Aha! I have figured it out my friends....

The Oceanic Crust is about 10km thick!
Check it out for yourself: [link to scign.jpl.nasa.gov]

If you go back and check out the 114 earthquakes that occurred at 10kms you will see that the vast majority of them occurred in the OCEAN.... and of course, how thick is the crust under the Ocean? You got it... the Oceanic Crust is about 10kms thick, or 6 miles for you Americans.

Now.... right underneath the Oceanic Crust is where you will find the UPPER MANTLE.

SO... it looks like there is a WORLDWIDE DISTURBANCE at the top of the UPPER MANTLE where it meets/touches the Oceanic Crust.

What other reason would there be?