Unexplained boom and shaking

At least that's the explanation.

So I was sitting at home this morning (taking a crap) when all of a sudden my apartment started shaking. There was creaking and rattling which lasted for probably 5-10 seconds. I live in San Diego, but am not from California, but was pretty certain that the only thing that could make my home shake would be an earthquake. I was fairly confident that I had just experienced a quake.

So I headed off to work, and was listening to the radio, and during one of the news blurbs, they mentioned that people all around San Diego were reporting a boom and shaking, but that there was no seismic activity in San Diego.

As the day went on I kept checking the local news, and articles were finally posted claiming that they "weren't sure what it was". Huh? So the entire county shakes, it's not an earthquake, but they don't know what it was? Some speculated it was a sonic boom from Miramar Air Force base, but military officials claimed it was not. They said that Camp Pendleton said they they were doing mortar testing, and that could have caused it.

I have to say, I'm a bit suspicious. I live about 50 miles from Camp Pendleton, so whatever they were doing, if it was them, would have to be pretty damn big to shake the entire county of San Diego. I actually just googled to see what exactly a mortar was, and it doesn't exactly seem like something that could shake the ground 50 miles away.

I think someone knows exactly what it was, and I think they are not telling us. Did anyone else in the area feel it?

Update: I just did a search which said mortar fire can be heard up to 50 miles away. So ok, maybe that's what it was. But I'm still suspicous. Why did I only feel one massive shaking if they were doing testing all week?