The earthquake originated from the Abruzzo region's Apennine fold-and-thrust belt, the same that caused the 1703 and 2009 earthquakes. A foreshock hit the Aterno River valley on 16 November before two much larger tremors struck on the 27th, a few hours apart beginning at 21:05 (although some historical sources say just after 05:00). The main shock had an estimated magnitude of 6.4, with its epicenter very close to the village of Poggio Picenze near the Aterno river south-east of L'Aquila. The quake sent many residents of Abruzzo running out of their houses in the night, and two hours later it was followed by a powerful aftershock which further destroyed L'Aquila's already severely-damaged buildings. Aftershocks continued very frequently into mid December and proved ruinous for the region. Around 20:00 on 17 December another strong aftershock collapsed more houses in L'Aquila, leaving more residents homeless and fearful of further collapses.