Details from USGS:

Magnitude 3.6
Date-Time Tuesday, December 28, 2010 at 08:36:50 UTC
Tuesday, December 28, 2010 at 12:36:50 AM at epicenter

Location 34.518°N, 118.681°W
Depth 18.9 km (11.7 miles)
Region SOUTHERN CALIFORNIA
Distances 6 km (4 miles) W (262°) from Castaic Lake dam, CA
16 km (10 miles) NE (41°) from Piru, CA
17 km (11 miles) NW (322°) from Valencia, CA
20 km (12 miles) NW (305°) from Santa Clarita, CA
65 km (40 miles) NW (322°) from Los Angeles Civic Center, CA

Location Uncertainty horizontal +/- 0.3 km (0.2 miles); depth +/- 0.7 km (0.4 miles)
Parameters Nph=124, Dmin=8 km, Rmss=0.43 sec, Gp= 29°,
M-type=local magnitude (ML), Version=1
Source California Integrated Seismic Net:
USGS Caltech CGS UCB UCSD UNR

Event ID ci10863861