The building started shaking pretty good just a few minutes ago, and it lasted well over 20 seconds. After 15 seconds or so, I started wondering how long it would last. I started considering getting in a “triangle of life” position. It gradually subsided. The epicenter was over 50 miles away, and the magnitude 5.6; that was an interesting experience.
UPDATE: It was actually 5.8 magnitude, closer to Chino Hills.
UPDATE 2: LA Times has it at 5.4 magnitude.