The 1561 Earthquake(s) in Southern Italy: New Insights into a Complex Seismic Sequence

Abstract

In the summer of 1561, a strong seismic sequence struck southern Italy, then the Spanish-ruled Kingdom of Naples. Both the Italian seismological tradition and the latest catalogues locate it in the Vallo di Diano (Diano Valley), a low-seismicity intermontane basin 100 km south-east of Naples. We explore the hypothesis that current perception of the 1561 earthquake is distorted by the nature of the historical dataset from which its parameters have been assessed, and which mostly derive from a single-albeit very detailed-primary source. We present and discuss several previously unconsidered original accounts. Our results cast doubts on the traditional interpretation of the earthquake, which could have been either one Vallo di Diano mainshock or several strong earthquakes within a time/space window compact enough for contemporary viewers to perceive them as one. Unquestionably, there is much more to the 1561 earthquake(s) than previously appeared. We hope that this groundbreaking effort will rekindle the interest of the seismological community in this seismic episode, our knowledge of which is still far from complete.

Seismotectonic of Southern Apennines from recent passive seismic experiments

“…Following the macroseismic data (Branno et al, 1983Alessio et al, 1995) and the most recent geological and geomorphological studies (Benedetti et al, 1998;Cello et al, 2003;Maschio et al, 2005), the active fault related to the destructive 1857 Basilicata earthquake (M e = 6.9; XI MCS) is hypothesized to be located within the Val d'Agri basin. Moreover, the background seismicity gap observed in the area is partially correlated in space with the epicentral zone of the complex seismic sequence occurred in 1561 (M e = 6.4; X MCS; Castelli et al, 2008). From a geological and a tectonical point of view the two strong events of 1561 and 1857 are located in an area characterized by the extensional basins of the Vallo di Diano and the Auletta.…”

“…Moreover, Irpinia experienced a macroseismic intensity X MCS in 1980 (M s = 6.9) in the same area as the 1694 historical event (Postpischel et al, 1985). It is noteworthy to mention the 1561 complex seismic sequence located between the Vallo di Diano and the Upper Ofanto Valley, which is reappraised by Castelli et al (2008). This sequence is characterized by two large earthquakes occurred within 20 days (31 July and 19 August) with maximum intensities in the range of X MCS (M e = 6.4).…”

Recurrence times of central‐southern Apennine faults (Italy): Hints from palaeoseismology

“…For instance, some segments of the Norcia fault system released at least two Mw ~ 6 events between the 99 bce and the 1703 Mw 6.9 earthquakes (Galli et al., 2019); the same occurred for the Upper Aterno system, where the southern segment (Paganica‐San Demetrio fault) sourced the “minor” 1461 and 2009 L’Aquila earthquakes, before and after the catastrophic one in 1703 (Galli, Giaccio, Messina, & Peronace, 2011; Moro et al., 2013). Last but not least, the Caggiano fault sourced the Mw 6.4, 1561 event, but it seemingly participated in generating the catastrophic 1857 earthquake (Mw 7.0), together with other still unknown faults (Castelli, Galli, Camassi, & Caracciolo, 2008).…”

“… b Here I consider the hypothesis that the Caggiano fault sourced part of the Mw 7.0 earthquake in 1857 (Castelli et al., 2008; Galli, Bosi, Piscitelli, Giocoli, & Scionti, 2006), which shortens considerably the recent return time. …”

Uncertainty in strain-rate from field measurements of the geometry, rates and kinematics of active normal faults: Implications for seismic hazard assessment

“…The structure responsible for the event was a complex fault ~35 km long, composed by different NW-dipping segments (Westaway and Jackson, 1987;Pantosti and Valensise, 1990), and a SW-dipping antithetic fault (Bernard and Zollo, 1989) ( Figure 1). The two seismic events of July and August 1561, (Mw=6.3 and Mw=6.7, CPTI15) caused about 600 casualties and had a damage distribution suggesting that they possibly involved rupture on the Auletta fault (Galli et al, 2006;Spina et al, 2007;Castelli et al, 2008;Villani and Pierdominici, 2010; see Figure 1). Although the Val d'Agri fault is widely accepted to be responsible for the 1857 event (Mw=7.1, CPTI15) (Benedetti et al, 1998;Barchi et al, 2007;Villani and Pierdominici, 2010), it has been hypothesised that the Auletta fault generated a northern shock associated with the 1857 earthquake (Galli et al, 2006), which had the highest damage localised in the northern part of the Vallo di Diano and Val d'Agri.…”