2014 M5.2 Minto Earthquake

Mainshock and Aftershocks: 

A magnitude 5.2 earthquake occurred on Saturday, August 30 at 7:06 pm AKDT (August 31, 3:06 UTC) in northern Alaska (red star on the map). It occurred at a depth of 16 km (10 miles) and was located 16 km (10 miles) E of Minto, 67 km (42 miles) N of Nenana and 70 km (43 miles) WNW of Fairbanks. The Alaska Earthquake Center reporded about 2,200 aftershocks through end of the year (open circles on the map). Two large delayed aftershocks occurred in October, magnitude 5.0 on October 21 and magnitude 4.9 on October 23. Another large aftershock, magnitude 4.2, occurred about 10 hours after the mainshock. As of end of December 2014, the seismic activity in the region remains above the background level. Time-magnitude plot for recorded aftershocks is illustrated in the below plot. Due to relatively good netowork coverage, aftershocks with magnitudes less than 1 are being detected.

Felt Reports: 

The M5.2 earthquake was felt widely in interior Alaska. Maximum intensity of shaking was reported as V - moderate. Multiple aftershocks were also felt in Interior Alaska communities.

Tectonic Setting: 

Tectonics in this region is dominated by large-scale right lateral strike slip faults: Denali in the south and Tintina in the north. In the region bounded by these faults prominent NE- to NNE-striking seismic zones exist, but have not been directly linked to surface fault exfions. These zones from west to east are referred to as the Minto Flats, Fairbanks and Salcha. Strong earthquakes were recorded in this region previously, such as the 1937 M7.3 earthquake in Salcha zone, three M5-6 events in 1967 in Fairbanks zone, and 1995 M6.0 Minto Flats earthquake (orange star on the above map). Prior to the 1995 earthquake, a magnitude 5.0 event was recorded just south of the 2014 earthquake source.

Source Mechanism: 

The elastic-wave radiation pattern of the M6.0 event indicates strike-slip faulting consistent with left-lateral motion along the faults within Minto Flats seismic zone or right-lateral motion on a conjugate fault. The latter is a preferred interpretation for this earthquake sequence.