An MD-83 Captain reported encountering wake turbulence behind a B747 on arrival to LAX that was strong enough to knock all three flight attendants off their feet.

Narrative

Just west of GRAAM intersection on RIIVR arrival to LAX we encountered wake turbulence descending out of FL190 from a B747 ahead. The wake rolled the airplane at least 30 degrees right and a few moderate jolts disconnected the autopilot and knocked all three flight attendants to the floor in the cabin. Arrival announcement had already been made and seat belt sign was on; so no passengers were out of their seats. The flight attendants reported to me that they were not injured and after checking the cabin determined no passengers were injured either. We got a visual on the traffic ahead that caused the wake and it appeared to be more than 5 but less than 10 miles ahead. The B747 split at RIIVR for 25L and we split for 24R at RIIVR and were no longer directly in trail. We kept the heavy traffic; still ahead and now offset to the left of us for the south complex; in sight and stayed above their flight path; especially with winds out of the southwest. We did not experience any more wake and landed normally on Runway 24R at LAX.