2006 M6.4 Rat Islands Earthquake

The June 14, 2006 earthquake occurred near the margin of the rupture zone of the M7.7 earthquake of November 17, 2003. The M7.7 event ruptured the boundary between the subducting Pacific and overriding North American plates.

The 2003 sequence was an underthrusting event, however this sequence in June 2006 was not. The faulting parameters estimated from the waveform inversion indicate strike-slip type of motion for both the mainshock and the largest aftershock. It's location, shallow, and above the down-dip end of the locked interface, is more consistent with this event occurring within the crust of overriding North American plate.

In the western Aleutians, the crust is partitioned into rotating blocks, such as Buldir Block to the east and Near block to the west of the June 14, 2006 event location. If this event is the manifestation of the block rotation processes, then the NE-striking focal plane is the fault plane for this sequence. It's mechanism is consistent with the clockwise rotation of the crustal blocks. The aftershock locations are also consistent with the rupture along the NE-trending fault plane.