All right! That was exciting and a little bit scary. Most all earthquakes scare me because I recognize they might get bigger or trigger a bigger one.
This earthquake is most likely on a northeast striking strike-slip fault in the downgoing Gorda plate. The GP is caught in a vice between the older and stronger North America and Pacific plates.
Here is a map I made in google earth showing historic earthquakes. Note the larger gray circle to the northeast of today’s earthquake. That is the 1980 Mw = 7.2 earthquake that caused extensive damage in Humboldt County (knocking the bridge partly down on hwy 101 near CR). Today’s earthquake appears to be along the same fault system that ruptured in 1980:
Here is the SCEC page: http://www.data.scec.org/recenteqs/Quakes/nc72086051.html