That's weird.  Our fast data logger caught the earthquake as a transient
change in orbit circumference, but not a step change.  I think the earthquake
may have shifted the beamline relative to the ring.  You probably
didn't see the alaska quake because it had a much longer period and probably
wavelength.

click on

http://www.aps.anl.gov/asd/diagnostics/ILquake040628.png

The funny thing is that there was another, much larger
earthquake in alaska four hours later, which we also
saw:

http://www.aps.anl.gov/asd/diagnostics/AKquake040628.png

GD