Roger, thanks for your response. I was happy to wake up this morning to the new thread.

Yes I would be very interested to have a look at your program. Do you have a link? It sounds very interesting. How does it get the data? Can it accept an automated hyperlink to the USGS list? Their data was recently made very Excel friendly.

Yes, perhaps any pattern is an illusion. Or is it extremely complex?

Just for interest sake, take a look at the 7 events, beginning with the North Sea at 22:20 on 3/14 from the USGS list. There is a trend there in lattitude that gives me the impression that the activity is moving in a specific direction. This is one type of trend that I often see. If the activity moves in a direction, how does that interact with historical trends? Thinking of one location only, it is easy to think how historical data is relevant. When the activity appears to have a direction, it makes it that much more complex but may also indicate an eventual relationship if a large enough data set is crunched.

I found Canie's response to be very interesting and will look forward to seeing your reply.