Like I said I really think it's just the Bangladeshis screwing up; it's either just the 8.5 Sumatra quake or one of the Andaman aftershocks, and because those quakes saturated their equipment they couldn't tell what was going on.
Neither NEIC or the Swiss Red Puma page have a quake in or near Bangladesh.
lol, but they have the most updated equipment! /sarcasm
http://www.pnsn.org/WEBICORDER/VOLC/LO2_SHZ_UW.2004122600.html
Interesting that the pen was swaying up and down in a long period cycle for at least ten minutes before the vibrations started. I wonder if that was caused by longer wavelengths traveling faster through the earth? Maybe a more direct route?