Earthquakes of size 6.6 are extremely rare, the last comparable quake was back in 1987 at 6.7 on the Richter scale. The good news is Geologists say that these strong earthquakes in Hawaii tend to be spaced out over time
According to the USGS and our information it looks like this earthquake was a strike slip earth quake. It had a component of up and down motion but primarily it was a strike slip earth quake. Not unlike what you would find along the San Andreas Fault. So in other words, in stead of the slippage moving up or down the fault, the earth's crust shifted side to side, so that's a bit unusual.