Hawaii is not on the edge of a tectonic plate like California. It is over a hot spot. The earthquake therefore is a result of Magma intrusion underneath that area. Hot spots within a plate are created by deep subterranean super heavy elements. The nuclear elements are decaying in a process called fission. This is similar to a nuclear power plant, but at a much larger scale. The immense heat created heats the magma so much that it rises and eventually breaks through the mantle under the ocean. The extruded magma has grown over time to create the Hawaii islands. The Hawaii islands are in a line because the Pacific Tectonic plate has moved, over millions of years, across the nuclear hot spot. Essentially every one of the Hawaii islands was formed from magma extrusion. When the magma is extruded above water level you have a volcano.
This earthquake could be a new magma fissure and the birth of a new island.