**Abstract**

On 23 June 2014, an *MW* 7.9 earthquake occurred in the Rat Islands region, Alaska, United States. We inverted the full moment tensor for the mainshock, and found the shallow-dip nodal plane (P1) is: strike 207.4°, dip 27.1°, slip 12.7°; the steep-dip plane (P2) is: strike 308.7°, dip 84.2°, slip 116.5°. The larger aftershocks that have depth phase records were relocated and found the majority were distributed along a moderate dipping trend. The steep-dip plane was selected as the causative plane. Using the steep-dip plane as the rupture plane, source rupture process inversions were performed. The obtained maximum slip was about 3.5 m. The optimal rupture velocity VR was about 2.0 km/s. The shallow-dip plane was also used as a rupture plane to perform rupture inversion trials. Curiously the overall waveform fit between the observed and the synthetic seismograms is slightly better than that when the steep-dip plane was used. The catalogue hypocenters of the aftershocks with magnitude ≥ 4.0 were used to simulate a spatial plane. The simulated plane is moderate dipping towards north-west. When the simulated plane was used as the rupture plane, the overall waveform fit was poor. The moderate dipping plane was not the causative plane.

**Keywords:** the 23 June 2014 Rat Islands *M*<sup>W</sup> 7.9 earthquake, source rupture model, aftershocks, master-event relocation, depth phase
