A magnitude 4.9 aftershock of last week's Southern California earthquakes has been felt widely in the region.

Aftershocks of last week's big earthquakes are still rumbling beneath the California desert, but seismologists say the probability of large quakes continues to decline.  

Southern California residents should remain on heightened alert until Tuesday for the increased possibility of a major earthquake, officials said.

"This is a big wake up call to take these seriously." After several earthquakes hit parts of Northern Nevada Tuesday night, experts say now is the time to prepare, for when the next possible temblor arrives.