National Weather Service United States Department of Commerce

A magnitude 7.9 earthquake occurred off the coast of Alaska early on Tuesday, January 23. Due to its location, damage in Alaska was minimized. However, the resulting underground movement was detected by seismometers far away. 

This seismograph is located near Mansfield, in Piatt County. Each of the lines represents a time frame, in 15 minute increments past the hour (black, :00 to :15, red, :15 to :30, blue, :30 to :45, and green :45 to :60).  Normally, they show very small oscillations. However, once the quake is detected, the oscillations change to a more sharp up-and-down register on the seismograph. While the quake occurred at 3:31 am CST, the underground movement took nearly 10 minutes to reach this far (around 3:40 am). 


Alaska earthquake 1/23/18