235
architect, and another expert of “physical phenomena” (“una persona istruita dei
fenomeni fisici,” what today we would call a geologist) to visit the area. The advisors were expected to evaluate if and how the damage could undermine the rebuilding of the town and to determine if the rumors about an imminent volcanic eruption
were plausible.
Father Secchi was a renowned scientist and thus the local authorities consulted
him. In his final report (Secchi 1860), which represents a summary of geology of
Umbria and central Italy, he stressed the importance of field observations, the basis
of modern science.
6
In his trip to the area of the epicenter, Secchi brought his scientific instruments
(Console et al. 2017) and all the contemporary geological books that defined the
sedimentary sequence of rocks forming the Central Apennines. The trip to Norcia
was not a simple journey; moving from Spoleto along the Nera, Corno and Sordo
Rivers valleys, he made several geological surveys of the outcrops he saw. He identified the soils and rocks, and drew the folded strata geometries, describing them as
twisted by internal forces (“molto tormentati”). It is important to remark on how
accurately and systematically Father Secchi verified the continuity of strata on both
sides of the valleys, in order to determine if their origin depended only on fluvial
erosion or if their morphology instead corresponded to major faults.
In the town of Norcia he inspected the buildings, looking for evidence of damage
made by previous earthquakes in the older houses, and the subsequent restoration,
which often had not been carried out in accordance with best practices (“non sempre
a regola d’arte”). He also made macroseismic studies, interviewing the local population about their perception of the events, from foreshocks (ignored or understated
by the majority of the people) to the main shock and aftershocks in the following months.
He correlated the building damage with the foundation soils, highlighting the
importance of local geological conditions in controlling the effect of ground movement and consequent shaking of those establishments. Consequently, he specified
that waste deposits, the backfill of excavation, or alluvial sediments were “mobile
soils,” a critical substratum of the sites where severe damage occurred, whereas
buildings resting on cemented conglomerates experienced minor effects. In other
words, more than a century ago, Secchi was already using the methods which nowadays are called “site effects” to identify the critical local conditions in seismic
microzonation studies.
Finally, there is another confirmation that Father Secchi was undoubtedly a pioneer: at the end of his field trip to Norcia in 1859, he also fought popular misbeliefs,
disproving the “fake news” about a volcanic risk in Umbria-Marche Apennines. No
evidence of volcanic activity, either ancient or recent, was found in that sector of the
mountain belt, taking also into account the magnetic measurements he made. Secchi
6 “Sulla parte geologica dirò solo quel poco che può essere accessibile (...); spero che altri, più
periti, attualmente non reperibili perché lontani, vorranno colà portarsi (...); si vedrà la grande
importanza di studiare quei siti col lume della moderna scienza”.
14 Angelo Secchi and the Development of Geophysics in Italy
architect, and another expert of “physical phenomena” (“una persona istruita dei
fenomeni fisici,” what today we would call a geologist) to visit the area. The advisors were expected to evaluate if and how the damage could undermine the rebuilding of the town and to determine if the rumors about an imminent volcanic eruption
were plausible.
Father Secchi was a renowned scientist and thus the local authorities consulted
him. In his final report (Secchi 1860), which represents a summary of geology of
Umbria and central Italy, he stressed the importance of field observations, the basis
of modern science.
6
In his trip to the area of the epicenter, Secchi brought his scientific instruments
(Console et al. 2017) and all the contemporary geological books that defined the
sedimentary sequence of rocks forming the Central Apennines. The trip to Norcia
was not a simple journey; moving from Spoleto along the Nera, Corno and Sordo
Rivers valleys, he made several geological surveys of the outcrops he saw. He identified the soils and rocks, and drew the folded strata geometries, describing them as
twisted by internal forces (“molto tormentati”). It is important to remark on how
accurately and systematically Father Secchi verified the continuity of strata on both
sides of the valleys, in order to determine if their origin depended only on fluvial
erosion or if their morphology instead corresponded to major faults.
In the town of Norcia he inspected the buildings, looking for evidence of damage
made by previous earthquakes in the older houses, and the subsequent restoration,
which often had not been carried out in accordance with best practices (“non sempre
a regola d’arte”). He also made macroseismic studies, interviewing the local population about their perception of the events, from foreshocks (ignored or understated
by the majority of the people) to the main shock and aftershocks in the following months.
He correlated the building damage with the foundation soils, highlighting the
importance of local geological conditions in controlling the effect of ground movement and consequent shaking of those establishments. Consequently, he specified
that waste deposits, the backfill of excavation, or alluvial sediments were “mobile
soils,” a critical substratum of the sites where severe damage occurred, whereas
buildings resting on cemented conglomerates experienced minor effects. In other
words, more than a century ago, Secchi was already using the methods which nowadays are called “site effects” to identify the critical local conditions in seismic
microzonation studies.
Finally, there is another confirmation that Father Secchi was undoubtedly a pioneer: at the end of his field trip to Norcia in 1859, he also fought popular misbeliefs,
disproving the “fake news” about a volcanic risk in Umbria-Marche Apennines. No
evidence of volcanic activity, either ancient or recent, was found in that sector of the
mountain belt, taking also into account the magnetic measurements he made. Secchi
6 “Sulla parte geologica dirò solo quel poco che può essere accessibile (...); spero che altri, più
periti, attualmente non reperibili perché lontani, vorranno colà portarsi (...); si vedrà la grande
importanza di studiare quei siti col lume della moderna scienza”.
14 Angelo Secchi and the Development of Geophysics in Italy