The US Geological Service said it had a magnitude of 4.7. The aftershock was preceded by more than a dozen weaker ones overnight and followed by another nine in the subsequent hour — some of the nearly 1,000 aftershocks that have rocked the seismic area in the two days since the quake Wednesday.
Rescue efforts continued in the night, but more than a day-and-a-half had passed since the last person was extracted alive.