I actually need to know this: I am assuming that the focal mechanism from NEIC/USGS and Harvard are lower hemisphere, not upper. Checking the M4.6, unless they redefined dip and plunge, it is indeed lower hemisphere. Seismologists will use upper hemisphere focal mechanisms, including in publications. They should probably stop doing that...confusing to structural and other geologists.

Otherwise, Mike is correct...but take a circular salad bowl and something planar ...paper cut in arc that fits salad bowl, and play around with the intersections...can draw on with crayon or chalk or something. Then look straight down: the 2D view is what you see on-line.

Chris