Earthquake. From where I'm sitting, it was perfectly harmless. Disorienting and perhaps nausea-inducing, but the many precarious stacks of objects surrounding me have not fallen over, the windows haven't shattered, and to the best of my knowledge, Southern California is not sinking into the ocean. This one felt like the land had been carefully scooped up and moved somewhere else. Big movement, but not sudden or violent.
I remember one like this which hit about 12 years ago. We were in marching band, practicing for an upcoming parade, and every last person thought this was dehydration kicking in.
And then, of course, I remember a much bigger quake more recently than that. I hope everyone's okay.