[Island Chris]

I don't think Brian has a science degree either, but, like me, he has a well developed skepticism. For M.7 earthquakes, saying they are getting shallower does not mean much for the following reasons, unless you are talking about 500 km vs 10 km. That is because a M7 will break a wide range of depths. Probably the Tohoku (Japan) March earthquake broke from 30 or 40 km depth right to the sea floor (but very deep sea floor, maybe 7 km). The depth given is just the depth of initiation of a big rupture. They get this wrong all the time on TV/online. For example, the earthquake is 300 km away, when it actually ruptured to 100 km away.

Also, when you see a depth that is an even number, it usually means that they just tell the location program to use that, or an automatic system uses that.

You may know this, but if you click on a quake on the usgs map, it bring up more Click on scientific and for larger quakes, it will give you one or more focal mechanism solutions. Click on that and it will tell you more.

Chris