The Dewatering of the Fucino Lake Did Not Promote the M7.1 1915 Fucino

Abstract

The powerful M7.1 earthquake that devastated the Fucino Basin (Central Italy) in 1915 results to be the only (except for a M5.7 event in 1904) remarkable event to have occurred in that area, according to the 900-year-long record of the Italian Seismic Catalogue. Curiously, the 1915 event occurred only 38years after the complete man-induced dewatering of the largest lake of peninsular Italy, which formerly occupied the basin. Hence, we investigate on a possible relationship between the dewatering of the lake and the occurrence of the 1915 earthquake. We perform some numerical simulations in order to estimate the stress changes induced by the dewatering of the Fucino Lake and by the 1904 earthquake. We compute the stress changes on two different seismogenic sources selected among the ones proposed in the literature. Our main results support that (1) the dewatering process has reduced effects of the state of stress in the area before the 1915 earthquake, (2) the primary effect of the dewatering on both sources is a decrease of stresses that hampers the slip on the fault planes, and (3) the positive stress changes associated to the 1904 event would be too weak to influence the occurrence of the 1915 earthquake. We also suggest that the dewatering may have delayed by 1.7years the 1915 earthquake occurrence.