2006 M5.4 Yukon Flats Earthquake

Mainshock and Aftershocks: 

The Alaska Earthquake Center located a moderate earthquake that occurred on Saturday, February 4th at 11:17 PM AKST in the north-central region of Alaska. This earthquake had a moment magnitude of 5.4 and was located at a depth of about 9 km (larger red star). It was located 54 km (34 miles) SE of Chalkyitsik and 67 km (42 miles) NE of Circle. The largest aftershock (M5.1) occurred at 7:43 AM AKST on February 5th (smaller red star). The AEIC located a total of 125 aftershocks through the end of February (white circles). 

Felt Reports: 

Both earthquakes were felt as far as Fairbanks.

Tectonic Setting: 

All events occurred north of the Tintina fault, a strike-slip structure striking SE-NW (red line). Due to the sparse station coverage in the area (yellow triangles), the earthquake locations have rather large uncertainties. 

Source Mechanism: 

The source parameters of the mainshock and larger aftershocks from wave-form modelling indicate strike-slip faulting, either left-lateral on a NE-striking focal plane or right-lateral on a SE-striking plane. The latter is consistent with the sense of motion along the Tintina fault. The former is similar to the NNE-trending seismic zones located farther south between the Denali and Tintina faults. A M4.5 aftershock later in the sequence has a normal faulting focal mehcanism, consistent with faulting on the NE-striking plane. Therefore, the NE-striking focal plane is a more likely fault plane of this sequence.