Although this article deals with an Alaskan earthquake having a direct effect on the hydrothermal activities in 2002, I found this part to be rather ominous:

"Could large earthquakes closer to Yellowstone trigger hydrothermal explosions?" they asked.

Thousands of years ago a steam and hot water explosion blasted out a hole that now is Mary's Bay on Yellowstone Lake.



Here is the rest of the article: www.cnn.com...

I just wish they told us who they were quoting there.