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In Troubled Times, in a Divided Country:
The 1789 Valtiberina Earthquake
V. Castelli
Abstract
The Valtiberina region (central Italy) has a seismic record going back to
the Middle Ages and including five Io
VIII MCS earthquakes, the earliest of which
(1352, 1389, 1458), though recently and extensively studied, remain rather poorly
known. This makes it all the more important to ensure that the later ones (1789,
1917) are as thoroughly studied as possible. The 1789 earthquake is listed by the
current Italian catalogue (CPTI Working Group 2004) with Io VIII-IX MCS and
Mm 5.8. These parameters were assessed from a database of twenty-eight macro-
seismic intensity data points (Castelli et al. 1996), which is less than plentiful for
a late 18th century earthquake. An analysis of the historical context of the 1789
earthquake and its influence on the production of contemporary accounts evidences
a few research paths that previous studies either did not or could not take. Fol-
lowing them, the macroseismic database of the 1789 earthquake can be noticeably
improved, providing the catalogue compiler with a mean to check the reliability of
its current parameters.
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1 Introduction
Late in the morning of September 30, 1789 a strong earthquake hit Valtiberina, the
upper valley of the Tiber, in central Italy. The seismic history of this area goes back
to the Middle Ages, with at least nine Io
VII MCS regional earthquakes (Fig. 1).
The 1789 earthquake - listed by (CPTI Working Group 2004) with Io VIII-IX
MCS and Mm 5.8 - is one of the five strongest regional earthquakes (Table 1).
Though recently and extensively studied (Boschi et al. 1995; Boschi et al. 1997;
Boschi et al. 2000; Castelli 2002; Guidoboni and Comastri 2005) the earliest of
these earthquakes (1352, 1389, 1458) remain rather poorly known, with less than ten
macroseismic intensity data points (MIDP) available for each (Table 1). This makes
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