AMQ29(1) 3 Galli 35-44.pub Available online http://amq.aiqua.it ISSN (print): 2279-7327, ISSN (online): 2279-7335 Alpine and Mediterranean Quaternary, 29 (1), 2016, 35 - 44 THE LITTLE-KNOWN EARTHQUAKE OF 1643 IN SICILY Paolo Galli 1,2 1 Dipartimento della Protezione Civile, Rome Italy 2 CNR - IGAG, Rome, Italy Corresponding author: P. Galli ABSTRACT: With earthquakes being most common to eastern Sicily (Mw >7.0), the mountainous region northwest of Mount Etna (Madonie-Nebrodi range) is affected by sparse, low magnitude seismicity (Mw≤ 5.0), with macroseismic intensities ≤ 7-8 MCS. Among these, the 1643 event is currently rated with an intensity of 6-7 MCS degree, related to only one locality (Troina, Enna province). New infor- mation retrieved from a coeval manuscript discovered in the National Library of Spain in Madrid, together with other unknown documents, allows now to provide a reliable damaging scenario for the mesoseismic area of the 1643 sequence. News concern five localities, account- ing for an epicentral intensity of 8 MCS and a related Mw 5.6, which is the strongest of the region. In some villages, the 1643 effects were even higher than in 1693, the catastrophic earthquake that razed to the ground dozen of towns in eastern Sicily, with damage from Malta to Palermo. The E-W elongated damage area fully matches the normal-fault plane solution of the focal mechanisms of two recent earth- quakes falling close to the 1643 epicenter, suggesting thus a similar trend for the seismogenic structure. The earthquake was also followed by an unreported activity of Mount Etna which was dormant since 1638. Keywords: historical seismology, 1643 earthquake, Nebrodi seismicity, Etna eruptions 1. INTRODUCTION The seismicity of Sicily is mainly clustered in the easternmost side of the island. Leaving aside the iso- lated 1968 Belice sequence in western Sicily (Mw 6.3), or the offshore seismicity paralleling the entire northern Tyrrenian coast, from Ustica to the Aeolian Islands (e.g., events of 2002, Mw 5.9; 1823, Mw 6.5; 1978, Mw 6.1), all the strongest historical earthquakes occurred be- tween the Hyblean Plateau to the south, and the Messina Strait to the north (Fig. 1). Among these, there are the most catastrophic events ever happened in Europe, as those in January 9 and 11, 1693 (Mw ~6 and Mw 7.3, respectively), with a possible ancestor in Febru- ary 4, 1169 (Mw ~6.5), and the December 28, 1908 earthquake and tsunamis (Mw 7.3). Furthermore, Mw>6 events occurred in 1542 (Lentini area: Mw 6.4), 1818 (southern Etna area: Mw 6.2), and 1786 (Patti area: Mw 6.2), besides sever others spanning 5.5