There was an earthquake with depth 511 km under the Yucatan today. Parameters from
NEIC are:
08May2001 18:41:56.7 19.4N 90.7W511 MB=4.2 M NEI YUCATAN PENINSULA, MEXICO

The Mexican subduction zone is generally considered a shallow subduction.
However 8 earthquakes with depths greater than 500 km have been recorded along
this zone. All of these, however have had magnitudes less than 4. The earthquake
today in the Yucatan, then is the largest earthquake recorded with depth greater
than 500 km along the Mexican subduction zone. This is a very rare event indeed.

This earthquake occurred as a strong wave of seismicity swept the Mexico
and Central American subduction zone including moderate quakes (M>=5)
in the Gulf of California, Jalisco, Guerrero, Chiapas/Guatemala and the Yucatan.

The initial portion of this episode was commented on earlier by members of
this board.