The second quake -- with a magnitude of 6.1 -- was 3.2 kilometers (2 miles) north of Visso and 58 km (36 miles) from Perugia, the USGS reported.
Just a few hours earlier, a magnitude-5.5 quake struck the same region. The epicenter was about 9 kilometers away, south-southwest of the town of Visso. The first quake hit at 7 p.m. (1 p.m. ET) between Perugia and Macerata, according to ANSA.
This part of Italy is full of narrow roads linking small stone villages. Rescuers are fearful of mudslides and even of risking bringing heavy equipment up the narrow roads.
There have been no reports yet of injuries, although there was damage in Visso and another town, Campi, where the historic church, San Salvatore, was destroyed by the tremors -- the first severely damaged the 15th century structure and the second finished it off.
CNN's Barbie Nadeau, in Campi, said that there were constant, small aftershocks.
Streetlights, likely powered by generators, remained on in Campi, but the town's houses remained dark. In many small towns, in the pre-dawn hours, there is little light, further hampering rescue efforts -- rescuers are forced to listen for people calling for help.
The main square and the church in nearby Norcia, a couple of miles to the south, are badly damaged, but the church there is still standing.
In Campi, hundreds of people were sleeping in their cars, with blankets covering the windows. The cars are parked everywhere -- streets, gas stations, parking lots. Some residents have taken their dogs with them in their cars.
Local media said one man had suffered a heart attack.
Residents were uncertain as to what might happen next, and expressed worry that another, bigger tremor, might cause even more damage.
The USGS said both earthquakes were shallow.
Civil protection spokesman Antonio Flippini told CNN that previously damaged buildings had suffered new collapses and that part of the Salaria highway in the Marche region near Amatrice have been closed over concerns of structural damage.
Della Longa said buildings that fell in the area have been unoccupied since the August quake. The area remains off-limits. Many people displaced by that quake have been forced to move once again.
Police have offered those living in tent camps the opportunity to stay farther away tonight as the rain falls.