Via The Los Angeles Times: Earthquake: 5.1 quake, aftershocks shakes Los Angeles, Southern California. The link will take you a rapidly updated feature story on the quake. Excerpt:
The 5.1 magnitude earthquake that rattled Southern California Friday night raises the possibility that a larger quake is on the way, seismologists said. (It was originally listed as 5.3 magnitude).
The swarm of earthquakes began at 8:03 p.m., when a 3.6 earthquake hit. That ended up being a foreshock of the largest earthquake to hit, a magnitude 5.1 at 9:09 p.m. At least two more aftershocks hit in the 3 range, a 3.4 at 9:11 p.m. and a 3.6 at 9:30 p.m.
U.S. Geological Survey seismologist Lucy Jones said the 5.1 quake has a 5% chance of being a foreshock of an even larger quake.
“There could be even a larger earthquake in the next few hours or the next few days,” Jones said at Caltech.