Due to seismic interference from the earlier quake, the mechanism, faulting geometry, and rupture details of the mainshock are not yet fully understood.

Aftershocks, some larger than magnitude 6.0, occurred along a 470-km-long segment of the subduction zone,[8] as well as on the outer-rise, and on a transform fault.

Several hours after the magnitude 7.5 quake, the U.S. Geologic Survey revealed that a second, much larger, and "complex" event had taken place three minutes after the occurrence of the 7.5.

Based on the presence of numerous aftershocks on the subduction zone and outer-rise, the earthquake likely ruptured the megathrust all the way to the trench.

The 7.5 Mw  foreshock consisted of two smaller sub-events that initiated along the deeper portion of a thrust fault, but ruptured up-dip.

The 7.6 Mw  sub-event involved breaking the shallow subduction zone, displaying characteristics of a tsunami earthquake.

The larger and shallower mainshock was a slow-rupturing tsunami earthquake that released 70 percent of the seismic moment.

[13] The South Sandwich Islands mainshock came just two weeks after a magnitude 8.2 earthquake struck the Alaskan Peninsula and triggered a small tsunami.

[37] The largest aftershock, measuring 7.1 Mw, occurred on August 22 on a shallow normal fault near the outer rise, within the subducting South American Plate.

[3] A tsunami with a maximum run-up height of around 75 cm (2.46 ft) was measured at King Edward Point, South Georgia Island.