.gov/eqcenter/recenteqsus/Quakes/us2007leak.php
These earthquakes were recorded on instruments in the Kentucky Seismic and Strong Motion Network, operated jointly by the Kentucky Geological Survey and the Department of Earth and Environmental Sciences at the University of Kentucky.
The graphic below is the actual record of the earthquake made by 10 Network instruments. Note the contrasting response of each instrument to the two earthquakes. The magnitude 6.1 earthquake released approximately twice the amount of energy as the 5.9 earthquake.
