We thought we had an earthquake today!

I've lived here for about 15 months now and have yet to feel an earthquake. The first one that I missed, I was in Vegas for a bachelorette party. Mike called me early in the morning all excited to tell me we'd had an earthquake. The second earthquake that I missed was an afternoon that I was out shopping. I had just had lunch with Mike and he'd gone back to work. I stopped off to get some things at the store before heading home. When I finally got in my car to drive home, there was talk of the tremor on the radio. Mike said he'd felt it in the hospital that he was working at that day, but I'd felt nothing in the store I was in only 3 blocks from him. This morning on my way to work, the radio all the sudden started talking about this tremor that had just occurred. Again, I felt nothing in my car. People were calling in the radio saying they'd felt it all over the county. I assumed as everyone else that we'd had an earthquake. Mike called me to tell me he felt it too. As the day went on, there was never any confirmation of an earthquake. Some people said they'd heard a "boom." Now this boom is a mystery. No one knows where it came from.
..."Speculation is it's a sonic boom or something along that line, but it is all speculation,” said Tom Amabile, a senior emergency services coordinator with the county Office of Emergency Services.
Pendleton in North County said they were doing routine artillery training Tuesday morning, but it was not known whether that was responsible for the rattling felt all over the region.
“I can't say we caused the boom, but I can say we are conducting training this morning with 81mm mortars,” said Marine Cpl. K.T. Tran. “The training started at 6 a.m. and it is going to end at midnight.” ...
Well, maybe we'll know the answer tomorrow?