Hi Amit, interesting if true. One problem is that the USGS catalogue makes not attempt to be complete. It is likely only M4.5+ for the globe. And, the effect you mention may be due to smaller quakes, which are mainly reported for USA. I don't know whether other catalogues are more complete for the globe down to smaller magnitudes.

But, I, and many of us, see patterns at times where they don't exist. That is one of the reasons Roger is so useful: he can check. Roger, do you think there is a catalogue you can use to check Amit's observations? I suppose you can just use all quakes in the USGS catalogue, and see what falls out.

Chris