2006 M5.4 Yukon Flats Earthquake
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).
Both earthquakes were felt as far as Fairbanks.
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.
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.