In 1964, the earthquake in the Plains occurred near the South Dakota / Nebraska border about 30 minutes before the Great Good Friday earthquake on March 27 (Local time - March 28 UT). It was felt throughout South Dakota and Nebraska. The event before today's earthquake occurred about 1.5 hours earlier than the Alaska earthquake in the same general area as the Good Friday earthquake. The two earthquakes in Kansas yesterday, as noted here were also reminiscent of the South Dakota events of March 24 and March 27, 1964.

The resemblances of the "foreshock" series in 1964 with the "foreshocks" to today's Alaska earthquake is quite uncanny, especially if there is no causative relation. It should at least give us pause to think of how the two sets of events may be related to each other.