Minor Tremors felt at 9221 Rumsey road, columbia, MD-08232011

I was sitting in my office when the walls in front of me started to shake. First of all I thought someone was moving something next door. Then the tremors extended to roof and every walls around me. So I thought someone was on the roof. But then I realized we did not have access to roof. That;s when my colleagues came running down and we all went outside where other people also had got out of their buliding. That is when we realized that we had just experienced a 3.5 point quake just like the one last year in July 2010. Did any one else experience this. Please share your experience
Thanks