USGS upgrades earthquake near Templeton to magnitude 4.0

The U.S. Geological Survey has updated its readings for an earthquake and aftershock that shook San Luis Obispo County near Templeton on Wednesday morning.

The first quake, which jolted residents awake at 3:58 a.m., initially registered as a magnitude-4.2, according to the USGS.

That reading soon was downgraded to 3.9 before the USGS later settled on 4.0.

The temblor was centered about 5.6 miles west of Templeton, according to the USGS.

In the same area, a second quake was felt hours later at 10:13 a.m., with a preliminary magnitude of 3.0. That measurement was later downgraded to a 2.9, according to the USGS.

This story was originally published December 14, 2016 at 9:15 PM with the headline "USGS upgrades earthquake near Templeton to magnitude 4.0."