Although they jangled nerves and rattled windows, the 4.4 and 4.5-magnitude earthquakes that shook Southern California and probably aren't signs of a pending Big One, experts said.
“There is nothing in this sequence, at this point, that tells us we need to be particularly worried,” said Elizabeth Cochran, a geophycist at the U.S. Geological Survey.
The two quakes belonged to a series of about 30 temblors that rattled the region in less than 24 hours.
The quakes could be a doublet, two main shocks accompanied by a series of aftershocks, she said. Or they could be part of a swarm, meaning another 4.0-ish quake could happen. But the chances of another large shaker are only about 2 percent, she added.
Nevertheless, that doesn't mean the rumbling is entirely over.
Southern California residents should brace for a series of aftershocks in the days and weeks to come, Cochran said: “We can definitely expect more of these small earthquakes in the magnitude range of 1 or 2."
Meanwhile, scientists are working to determine which fault is responsible for the latest quakes. For now, they suspect the Whittier fault zone, a particularly active fault that was responsible for a 4.8-magnitude quake back in 2002.
Did you feel both of the quakes in Sierra Madre? Do you have an emergency preparedness plan?