A moderate earthquake struck on Tuesday on the edge of the Salton Sea in Southern California's interior, but there were no reports of injuries or damage. The magnitude-4.8 quake struck at 4:55 am at a depth of about 3.5 miles (5.6 kilometers), said seismologist Amy Vaughn of the US Geological Survey. It was centered two miles south of the small town of Bombay Beach on the eastern shore of the Salton Sea, about 90 miles (145 kilometers) east of San Diego.
The main quake was followed by at least 18 smaller aftershocks. It was the largest in a swarm of earthquakes that have rattled the Salton Sea area since the weekend. More than 40 small quakes have been detected, most under magnitude-3.
Scientists are keeping close watch on the increased earthquake activity because it is near a section of the San Andreas Fault that has not popped loose in more than 300 years.
There was a 1 per cent to 5 per cent chance of a San Andreas quake over the next several days, but the probability decreases rapidly with time, according to the California Earthquake Prediction Evaluation Council.
A rupture on the southern San Andreas could set off the "Big One" that would devastate a large swath of Southern California. Last year, scientists estimated that a magnitude-7.8 earthquake on the southern San Andreas could cause 1,800 deaths and $200 billion in damages.