A 2.9 magnitude quake with an epicenter three miles north of La Cañada struck the area today at 3:58 p.m., according to the United States Geological Survey office in Pasadena.
The quake was small, but close to the surface.
"The preliminary depth is shallow, that explains why it was felt," said USGS Scientist Susan Hough.
People from North Hollywood to Monrovia reported feeling the tremor.
"With a quake that small," Hough continued, "it’s hard to say which fault it is, but this one was close to the Sierra Madre fault. It was probably a small fault just off of the Sierra Madre."
According to the USGS website, 83 people in La Cañada felt the earthquake and reported it within the first hour following the event.
"This was probably an isolated incident," Hough said. "There’s always a 5% chance this could be a foreshock but odds are it isn’t."
The last major quake on the Sierra Madre fault was on June 28, 1991, a 5.8 magnitude quake that struck at 7:43 a.m. The quake caused two deaths.