re: #201 lawhawk

[Link: earthquake.usgs.gov…]

Tons of aftershocks, and some of them are pretty serious in their own right.

Yep. The quake was over 6 miles down, which is really frakking deep. It would have to be on or in a subducted plate margin, since at that depth the normal geothermal gradient would mean you would have plastic deformation (no earthquakes) instead of brittle deformation. On subduction boundaries like the west coast of America and the east coast of Japan, the old, cold oceanic crust that is being over-ridden by the less dense continent tends to cool and rheostatically strengthen the surrounding lithosphere. The geothermal gradient is radically depressed, and you can get earthquakes much deeper what you would normally experience.