In Troubled Times, in a Divided Country: The 1789 Valtiberina Earthquake - Historical Seismology: Interdisciplinary Studies of Past and Recent Earthquakes - page 240

Fig. 1 Valtiberina historical seismicity according to the Italian catalogue (CPTI Working

Group 2004)

Ta b l e 1 Valtiberina major historical earthquakes according to the Italian catalogue (CPTI Working
Group 2004)
Year Mo Da Epicentral zone MIDP Io MCS Lat Lon Mm

1352 12 25 Monterchi 7 IX 43 . 465 12 . 127 6 . 0

1389 10 18 Bocca Serriola 9 IX 43 . 523 12 . 295 6 . 0

1458 04 26 Citta di Castello 5 IX 43 . 456 12 . 239 6 . 0

1789 09 30 Valtiberina 28 VIII-IX 43 . 505 12 . 208 5 . 8

43 . 465 12 . 125 6 . 0 1917 04 26 Monterchi-Citerna 128 IX

MIDP: Macroseismic Intensity Data Points

it all the more important that the two later ones (1789 and 1917) are as thoroughly
studied as possible. This paper deals with the 1789 earthquake, whose current epi-
central parameters have been assessed from a database of 28 MIDP (Fig. 2). Taking
into account the MIDP-per-earthquake ratio in the 18th century time-window of
the Italian catalogue (Table 2), a database of this size suggests that the 1789 earth-
quake is better known than most 18th century events but not quite as well as a good
many of them. Moreover, the MIDP distribution in the 1789 intensity map (Fig. 2)
seems sparser in the lesser damage intensity ranges (VII and VI MCS), than in the
higher damage ones (VIII and IX MCS), most MIDP being located south of the
border which runs through the Figure, marking the present administrative boundary
between Tuscany and Umbria (or, in 1789, between the Grand-Duchy of Tuscany
and the Papal States). Both circumstances seem to hint that part of the information
pertaining to this earthquake could be lacking. Why should it be so? And what could
be done to improve this situation?