Two days after the Mw 7.5 subduction zone earthquake along the New Britain trench, we get a swarm of seismicity further south offshore of Bougainville! (near the Solomon Islands) The largest earthquake has a magnitude M = 7.1. Here is my post about the Mw 7.5 earthquake.
One may come to the conclusion that these are related. They are regionally close in proximity. I would need to run a coulomb model (or look up an analogy, but I am late for a meeting right now) to see if these are related based on changes in stress following the subduction earthquake. Today’s earthquake is probably more related to the M 7.5 earthquake from April 2014 (see map below).
Today’s earthquake is extensional and most likely the result of flexure on the down going plate. The orientation of the moment tensor is aligned with the subduction zone to the east, so fits well with this model of plate flexure. As the downgoing plate (in a subduction zone) is locked and bends downwards. The uppermost part of the plate experiences extension and normal faults form (or reactivate pre-existing faults). This earthquake is likely along one of these “bending moment normal faults.”
Here is my interpretation: