Paleoseismic history of the intermountain Rieti Basin (Central Apennines, Italy)

From the paleoseismological and seismotectonic point of view, the intermountain basins of the Central Apennines of Italy are one of the most studied areas worldwide. Within this context, however, the Rieti Basin, bounded at its sides by active normal faults and with its peculiar rhombohedral shape, is a relatively overlooked area, and its most recent paleoseismological studies date back to the 90s. This is a key area both for completing the paleoseismological history of this sector of the chain and for understanding how the present-day extensional regime is accommodated through time by the faults bounding the basin. With this aim in mind, we excavated 17 paleoseismological trenches along the normal faults bordering the Rieti Basin (Central Apennines, Italy) and unveiled at least 6 paleoearthquakes that ruptured the faults during the last ca. 20 kyr. Our analysis of the paleoearthquake succession along the basin-bounding faults suggests that a spatial pattern is followed during sequences of rupturing events, with a maximum credible earthquake of M w 6.5, consistently within this sector of the Central Apennines.