The depth (73 miles, 118 km) and location of this earthquake indicate that it occurred inside the subducting Pacific Plate as an intraplate event rather than at the plate interface. The rupture was caused by extension of the plate as it is pulled into the mantle by its own weight.

Hypocentral relocations done by Macpherson and Ruppert 2015 show that most aftershocks did not occur on the rupture plane, but are concentrated in the adjacent Wadati‐Benioff zone.

Below is a plot of 1465 relocated aftershocks recorded between June 23 and December 31, 2014 color coded by depth. All 10 gCMT solutions for this time period are plotted with their new locations. Cross sections are plotted parallel to the dip of the main shock nodal planes from the mainshock’s gCMT solution. The red dashed lines are oriented parallel to the dip of the nodal planes in order to show alignments (or lack thereof) with the seismicity. The white contours are the depth to the top of the subducting slab, from Slab 1.0. (Macpherson and Ruppert 2015)

A secondary plane of seismicity aligns well with a moderately dipping nodal plane reported by the Global Centroid Moment Tensor Project, and the separation of these locations and the main shock hypocenter from the slab indicates that the main shock ruptured into the oceanic mantle (Macpherson and Ruppert 2015).